Bull AIX Glossary

AIX

86 A2 79JX 01

ORDER REFERENCE

Bull AIX Glossary

AIX

Software

December 1998

BULL ELECTRONICS ANGERS

CEDOC

34 Rue du Nid de Pie – BP 428

49004 ANGERS CEDEX 01

FRANCE

86 A2 79JX 01

ORDER REFERENCE

The following copyright notice protects this book under the Copyright laws of the United States of America

and other countries which prohibit such actions as, but not limited to, copying, distributing, modifying, and

making derivative works.

Copyright Bull S.A. 1992, 1998

Printed in France

Suggestions and criticisms concerning the form, content, and presentation of

this book are invited. A form is provided at the end of this book for this purpose.

To order additional copies of this book or other Bull Technical Publications, you

are invited to use the Ordering Form also provided at the end of this book.

Trademarks and Acknowledgements

We acknowledge the right of proprietors of trademarks mentioned in this book.

AIX� is a registered trademark of International Business Machines Corporation, and is being used under

licence.

UNIX is a registered trademark in the United States of America and other countries licensed exclusively

through the Open Group.

The information in this document is subject to change without notice. Groupe Bull will not be liable for errors

contained herein, or for incidental or consequential damages in connection with the use of this material.

iiiPreface

Contents

Special Characters 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Alphabetical List 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B 1-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C 1-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D 1-38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

E 1-50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F 1-57. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

G 1-63. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

H 1-66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I 1-69. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

J 1-78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

K 1-79. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

L 1-81. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

M 1-89. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

N 1-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

O 1-102. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P 1-107. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q 1-123. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

R 1-124. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

S 1-134. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T 1-153. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

U 1-161. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

V 1-164. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

W 1-168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

X 1-171. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Y 1-173. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Z 1-174. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

iv Glossary

vPreface

Master Glossary

This glossary provides definitions of specialized terms used in the AIX documentationlibrary. Terms that are defined in nontechnical dictionaries and that have no special meaningin information processing are not defined in this glossary.

This glossary includes terms and definitions from the following publications:

ISO Vocabulary––Information Processing, developed by the International Organization forStandardization, Technical Committee 97, Subcommittee 1, as well as definitions from draftinternational standards, draft proposals, and working papers in development by theISO/TC97/SC1 vocabulary subcommittee.

CCITT Eighth Plenary Assembly Red Book, Terms and Definitions and working documentspublished by the International Telegraph and Telephone Consultative Committee of theInternational Telecommunication Union, Geneva, 1985.

American National Dictionary for Information Processing Systems, by the Computer andBusiness Equipment Manufacturers Association (CBEMA), copyright 1982.

X/Open XAE Specification System Interface Definitions, Issue 4, published by X/OpenCompany, Ltd., U.K., copyright 1992.

vi Glossary

1-1Glossary

Special Characters

2–1/2 dimension. A drafting term that describeslimited associativity between orthogonal views; twodimensions with a perspective view that cannot bemodified once created and that cannot be rotated.Allows for semi–automatic creation of isometricviews.

3270 Device Emulation. Support that allows alocal or remote device on one system to appear asa 3270 device to another system.

3270 Host Connection Program (HCON). Aprogram that allows a system unit to emulate aworkstation or printer attached to a System/370host. See also session profile and HCONuser.

$HOME. An environment variable, set by thesystem, that designates a user’s home directory.Many programs use this variable to designate adirectory where they store temporary work files.

/usr file system. Contains files and programsnecessary for operating the machine.

/tmp file system. A shared storage location forfiles.

/var file system. Contains files that are variable ona per–client basis, such as spool and mail files.

/ file system. The root file system; contains filesthat contain machine–specific configuration data.

1-2 Glossary

Alphabetical List

AA. See ampere.

abbreviation. A character string representing alonger character string.

abend. (1.) The abnormal end of a task. (2.) Theending of a task before its completion because ofan error condition that recovery facilities cannotresolve while the task is running.

abort. This term refers to transactions that do notcomplete. Any changes made by a transaction thatis aborted, for whatever reason, must be undone.Once a transaction is undone (rolled back), noevidence that the transaction was ever attemptedremains outside of records in the transactionprocessing system’s log. See also rolled back.

absolute address. An address that, without theneed for further evaluation, identifies a storagelocation or a device.

absolute device. A locating device, such as atablet, that reports its position to the operatingsystem as a set of numbers on a coordinatesystem.

absolute time. A point on a time scale.

absolute value. The numeric value of a realnumber regardless of its algebraic sign (positive ornegative).

abstract class. A SOM class that is not designedto be instantiated, but serves as a base class forthe definition of subclasses. Regardless of whetheran abstract class inherits instance data andmethods from parent classes, it will alwaysintroduce methods that must be overridden in asubclass, in order to produce a class whoseobjects are semantically valid.

Abstract Syntax Notation One (ASN.1). Anotation that enables both complicated types to bedefined and values of these types to be specified.

abstraction (data). A data type with a privaterepresentation and a public set of operations.

accelerator. In AIXwindows, a keyboard alternativeto a mouse button action. For example, holding the<Shift> and <M> keys on the keyboard can bemade to post a menu in the same way that amouse button action does. Accelerators typicallyprovide increased input speed and greaterconvenience.

access. To obtain data from or to put data instorage.

access control list (ACL). (1.) A file attribute thatcontains the basic and extended permissions thatcontrol access to the file. (2.) A list of hosts(maintained by Enhanced X-Windows) that haveaccess to client programs. By default, onlyprograms on the local host and those in this list,also known as ”access list,” can use the display.The list can be changed by clients on the localhost; some server implementations can also modifythe list. The authorization protocol name and datareceived by the server at connection setup mayaffect the list as well. See also discretionary accesscontrol.

access control list entry. Data in an accesscontrol list that specifies a set of permissions. Inthe case of a principal or group entry, thepermission set is that which may be granted to aprincipal having the privilege attribute specified inthe entry; in the case of a mask entry, thepermission set is that which masks the permissionset in a principal or group entry.

access declaration. Used to restore access tomembers of a base class.

access level. In computer security, the level ofauthority a user has while accessing a secured fileor library.

access permission. A group of designations thatdetermine who can access a particular file and howthe user can access the file. See also permissioncode.

access procedure. The procedure or protocolused for gaining access to a shared resource. In alocal area network, the shared resource is thetransmission medium. The medium accessprocedures specified by the IEEE 802 standard areCSMA/CD token bus and token ring.

access resolution. The process by which theaccessibility of a particular class member isdetermined.

access right. See permission.

accessible. Said of an object for which the clientpossesses a valid designator or handle.

account. The log in directory and other informationthat give a user access to the system.

accounting system. A utility that monitors variousaspects of system operations; it collects detailed

1-3Glossary

data on each transaction and provides tools forprocessing the data to produce different kinds ofreports.

ACK. See acknowledgment character.

ACK0. A transmission control character for evenpositive acknowledgment; indicates that text wasreceived without transmission errors.

ACK1. A transmission control character for oddpositive acknowledgment; indicates that text wasreceived without transmission errors.

acknowledge. (1.) To answer. To respond to a poll,address, or message. (2.) In the X.25 API, toconfirm that a data packet with the D–bit set hasarrived.

acknowledge timeout. The number of secondsthat a station should wait for an acknowledgmentfrom a remote station after sending data.

acknowledgment character (ACK). In binarysynchronous communications, a transmissioncontrol character sent as an affirmative response toa data transmission.

ACL. See access control list.

ACM. Association for Computing Machinery.

ACSE. Association Control Service Element.

action. (1.) A defined task that an applicationperforms. An action modifies the properties of anobject or manipulates the object in some way. Aprocessing step or operation. (2.) In the awkcommand, the lex command, and the yacccommand, a C language program fragment thatdefines what the program does when it recognizesinput. (3.) In CDE, a desktop construct thatprovides a method for running applications,executing commands, and other activities such asprinting, removing files, and changing directories.Actions are defined in a database of configurationfiles.

action icon. In CDE, an icon that represents anaction in a File Manager or Application Managerwindow, or in the workspace. An action icon iscreated by creating an empty executable file withthe same name as the action it represents.

action label. In CDE, the name displayed underthe icon of an action. See also action name.

action name. In CDE, the name associated withan action, which by default is displayed under theicon for the action. See also action label.

action statement. C language program fragmentsthat define how the generated lexical analyzerreacts to regular expressions that it recognizes.

action table. In Xtoolkit, a table that specifies themapping of externally available procedure stringsto the corresponding procedure implemented bythe widget class. All widget class records containan action table.

activate. To point with the mouse pointer anddouble–click, successfully causing something tohappen.

active. (1.) The windowpane in which the textcursor is currently positioned is said to be ”active.”(2.) One of the states in the lifetime of atransaction. This is the state during which it isaccessing or modifying data.

active gateway. A gateway that is treated like anetwork interface in that it is expected to exchangerouting information. If it does not do so for a periodof time, the route associated with the gateway isdeleted. Contrast with passive gateway. See alsogateway.

active grab. In Enhanced X-Windows, a grabactually owned by the grabbing client. Contrast withpassive grab. See also button grabbing and grab.

actual parameter. The actual value passed to aroutine. Contrast with formal parameter.

ACU. See automatic calling unit or auto–call unit.

adapter. (1.) A mechanism for connecting twounlike parts or machines. (2.) A printed circuit cardthat modifies the system unit to allow it to operatein a particular way. See also communicationsadapter and card.

adapter code. In X.25 communications, the X.25Interface Co-Processor/2 Protocol Code, whichcontrols the frame–level and packet–levelcommunication processing.

adapter descriptor file (ADF). A file of predefinedinformation used to set up the programmableoption select (POS) registers for an adapter. Theadapter descriptor file database is on a systemhard disk.

add mode. In addition and subtraction operations,a mode in which the decimal marker is placed at apredetermined location with respect to the last digitentered. In selection actions, a mode that allowsthe selection to be unaffected by keyboardnavigation.

address. (1.) The telephone number that remotesystems use to call the system. (2.) To refer to adevice or an item of data by its address. (3.) Inword processing, the location, identified by anaddress code, of a specific section of the recordingmedium or storage. (4.) In data communication, the

1-4 Glossary

unique code assigned to each device orworkstation connected to a network. See alsonetwork user address. (5.) A numbering systemused in network communications to identify aspecific network or host with which tocommunicate. Addresses are often denoted indotted decimal form. See also presentationaddress.

address extension. In X.25 communications, thecalled and calling address extensions are optionalCCITT–specified facilities, available on networksthat conform to the 1984 version of X.25.Synonymous with extended address.

address family. See protocol family.

address field. The part of a packet containingaddressing information. See also packet.

address list. The list used by the xtalk commandto associate users’ names with network useraddresses and other information, for the purpose ofmaking outgoing X.25 calls without the callerhaving to know the addresses. There is oneaddress list for the system and one for each user.See also system address list and user address list.

Address Resolution Protocol (ARP). One of theprotocols provided by TCP/IP that dynamicallymaps between Internet addresses, BasebandAdapter addresses, X.25 addresses, andToken–Ring Adapter addresses on a local areanetwork.

address space. The code, stack, and data that isaccessible by a process.

Address Translation Register (ATR). Amechanism that translates real addresses to virtualaddresses.

addressing. (1.) In data communications, the waythat the sending or controlling station selects thestation to which it is sending data. (2.) A means ofidentifying storage locations. (3.) Specifying anaddress or location within a file. (4.) Theassignment of addresses to the instructions of aprogram. See also selection.

ADF. See adapter descriptor file.

adjust. The process of moving text to fit betweenthe left and right margins.

ADK (Application Developer’s Kit). Thecomponent of the License Use Managementsystem that is used by software developers todefine and create licenses for software products.

administration environment. The part of theMonitor that facilitates system configuration andmanagement.

ADU. See automatic dialing unit.

Advanced Program–to–ProgramCommunication (APPC). A communicationsarchitecture that allows transaction programs toexchange information on a peer–to–peer basis.SNA LU 6.2 allows APPC architecture to operateon an SNA network.

advisory lock. A type of lock that a process holdson a region of a file preventing any other processfrom locking the region or an overlapping region.See also enforced lock.

affinity group. In SOM, an array of class objectsthat were all registered with the SOMClassMgrobject during the dynamic loading of a class. Anyclass is a member of at most one affinity group.

aggregate. (1.) An array, structure, or union. (2.) Inprogramming languages, a structured collection ofdata objects for a data type. (3.) A transmittedcarrier signal that consists of the 12 single–sidebands being sent over the transmission circuit.

aggregate type. In SOM, a user–defined data typethat combines basic types (such as, char, short,float, and so on) into a more complex type (such asstructs, arrays, strings, sequences, unions, orenums).

AIX. The operating system that exists between thehardware and the application programs.

AIX command line. The area of the screen wherecommands are displayed as they are typed.

CDE Desktop. A visual user interface for theoperating system consisting of icons and menuswithin an AIXwindows window. An iconic view ofthe file system providing users with windows, icons,and menus to perform program and filemanagement tasks.

AIXwindows Environment. A software graphicaluser interface environment based on OSF/MOTIFconsisting of the AIXwindows toolkit, graphicslibraries, window manager, and desktop running ontop of a compatible operating system.

AIXwindows Resource Manager (MRM). Adatabase management system that allows a userto effectively retrieve and assign information, suchas specific values and other attributes, especiallyregarding applications that allow a user to selectcolor, font, and other resource preferences. TheMRM system consists of library subroutines thataccess the AIXwindows User Interface Language(UIL) at run time and create user interfaces. Seealso AIXwindows User Interface Language (UIL).

1-5Glossary

AIXwindows Toolkit. An object–oriented collectionof C language data structures and subroutines thatsupplement the Enhanced X-Windows toolkit andsimplify the creation of interactive client applicationinterfaces.

AIXwindows User Interface Definition (UID). Afile containing the definitions for all objects includedin a particular user application. The UID is a subsetof the AIXwindows User Interface Language (UIL)and functions similarly to the UIL for the particularapplication to which it belongs. See alsoAIXwindows User Interface Language (UIL).

AIXwindows User Interface Language (UIL). Acompiled–specific language for describing the initialstate of a user interface. UIL specifies the widgets,gadgets, and compound objects that make up theinterface; it also identifies the subroutines to becalled whenever the interface changes state as aresult of user interaction. See also AIXwindowsUser Interface Definition (UID).

alarm. An audible signal at a workstation or printerthat is used to get the operator’s attention.

alert. In SNA, an error message sent to the systemservices control point (SSCP) at the host system.

algorithm. A finite set of well–defined rules for thesolution of a problem in a finite number of steps; forexample, a complete specification of a sequence ofarithmetic operations for evaluating sine x to agiven precision.

alias. (1.) An alternate name for a node or a filethat can be used in place of the real name of thenode or file. (2.) An alternate label for a dataelement or point in a computer program. (3.) Analternate name for a member of a partitioned dataset. (4.) Unofficial name used for the network.Synonymous with nickname. (5.) An assumed oractual association between two data entities, orbetween a data entity and a pointer.

aliasing. (1.) A compilation process that attemptsto determine what aliases exist, so thatoptimization does not result in incorrect programresults.

alignment. The position in main storage of afixed–length field, such as halfword or doubleword,on an integral boundary for that unit of information.For example, a word boundary is a storageaddress evenly divisible by four.

All Points Addressable (APA) display. A displaythat allows each picture element (pel) to beindividually addressed and displayed. An APAdisplay permits the display of images that are notpredefined in character boxes. Contrast withcharacter display. See also bitmapped display.

allocate. (1.) To assign a resource, such as a diskfile or a diskette file, to perform a specific task.Contrast with deallocate. (2.) A request to allocatea session between the local LU and a remote LU.(3.) In NCS, to create a Remote Procedure Call(RPC) handle that identifies an object.

alphabetic character. A letter or other symbol,excluding digits, used in a language. Usually theuppercase and lowercase letters A through Z plusother special symbols (such as $ and _) allowed bya particular language. See also alphanumericcharacter.

alphanumeric character. Consisting of letters,numbers, and often other symbols, such aspunctuation marks and mathematical symbols. Seealso alphabetic character.

alphanumeric set. Character set composed ofuppercase and lowercase letters and numbers, butno symbols. See also alphanumeric character.

alternate cell (isolated cell). An NCS cell thatrestricts access to a partial group of nodes in thenetwork. This cell type is usually used to confineLicense Use Management license transactions to aparticular set of nodes in the network.

alternate character set. A set of characters thatincludes some special characters, such asmathematical characters and Greek characters,and that is defined for some printers.

ALU. Arithmetic and logical unit.

ambient light. In three–dimensional graphics, lightthat reflects off one or more surfaces in the scenebefore arriving at the target surface. Ambient lightis assumed to be nondirectional, and is reflecteduniformly in all directions by the reflecting surface.In GL, ambient light is mocked up by use ofambient terms in the lighting equation, rather thanactually computing the reflections.

ambiguous derivation. Derivation is ambiguous ifa C++ class is derived from two or more baseclasses that have the same name.

American National Standard Code forInformation Interchange (ASCII). The codedeveloped by ANSI for information interchangeamong data processing systems, datacommunications systems, and associatedequipment. The ASCII character set consists of7–bit control characters and symbolic characters.

American National Standards Institute (ANSI).An organization sponsored by the Computer andBusiness Equipment Manufacturers Associationthrough which accredited organizations create andmaintain voluntary industry standards.

1-6 Glossary

amp. See ampere.

ampere (A or amp). A unit of measurement forelectric current that is equivalent to a flow of 1coulomb per second, or to the current produced by1 volt applied across a resistance of 1 ohm.

amplitude. The size or magnitude of a voltage orcurrent wave form.

ancestor. In Enhanced X-Windows, a widget thathas inferior widgets. In other words, the superior orpredecessor of an inferior widget. If W is an inferiorof A, then A is an ancestor of W.

ancestor class. A SOM class from which anotherclass inherits instance methods, attributes, andinstance variables, either directly or indirectly. Adirect descendant of an ancestor class is called achild class, derived class, or subclass. A directancestor of a class is called a parent class, baseclass, or superclass.

annotation. See license annotation.

anonymous union. A union in C++ without a classname. It must not be followed by a declarator.

ANSI. See American National Standards Institute.

antialiasing. Techniques used to smooth the”jaggies” otherwise found on lines and polygonedges caused by scan conversion. Commontechniques include adjusting pixel positions orsetting pixel intensities according to the percent ofpixel area coverage at each point.

a.out. (1.) An output file produced by default forcertain commands. By default, this file isexecutable and contains information for thesymbolic debug program. (2.) The object file formatcreated by the cc command and expected by theexec subroutine.

APA. See All Points Addressable Display.

APAR. Authorized program analysis report. Areport of a problem caused by a suspected defectin a current unaltered release of a program.

API. See application program interface.

APL. A programming language. A general–purposelanguage for diverse applications such ascommercial data processing, system design,mathematical and scientific computation, databaseapplications, and the teaching of mathematics andother subjects.

AppBuilder. In CDE, a software application usedfor constructing a graphical user interface.

APPC. See Advanced Program–To–ProgramCommunications.

append. (1.) The action that causes data to beadded to the end of existing data. (2.) In word

processing, to attach a file to the end of anotherfile.

applet. A program, intended for delivery over theInternet, which can be included in an HTML page,just as an image can be included.

application. (1.) A program or group of programsthat apply to a particular business area, such asInventory Control or the Accounts Receivableapplication. (2.) Software coded by or for end usersthat performs a service or accomplisheswork–related tasks. (3.) In AIXwindows andEnhanced X-Windows, the environment is modeledon a traditional client–server relationship in whichcompatible applications are considered clients ofthe Enhanced X-Windows server.

Application Developer’s Kit. See ADK.

application development environment. TheMonitor functions used to construct transactionalapplications.

application group. In CDE, an ApplicationManager folder that holds a specific softwareapplication or set of software applications.

application icon. See action icon.

application identifier (ID). A unique identifier usedto identify an application in the RPCs sent in adistributed environment.

Application Manager. In CDE, a windowcontaining objects representing the system actionsavailable to you.

application program. A program used to performan application or part of an application.

application program interface (API). (1.) A set ofrun–time routines or system calls that allows anapplication program to use a particular serviceprovided by either the operating system or anotherlicensed program. (2.) The formally definedprogramming language interface that is between asystem control program or a licensed program andthe user of the program.

application programmer. A programmer whouses an API to produce an application.

application server. In CDE, a host computer thatprovides access to a software application.

application shell. A subclass of top–level shell,this shell is used primarily for an application’stop–level window.

application transaction program. (1.) A programthat performs an application or part of anapplication. (2.) A program that connects andcommunicates with stations in a network, enablingusers to perform application–oriented activities.

1-7Glossary

See also transaction program and servicetransaction program.

application window. A rectangular area thatdisplays the graphics associated with a specificapplication. Application windows can be opened,closed, combined with other types of windows,moved, stacked, and otherwise manipulatedthrough user interaction with a window manager.

apply. (1.) In journaling, to place after–images ofrecords into a physical file member. Theafter–images are recorded as entries in a journal.(2.) When a service update is installed or applied, itenters the applied state and becomes the currentlyactive version of the software. When an update isin the applied state, the previous version of theupdate is stored in a special save directory. Thisallows you to restore the previous version, ifnecessary, without having to reinstall it. Softwarethat has been applied to the system can be eithercommitted or rejected. The installp –s commandcan be used to get a list of applied products andupdates that are available to be either committedor rejected. See also commit and reject.

Apply. In CDE, a choice that causes a selection (orgroup of selections) in a dialog box to take effect.

apply list file. A file that contains an entry for eachfile to be restored during an installation or anupdate procedure.

apply stub. A SOM procedure corresponding to aparticular method that accepts as arguments: theobject on which the method is to be invoked, apointer to a location in memory where the method’sresult should be stored, a pointer to the method’sprocedure, and the method’s arguments in the formof a va_list. The apply stub extracts the argumentsfrom the va_list, invokes the method with itsarguments, and stores its result in the specifiedlocation. Apply stubs are registered with classobjects when instance methods are defined, andare invoked using the somApply function. Typically,implementations that override somDispatch callsomApply to invoke a method on a va_list ofarguments.

Appointment Editor. In CDE, in Calendar, awindow you use to schedule, change, or delete anappointment.

Appointment List. In CDE, a chronological list ofappointments displayed by Calendar.

Arabic numerals. The 10 numerals used fordepicting decimal numbers: the digits 0, 1, 2, 3, 4,5, 6, 7, 8, and 9. No font is implied. See alsoRoman numerals.

archive. (1.) To store programs and data forsafekeeping. (2.) A copy of one or more files or a

copy of a database that is saved in case theoriginal data is damaged or lost.

archive library. A place where programs arestored for safekeeping.

arg pointer. A pointer to a subroutine parameterargument.

argument. (1.) Numbers, letters, or words thatexpand or change the way a command works. (2.)A parameter passed between a calling routine anda called routine. (3.) An independent variable.

argument list. A string of arguments.

argument string. An ordered list of parameterspassed between programs or routines.

arithmetic constant. In a programming language,a constant of type integer, real, double precision, orcomplex. See also arithmetic expression andarithmetic operator.

arithmetic expression. One or more arithmeticoperators and arithmetic primaries, the evaluationof which produces a numeric value. An arithmeticexpression can be an unsigned arithmetic constant,the name of an arithmetic constant, a reference toan arithmetic variable, array element, or function,or a combination of such primaries formed by usingarithmetic operators and parentheses. See alsoarithmetic constant and arithmetic operator.

arithmetic object. An integral object or objectshaving the float, double, or long double type. The CFor AIX compiler also recognizes objects havingthe long double type as arithmetic objects.

arithmetic operator. A symbol that directs acompiler to perform an arithmetic operation. Seealso arithmetic expression and arithmetic constant.

ARK (Administrator Runtime Kit). In License UseManagement, the run–time environment forlicensed software products. It consists of thenetwork license server daemon (netlsd) and itsassociated tools: ls_admin, ls_rpt, and ls_stat.

ARP. See Address Resolution Protocol.

ARPA. Advanced Research Projects Association.

ARPA RFC 822. Standard of ARPA internet textmessages.

array. (1.) A structure that contains an orderedgroup of data elements. All elements in an arrayhave the same data type. (2.) An arrangement ofdata in one or more dimensions, such as a list,table, or multidimensional arrangement of items.(3.) In programming languages, an aggregate thatconsists of data elements, with identical attributes,each of which may be uniquely referenced bysubscripting.

1-8 Glossary

array declarator. The part of a statement thatdescribes an array used in a program unit. Thedescription includes the name of the array, thenumber of dimensions, and the size of eachdimension.

array element. A single data item in an array.

array name. The name of an ordered set of dataitems.

array padding. In a multiple–array definition, theoptimization of adding elements to each array, oradding small arrays between user–defined arrays,to improve the memory–access characteristics ofthe arrays.

arrow button. A graphic control that simulates apush button with a directional arrow. People usethe pointer and mouse to push the button and startsome action that has an associated direction.

arrow keys. In CDE, the four directional keys on akeyboard.

art tag. In hypertext, a tag linking text to an artworkwindow.

artwork frame. In Interleaf, the container forgraphical data.

ASCII. See American National Standard Code forInformation Interchange.

ASCII characters. The characters that make upthe ASCII character set. The ASCII character setconsists of 7–bit control characters and symboliccharacters. See also American National StandardCode for Information Interchange.

ASCII flat file. See flat file.

ASCIIZ format. A string ending with a nullcharacter.

ASN.1. See Abstract Syntax Notation One.

aspect ratio. The ratio of the height of a primitiveto its width. A rectangle with a width of 10 inchesand a height of 5 inches has an aspect ratio of 10/5or 2.

assemble. To translate an assembly program intoa computer language. Assembling is usuallyaccomplished by substituting the computerlanguage operation codes for the assemblylanguage operation code, and by substitutingabsolute addresses, immediate addresses,relocatable addresses, or virtual addresses forsymbolic addresses.

assembler. A computer program that convertsassembly language instructions into object code.Synonymous with assembly program.

assembler language. A symbolic programminglanguage in which the set of instructions includes

the instructions of the machine and whose datastructures correspond directly to the storage andregisters of the machine.

assembly program. Synonym for assembler.

assertion. See program assertion.

assignment compatible. Indicates whether thetype of a value allows it to be assigned to avariable. See also compatible types.

assignment conversion. A change to the form ofthe right operand that makes the right operandhave the same data type as the left operand.

assignment expression. In C For AIX, anexpression that assigns the value of the rightoperand expression to the left operand variableand has as its value the value of the right operand.

assignment statement. In programminglanguages, a statement that assigns the value ofan expression to a variable.

associative transformation. An optimization thatinvolves changing the order of an expression. Anassociative transformation yields mathematicallyidentical results but not always bitwise identicalresults.

associativity. The order for grouping operandswith an operator (either left–to–right orright–to–left).

async. See asynchronous transmission.

asynchronous. Not synchronized in time. Forexample, input events are controlled by the user;the program can read them later.

asynchronous device. A device using datatransmission in which transmission of a characteror a block of characters can begin at any time, butin which the bits that represent the character orblock have equal time duration.

asynchronous operation. An operation that doesnot of itself cause the process requesting theoperation to be blocked from further use of theCPU. This implies that the process and theoperation are running concurrently.

asynchronous terminal. A computer terminalusing asynchronous signals to communicate with ahost machine.

Asynchronous Terminal Emulation. A programthat provides emulation of a remote asynchronousterminal.

asynchronous transmission. Data transmissionin which transmission of a character or block ofcharacters can begin at any time, but in which thebits that represent the character or block have

1-9Glossary

equal time duration. Contrast with synchronoustransmission. See also start–stop.

ATE. See Asynchronous Terminal Emulation.

ATM. Asynchronous transfer mode. Acell–switching, connection–oriented technology. InATM networks, end stations attach to the networkusing dedicated full duplex connections.

atom. (1.) A unique ID corresponding to a stringname. Atoms are used to identify properties, types,and selections. (2.) A 32–bit number thatrepresents a string value. See also X Atom.

atomic operation. An operation in which signalscannot occur between the operations of setting themasks and waiting for the signal.

ATR. See Address Translation Register.

attachment. (1.) The physical connection to thenetwork that makes it work. (2.) A type of resourcethat controls CPs, logical link control, and physicallink control. (3.) In CDE, In Mailer, a data objectwithin an electronic mail message that is displayedas an icon in the Attachments list. An attachmentcan be text, sound, or a graphic. Multiplemessages can be added (attached) to a singleelectronic mail message.

attachment class. The attachment class specifiesthe mode in which a station will connect to theFDDI network. A station may be a dual attachmentstation (DAS) or a single attachment station (SAS).

attachment profile. Contains parameters thatassociate other defined profiles with the attachmentof the LU to the network. These parameters alsodefine the type of network being used.

attenuation. (1.) A decrease in magnitude ofcurrent, voltage, or power of a signal intransmission between points. It may be expressedin decibels or nepers. (2.) In 3D graphics, the falloff of light intensity with distance.

attribute. (1.) A characteristic or property of one ormore objects or entities. For example, the attributefor a displayed field could be ”blinking.” (2.) In GL,a parameter that can affect the appearance of adrawing primitive. For instance, color is anattribute. If the color is set to ”RED,” it will remainred until changed, and everything that is drawn willbe drawn in red. Other attributes include linestyle,linewidth, pattern, and font. For a list of attributesand pipeline options, see also pipeline options. (3.)In devices, a characteristic of a defined orconfigured device. (4.) In SOM, A specialized SOMsyntax for declaring ”set” and ”get” methods.Method names corresponding to attributes alwaysbegin with ”_set_” or ”_get_”. An attribute name isdeclared in the body of the interface statement fora class. Method procedures for get/set methods

are automatically defined by the SOM Compilerunless an attribute is declared as ”noget/noset”.Likewise, a corresponding instance variable isautomatically defined unless an attribute isdeclared as ”nodata”. IDL also supports ”readonly”attributes, which specify only a ”get” method.Contrast with instance variable. See also resourcevalue.

attribute file. In system configuration, a text filethat is organized into stanzas, each of which has astanza name and a set of attribute definitions in theform of Attribute=Value pairs. Configuration fileshave the attribute file format.

attribute (of file). Some portion of the informationabout a file that determines its access andorganizational characteristics.

attribute pair. See attribute, value, and resourcevalue.

attribute value. See attribute, value, and resourcevalue.

audit events. Occurrences on the system that maybe security violations. These events cause an auditrecord to be written.

audit trail. A collection of audit records.

auditing subsystem. A mechanism that lets anadministrator detect potential or actual securityviolations in the system. Components of thissubsystem detect audit events, log and collectaudit events in a system audit trail, and process theaudit trails.

authentication. Verifying the identity of a userwhen the login or su command is given. Forexample, the operating–system method ofauthentication consists of checking the passwordentered by a user against the encrypted version ofthe password previously defined for that user. Asecondary authentication method can be added foradditional checks, such as verifying the identity of auser to a network.

authoring environment. The organization andequipment that allow the creation of hypertextdocuments.

authorization. (1.) The determination of aprincipal’s permissions with respect to a protectedobject. (2.) The approval of a permission sought bya principal with respect to a protected object.

authorization protocol. A formal procedure forestablishing the authorization of principals withrespect to protected objects.

authorize. (1.) To grant to a user the right tocommunicate with or make use of a computersystem or display station. (2.) To give a user either

1-10 Glossary

complete or restricted access to an object,resource, or function.

auto–answer. The ability of a station to receive acall over a switched line without operator action.

auto–call. The ability of a station to place a callover a switched line without operator action.Contrast with manual call.

auto–call unit (ACU). In X.25 communications, adevice that automatically makes and answers calls.

autodialer. See automatic dialing unit.

autoexec. A command or list of commands run atlogin time.

AUTOLOG. A menu–driven utility programprovided in the 3270 Host Connection Program 2.1and 1.3.2 for AIX and used to create logonprocedures.

automatic calling unit (ACU). A device that allowsa host to automatically dial the number of a remotedevice.

automatic dialing unit (ADU). A device that canautomatically generate dialing digits.

automatic scrolling. The scrolling action thattakes place automatically when a cursor is movedto the border of a pane.

automatic variable. A variable allocated on entryto a routine and deallocated on the return. Contrastwith static variable.

autonomous system. A group of networks andgateways for which one administrative authorityhas responsibility. An autonomous system can besmall or very large.

autonumber. A unique number associated with theprefix of each component in the Interleaf desktoppublishing software. Because each autonumberhas a unique value, these numbers are used tocreate references to their components elsewhere inthe text. In hardcopy, an autonumber can be usedto create a page reference that renumbersautomatically as its associated component movesto a different page. In hypertext, autonumbers areused to create the hypertext links that jump to thecorresponding component. For the ordered–list

item component and the figure caption component,the autonumbers are visible and are used tonumber a series of these items in the proper order.

autonumber reference. A hardcopy or softcopyreference created from an autonumber. Theautonumber reference automatically renumbers toreflect the status of its corresponding autonumber.In softcopy, an autonumber reference is associatedwith a hypertext link so that the link jumps to thecorresponding autonumber. See also autonumber.

autopush. A STREAMS mechanism that enables aprespecified list of modules to be pushedautomatically onto the stream when a STREAMSdevice is opened.

auxiliary class data structure. A SOM structureprovided by the SOM API to support efficient staticaccess to class–specific information used indealing with SOM objects. The structure’s name is<className>CClassData. Its first component(parentMtab) is a list of parent–class method tables(used to support efficient parent method calls). Itssecond component (instanceDataToken) is theinstance token for the class (generally used tolocate the instance data introduced by methodprocedures that implement methods defined by theclass).

available state. The state a device is in when it isconfigured. The device status field in theCustomized Devices Object Class in the ODMreflects whether a device is in the available state ornot.

AZERTY keyboard. A keyboard in which the keysin the second–from–top row (row D) are labeled(from left to right): A, Z, E, R, T, Y, U, I, O, and P.See also QWERTY keyboard.

azimuthal angle. In GL, if a primitive is sitting onthe ground, with its z coordinate straight up, theazimuthal viewing angle is the angle the observermakes with the y axis in the x–y plane. If theobserver walks in a circle with the primitive at thecenter, the azimuthal angle is the only thing thatvaries.

azizo. In Performance Toolbox, a tool used toanalyze performance recordings.

1-11Glossary

Bback margin. The margin of a page that is closestto the binding edge. Normally, this is the left marginof the recto page and the right margin of the versopage.

back up. To copy information, usually onto disketteor tape, for safekeeping.

backdrop. In CDE, the pattern that covers theworkspace background.

backend. The program that sends output to aparticular device. There are two types of backends:friendly and unfriendly.

backend program. See backend.

backfacing polygon. In GL, a polygon whosevertices appear in clockwise order in screen space.If backface culling is enabled, such polygons arenot drawn.

background. (1.) In multiprogramming, theconditions under which low–priority, noninteractiveprograms are run. Contrast with foreground. Seealso program level. (2.) In CDE, the underlyingarea of a window on which elements, such asbuttons and lists, are displayed.

background activity. See background process.

background color. In AIXwindows and EnhancedX-Windows, the single electronic color assigned tothe graphic field that appears behind theforeground elements inside the border of adisplayed widget or gadget. Contrast withforeground color.

background process. (1.) A process that does notrequire operator intervention but can be run by thecomputer while the workstation is used to do otherwork. (2.) A mode of program execution in whichthe shell does not wait for program completionbefore prompting the user for another command.Contrast with foreground process.

backing store. The collection of off–screen, savedpixels maintained by the Enhanced X-Windowsserver.

backscrolling. (1.) Reversing the normal(top–to–bottom) direction of flow of paper through aprinter. (2.) In reference to a video display, movingtext through the viewing area from top to bottom.

Backtrack. In CDE, in Help Manager, a button andNavigate menu item you use to follow linksbackward, in the reverse order they weretraversed.

backup. Pertaining to a system, device, file, orfacility that can be used in the event of amalfunction or loss of data.

backup copy. A copy, usually of a file or group offiles, that is kept in case the original file or files areunintentionally changed or destroyed.

backup format. When the backup commandmakes a copy of a file, it writes the file in thisformat. A file in this format must be restored by therestore command before it can be used.

backup format file. A file in backup format.

backup system. See dump and restore.

bad block. A portion of a disk that can never beused reliably.

bandwidth. Data rate transfer in K bits, K bytes, Mbits, and M bytes per second.

base address. The beginning address forresolving symbolic references to locations instorage.

base address register. Synonym for base register.

base class. A C++ class from which other classesare derived. A base class may itself be derivedfrom another base class.

base line. See baseline.

base name. (1.) The last element to the right of afull path name. (2.) A file name specified without itsparent directories. (3.) In Ada language, acompilation unit name specified without its typequalifier of lib/ or sec/. (4.) In CDE, The file nameof an icon file minus the file–name suffixes for size(.l, .m, .s, .t) and type (.bm, .pm). For example, thebase name of an icon file named myicon.m.pm ismyicon.

base number. The part of a self–check field fromwhich the check digit is calculated.

Base Operating System (BOS) installation. Theprocess of installing and configuring the minimumamount of software needed to bring a machine tothe running state.

base permission. An access mode that isassigned to a file owner, file group, or others whowant access to the file. Access modes include read(r) permission, write (w) permission, andexecute/search (x) permission. See alsodiscretionary access control.

base register. A general purpose register that theprogrammer chooses to contain a base address.

1-12 Glossary

Synonym for base address register. See alsoindex.

base scalar type. In Pascal, the type from which aset type or subrange type is derived. See alsosubrange scalar type.

baseband system. A communications systemwhereby information is encoded, modulated, andimpressed on the transmission medium withoutshifting or altering the frequency of the informationsignal. At any point on the medium, only oneinformation signal at a time is present.

baseline. In a font, the imaginary line on which thebottom of each character is aligned.

BASIC (beginner’s all–purpose symbolicinstruction code). (1.) A programming languagedesigned for interactive systems. Originallydeveloped at Dartmouth College to encouragepeople to use computers for simpleproblem–solving operations. (2.) A high–levelprogramming language with a small number ofstatements and a simple syntax. BASIC isdesigned to be easily learned and used and iswidely used for interactive applications onmicrocomputers.

basic conversation. A connection between twotransaction programs that allows them to exchangelogical records that contain a 2–byte prefix thatspecifies the length of the record. LUs 1, 2, and 3do not use the 2–byte prefix; however, LU 1, 2, and3 conversations must be basic conversations. Thisconversation type is used by service transactionsand LU 1, 2, and 3 application transactionprograms. Contrast with mapped conversation.

Basic Encoding Rules (BER). A set of rules usedto encode ASN.1 values as strings of octets.

basic increment. The smallest unit of motion ofwhich a device is capable.

Basic Input/Output System. See BIOS.

Basic Networking Utilities (BNU). A group ofprograms and files, sometimes called theUNIX–to–UNIX Copy Program, that provides basicnetworking utilities, such as the uucp command.BNU includes a set of directories, files, programs,and commands that allow the user to communicatewith a remote AIX or UNIX system over adedicated line or a telephone line. See alsoUNIX–to–UNIX Copy Program and UUCP login ID.

basic real constant. A string of decimal digitscontaining a decimal point and expressing a realvalue.

basis. In GL, a curve or patch basis is a 4x4 matrixthat controls the relationship between control pointsand the approximating spline. B–splines, Bezier

curves, and Cardinal splines all differ in that theyhave different bases.

batch printing. Queueing one or more documentsto print in a separate job as a background process.The operator can type or revise additionaldocuments at the same time. This is a backgroundprocess. See also background process.

batch processing. A processing method in whichone or more programs process records with little orno operator action. This is a background process.Contrast with interactive processing.

battery backup. A power source that allows theprocessor drawer and other data storage devicesto continue operating during a primary AC powersource outage.

baud. (1.) The number of changes in signal levels,frequency, or phase per second on acommunication channel. If each baud represents 1bit of data, baud is the same as bits per second.Informally (as used by programmers) synonymouswith ”bits per second.” Named for J. Baudot,1845–1903, French inventor. However, it ispossible for one signal change (1 baud) to equalmore than 1 bit of data. (2.) A unit of signalingspeed equal to the number of discrete conditions orsignal events per second. For example, 1 baudequals one–half dot cycle per second in Morsecode, 1 bit per second in a train of binary signals,and one 3–bit value per second in a train of signalsthat can each assume one of eight different states.(3.) In asynchronous transmission, the unit ofmodulation rate corresponding to one unit intervalper second; for example, if the duration of the unitinterval is 20 milliseconds, the modulation rate is50 baud. See also bps.

baud rate. In remote communications, thetransmission rate that is synonymous with signalevents. The baud rate is usually expressed in bitsper second.

BCUG. See bilateral closed user group.

behavior (of an object). In SOM, the methods thatan object responds to. These methods are thoseeither introduced or inherited by the class of theobject. See also state.

BEL. The bell character. A control character thatactivates an alarm or other attention devices whenhuman attention is required. Synonym for consolebell.

benchmark. A program designed to test therelative performance of computers of differentarchitectures, or of different implementations of anarchitecture. The combination of a rigorouslyspecified workload and a method of quantifying theperformance of a system when processing that

1-13Glossary

workload. The performance metric is usuallyderived from the time required to process theworkload.

BER. See Basic Encoding Rules.

Bezier cubic curve. In GL, a cubic splineapproximation to a set of four control points thatpasses through the first and fourth control points,and has a continuous slope where two splinesegments meet. See also parametric cubic curve.

BGP. Border Gateway Protocol.

bibliography. A list of documents referred to withina document. For each document, the following isgenerally listed: the author, the document, notesabout the document, and sometimes notes aboutits author.

bid. In the contention form of invitation or selection,an attempt to gain control of a line to transmit data.

bidirectional. See shared port.

big endian. An attribute of data representation thatreflects how multi–octet data are stored in memory.In big endian representation, the lowest addressedoctet of a multi–octet data item is the mostsignificant. See also endian and little endian.

big endian order. The method of storage in whichinteger values are stored most significant byte first.See also little endian order.

big word. In the vi editor, a contiguous set ofalphanumeric characters bounded at the beginningand end by blank spaces, tabs, or new–lineindicators. See also small word.

bilateral closed user group (BCUG). In X.25communications, an optional facility that allowscalls to be made only between two designatedDTEs. See also closed user group.

bin collection. A method of collecting auditingdata that writes audit records to a temporary binfile. After the data is processed by the auditbindaemon, records are written to an audit trail file forstorage.

binary. (1.) Pertaining to a system of numbers tothe base two. The binary digits are 0 and 1. (2.)Involving a choice of two conditions, such as on–offor yes–no. (3.) In ODM, a terminal descriptor typeused to define a variable as a bit string that is notnull–terminated. See also terminal descriptor.

binary constant. A constant that is made up ofone or more binary digits.

binary digit. Synonym for bit.

binary expression. An expression containing twooperands and one operator.

binary file. A file that contains codes that are notpart of the ASCII character set. Binary files canutilize all 256 possible values for each byte in thefile.

binary–image transfer. See bit block transfer.

binary operator. (1.) A symbol representing anoperation to be performed on two data items,arrays, or expressions. The four types of binaryoperators are numeric, character, logical, andrelational. Contrast with unary operator. (2.) Anarithmetic operator that has two terms. Synonymfor dyadic operator.

binary search tree. A search structure in which, ateach step of the search, the set of data elements isdivided by two; some appropriate action is taken inthe case of an odd number of data elements.

binary synchronous communication (BSC). Aform of telecommunication line control that uses astandard set of transmission control characters andcontrol character sequences for binarysynchronous transmission of binary–coded databetween stations. Contrast with synchronous datalink control.

bind. (1.) To associate a variable with an absoluteaddress, identifier, or virtual address, or with asymbolic address or label in a program. (2.) InSNA, a request to activate a session between twological units. See also bind session. (3.) Forinformation on how to set a binding, see also set.

BIND. See bind session.

bind image. In SNA, the session parameters thatthe system services control point (SSCP) sends tothe primary logical unit (PLU) and the PLU sends inthe BIND request to the secondary logical unit(SLU); these parameters specify the proposedprotocol options for an LU–LU session.

BIND password. One of the two communicationsecurity passwords. In an LU–LU session, it is thepassword that the system checks against theremote system to verify that the program to whichthe user is connected is the correct one. See alsonode verification and communications authoritypassword.

bind session (BIND). In SNA products, a requestto activate a session between two logical units. Seealso bind.

binder. See linkage editor.

binding. (1.) A temporary association between aclient and both an object and a server that exportsan interface to the object. A binding is meaningfulonly to the program that sets it and is representedby a bound handle. (2.) In SOM,

1-14 Glossary

Language–specific macro or procedure that makesimplementing and using SOM classes moreconvenient. These bindings offer a convenientinterface to SOM that is tailored to a particularprogramming language. The SOM Compilergenerates binding files for C and C++. Thesebinding files include an implementation template forthe class and two header files, one to be includedin the class’s implementation file and the other inclient programs. (3.) In a multiprocessor context,constraining a thread to a specific physicalprocessor to gain the benefit of processor affinity.

binding edge. The edge of a page, perforated forloose binding, to be bound, stapled, or drilled.

BIOS (Basic Input/Output System). In thePersonal Computer AT, microcode that controlsbasic hardware operations such as interactionswith diskette drives, fixed–disk drives, and thekeyboard.

bis . Describes a secondary recommendation thatis an alternative to a primary recommendation.

BIST. Built–in self–test.

bit. Either of the binary digits 0 or 1 used incomputers to store information. Synonymous withbinary digit. See also byte.

bit block transfer (BLT). The movement of abinary image (bitmap or pixmap) by specifying thelower–left and upper–right corners of the imageand the destination address.

bit BLT. See bit block transfer.

bit clocking. In an EIA–232C or D interface, thefield that indicates which piece of equipment, eitherthe modem (DCE) or the computer (DTE), providesthe clock signal for synchronized data transactions.

bit field. A member of a structure or union thatcontains 1 or more named bits.

bit gravity. In Enhanced X-Windows, the attractionof window contents for a location in a window.When a window is resized, its contents can berelocated. The server can be requested to relocatethe previous contents to a region of the window.See also gravity.

bit planes. In computer graphics, a bitplanesupplies one bit of color information per pixel onthe display. Thus, an eight bitplane system allows 2to the eighth power different colors to be displayedat each pixel.

bit rate. The speed at which bits are transmitted,usually expressed in bits per second.

bit scattering. A technique for mapping memorybits to ensure that a minimum number of bits in amemory word are stored in a single DRAM. With a

minimum number of bits, the ECC is better able todetect and correct errors caused by a bad DRAM.

bitmap. A pixmap with a depth of one bit plane.

bitmap file. The file containing the height andwidth instructions for creating a bitmap.

bitmapped display. A display with a displayadapter that has a hardware representation of eachseparately addressable point on the display. Thehardware representation can be processor memoryor adapter memory. See also All PointsAddressable Display.

bits per character. The number of bits in a datacharacter.

blank common. In FORTRAN, an unnamedcommon block.

blind folio. A document in which the pages of thedocument are counted but not numbered. See alsofolio, dropped folio, and expressed folio.

blit. Bit block transfer.

block. (1) A group of contiguous records recordedor processed as a unit. Blocks are separated byinterblock gaps and each block may contain one ormore records. (2) In data communications, a groupof records that is recorded, processed, or sent as aunit. (3) In programming languages, a compoundstatement that coincides with the scope of at leastone of the declarations contained within it. A blockmay also specify storage allocation or segmentprograms for other purposes.

block data subprogram. In FORTRAN, asubprogram headed by a BLOCK DATA statementthat is used to initialize variables in namedcommon blocks.

block device. (1.) One of the types of files in theAIX file system, described by an i–node. (2.) Adevice that is accessed by means of an AIX devicedriver.

block file. A file listing the usage of blocks on adisk. See also special file and character special file.

block input/output communication area(BIOCA). A block of storage in the kernel addressspace that is used to communicate with a block I/Osubsystem.

block I/O. Input/output operations on blocks ofdata stored in random locations.

block special file. A special file for a block device.The file provides access to an input or outputdevice that uses in–core buffers and is capable ofsupporting a file system. See also character specialfile.

1-15Glossary

block statement. Any number of data definitions,declarations, and statements that appear betweenthe symbols { (left brace) and } (right brace). The Clanguage, for example, reads a block statement asa single C language statement. In Ada language, ablock statement is a single statement that maycontain a sequence of statements. It may alsoinclude a declarative part, and exception handlers;their effects are local to the block statement. Seealso statement.

blocking. An optimization that involves changingthe access order of loops that access large arrays,so that each array element is accessed asinfrequently as possible.

blocking call. A call in which a caller is suspendeduntil a called procedure completes.

blocking factor. The number of iterations of aninner loop that are executed for each pass of acorresponding blocking loop.

BLT. See bit block transfer.

BNC. A connector used with some coaxial cables.

BNU. See Basic Networking Utilities.

BOA (basic object adapter) class. In SOM, aCORBA interface (represented as an abstract classin DSOM), which defines generic object–adapter(OA) methods that a server can use to registeritself and its objects with an ORB (object requestbroker). See also SOMOA (SOM object adapter)class and ORB (object request broker).

body. (1.) On a printed page, the portion of thepage that contains the main text, excluding themargins, headers, footers, and footnotes. (2.) In abook, the portion between the front matter and theback matter. (3.) In Ada language, a body definesthe execution of a subprogram, package, or task. Abody stub is a form of body that indicates that thisexecution is defined in a separately compiledsubunit.

boldface. A heavy–faced type, generally a heavierversion of a regular text font. Also, the process ofprinting in this type. See also double–strike andemphasized.

Boolean. A binary numbering system named aftermathematician George Boole in which zero andone are the only two values that can be returned.Traditionally, a value of zero represents FALSEwhile a value of one represents TRUE. A value ofTRUE or FALSE, where TRUE=1 AND FALSE=0.

boot. See initial program load.

boot block. In a file system, the first block wherethe bootstrap program resides. See also bootstrapblock.

boot device. The device that assigns the fixed diskwithin the root volume group (rootvg) that willcontain the startup (boot) image.

boot image. An image containing the kernel, filesystems, libraries, and programs. The boot imageis loaded after the machine is turned on or resetand brings it to a running state.

boot processing. The type of processing thatoccurs when a boot image is loaded. The type ofboot device (disk, tape, or network) determines thetype of boot processing that occurs. Bootprocessing over the network brings a machine tothe running state, the BOS installing state, or thediagnostic state depending on the configuration file.

bootstrap. A small program that loads largerprograms during system initialization.

bootstrap block. Synonym for boot block.

border. A visual boundary that separates adisplayed object from everything else on a screen.

BOS (Base Operating System). The collection ofprograms that controls the resources and theoperations of the computer system.

bosinst.data. The file that controls the actions ofthe BOS installation program.

bottleneck. An area of code within a program thatuses CPU resources inefficiently and thereforecauses unnecessary delays.

bottom shadow. In AIXwindows, a narrow band ofa dark color across the bottom of a rectangulargraphical object (a widget or gadget) that creates athree–dimensional appearance when the object ismanipulated.

boundary alignment. The position in main storageof a fixed–length field, such as halfword ordoubleword, on an integral boundary for that unit ofinformation. For example, a word boundary is astorage address evenly divisible by four.

bounding box. (1.) In computer graphics, thebounding box of a character is the smallestrectangle that encloses the shape at the x, y origin.(2.) In GL, a two–dimensional rectangle thatbounds a primitive. A bounding box can be used todetermine whether the primitive lies inside aclipping region. See also character cell andclipping.

bounds violation. An attempt to access an arrayusing an index or pointer that references storageoutside of the array.

box. A line enclosure around text or a table.

bpi. Bits per inch, a measure of linear density forstorage products.

1-16 Glossary

bps. Bits per second. In serial transmission, theinstantaneous bit speed with which a device orchannel transmits a character. See also baud.

braces. (1.) The characters { (left brace) and }(right brace), also known as ”curly brackets.” TheseASCII characters are primary symbols in the Cprogramming language in which the operatingsystem is written. (2.) In Pascal, commentdelimiters.

bracket read lock. A shared lock that is obtained,held only for the duration of the current operation,and then immediately dropped. This lock modeensures that only committed data is read. It doesnot guarantee that successive reads of the data willyield the same value, because other transactionscan immediately modify the value after the readoperation is complete and the lock is dropped.

brackets. (1.) The ASCII characters [ (left bracket)and ] (right bracket), also known as ”squarebrackets.” (This usage does not follow the Britishusage of ”brackets” to mean parentheses, thecharacters that enclose this sentence.) (2.) In SNA,one or more chains of request units and theirresponses, which are exchanged between twoLU–LU half–sessions and represent a transactionbetween them. A bracket must be completedbefore another bracket can be started. Examples ofbrackets are database inquiries and replies, updatetransactions, and remote–job–entry outputsequences to workstations.

branch. In a computer program, an instruction thatselects one of a number of alternative sets ofinstructions. A conditional branch occurs only whena specified condition is met. An instruction thatselects one of a number of alternative sets ofinstructions.

branch processing unit. A processing unit thatprocesses branch instructions and dispatchesfixed– and floating–point instructions to thefixed–point unit and floating–point unit.

break condition. In the TTY subsystem, acharacter framing error in which the data is allzeros.

break signal. A signal sent over a remoteconnection to interrupt current activity on theremote system.

break statement. A C language control statementthat contains the keyword break and a semicolon.

break value. In allocating data segment space, theaddress of the first location beyond the current endof the data segment.

breakpoint. A place in a computer program,usually specified by an instruction, where execution

may be interrupted by external intervention or by amonitor program.

bridge. (1.) In the connection of local loops,channels, or rings, the equipment and techniquesused to match circuits and facilitate accurate datatransmission. (2.) A functional unit that connectstwo local area networks (LANs) that use the samelogical link control (LLC) procedure but may usedifferent medium access control (MAC)procedures. Contrast with gateway.

broadband. Transmission media and techniquesthat use a broad frequency range, divided intosub–bands of narrower frequency, so that differentkinds of transmission can occur at the same time.

broadband channel. A data transmission channel6 MHz wide. Synonym for wide band channel.

broadcast. Simultaneous transmission of data tomore than one destination.

broadcast topology. The topology in which allstations are connected in parallel with the mediumand are capable of concurrently receiving a signaltransmitted by any other station connected to themedium.

broken pipe message. A message that occurs ifthe pipe becomes unsynchronized.

broker. In NCS, a server that manages informationabout objects and interfaces to the objects. Aprogram that wishes to become the client of aninterface can use a broker to obtain informationabout servers that export the interface. See alsoLocation Broker.

browse. (1.) A function available when you selectthe List of Books button at the bottom of anavigation window. You can move forward andbackward through an online book in the same wayyou can move through a book in hardcopy. (2.) Inthe xtalk and xroute commands, to view thedetails of an entry in the routing list or address list.

BSC. See Binary Synchronous Communication.

BSD. Berkeley Software Distribution.

B–spline cubic curve. In computer graphics, acubic spline approximation to a set of four controlpoints having the property that slope and curvatureare continuous across sets of control points. Seealso parametric cubic curve.

BTU. (1.) British thermal unit. (2.) In SNA, basictransmission unit.

bucket. One or more fields that accumulate theresult of an operation.

1-17Glossary

bucket counts. The number of elements greaterthan or equal to the lowest limit and less than orequal to the higher limit.

buffer. (1.) A temporary storage unit, especiallyone that accepts information at one rate anddelivers it at another rate. (2.) An adjustablememory storage space, temporarily reserved forperforming input or output, into which data is reador from which data is written.

buffer length. The maximum length of a datasegment that can be stored in a given buffer.

bug. An error in a program or a logic problem inthe intent of the program.

BUID. See bus unit identification.

build code. The program that runs the buildprocess to convert source files into a hypertextdatabase. The build code defines which items canbe built into hypertext and which cannot. Forexample, an illegal font does not build because it isnot included in the build code.

built–in function. A function known to thecompiler, whose code is incorporated directly into aprogram module rather than referenced through alibrary call.

bulletin board. A graphic object that simulates areal–life bulletin board in that it displays text andgraphic information in the form of messages to theuser from client applications that are currentlyrunning.

bundle. A collection of software products availablefor installation.

burst pages. On continuous–form paper, pages ofoutput that can be separated at the perforations.

bus. (1.) In a processor, a physical facility on whichdata is transferred to all destinations but fromwhich only addressed destinations can read inaccordance with appropriate conventions. (2.) Acomputer configuration in which processors areinterconnected in series. (3.) One or moreconductors that transmit signals or power.

bus–in. A unidirectional data bus that is part of theSystem 360/370 parallel–I/O interface. This buspasses data from the system unit to the host.

Bus Master. A device on the Micro Channel busthat has its own built–in DMA controller instead ofusing the system–provided DMA controller. Thisallows the device to set up the DMA transfer itself

instead of relying on the system software to set upthe system DMA controller, giving the devicegreater flexibility in function and, in general, bettersystem performance than a DMA slave device. Seealso DMA slave.

bus–out. A unidirectional data bus that is part ofthe System 360/370 parallel–I/O interface. This buspasses data from the host to the system unit.

bus unit identification. A field in the I/O Segmentregister that is decode to select the IOCC for theparticular hardware implementation.

busy light. In CDE, a control that blinks when aFront Panel action has been invoked prior to theappearance of a window or when reloading actions.

button. (1.) A word or picture on the screen thatcan be selected. Once selected and activated, abutton begins an action in the same manner thatpressing a key on the keyboard can begin anaction. (2.) Buttons include those on the keyboard,mouse, lightpen, or buttons on the dial and buttonbox.

button grabbing. Enacting an active grab using amouse button. See also grab, pointer grabbing, keygrabbing, passive grab, and active grab.

button press. The initiation of a function bypressing a mouse button.

byte. (1.) The amount of storage required torepresent 1 character; a byte is 8 bits. (2.) A binarycharacter operated on as a unit and usually shorterthan one word. (3.) A string that consists of acertain number of bits (usually 8) treated as a unit,and that represents a character. (4.) A group of 8adjacent binary digits representing 1 EBCDICcharacter. (5.) In X.25, a byte is called an octet.See also bit.

byte boundary. Memory addressing based on8–bit intervals. Each memory location contains an8–bit value that can range from 0 to 255 in decimalnotation.

byte constant. In FORTRAN, a named constantthat is of type byte.

byte order. In Enhanced X-Windows, the order ofbytes as defined by the server for pixmap or bitmapdata. Clients with different native byte orderingmust swap bytes as necessary.

byte type. In FORTRAN, a binary characteroperated on as a unit and usually shorter than acomputer word.

1-18 Glossary

CC. Celsius or country.

C interface. The interface, defined at a level thatdepends on the variant of C standardized by ANSI.

C language. A general–purpose programminglanguage that is the primary language of theoperating system.

C library. A system library that contains common Clanguage subroutines for file access, stringoperators, character operations, memoryallocation, and other functions.

C++ language. A programming language based onthe C language and developed by BjarneStroustrup. C++ defines data types called classes.Classes provide data abstraction and arecomposed of data (data members) and operationsthat operate on that data (member functions). C++also implements the object–oriented programmingconcepts of inheritance through class derivationand polymorphism through virtual functions andoverloading.

C++ language statement. A C++ languagestatement contains zero or more expressions. AllC++ language statements, except blockstatements, end with a ; (semicolon) symbol. Ablock statement begins with a { (left brace) symbol,ends with a } (right brace) symbol, and containsany number of statements.

C++ library. A system library that containscommon C++ language subroutines for file access,memory allocation, and other functions.

cable. The physical media for transmitting signals;includes copper conductors and optical fibers.

cache. (1.) A high–speed buffer storage thatcontains frequently accessed data or instructionsand that can deliver that data or instructions fasterthan the storage medium on which that informationusually resides. A cache is used to reduce accesstime. See also write back cache. (2.) To place,hide, or store in a cache. A technique (usuallysoftware–based) whereby high–speed storage thatis not immediately required for other purposes isused to retain data that has been loaded into itonce, in the hope that another request for the datawill occur before the high–speed storage must bereassigned.

cache coherency. The need to ensure thatmultiple threads on multiple processors changing asingle cache line do not create inconsistentversions of the cache line in the different caches.

cache hit. A processor storage reference that issatisfied by information from a cache.

cache line. The cache component that is normallyloaded, stored, and interrogated during cachelookup. See also set associativity.

cache line tag. The information kept with eachcache line to identify the part of virtual storage itcontains.

cache lookup. The process of determiningwhether or not a cache contains the informationnecessary to satisfy a storage reference. A definedset of bits in the address being referencedidentifies the line or lines to be interrogated.

cache miss. (1.) A delay that occurs when theCPU references data or instructions that are notalready in the data cache or instruction cache. (2.)A processor storage reference that cannot besatisfied from a cache and therefore requires aRAM access.

CAD/CAM. Computer–AidedDesign/Computer–Aided Manufacturing.

CAI. See computer–aided instruction.

Calculator. In CDE, a software application thatmimics the function of a handheld calculator.

Calendar. In CDE, a software application thatenables you to schedule appointments and createTo Do lists.

Calendar view. In CDE, the day, week, month, oryear displayed in the main Calendar window.

call. (1.) To activate a program or procedure,usually by specifying the entry conditions andjumping to an entry point. See also load. (2.) Indata communications, the action necessary inmaking a connection between two stations on aswitched line. (3.) In X.25 communications, aconversation between two users.

call–accepted packet. In X.25 communications, acall supervision packet transmitted by a called DTEto inform the DCE of the acceptance of the call.See also packet.

call–back. A characteristic of the UUCP fileUSERFILE that tells a remote system whether thelocal system it tries to access will call back to checkits identity.

call collision. See collision.

call–connected packet. In X.25 communications,a call supervision packet transmitted by a DCE toinform the calling DTE of the completeestablishment of the call. See also packet.

1-19Glossary

call redirection notification. In X.25communications, an optional CCITT–specifiedfacility that informs the caller that the call has beenredirected to another DTE.

call request (CRQ). A signal sent by a computer torequest from data communications equipment thata communications connection be established withanother computer in the network.

call–request packet. In X.25 communications, acall supervision packet transmitted by a DTE to askfor a call establishment through the network. Seealso packet.

call user data (CUD). In X.25 communications,data optionally included in the call–request packetby the user application.

callback. (1.) A procedure that is called if andwhen certain specified conditions are met. This isaccomplished by specifying the procedure in acallback list. Synonymous with callback function.See also callback routines. (2.) In SOM, auser–provided procedure or method to the EventManagement Framework that gets invoked when aregistered event occurs. See also event.

callback function. Synonym for callback.

callback list. (1.) A list of procedures that arecalled if and when certain specified conditions aremet. (2.) In AIXwindows, individual widgets candefine callback lists as required.

callback reason. The conditions that, if met, resultin a callback procedure being called.

callback routine address. The internal address ofa given callback routine.

callback routines. Procedures that are called ifand when certain specified conditions are met. Seealso callback.

called. In X.25 communications, an adjectiveapplied to the location or user to which a call ismade.

called address extension. See addressextension.

called DLS user. The data link service (DLS) userin connection mode that processes requests forconnections from other DLS users.

called line address modified notification. InX.25 communications, an optional CCITT–specifiedfacility.

called NS user . A network service (NS) withwhom a calling NS user wants to establish anetwork connection.

called subaddress. See subaddress.

calling. In X.25 communications, an adjectiveapplied to the location or user that makes a call.

calling address. See network user address.

calling address extension. See addressextension.

calling conventions. Specified ways for routinesand subroutines to exchange data with each other.

calling DLS user. The data link service (DLS)user in connection mode that initiates theestablishment of a data link connection.

calling NS user . A network services (NS) userthat initiates a network connection.

calling tree. The tree of control of a program. Themain procedure is the calling tree’s trunk; anyprocedure referenced by the main procedurebranches off from the trunk, and any procedurereferenced by another procedure is a branch offthat branch. A branch that does not reference otherprocedures is known as a leaf.

callout. A kernel parameter that establishes themaximum number of scheduled activities that canbe pending simultaneously.

callout table. A kernel table that keeps track of allsleeping processes and the channel on which eachis waiting.

cancel. To end a task before it is completed.

Cancel. In CDE, a push button that removes awindow without applying any changes made in thatwindow.

canonical processing. Processing that occursaccording to a defined set of rules. This is the styleof input that is typically used by the shell andsimple commands.

caps. (1.) Capital letters, an uppercase font. (2.) Aprinting style that uses two type sizes of a singleuppercase font. The smaller size is used instead ofa lowercase font.

caption. Text associated with, and describing, atable or figure.

capture. To digitize an image into the videomemory of the M–Video Capture Adapter.

capture file. A file used by a communicationsprogram to capture, or record, data coming in overa connection to a remote system or device.

capture key. A toggle control key that starts orstops the process of saving the data displayed onthe screen during an active connection.

card. An electronic circuit board that is pluggedinto a slot in the system unit. See also adapter.

1-20 Glossary

cardinal spline cubic curve. In computergraphics, a cubic spline whose endpoints are thesecond and third of four control points. A series ofcardinal splines have a continuous slope and passthrough all but the first and last control points. Seealso parametric cubic curve.

carriage return. (1.) In text data, the action thatindicates to continue printing at the left margin ofthe next line. A carriage return is equivalent to thecarriage return of a typewriter. (2.) A keystrokegenerally indicating the end of a command line.

carrier. In data communication, a continuousfrequency that can be modulated or impressed withan information–carrying signal.

carrier sense multiple access with collisiondetection (CSMA/CD). The generic term for aclass of medium access procedures that allowsmultiple stations to access the medium at will,without explicit prior coordination, and avoidscontention by way of carrier sense and deference.Contention is resolved by way of collision detectionand transmission.

carrier signal. A signal with a constant frequencythat can be modulated to carry a data signal.

cascade button. In AIXwindows, a rectangulargraphic control that can be made to appear frombehind another graphic control to provide anadditional option or range of options.

cascading menu. A submenu of related choicesthat is invoked when the parent item, is selected.Usually, a choice that offers a cascading menu isdesignated by an arrow to the right of the choice.Similar to a context line.

case clause. In a C For AIX switch statement, acase label followed by any number of statements.

CASE. Computer Assisted Software Engineering.A set of tools or programs to help develop complexapplications.

CASE label. In Pascal, a value or range of valuesthat comes before a statement in a CASEstatement branch. When the selector is evaluatedto the value of a CASE label, the statementfollowing the case label is processed.

case label. The word case followed by a constantexpression and a colon. When the selector isevaluated to the value of the constant expression,the statements following the case label areprocessed.

case–sensitive. Able to distinguish betweenuppercase and lowercase letters.

cast. In C language, an expression that convertsthe value of the operand to a specified scalar datatype (the operator).

casted dispatching. In SOM, a form of methoddispatching that uses casted method resolution;that is, it uses a designated ancestor class of theactual target object’s class to determine whatprocedure to call to execute a specified method.

casted method resolution. In SOM, a methodresolution technique that uses a method procedurefrom the method table of an ancestor of the classof an object (rather than using a procedure fromthe method table of the object’s own class).

C.A.T. Computer–assisted typesetting.

catalog. A set of predefined components andattributes used to create Interleaf documents.

catastrophic cancellation. A programming errorin which values with very large negative exponentsare added or multiplied together until a zero valueis produced, which is then propagated intosuccessive computations.

catch block. A block in a C++ program thatreceives control when an exception matching itsargument is thrown. Each catch block is associatedwith a try block.

cathode ray tube (CRT). A vacuum tube in whicha beam of electrons can be moved to draw lines orto form characters or symbols on its luminescentscreen.

cause code. In X.25 communications, a 1–bytecode included in clear– and reset–indicationpackets that indicates the origin of the packet andthe reason for sending it. Synonymous with clearcause. See also diagnostic code.

CBEMA. Computer and Business EquipmentManufacturers Association.

CCITT. Comite Consultatif InternationalTelegraphique et Telephonique. See alsoConsultative Committee on InternationalTelegraphy and Telephone.

CCW. Channel control word. This is a definedcontrol encoding that is used to control theoperations of I/O units on the System 360/370channel.

CD. Carrier detect. See also DCD.

CDE. An acronym for Common DesktopEnvironment, a graphical user interface running onUNIX.

CDLI. Common Data Link Interface. Device driversthat interface with kernel services to providesupport for sockets and STREAMS interfaces.

CD–ROM. High–capacity read–only memory in theform of an optically read compact disc.

CDS. Cell Directory Service.

1-21Glossary

CDS–defined attribute. A standard attribute thatCDS associates with names. A specificCDS–defined attribute has the same meaning nomatter what type of entry (clearinghouse, directory,object) it is associated with. However, differenttypes of entries can have different CDS–definedattributes. For example, every CDS name has theCDS–defined attributes of Creation Timestamp(CDS_CTS), Update Timestamp (CDS_UTS), andAccess Control Set (CDS_ACS). In addition tothose attributes, a soft link has uniqueCDS–defined attributes containing its expirationtime and the name it points to.

CDS directory. A logical unit for storing entriesunder one name (the directory name) in a CDSnamespace. In addition to object entries, adirectory can contain soft links and child pointers.You can copy, delete, and control access to adirectory. Each physical instance of a directory iscalled a replica.

CDSPI. Cell Directory Service Portable Interface.

CDSTL. See connect data set to line.

CEC. Central Electronics Complex.

cell. The rectangular juncture of a horizontal rowand a vertical column. Examples include the cellsof an electronic spreadsheet and the cells utilizedby an XmRowColumn widget in an AIXwindowsgraphic interface. In Interleaf, a table cell is actuallya modified frame that can contain data.

cell–relative name. See local name.

centered dot. A heavy bullet used as a mark to setoff a paragraph or list item.

central processing unit (CPU). The part of acomputer that includes the circuits that control theinterpretation and running of instructions.

CFM. Cubic feet per minute.

CGA. Color Graphics Adapter.

CGM. See Computer Graphics Metafile.

change bit. A bit in each page–frame table entrythat denotes the corresponding page has beenwritten to since the last time the operating systemcleared the page.

channel. (1.) A path along which signals or datapasses. (2.) The portion of a storage medium thatis accessible to a given reading or writing station.(3.) In data communication, a means of one–waytransmission. (4.) A functional unit, controlled by ahost computer, that handles the transfer of databetween processor storage and local peripheralequipment. (5.) The system element that controls asingle channel path, whose mode of operationdepends on the type of hardware to which it is

attached. (6.) A device connecting the processor toinput and output devices. (7.) One of 32 bits in atable used to represent which event classes areactive or inactive. The most significant bit is calledchannel 0 and the least significant bit is calledchannel 31. See also logical channel.

channel control word. See CCW.

channel ID. A channel identification passed backfrom a multiplexed device to the file system as aresult of calling the ddmpx entry point.

channel number. A number that identifies the pathby which data is transferred between a particularinput or output device and the processor of thecomputer. The major device, minor device, andchannel numbers uniquely identify a hardwaredevice.

channel path. A single interface attaching one ormore control units.

channel–path Identifier (CHPID). In aSystem/390 channel subsystem, a value assignedto each installed channel path of the system thatuniquely identifies that path to the system.

char. In Object Database Manager, a terminaldescriptor used to define a variable as afixed–length, null–terminated string. See alsoterminal descriptor.

char specifier. The keywords char and unsignedchar, which describe the type of data a variablerepresents.

character. A letter, digit, or other symbol.

character cell. The physical width and height inpels of a font. See also bounding box.

character class. (1.) Ranges of characters thatmatch a single character in the input stream. (2.) Aset of characters enclosed in sequence, or square[], brackets.

character constant. (1.) A constant value whosedata attribute is character. (2.) In programminglanguages, a character or an escape sequenceenclosed in single quotation marks.

character data indexing. An input/outputoptimization that reduces I/O access time bysearching for a string in a small index file, andusing the obtained index to find a record in themain data file.

character delete. In text data, the action thaterases the character at the current cursor locationand moves any trailing text one character positionto the left.

character device. A device that handles data onecharacter at a time. See also character special file.

1-22 Glossary

character display. A display that uses a charactergenerator to display predefined character boxes ofimages (characters) on the screen. This kind ofdisplay cannot address the screen any less thanone character box at a time. Contrast with AllPoints Addressable display.

character expression. A character constant orvariable, character array element, charactersubstring, character–valued function reference, orsequence of the preceding separated by theconcatenation operator, with optional parentheses.

character graphics. (1.) The visual representationof a character, defined by toned or intoned pictureelements (pels). (2.) Graphics that are composedof symbols printed in a monospace font. Somesymbols are standalone; others are intended forassembling larger figures.

character key. (1.) A keyboard key that allows theuser to enter the character shown on the key. Seealso function keys. (2.) In word processing, acontrol used to process text one character at atime.

character literal. A symbol, quantity, or constant ina source program that is itself data, rather than areference to data. Contrast with numeric literal.

character position. On a display, the location of acharacter.

character set. A group of characters used for aspecific reason; for example, the set of charactersa printer can print or a keyboard can support.

character special file. A special file that providesaccess to an input or output device. The characterinterface is used for devices that do not use blockI/O. See also character device, block file, specialfile, and block special file.

character string. A sequence of consecutivecharacters. In the C programming language, astring must be null–terminated.

character substring. A contiguous portion of acharacter string.

character translation. In international charactersupport, the dd command and various conversionsubroutines that translate between extendedcharacters and ASCII escape strings to preserveunique character information.

character type. A data type that consists ofalphanumeric characters. See also data type.

character variable. In the C language, a dataobject whose value can be changed during therunning of a program and whose data type is charor unsigned char.

characteristic attribute. A type of attribute thatreflects or affects the behavior of a software entity.You generally can set or change characteristicattributes.

charging requesting service. In X.25communications, an optional facility that specifiesthat charging information (segment count data,monetary unit data, or call duration data) isrequired.

chat script. In remote communications, a list ofexpect–send sequences that a modem uses toestablish a communication link with anothermodem. See also handshaking and expect–sendsequence.

checkbox. A small square box that can be turnedon or off to indicate the state of an option.

checkpoint. A snapshot of the current state of therecoverable data being used by an application.Checkpoints are used to capture the state ofrecoverable data between backups, thusminimizing the time involved in restarting systemswhich use that data by providing a more recentimage of that data.

checksum. (1.) The sum of a group of dataassociated with the group and used for checkingpurposes. (2.) On a diskette, data written in asection for error detection purposes.

child. (1.) Pertaining to a secured resource, eithera file or library, that uses the user list of a parentresource. A child resource can have only oneparent resource. (2.) In the operating system, achild is a process, started by a parent process, thatshares the resources of the parent process.Contrast with parent. (3.) In Enhanced X-Windowsand AIXwindows, a first–level subwindow. A widgetmanaged by another widget is said to be the childof the managing parent widget. For example,Composite widgets typically manage the Primitivechildren widgets attached to them. The parentwidget typically controls the placement of the childas well as when and how it is mapped.

child class. A SOM class that inherits instancemethods, attributes, and instance variables directlyfrom another class, called the parent class, baseclass, or superclass, or indirectly from an ancestorclass. A child class may also be called a derivedclass or subclass.

child device. A hierarchical location term. Itindicates what can be connected to a parentdevice. For example, an SCSI disk can be a childdevice of an SCSI adapter.

1-23Glossary

child gadget. A windowless child widget. See alsochild widget.

child process. In the operating system, a process,started by a parent process, that shares theresources of the parent process.

child resource. Pertaining to a secured resource,either a file or library, that uses the user list of aparent resource. A child resource can have onlyone parent resource.

child widget. In AIXwindows and EnhancedX–Windows, a widget managed by another widgetis said to be the child of the managing parentwidget. For example, Composite widgets typicallymanage the Primitive children widgets attached tothem. The parent widget typically controls theplacement of the child as well as when and how itis mapped. When a parent widget is deleted, all thechildren controlled by that parent are automaticallydeleted as well. See also child gadget.

children. Plural of child.

children spacing. In AIXwindows and EnhancedX–Windows, widgets managed by another widgetare said to be the children of the managing parentwidget. The parent widget typically controls thephysical spacing and placement of the childrenwithin the border of the parent.

choice. An option in a pop–up or menu used toinfluence the operation of the system.

chord. In graphics, a short line segment whoseend points lie on a circle. Chords are a means forproducing a circular image from straight lines. Thehigher the number of chords per circle, thesmoother the circular image.

CHPID. Channel path identifier.

CICS. See Customer Information Control System.

CID. See connection identifier.

ciphertext. The output of an encryption function.Encryption transforms plaintext into ciphertext.

circuit. See virtual circuit.

circuit switching. A process that, on demand,connects two or more data terminal equipments(DTEs) and permits the exclusive use of a datacircuit between them until the connection isreleased. Synonym for line switching. See alsopacket switching.

C–ISAM. C–language Indexed Sequential AccessMethod.

CLA. See communications line adapter.

class. (1.) Pertains to the I/O characteristics of adevice. In this operating system, devices areclassified as block or character. (2.) In Enhanced

X-Windows, a general group to which a specificobject belongs. See also widget class and classrecord. (3.) In AIXwindows, an object–oriented datastructure containing generalized information abouta group of similar graphical objects known aswidgets or gadgets. Each class of graphical objectsinherits some or all of the appearancecharacteristics and behavior characteristics of theclasses that precede it in the object hierarchy. (4.)A C++ class is a user–defined data type. A classdata type can contain both data representations(data members) and functions (member functions).See also object class. (5.) In SOM, a way ofcategorizing objects based on their behavior (themethods they support) and shape (memory layout).A class is a definition of a generic object. In SOM,a class is also a special kind of object that canmanufacture other objects that all have a commonshape and exhibit similar behavior. Thespecification of what comprises the shape andbehavior of a set of objects is referred to as the”definition” of a class. New classes are defined interms of existing classes through a techniqueknown as inheritance. See also class object.

class data structure. A structure provided by theSOM API to support efficient static access toclass–specific information used in dealing withSOM objects. The structure’s name is<className>ClassData. Its first component(classObject) is a pointer to the correspondingclass object. The remaining components (namedafter the instance methods and instance variables)are method tokens or data tokens, in order asspecified by the class’s implementation. Datatokens are only used to support data (public andprivate) introduced by classes declared usingOIDL; IDL attributes are supported with methodtokens.

class key. One of the C++ keywords: class,struct, and union.

class library. A collection of C++ classes.

class manager. An object that acts as a run–timeregistry for all SOM class objects that exist withinthe current process and which assists in thedynamic loading and unloading of class libraries. Aclass implementor can define a customized classmanager by subclassing SOMClassMgr class toreplace the SOM–supplied SOMClassMgrObject.This is done to augment the functionality of thedefault class–management registry (for example, tocoordinate the automatic quiescing and unloadingof classes).

class member operators. Used to access C++class members through class objects or pointers toclass objects. They are ., –>, .*, and –>*.

1-24 Glossary

class method. Also known as factory method orconstructor.) A SOM class method is a method thata class object responds to (as opposed to aninstance method). A class method that class <X>responds to is provided by the metaclass of class<X>. Class methods are executed without requiringany instances of class <X> to exist, and arefrequently used to create instances of the class.See also metaclass.

class name. (1.) For widgets and gadgets, thename in the code corresponding to the resourcedatabase containing the generic properties for allobjects in the class. (2.) A unique identifier of aC++ class type that becomes a reserved wordwithin its scope.

class object. The run–time object representing aSOM class. In SOM, a class object can perform thesame behavior common to all objects, inheritedfrom SOMobject. See also class.

class record. A particular widget record thatcontains the data objects pertaining to the class ofany given widget. See also record, widget record,and class.

class scope. The scope of C++ class members.

class template. A blueprint describing how a set ofrelated C++ classes can be constructed.

class variable. In SOM, instance data of a classobject. All instance data of an object is defined(through either introduction or inheritance) by theobject’s class. Thus, class variables are defined bymetaclasses.

CLAW. See Common Link Access to Workstation.

clean up. The clean–up procedure instructs thesystem to attempt to remove software products thatwere partially installed. The system also attemptsto revert to the previous version of the removedproduct. If the system successfully reverts to theprevious version, it becomes the currently activeversion. If this cannot be done, then the softwareproduct is marked as broken. After the clean–upprocedure is complete, you can attempt to installthe software again.

clean–up code. In loops that have been unrolledor blocked, an additional loop or set of loops thatensures that all iterations of the original code areexecuted in the unrolled or blocked code.

clear. In X.25 communications, to reject a call (if ithas not yet been accepted) or end a call.

clear cause. See cause code.

clear collision . A condition that occurs when aSTE and a DCE simultaneously transmit a clearrequest packet and a clear indication packet overthe same logical channel. See also collision.

clear–confirmation packet. In X.25communications, a packet transmitted by the DTEto inform the DCE that a call has been cleared. Seealso packet.

clear diagnostic. See diagnostic code.

clear–indication packet. In X.25 communications,a call supervision packet transmitted by a DCE toinform a DTE of the clearing of a call. See alsopacket.

clear–request packet. In X.25 communications, acall supervision packet transmitted by a DTE to askfor a call to be cleared. See also packet.

clear user data. In X.25 communications, dataoptionally included in the clear–request packet bythe user application.

click. In CDE, to press and release a mouse buttonwithout moving the mouse pointer. Unlessotherwise specified, mouse button 1 is assumed.

client. (1.) In a distributed file system environment,a system that is dependent on a server to provide itwith programs or access to programs. (2.) InEnhanced X-Windows, an application program thatconnects to an Enhanced X-Windows server by aninter–process communication (IPC) path, such as aTransmission Control Protocol (TCP) connection ora shared memory buffer. The program can bereferred to as the client of the server, but it isactually the IPC path itself. Programs with multiplepaths open to the server are viewed as multipleclients by the protocol. See also inter–processcommunication. (3.) In Enhanced X–Windows, aToolkit routine that uses a widget in an applicationor for composing another widget. (4.) InAIXwindows, a software application that fills therole of the client in the traditional client–servermodel upon which Enhanced X-Windows andAIXwindows are based. See also client application.(5.) In NCS, a program that uses an interface tomake remote procedure calls (RPCs).

client agent. See Location Broker Client Agent.

client application. A type of application. See alsoclient and application.

client code. (Or client program or client.) A SOMapplication program, written in the programmer’spreferred language, which invokes methods onobjects that are instances of SOM classes. InDSOM, this could be a program that invokes amethod on a remote object.

client program. A program that uses a C++ class.The program is said to be a client of the class.

client–side caching. A high–speed buffer storagethat contains frequently accessed informationassociated with a client application. The primary

1-25Glossary

purpose of client–side caching is to reduce accesstime to key information.

clip. In computer graphics, to remove those partsof a display image that lie outside of a givenboundary.

clip list. In Enhanced X-Windows, a list ofrectangles designated for clipping.

clipboard. A storage space set aside for thetemporary storage and retrieval of text or graphicsduring cut–and–paste operations. Data in theclipboard is available to other applications.

clipboard selection. Data selected and pasted tothe clipboard that can be pasted or passed to afunction. Data can include such elements as text,graphics, and widgets.

clipping. In GL, if a primitive overlaps theboundaries of a window, it is clipped. The part of aprimitive that appears in the window is displayedand the rest is ignored. There are several types ofclipping that occur in the system. Three–D drawingprimitives are clipped to the boundaries of afrustum (for perspective transformations) or to arhombohedron (for orthographic projections). This3–D clipping applies as well to the origin ofcharacter strings, but not to the charactersthemselves. A 2–D clipping is also performed,where all drawing is clipped to the boundaries ofthe AIXwindows window. The area of 2–D clippingcan be controlled with the screenmask. See alsoclipping planes, fine clipping, gross clipping,screenmask, bounding box, culling, transformation,and window.

clipping planes. In GL, before clipping occurs,primitive space is mapped to normalized devicecoordinates. The clipping planes x=+/–w; y=+/–w;or z=+/–w correspond to the left, right, top, bottom,near, and far planes bounding the viewing frustum.See also gross clipping, clipping and frustum.

clipping region. In Enhanced X-Windows, a typeof graphics output. In a graphics context, the imagedefined by the bitmap or rectangles used to restrictoutput to a particular region of a window.

CLK. See clock.

Clock. In CDE, a Front Panel control that displaysthe local time.

clock (CLK). (1.) A device that generates periodicsignals used for synchronization. (2.) In datacommunication, equipment that provides a timebase used in a transmission system to control thetiming of certain functions, such as sampling, andto control the duration of signal elements.

clocking. (1.) In binary synchronouscommunication, the use of clock pulses to control

synchronization of data and control characters. (2.)In data communications, a method of controllingthe number of data bits sent on a communicationsline in a given time.

clone device. A STREAMS device that returns anunused major or minor device when initiallyopened, rather than requiring the minor device tobe specified by name in the open call.

close. (1.) To end an activity and remove thatwindow from the display. (2.) A data manipulationfunction that ends the connection between a fileand a program. Contrast with open.

closed user group (CUG). In X.25communications, a subgroup of users that isassigned to a facility that enables a member of onesubgroup to communicate only with other membersof the subgroup. A DTE can belong to more thanone closed user group. See also bilateral closeduser group and optional facility.

cluster. (1.) Any configuration of interconnectedworkstations for the purpose of sharing resources(for example, local area networks, host attachedworkstations, and so on). (2.) A group of storagelocations allocated at one time. (3.) A station thatconsists of a control unit (cluster controller) and theworkstations attached to it. (4.) A page–size(4096–byte) buffer provided by the mbufmanagement facility to the various layers ofcommunication software in AIX. (Also called”cluster mbuf,” ”mbuf cluster,” and ”mapped page.”)

clustered file. Files in which records with adjacentkey values are physically clustered together. Theclustered file organization optimizes sequentialaccess through the primary index to records in thefile.

CMOS. Complementary metal–oxidesemiconductor. CMOS is a technology thatcombines the electrical properties of n–typesemiconductors and p–type semiconductors.

coaxial cable. A cable consisting of one conductor,usually a small copper tube or wire, within andinsulated from another conductor of largerdiameter, usually copper tubing or copper braid.

COBOL. Common business–oriented language. Ahigh–level programming language, based onEnglish, that is used primarily for businessapplications.

code. (1.) Instructions to the computer. (2.) To writeinstructions for the computer; to program. (3.) Arepresentation of a condition, such as an errorcode.

code page. (1.) An assignment of graphiccharacters and control function meanings to all

1-26 Glossary

code points. (2.) Arrays of code points representingcharacters that establish the ordinal sequence(numeric order) of characters. This operatingsystem uses 256–character code pages. See alsocode point and extended character. (3) An orderedset of up to 256 predefined display symbols. Thefirst 32 code points of each code page arereserved for control codes and are the same for allcode pages, leaving up to 224 distinct displaysymbols per page.

code point. A character within a code page. Seealso code page and extended character.

code segment. See segment.

code server. A system that is providing a codeservice for other computers on a network.

code set. In the XPG4 system interface, a set ofunambiguous rules that establish a character setand the one–to–one relationship between eachcharacter of the set and its bit representation.

col. A typesetter postprocessor that buffers typesetoutput to allow printing on printers and workstationsthat do not support backscrolling.

collapse. To remove the contents of a directoryfrom the display (close it) using the CDS Browser.To collapse an open directory, you double–click onits icon. Double–clicking on a closed directoryexpands it.

collating element. One or more characters thatmatch a sequence in a regular expression.

collating sequence. The sequence in whichcharacters are ordered within the computer forsorting, combining, or comparing.

collation. The process of character and stringsorting based on alphabetical order andequivalence class.

collation table. Provides an ordered character setand character equivalence classes used byfunctions.

collection. In Ada language, the entire set ofobjects created by evaluation of allocators for anaccess type.

colliding find request. A condition that occurswhen two link stations attempt to call each other atthe same time.

collision. (1.) An unwanted condition caused byconcurrent transmissions on the medium thatresults in garbled data. (2.) In X.25communications, a condition that occurs when aDTE and a DCE simultaneously transmit packets(for instance, a clear–request packet and aclear–indication packet) over the same logical

channel. This can be a clear collision, call collision,or reset collision. See also clear collision.

colon format. A format into which data files can beorganized. Each data record consists of one line inthe colon file, and data fields in each data recordare separated by colons.

color cell. In Enhanced X-Windows, an entry in acolormap that consists of three values based onred, green, and blue intensities. The values are16–bit, unsigned numbers. Zero represents theminimum intensity. The values are scaled by theserver to match the particular display in use.

color display. A display device capable ofdisplaying more than two colors and the shadesproduced by combinations of two colors, asopposed to a monochrome display.

color expansion operation. A graphicsprogramming operation that occurs automaticallywhen the source pixel map data area contains only1 byte per pixel and the destination pixel map dataarea is a color display adapter buffer frame definedto have more than 1 bit per pixel.

color graphics adapter. An adapter that allows acomputer to use a color display.

color lookup table. Synonym for color map.

color map. (1.) In computer graphics, a lookuptable where each index is associated with a red,green, and blue value. Synonymous with colorlookup table, color palette, and color table. (2.) InEnhanced X-Windows, a set of color cells. A pixelvalue indexes the color map to produceRGB–value intensities. A color map consists of aset of entries defining color values that, whenassociated with a window, is used to display thecontents of the window. Depending on hardwarelimitations, one or more color maps can be installedat one time such that windows associated withthose maps display correct colors. The two classesof color maps are direct color and pseudocolor. (3.)In GL, a lookup table that translates color indexesinto RGB triplets. The lookup table is sandwichedbetween the frame buffer and the digital–to–analogconverters (DACs) and serves to translate the colorindex value stored in the frame buffer into the red,green, and blue values required by the DACs. Onmost hardware configurations, the color map iseither 8 or 12 bits deep, allowing the simultaneousdisplay of 256 or 4096 colors. On most hardwareconfigurations, the DACs have an 8–bit per coloraccuracy, allowing the user to choose among16,777,216 colors.

color map mode. A configuration of the hardwarethat passes the values stored in the frame buffer

1-27Glossary

through a color lookup table (color map), fromwhich the red, green, and blue values are obtainedfor display. Entries in the color map are referred toas color indexes. In color map mode, the valuesstored in the frame buffer are treated as color mapindexes. See also RGB mode.

color palette. Synonym for color map.

color ramp. A progression of colors in a color map.Most color ramps are smooth and have only asmall number, if any, of discontinuities. Forinstance, if the full set of colors of the rainbow wereloaded into the color map, that would constitute acolor ramp.

color table. Synonym for color map.

color viewer. In AIXwindows, an interface thatallows the user to choose a color as a value for awidget property.

column. A vertical arrangement of characters orother expressions.

column headings. Text appearing near the top ofa column of data for the purpose of identifying ortitling the data in the column.

column inch. A unit of measure for printed text.One column inch is the amount of text contained inan inch of type depth, one column wide.

column–major order. A way of storing arrayelements such that the leftmost subscript variesmost rapidly as memory–adjacent elements areaccessed.

combined I and D cache. A cache that containsboth instructions and data, distinguishable only bythe cache line tag.

comma expression. An expression that containstwo operands separated by a comma. Although thecompiler evaluates both operands, the value of theright operand is the value of the expression. If theleft operand produces a value, the compilerdiscards this value.

command. (1.) A request to perform an operationor run a program. When parameters, values, flags,or other operands are associated with a command,the resulting character string is a single command.(2.) In data communication, an instructionrepresented in the control files of a frame andtransmitted by a primary or combined station. Itcauses the addressed station to run a data linkcontrol function.

command frame. A link–level frame or packet thatis serviced as a command and (in most cases)expects a response.

command history. An automatic listing ofpreviously issued commands.

command interpreter. A program that sendsinstructions to the kernel. Synonym for interface.See also shell.

command line. The area of the screen wherecommands are displayed as they are typed.

command line editing keys. Keys for editing thecommand line.

command mode. A state of a system or device inwhich the user can enter commands. See also textinput mode.

command module. A file that executes acommand or process. The file may be activatedwhen the user enters a command at the commandline or by another command module.

command name. (1.) The first or principal term ina command. A command name does not includeparameters, values, flags, or other operands. (2.)The full name of a command when an abbreviatedform is recognized by the computer (for example,print working directory for pwd).

command programming language. Facility thatallows programming by the combination ofcommands rather than by writing statements in aconventional programming language.

command string. A request to perform anoperation, along with the operands that provide allinstructions needed for running the operation.

command substitution. The ability to capture theoutput of any command as a value to anothercommand by placing that command line within ‘ ‘(grave accents). The shell first runs the commandor commands enclosed within the grave accentsand then replaces the whole expression, includinggrave accents, with their output. This feature isoften used in assignment statements.

command word. The name of the 16–bit unitsused for storing graphic primitive strings. The firstcommand word determines the primitive type andsets the length of the string. Subsequent commandwords contain information in multiples of quid, or 4bits of data.

commit. (1.) To make permanent all changes thathave been made to the database file since the lastcommitment operation and to unlock the records sothey are available to other users. Contrast withreject. (2.) When you commit software, you aremaking a commitment to that version of thesoftware product. When you commit a product, thesaved files from all previous versions of thesoftware product are removed from the system,thereby making it impossible to return to a previousversion of the software product. In SMIT, softwarecan be committed at the time of installation bysetting the COMMIT software? question to yes (or

1-28 Glossary

by using the –ac flags with the installp command).Note that committing already applied software doesnot change the currently active version of thesoftware product. It merely removes saved files forthe previous version of the software product. Therejection of the installation level of the product doesnot have the same meaning as the rejection ofupdates to the product. Once you commit a newversion of a product, you must reinstall theprevious version if you want to use that versionagain. Compare to apply and contrast with rejectand remove.

commit operation. An operation that saves a fileto permanent storage.

common block. In FORTRAN, a storage area thatcan be referred to by a calling program and one ormore subprograms.

common carrier. Any government–regulatedcompany that provides communication services tothe general public.

Common Link Access to Workstation (CLAW).The architecture that defines the channelcommands used between the host and the channelattachment adapter.

common subexpression enhancement. Anoptimization that enables a compiler to detect thattwo or more distinct subexpressions within anexpression or loop are identical and need only becomputed once.

communications. The transmission of dataaccording to a protocol between computers orremote devices, usually over a long distance.

communications adapter. A circuit card withassociated software that enables a processor,controller, or other device to be connected to anetwork. See also adapter.

communications authority password. One of thetwo communications security passwords. It controlsaccess to communication configuration menus sothat only authorized persons can change theprofiles, encrypt a portion of the communicationprofile database, or control the startup of SNAprocesses. The password must be a30–to–80–character phrase, with interior blanksallowed. See also BIND password.

communications channel. An electrical path thatfacilitates transmission of information from onelocation to another.

communications co–processor. Amicroprocessor on an expansion board thatsupplements the operations of the processor in thesystem unit, enabling a computer to usecommunication services in parallel with otheroperations.

communications endpoint. In X.25, the localcommunication channel between a DLS user and aDLS provider.

communications line. The line over which datacommunications take place; for example, atelephone line. See also X.25 line.

communications line adapter (CLA). A functionalunit that converts the serial–by–bit output of astation to a parallel bit form and from a parallel bitform to serial–by–bit input to a station. See alsoline adapter.

communications link. See data link.

communications service. The service performedby the Sockets Application Programming Interface,which allows data packets to be delivered to thespecified destination. There are three types ofcommunications services offered: reliable streamdelivery, connectionless datagram delivery, andraw socket delivery.

compatibility. (1.) The ability to perform tasksidentically in different environments without majormodifications. (2.) The capability of a functional unitto meet the requirements of a specified interface.

compatible. Pertaining to computers on which thesame program can be run without appreciablealteration.

compatible types. Different data types that can beoperands for the same operation.

compilable unit. In Pascal, synonymous withcompilation unit. See also unit.

compilation. In Ada language, a compilation isgenerally the translation of an Ada source programinto an executable object module. When using theAda language debugger, a compilation consists ofone or more compilation units in a single file. If youinclude three package specifications and twopackage bodies in one file, that file represents onecompilation consisting of five compilation units:three library units and two secondary units. Thereis usually only one compilation unit in acompilation.

compilation time. The time during which a sourceprogram is translated from a high–level languageinto a machine language.

compilation unit. A portion of a computer programsufficiently complete to be compiled correctly. InPascal, there are two types of units: the programunit and the segment unit. In Ada language, acompilation unit is the declaration or the body of aprogram unit, presented for compilation as anindependent text. It is optionally preceded by acontext clause, naming other compilation unitsupon which it depends by means of one more with

1-29Glossary

clauses. See also compilable unit and externalvariable.

compile. To translate a program written in ahigh–level programming language into anintermediate language, assembly language, or amachine language. See also interpreted routine.

compiler. (1.) A program that translates a sourceprogram into an executable program (an objectprogram). (2.) A program that translatesinstructions written in a high–level programminglanguage into machine language.

compiler directing statement. Synonym forcompiler directive.

compiler directive. A statement that controls whatthe compiler does rather than what the userprogram does.

complement of a number. The value that whenadded to the number equals a given value.

complete class name. The complete qualificationof a nested C++ class name including all enclosingclass names.

complete overwrite installation. An installationmethod that completely overwrites an existingversion of BOS that is installed on your system.This procedure may impair recovery of data ordestroy all existing data on your hard drives. Besure to back up your system before doing acomplete overwrite installation.

complete packet sequence. Either an individualX.25 data packet or a sequence of packets with theM–bit set to 1 and the D–bit set to 0, followed by afurther data packet with the M–bit set to 0 and theD–bit set as required.

complex constant. In FORTRAN, an ordered pairof real or integer constants separated by a commaand enclosed in parentheses. The first constant ofthe ordered pair represents the real part of acomplex number; the second represents theimaginary part.

Complex Mathematics Library. A C++ classlibrary that provides the facilities to manipulatecomplex numbers and perform standardmathematical operations on them.

complex number. A number consisting of anordered pair of real numbers, expressible in theform a+bi, where a and b are real numbers and isquared equals minus one. A complex number ismade up of two parts: a real part and an imaginarypart, where a is the value of the real part and b isthe value of the imaginary part and where i is thesquare root of –1.

complex type. In FORTRAN, a data type thatrepresents values of complex numbers. A value is

expressed as an ordered pair of real data itemsseparated by a comma and enclosed inparentheses. The first item represents the real partof the complex number, and the second itemrepresents the imaginary part.

component. (1.) One part of a structured type orvalue, such as an array element or a record field.(2.) In AIXwindows or Enhanced X-Windows, thewidget, gadget, or other graphical object thatmakes up an interactive user interface. (3.) In Adalanguage, a value that is a part of a larger value, oran object that is part of a larger object.

component bar. In an Interleaf document, theblack bar at the left margin that contains thecomponent identifiers for the componentscontained in that document.

component dump table. A structure used bykernel components to identify data structures thatshould be collected by the kernel dump program.

compose. To set type.

Compose window. In CDE, in Mailer, the windowyou use to create new electronic mail messages.Several message–composing options are availablefrom the Compose window menu bar.

Composite Manager. In AIXwindows, a managerwidget with special knowledge about the handlingof one or more of its children widgets. Normally, amanager widget has no knowledge of its children,but a TitleBar widget and a ScrollBar widget canbe registered as children of a certain type ofComposite Manager widget known as a Panelwidget, and the Panel widget will correctly controlthe positioning of the TitleBar and ScrollBarwidgets.

composite type. In Ada language, a compositetype is one whose values have components. Thereare two kinds of composite type: array types andrecord types.

composite video. The combined luna, chroma,and sync signals in accordance with the NTSCstandards in the U.S., and the PAL standards inEurope. Also called NTSC or PAL (Europe).

composite widget. In Enhanced X-Windows, awidget that is a container for an arbitrary,implementation–defined collection of children.These children may be instantiated by thecomposite widget itself, by other clients, or by acombination. Composite widgets contain methodsfor managing the geometry (layout) of any childwidget. A composite widget is a subclass of theCore widget. See also widget.

Composite widget class. In EnhancedX–Windows, a metaclass that does not instantiateany widgets of its own but provides the resources

1-30 Glossary

and functionality that allow parent widgets tomanage the layout and mapping of their childrenwidgets and gadgets.

compound license. In License Use Management,a type of license that allows a system administratorto generate license passwords for a given numberof licenses. Such a license is valuable when anadministrator needs a certain number of licenses,but does not yet know what machines or who willuse them. A compound license can generate eithernodelocked or non–nodelocked licenses, not both.

compound object. In AIXwindows, a graphicalobject made up of several widgets and gadgetscollected within a single container widget.

compound string. A type of string designed tosimplify foreign language support by allowing textto be displayed without hard–coding thelanguage–dependent attributes (character set, text,and direction).

compress. (1.) To move files and libraries togetheron disk to create one continuous area of unusedspace. (2.) In data communications, to delete aseries of duplicate characters in a character string.

compressed output. Synonym for compression.

compression. (1.) A technique for removingstrings of duplicate characters, gaps, empty fields,and trailing blanks before transmitting data.Synonymous with compressed output. (2.) In SNA,the replacement of a string of up to 64 charactersby an encoded control byte to reduce the length ofthe data stream sent to the LU–LU session partner.

computational memory. The set of allvirtual–memory pages in real memory that are partof working–storage or program–text segments.

computed time. The result of the synchronizationprocess––the time value that the clerk or serverprocess computes according to the values itreceives from several servers.

computer aided instruction (CAI). A dataprocessing application in which a computingsystem is used to assist in the instruction ofstudents.

Computer Graphics Metafile. Adevice–independent graphics file format used forstoring object–oriented graphics.

computer instruction. An instruction that can berecognized by the processing unit of the computerfor which it is designed. Synonymous with machineinstruction.

computer language. Synonym for machinelanguage and machine instruction.

computer word. Synonym for word.

concatenate. (1.) To link together. (2.) To join twocharacter strings.

concatenation. (1.) Linking together. (2.) Joiningtwo character strings. (3.) In GL, combining aseries of geometric transformations such asrotations, translations, and scaling. Concatenationof transformations corresponds to matrixmultiplication.

concave and convex polygons. In computergraphics, a polygon is convex if a line segmentjoining any two points in the figure is completelycontained within the figure. Nonconvex polygonsare sometimes called concave. Algorithms thatrender only convex polygons are much simplerthan those that can render both convex andconcave polygons.

concentrator. An FDDI node that has additionalparts beyond those required for its own attachmentto a FDDI network. These additional parts (type M)are for attaching other FDDI nodes (type S) in atree topology. Primarily, a concentrator is used toallow more than two single attachment stations(SAS) to communicate. It can also connect multipleSAS to a dual attachment station (DAS) ring.

concrete class. An OM class of which instancesare permitted.

concurrent–use license. In License UseManagement, a type of license administered by thelicense server that can be used by different usersat any node that is connected to a license servernode. Concurrent–use licenses allow as manyusers to use a software product concurrently asthere are licenses.

condensed print. A print format where charactersare smaller and spaced closer togetherhorizontally, typically at a density of 17 charactersper inch.

condition. An expression in a program orprocedure that can be evaluated to a value ofeither true or false when the program or procedureis running.

condition code. Synonym for flag.

conditional. Conditionals test for certaincircumstances to carry out particular commands.

conditional branch. A branch that is taken when aspecified condition is met.

conditional compilation statement. Apreprocessor statement that causes thepreprocessor to process specified code in the filedepending on how a specified condition evaluates.

conditional expression. A C language expressionthat contains a condition (the first expression), anexpression to be evaluated if the condition has a

1-31Glossary

nonzero value (the second expression), and anexpression to be evaluated if the condition has thevalue 0 (zero).

conditional statement. (1.) A statement that runsif a specified expression evaluates to a nonzerovalue. (2.) A statement that permits execution ofone of a number of possible operations, with orwithout a transfer of control. (3.) A statement usedto express an assignment or branch based onspecified criteria.

condition variable. A synchronization object usedin conjunction with a mutex. A condition variableallows a thread to block until some event happens.

conditioning. (1.) The use of indicators to controlwhen calculations or output operations are to beperformed. (2.) In data communications, theaddition of equipment to a nonswitchedvoice–graded channel to provide minimum valuesof line characteristics required for datatransmission.

conduit. A pipe for protecting electrical wires orcables.

configuration. (1.) The group of machines,devices, and programs that make up a dataprocessing system or network. (2.) The process ofdescribing to a system the devices, optionalfeatures, and program products that have beeninstalled so that these features can be used.Contrast with customization and systemcustomization.

Configuration Assistant. A graphical interfaceapplication used to perform post–installationsystem configuration tasks.

configuration feedback window. In AIXwindows,a window displayed in the center of the screenwhen AIXwindows Manager is restarted or when abehavior switch is requested. The window containssuch variables as the size and location of a clientwindow.

configuration file. A file that specifies thecharacteristics of a system or subsystem; forexample, the operating system queueing system.

configuration manager. A program to supervisedevice configuration during initial program load(IPL).

configuration operation/procedure. Themultistep process, performed in the host computer,of constructing a configuration image for a 3601Finance Communication Controller.

Configuration Rules Object Class. An objectclass that contains the configuration rules used bythe configuration manager during initial programload (IPL).

configure. To describe to a system the devices,optional features, and program products installedon a system.

configure method. Takes a device from thedefined state to the available state. If a device hasa device driver, the configure method is responsiblefor loading and binding the driver into the kernel. Ifthe device supports the optional stopped state, theconfigure method takes the device from the definedstate to the stopped state.

confirm. In X.25 communications, to respond tothe arrival of a clear–indication or reset–indicationpacket.

CONFIRM. A request that asks the remotetransaction program to tell whether the lasttransmission was received successfully.

confirmation. A transmission by a receiver thatpermits a sender to continue.

CONFIRMED. A response to the CONFIRMrequest indicating that the remote site received thetransmission without detecting any errors.

conformant string. In Pascal, a string whosedeclared length does not match that of a formalparameter. See also formal parameter.

congruence class. In a cache, the group of linesto which a given memory location can be mapped.

connect. In X.25 communications, to connect aport to the X.25 network.

connect data set to line (CDSTL). In SNA, anoption that determines how the data terminal ready(DTR) signal to the modem operates. It is used ifDTR indicates an unconditional command from theDTE (data terminal equipment) to the attachedDCE (data circuit–terminating equipment) toconnect to or remove itself from the network.

connect–time accounting. The record of theamount of time each user spends logged in to thesystem.

connected unit. In FORTRAN, a unit that isconnected to a file by either an OPEN, READ, orWRITE statement.

connection. (1.) In SNA, the network path thatlinks together two LUs in different nodes to providecommunications channels between them for theapplication programs running at the respectiveLUs. (2.) In X.25 communications, the existence ofa virtual circuit between two data terminalequipments (DTEs). A switched virtual circuit(SVC) connection is for the duration of a call; apermanent virtual circuit (PVC) connection is apermanent connection between the DTEs. (3.) InEnhanced X-Windows, the IPC path between theserver and a client program. A client program

1-32 Glossary

typically, but not necessarily, has one connection tothe server over which requests and events aresent. (4.) In system communications, acommunication link over which data can be passedbetween two systems or between a system and adevice.

connection close. All events made by the clientare discarded and the server resets its state tohaving no connections.

connection establishment. The phase inconnection mode that enables two data link service(DLS) users to create a data link connectionbetween them.

connection identifier (CID). (1.) A value used toidentify a resource. The value is returned to theconnecting program after connect processing hasestablished a session and must be used onsubsequent requests to the resource. (2.) In theX.25 API, the name used to identify a call that hasbeen made or received.

connection key. Identifies a subclass of devicesthat can connect to the intermediate device at thespecified location.

connection location. Identifies a specific locationon the intermediate device where a child devicecan be connected.

connection management stream. In X.25, aspecial stream that receives all incoming connectindications destined for DLSAP addresses that arenot bound to any other streams associated with aparticular PPA.

connection mode. A circuit–oriented mode oftransfer in which data is passed from one user toanother over an established connection in asequenced manner.

connection–oriented protocol. Aconnection–based, reliable, virtual–circuit transportprotocol, such as TCP; an RPC protocol that runsover a connection–based transport protocol.

connection profile. A data management file thatcontains parameters that associate other definedprofiles to the connection of two logical units.

connection type. This is a field in the PredefinedConnection Object Class. For an intermediatedevice, it identifies the subclass of devices that canbe connected to it.

connectionless mode. A mode of transfer inwhich data is passed from one user to another inself–contained units with no logical relationshiprequired among the units.

connectionless packet delivery. A method ofdata packet delivery that treats each packet of

information individually and does not guaranteedelivery.

connectivity. An algorithm that determines if twomachines on different networks can communicate.If the machines can communicate, connectivity alsodetermines which host names should be used andwhich TCP/IP routing information must be added.

connector. (1.) An electrical part used to join twoother electrical parts. (2.) A flowchart symbol thatrepresents a break in a flow line and indicateswhere the flow line is continued. (3.) A means ofestablishing electrical flow.

consistent. Pertaining to a file system, withoutinternal discrepancies.

console. The main operating system displaystation. Synonym for system console.

console bell. Synonym for BEL.

console device. During the installation of the BaseOperating System (BOS), the system console isthe display device at the system on which you areinstalling the software.

console display. A display at a system console onwhich an operator can display, send, and reply tomessages and use all control commands.

constant. A data item with a value that does notchange during the running of a program. Contrastwith variable. For Ada programming, see alsoobject.

constant expression. An expression having avalue that can be determined during compilationand that does not change during the running of theprogram.

constant folding. Performing operations in whichoperands are all constants at compilation time andtreating the results as constants. See also fold.

constant–width characters. A character setdesigned so each character is the same width asthe other characters.

constraint. In Ada language, a constraintdetermines a subset of the values of a type. Avalue in that subset satisfies the constraint.

Constraint. In AIXwindows, a class of objects fromwhich a unique resource set can be inherited. Forexample, a PanedWindow widget can specify thesize of its children by using the inherited XtNminand XtNmax Constraint resources. The referencematerial associated with each widget specifiesthose that inherit resources from the Constraintclass.

constraint widget. In Enhanced X-Windows, awidget that is a subclass of a composite widget. It

1-33Glossary

manages the geometry of its children based onconstraints associated with each child.

constructor. A special C++ member function thathas the same name as a class. It is used toconstruct class objects and may initialize them.

Consultative Committee on InternationalTelegraphy and Telephone (CCITT). A UnitedNations Specialized Standards group whosemembership includes common carriers concernedwith devising and proposing recommendations forinternational telecommunications representingalphabets, graphics, control information, and otherfundamental information interchange issues.

contact port. Synonym for well–known port.

container. In CDE, a control intended to holdobjects or data. A folder and a notebook areexamples of containers. In Mailer, your electronicmailbox and filing system that contains all mailmessages. Once a message is put in a container,you can display, modify, delete, print, include,forward, and reply to it.

containment. A pointer is ”contained” if the pointeris located in the window, and not within an inferiorof the window, and the cursor hotspot is within avisible region of a viewable window or one of itsinferiors. The border of the window is consideredpart of the window.

contention. (1.) In a local area network, acondition on a communications channel when twoor more stations are allowed by the protocol to starttransmitting concurrently and thus risk collision. (2.)A condition on a session when two programs try tostart a conversation at the same time.

contention scope. The group of threads againstwhich a given thread must compete for the CPU. Iflocal, the thread competes against other threads inthe same process. If global, the thread competesagainst all other threads in the system.

context address. A regular expression enclosed inslashes (/).

context clause. For Ada programming, seecompilation unit.

context expression. In SOM, an optionalexpression in a method’s IDL declaration,specifying identifiers whose value (if any) can beused during SOM’s method resolution processand/or by the target object as it executes themethod procedure. If a context expression isspecified, then a related Context parameter isrequired when the method is invoked. (ThisContext parameter is an implicit parameter in theIDL specification of the method, but it is an explicitparameter of the method’s procedure.) No

SOM–supplied methods require contextparameters.

context line. In the Performance Toolbox, menuitems ending in a slash and three dots (/...). Theslash and three dots signify that the line itselfrepresents a list at the next hierarchical level.Contrast with statistic line. See also cascadingmenu.

context structure. An ordered group of variablesspecifying the interface properties (notablylocation) of a shadow widget.

continuation line. A line of a source statementinto which characters are entered when the sourcestatement cannot be contained on the previouslines.

continuation reference. A continuation referencedescribes how the performance of all or part of anoperation can be continued at a different DSA orDSAs.

continue statement. A C language controlstatement that contains the keyword continue anda semicolon.

control. In CDE, a generic term for a variety ofelements (such as buttons, check boxes, and scrollbars) that perform an action or indicate an optionsetting. See Front Panel control.

control block. A storage area used by a programto hold control information.

control character. (1.) A character that is not agraphic character such as a letter, number, orpunctuation mark. Such characters are calledcontrol characters because they frequently act tocontrol a peripheral device. RETURN andFORM–FEED are control characters that control aworkstation or printer. Synonymous withnonprinting character. (2.) The Ctrl key on thekeyboard. (3.) A character, occurring in a particularcontext, that initiates, modifies, or stops anyoperation that affects the recording, processing,transmission, or interpretation of data (such ascarriage return, font change, and end oftransmission). (4.) A nonprinting character thatperforms formatting functions in a text file.

control commands. Commands that allowconditional or looping logic flow in shell procedures.

control state. A state that represents the currentnetwork installation management (NIM) operationbeing performed on a machine. This state is one oftwo machine states.

control key. (1.) The keyboard key labeled Ctrl.(2.) A key combination, made by pressing the Ctrl

1-34 Glossary

key followed by another key on the keyboard, thatperforms a function or makes a special character.

control path. The set of line, hardware, andcontrol disciplines that determine the currentcharacteristics of a particular TTY.

control point profile name. The name of thecontrol point profile that defines the node ID of thephysical unit associated with the attachment.

control points. In computer graphics, points inreal space that control the shape of a spline curve.The system provides hardware support for wireframe rational cubic splines, and for NURBSsurfaces, the specifications of which require fourcontrol points.

control program (CP). Part of the operatingsystem that determines the order in which basicfunctions should be performed.

control statement. In programming languages, astatement that is used to alter the continuoussequential execution of statements. A controlstatement can be a conditional statement or animperative statement.

control station. The primary or controllingcomputer on a multipoint line. The control stationcontrols the sending and receiving of data.

control unit terminal (CUT) mode. A protocolused for communications with a 3174/3274Controller or other appropriate interface unit. In thisprotocol, a program in the workstation is emulatinga 3278/79 terminal for a user, and the interface unitis responsible for enforcing the protocol.

controlling terminal. This term refers to an activeworkstation at which a user is authorized to entercommands that affect system operation. Thecontrolling terminal for any process normally is theactive workstation from which the process group forthat process was started. A workstation can haveno more than one controlling process group and aprocess group can have no more than onecontrolling terminal. The controlling process groupreceives certain interrupt signals from thecontrolling terminal.

convenience creation subroutine. Createscertain useful combinations of widgets known asconvenience widgets or convenience dialogs,including the appropriate Shell widgets wherenecessary. See also convenience interface.

convenience dialog. A widget or collection ofwidgets created by an AIXwindows Dialogconvenience subroutine.

convenience function. A function that performs afrequently needed series of tasks automatically tocreate or manage widgets or other code structures.

Convenience functions are included in theAIXwindows Toolkit.

convenience interface. An interface created by anAIXwindows convenience creation subroutine. Seealso convenience creation subroutine.

converged peripheral node. In SNA, a type ofphysical unit that has limited addressing and pathcontrol routing capabilities. It provides generalconnectivity to other SNA nodes and supportsparallel sessions, multiple sessions per LU, primaryand secondary LUs, and multiple lines per node.

conversation. (1.) In SNA, the logical connectionbetween a pair of transaction programs for seriallysharing a session between type 6.2 logical unitsfrom transaction to transaction. While aconversation is active, it has exclusive use of anLU–LU session as delimited by a distinct bracket;successive conversations may use the samesession. (2.) An interchange of informationbetween two application programs. (3.) A pathwaybetween two application programs that allows themto exchange information. (4.) Interaction between acomputer and a user by means of a keyboard.

conversation correlator. An internal SNAidentifier used by the LU services to track whichapplications are using which conversations. Anidentifier of 1 to 8 bytes that is assigned by theattach function and maintained by LU services.

conversation key. A short–lived encryption keyprovided by the Authentication Service to twoprincipals for the purpose of ensuring securecommunications between them. See also sessionkey.

conversation mode. A mode of operation of acomputer system in which a sequence ofalternating entries and responses between a userand the system takes place in a manner similar to adialog between two persons.

conversion. (1.) In programming languages, thetransformation between values that represent thesame data item but belong to different data types.(2.) A change in the type of value. For example,when you add values having different data types,the compiler converts both values to the same formbefore adding them. See also transaction program.

conversion code. In a print function call, aspecification of the type of the value, as the valueis to be printed (in octal format, for example).

conversion function. A C++ member function thatspecifies a conversion from its class type toanother type.

conversion specification. In a print function call,a specification of how the system is to place the

1-35Glossary

value of zero or more format parameters in theoutput stream. Each conversion specificationcontains a % (percent) symbol that is followed byconversion modifiers and a conversion code.

converter. A device that converts data from oneform to another without altering the underlyinginformation.

converter cache. A high–speed buffer storage thatcontains frequently accessed informationassociated with a client application. The primarypurpose of a converter cache is to reduce accesstime to key information.

coordinate system. A given convention forlocating pixels on a given display or window,where, in AIXwindows, X is the horizontal axis andY is the vertical axis. The origin is [0,0] at theupper–left or lower–left corner, depending on theconvention in use. For a window, the origin is at theupper left or lower left (depending on theconvention in use), inside the border. Coordinatesare discrete and specified in pixels. Each windowand pixmap has its own coordinate system.

coprocessor. (1.) A supplementary processor thatperforms operations in conjunction with anotherprocessor. (2.) In personal computers, amicroprocessor on an expansion board thatextends the address range of the processor in thesystem unit or adds specialized instructions tohandle a particular category of operations.

copy. (1.) The action by which the user makes awhole or partial duplicate of an already existingdata object. (2.) Either a copy of an entry stored inother DSAs through bilateral agreement, or alocally and dynamically stored copy of an entryresulting from a request (a cache copy).

copy constructor. A C++ constructor used tomake a copy of a class object from another classobject of the same class type.

copy–link. A link established between a target fileand the copied version of the same file. Anychanges made to the copied version of the targetfile are automatically made to the original targetfile.

copy–on–write. An option that creates a mappedfile with changes that are saved in the systempaging space, instead of saving the changes to thecopy of the file on the disk.

CORBA. In SOM, the Common Object RequestBroker Architecture established by the ObjectManagement Group. IBM’s Interface DefinitionLanguage used to describe the interface for SOMclasses is fully compliant with CORBA standards.

Core. In AIXwindows, Core is the top–levelsuperclass from which all widgets and gadgets are

derived. Core consists of three subclasses (Object,RectObject, and WindowObj) that collectivelyprovide the appearance resources and behavioralresources required by all widgets and gadgets inthe AIXwindows toolkit.

core sequence controller. One of three controlprograms for the initial program load (IPL) ROM.The core sequence controller accepts control fromthe initial sequence controller and passes control tothe IPL controller.

core widget. In Enhanced X-Windows, the widgetthat contains the definitions of fields common to allwidgets. All widgets are subclasses of the corewidget. See also widget.

corequisite. A product or update that must beinstalled concurrently with another specifiedproduct or update.

correlator. A value passed between two or moreprograms that allows correlation or identification ofmutual resources.

counter. (1.) A register or storage location used toaccumulate the number of occurrences of anevent. (2.) In the X.25 API, a variable that isincreased by one when a packet arrives and isdecreased by one when a packet is received; it canbe used to notify the application program ofincoming packets.

counter identifier. In the X.25 API, the name of acounter.

country code. In X.25 communications, the 3–digitnumber that precedes the national terminal numberin the network user address (for public networks).

coupler. A device connecting a modem to atelephone network.

courier. In DTS, a local server that requests a timevalue from a randomly selected global server eachtime it synchronizes.

CP. See control program.

CPS. Characters per second.

CPU. See central processing unit.

CPU lock. See nodelocked license.

CPU time. The amount of time a program isrunning in the CPU or is being serviced by theoperating system. Does not include timeassociated with the program’s I/O or time in whichother processes preempt the program’s use of theCPU.

crash. An unexpected interruption of computerservice, usually due to a serious hardware orsoftware malfunction.

CRC. See cyclical redundancy check character.

1-36 Glossary

Create Action. In CDE, a software application thatenables you to associate an icon with a commandso that the command can be issued by clicking onthe icon. Create Action is also used to definespecific data types for an application’s data filesand to associate icons with those data types.

creation date. The date when the file was created.See also session date and system date.

critical resource. The system resource whosespeed and/or size limits the speed with which aparticular workload can be processed.

critical sections. Portions of shared data to whichsimultaneous access by multiple threads orapplications must be prevented.

cross–referencer. In Ada language, a tool thatprovides a listing of all places where symbols aredeclared, assigned to, or referenced within acompilation unit. Symbols are identified by name,class, and enclosing unit, and references to thesymbol are identified by source file line numbers.

CRQ. See call request.

CRT. See cathode ray tube.

CSC. See core sequence controller.

CSMA/CD. See carrier sense multiple access withcollision detection.

CSX. Host–based diagnostics program.

C–stub. The part of the DUA that implements theconnection with the communications network.

CTC. Channel–to–channel.

CTS. Clear to send. Used with EIA–232 protocol.

CUD. See call user data.

CUG. See closed user group.

culling. (1.) In GL, if a primitive is smaller than theminimum size specified in the command, it isculled: no further commands in the primitive areinterpreted. See also clipping and pruning. (2.) Inthe graPHIGS API, if a polygon is backfacing, itmay be culled, or not rendered.

currency time. The time at which a user readsnews items. The news command considers onlythe items posted after this time to be current for theuser.

current. For an Ada–language compilation unit, thestate where none of that unit’s supporters has beenrecompiled since the unit itself was compiled. Thisimplies that all of the supporters exist, since theAda language requires this in order for the programto be compiled. Currency implies that all supportersof a unit were compiled in the correct order, asdefined by Ada language rules.

current character position. The two–dimensionalscreen coordinates where the next character stringor pixel read/write operation will occur.

current color. The color that is employed to colorall subsequent drawing primitives. All drawingprimitives are drawn with this color until it ischanged.

current directory. The directory that is active andcan be displayed with the pwd command. Relativepath name resolution begins in the currentdirectory. Synonymous with current workingdirectory and working directory.

current file. (1.) The file being edited. If multiplewindows are in use, the current file is the filecontaining the cursor. (2.) In the make command,the file that the make command is working with at agiven moment. The make command replaces the$* macro with the name of the current file.

current folder. In CDE, the currently opened folderin an active File Manager view.

current graphics position. The homogeneousthree–dimensional point from which geometricdrawing commands draw. The current graphicsposition is not necessarily visible.

current graphics window. In GL, the window towhich the system directs the output from graphicsroutines.

current heap. In Pascal, the area of storage wheredynamic variables allocated by calls to NEWreside. Other heaps can exist at the same time, butonly one is current.

current host. Synonym for local host.

current line. The line on which the cursor islocated.

current record. (1.) The record pointed to by thecurrent line pointer. (2.) The record that is currentlyavailable to the program.

current record pointer (CRP). A logical indicatorused when sequentially processing SFS files orselected ranges of records from those files. TheCRP tracks which of the records in the selectedrange has just been processed and which will beprocessed next.

current selection. A highlighted text block orelement.

current session. In CDE, the session saved bySession Manager when you log off. At the nextlogin, unless you specify otherwise, this sessionautomatically opens, enabling work to continuewhere you left off. Contrast with home session.

current transformation matrix. Thetransformation matrix on top of the matrix stack. All

1-37Glossary

points passed through the graphics pipeline aremultiplied by the current transformation matrixbefore being passed on. The currenttransformation matrix is a concatenation of thecurrent modeling and viewing matrices. See alsotransformation and matrix stack.

current window. The window to which the systemdirects the output from graphics routines. See alsowindow.

current working directory. Synonym for currentdirectory.

cursor. (1.) A movable symbol (such as anunderline) on a display that indicates to the userwhere the next typed character will be placed orwhere the next action will be directed. (2.) InEnhanced X-Windows, the visible shape of thepointer on a screen. A cursor consists of a hotspot,a source bitmap, and a pair of colors. (3.) Aprimitive such as an arrowhead that can be movedabout the screen by means of an input device(typically a mouse).

cursor glyph. In GL, a 16x16 or 32x32 rasterpattern (bitmap that determines the shape of thecursor. A GL cursor glyph can be one or two bitsdeep; thus, a GL cursor can use up to three colors.Color 0 is always transparent.

cursor ID. In Enhanced X-Windows, a uniqueidentification number that is associated with eachunique type of cursor.

cursor movement keys. The directional keys usedto move the cursor without altering text.

cursor stability. In file systems other than onemanaged by SFS, the ability to simultaneouslymaintain multiple contexts within a single filesystem. The SFS equivalent of a cursor is providedby the ability to simultaneously obtain multipleOFDs on a single file.

Customer Information Control System (CICS). Alicensed program that enables transactions enteredat remote workstations to be processedconcurrently by user–written application programs.It includes facilities for building, using, andmaintaining databases.

customization. (1.) In the NIM environment, this isoptional software installation. (2.) The process of

describing optional changes to defaults of asoftware program that is already installed on thesystem and configured so that it can be used.Contrast with configuration. See also systemcustomization.

customization profile. A file containing thedescriptions of optional changes to the defaultsettings of a device or a software program. Seealso profile.

customize. (1.) To describe to the system thedevices, programs, users, and user defaults for aparticular data processing system or network. (2.)To describe optional preferences or changes todefaults in a software program that is alreadyinstalled and configured. Contrast with configure.

Customized Database. An entity within the ODMthat contains configuration data for defined oravailable devices in the system. See also DeviceConfiguration Database and Predefined Database.

Customized Devices Object Class. Arepresentation within the ODM of each deviceinstance as distinguished by a unique logical name.The Customized Devices Object Class containsbasic information about the device such as devicestatus and how to access the information containedin other object classes.

CUT. See control unit terminal mode.

cycle time. (1.) The time elapsed during one cycleof the processor. Cycle time varies from one type ofprocessor to another. (2.) The minimum timeinterval between starts of successive read/writecycles of a storage device.

cyclic redundancy check (CRC) character. Acharacter code used in a modified cyclic code forerror sensing and correction.

cylinder. All fixed disk or diskette tracks that canbe read or written without moving the disk drive ordiskette drive read/write mechanism.

cylindrical coordinate system. An array wherethe left edge of each row is functionally adjacent tothe right edge of the same row.

Cyrillic. Cyrillic alphabet. An alphabet used forwriting Old Church Slavonic and for Russian andvarious other Slavic languages.

1-38 Glossary

DDAC. See digital–to–analog converter.

daemon. A program that runs unattended toperform a standard service. Some daemons aretriggered automatically to perform their task; othersoperate periodically. An example is the crondaemon, which periodically performs the taskslisted in the /var/spool/cron/crontabs directory.Synonym for demon.

daemon process. A process begun by the rootuser or the root shell that can be stopped only bythe root user. Daemon processes generally provideservices that must be available at all times, such assending data to a printer.

DAF. Destination Address Field.

dangling else. A condition arising as a result ofnesting an IF statement in the IF part of anIF–ELSE statement. The ELSE statement isassociated with the closest IF statement, in thiscase, the inner one. Placing an empty ELSEstatement in the nested statement preventsmisinterpretation by forcing the outer ELSEstatement to associate with the outer IF statement.

DAS. Dual–attachment station. A station thatconnects to both the primary and secondary FDDIrings.

DASD. Direct access storage device. A device inwhich access time is effectively independent of thelocation of the data. Information is entered andretrieved without reference to previously accesseddata. DASDs include both fixed and removablestorage devices.

data. A representation of facts or instructions in aform suitable for communication, interpretation, orprocessing by human or automatic means. Dataincludes constants, variables, arrays, and characterstrings.

data area. An area of memory that containsspecific control variables that are normallypredefined in structures or vectors.

data block. See block.

data cache. A cache for providing data to theprocessor faster than it can be obtained from RAM.

data cache unit (DCU). See cache.

data circuit. A pair of associated transmit andreceive lines that provide a means of two–way datacommunications.

data–circuit–terminating equipment (DCE). In adata station, the equipment installed at the user’spremises that provides all the functions required to

establish, maintain, and end a connection, and thesignal conversion and coding between the dataterminal equipment (DTE) and the line.

data communications. See communications.

data consumer. In Performance Toolbox, adescription of a program that receives statisticsover the network from the xmservd daemon andprints, post–processes, or otherwise manipulatesthe raw statistics. Synonymous with client. Contrastwith data supplier.

data definition. A program statement thatdescribes the features of, specifies relationships of,or establishes the context of, data. A data definitioncan also provide an initial value. Definitions appearoutside a function or at the beginning of a blockstatement.

data dependency. A situation in which a sourceoperand for a computation is the result of apreceding computation.

data description. For data objects that are notself–describing, components of the data object thatdescribe the data so that it may be processed.

Data Encryption Standard (DES). A dataencryption algorithm widely used in the UnitedStates.

data item. A unit of data to be processed thatincludes constants, variables, array elements, andcharacter substrings.

data link. (1.) The assembly of parts for two dataworkstations that are controlled by a link protocoland the interconnecting data circuit, which enablesdata to be transferred from a data source to a datasink. (2.) The interconnecting data circuit and thelink protocol between two or more workstations, notincluding the data source or data sink. (3.) Thephysical connection and the connection protocolsbetween units that exchange data over atelecommunications line. See also X.25 link.

data link control layer. In SNA and X.25, the layerthat consists of the link stations that schedule datatransfer over a link between two nodes andperform error control for the link.

data link control (DLC) protocol. In SNA, the setof rules used by two nodes on a data link toaccomplish an orderly exchange of information.

data link escape (DLE) character. In BSC, atransmission control character usually used intransparent text mode to indicate that the nextcharacter is a transmission control character.

data–link level. In the hierarchical structure of adata station, the conceptual level of control orprocessing logic between high level logic and the

1-39Glossary

data link that maintains control of the data link. Thedata link level performs such functions as insertingtransmit bits and deleting receive bits; interpretingaddress and control fields; generating, transmitting,and interpreting commands and responses; andcomputing and interpreting frame checksequences. Synonym for frame level. See alsopacket level, physical level.

data lock. (1.) The insurance of data availability toa single application program as a protectionagainst conflicting updates to a data record. (2.)The system lock that locks data segment intomemory.

data object. A collection of data referred to by asingle name. See also object.

data packet. In X.25 communications, a packetused for the transmission of user data on a virtualcircuit at the DTE/DCE interface. See also packet.

data storage interrupt. An interrupt posted whena fault is encountered accessing storage or I/Ospace. A typical data storage interrupt is a pagefault or protection violation.

data stream. (1.) All information (data and controlinformation) transmitted over a data channel in asingle read or write operation. (2.) A continuousstream of data elements being transmitted, orintended for transmission, in character orbinary–digit form using a defined format. (3.) Allinformation sent to the terminal device driver with awrite subroutine. Synonymous with stream.

data supplier. In Performance Toolbox, a programthat supplies statistics across a network.Synonymous with server. Contrast with dataconsumer.

data terminal equipment (DTE). (1.) The part ofdata processing unit that serves as a data source,data sink, or both. (2.) The user of the network.

data terminal ready (DTR). A signal to the modemused with EIA–232 protocol.

data token. In SOM, a value that identifies aspecific instance variable within an object whoseclass inherits the instance variable (as a result ofbeing derived, directly or indirectly, from the classthat introduces the instance variable). An objectand a data token are passed to the SOM run–timeprocedure, somDataResolve, which returns is apointer to the specific instance variablecorresponding to the data token. See also instancetoken.

data transfer. The movement, or copying, of datafrom one location and the storage of the data atanother location.

data type. (1.) In programming languages, a set ofvalues together with a set of permitted operations.(2.) The mathematical properties and internalrepresentation of data and functions. (3.) Anattribute used for defining data as numeric orcharacter. (4.) The type, format, or classification ofa data object. (5.) In CDE, a mechanism thatassociates particular data files with the appropriateapplications and actions. Data types can determinethe type of a file based on file–naming conventions,such as a particular extension name, or on thecontents of the file. See also character type andtype.

database. A collection of facts and instructionscomprising at least one file that is sufficient for agiven purpose.

datagram. (1.) In packet switching, aself–contained packet, independent of otherpackets, that carries information sufficient forrouting from the originating data terminalequipment (DTE) to the destination DTE withoutrelying on earlier exchanges between the DTEsand the network. (2.) In DCE, an unreliable networkdata packet that is independent of all other packetsand lacks any guarantees of delivery orsequentiality.

datagram protocol. A connectionless,datagram–based transport protocol, such as UDP;an RPC protocol that runs over a connectionlesstransport protocol.

dataless. A workstation without local file systemsor local boot images that accesses some of itsresources remotely. Dataless clients use a localdisk used for paging and dump devices.

dB. See decibel.

DB. Database.

DBA. See direct–bus attached.

DBCS. See Double–Byte Character Set.

D–bit. In X.25 communications, the bit in a datapacket or call–request packet that is set to 1 ifend–to–end acknowledgment (deliveryconfirmation) is required from the recipient.

DC. See DCU.

DCD. Data carrier detect used with EIA–232protocol. See also CD and decode.

DCE. See Distributed Computing Environment anddata–circuit–terminating equipment.

DCN. Distributed Computer Network.

DCU. Data cache unit. See also cache.

1-40 Glossary

DD. See device driver.

DDN. Department of Defense Network.

dead code elimination. A compiler optimizationthat removes code that is never referenced, or thatis always branched over. A compiler optimizationthat removes store instructions for data entitieswhose final values are not used.

dead letter file. A file containing mail messagesthat could not be sent to a proper destination file.

dead variable. In Ada language, a variable that isinitialized, but is not used within the context of theprogram. Like unreachable code, dead variablesare detected and removed by the optimizer.

dead zone. An area of a tablet from which no inputreports are generated. Each virtual terminal can setits own dead zones. Synonymous with no–inputzone.

deadlock. (1.) An error condition in whichprocessing cannot continue because each of twoelements of the process is waiting for an action byor a response from the other. (2.) Unresolvedcontention for the use of a resource. (3.) Animpasse that occurs when multiple processes arewaiting for the availability of a resource that doesnot become available because it is being held byanother process that is in a similar wait state.

deallocate. To release a resource assigned to aspecific task. Contrast with allocate.

DEALLOCATE. A request to remove the allocationof the specified conversation from the localtransaction program.

deallocation. An operation that removes a client’spermission to use a resource.

debug. To detect, locate, and correct errors in theconfiguration of a computer system or a softwareprogram.

debugger. A program or programs used to detect,trace, and eliminate errors in computer programsor software.

debugging. Acting to detect and correct errors insoftware or system configuration.

debugging mode. A special mode in which aprogram provides detailed output about its activitiesto aid a user in detecting and correcting errors inthe program itself or in the configuration of theprogram or system.

decibel (dB). (1.) One tenth of a bel. (2.) A unit ofsignal strength, such as the signal on a datacommunications channel. (3.) A unit for measuringrelative power. The number of decibels is 10 timesthe logarithm (base 10) of the ratio of themeasured power levels.

decimal. (1.) Pertaining to a system of numbers tothe base 10. The decimal digits range from 0through 9. (2.) Characterized by a selection,choice, or condition that has 10 possible differentvalues or states.

decimal constant. A number containing any digits0 through 9.

declaration. (1.) A description that makes adefined object available to a function or a block.(2.) In programming languages, the mechanism forestablishing a language object. A declarationnormally involves attaching an identifier andallocating attributes to the language objectconcerned. (3.) In a programming language, ameaningful expression that affects theinterpretation of other expressions in thatlanguage. (4.) In Ada language, a declarationassociates an identifier (or some other notation)with an entity. This association is in effect within aregion of text called the scope of the declaration.Within the scope of a declaration, there are placeswhere it is possible to use the identifier to refer tothe associated declared entity. At such places theidentifier is said to be a simple name of the entity;the name is said to denote the associated entity.See also declare, simple name, scope, and name.

declarative part. In Ada language, a sequence ofdeclarations. It may also contain relatedinformation such as subprogram bodies andrepresentation clauses.

declarator. An identifier and optional symbols thatdescribe the data type.

declare. A selection available from the Interpreter’sInterpret menu that allows a user to assign variablenames and structure definitions. See alsodeclaration.

decode. (1.) To convert data by reversing the effectof some previous encoding. (2.) To interpret acode. See also DCD.

default. A value, attribute, or option that isassumed when no alternative is specified by theuser. See also default value.

default accelerators. See accelerator.

default arguments. Arguments that are declaredwith default values in a C++ function prototype ordeclaration. If a call to the function omits thesearguments, default values are used. Argumentswith default values must be the trailing argumentsin a function prototype argument list.

default button labels. In AIXwindows, XmLabelwidgets or gadgets that are used when no otherbutton label has been specified.

1-41Glossary

default cell (global access). An NCS cell thatallows access from any node in the network. This isthe most common cell used in License UseManagement configurations because it allows allother License Use Management servers in thedefault cell to communicate freely.

default clause. In a C switch statement, thekeyword default followed by a colon and one ormore C statements. When the conditions of thespecified case labels in the switch statement do nothold, the default clause is chosen.

default constructor. A C++ constructor that takesno arguments, or if it takes any arguments, all itsarguments have default values.

default device. The device attached to yourcomputer (such as a printer or disk drive) that isused when no alternative is specified by theoperator.

default directory. The directory name supplied bythe operating system if none is specified.

default drive. The drive name supplied by theoperating system if none is specified.

default files. Data files in which resource defaultvalues are stored in ASCII form to permit theassignment of alternative resource values at runtime without need for rewriting or recompilingsource code.

default initialization. The initial value assigned toa data object by the compiler if no initial value isspecified by the programmer. In C language,external and static variables receive a defaultinitialization of zero, while the default initializationfor auto and register variables is undefined. Seealso default value.

default label. See label.

default printer. A printer that accepts all theprinted output from a display station assigned to it.

default shell. In AIXwindows, the shell that is usedwhen no other shell properties have beenspecified.

default value. A value stored in the system that isused when no other value is specified. See alsodefault and default initialization.

defaults file. See default files.

define. Creates an entry in the ODM CustomizedDevices Database and establishes the parentdevice and connection location.

define method. Used to create a device instancein the ODM Customized Database. It takes adevice from the undefined or nonexistent state tothe defined state.

define statement. A preprocessor statement thatcauses the preprocessor to replace an identifier ormacro call with specified code.

defined state. The state a device is put into whenits defined method is run or when an availabledevice’s unconfigure method is run. The device isnot a usable device at this point.

DEL. See delete character.

delayed port. A port that is enabled like a sharedport except that the login herald is not displayeduntil you type one or more characters (usuallycarriage returns). A port directly connected to aremote system or intelligent modem is usuallyenabled as a delayed port.

delete. (1.) To remove. For example, to delete afile. See also erase. (2.) The C++ keyword deleteidentifies a free store deallocation operator. In C++,the delete operator is used to destroy objectscreated by new.

delete character (DEL). (1.) A control characterused primarily to obliterate an erroneous orunwanted character. (2.) A character that identifiesa record to be removed from a file.

delimiter. (1.) A character or sequence ofcharacters that marks the beginning or end ofcharacter string or unit of data. (2.) A character thatgroups or separates words or values in a line ofinput.

deliver (callback). Delivering a callback or upcallmeans to cause its invocation.

delivery–confirmation bit. See D–bit.

delta. The finite increment of a variable.

demangling. The conversion of mangled C++names back to their original source code names.During compilation, identifiers such as function andstatic class member names are mangled (encoded)with type and scoping information to ensuretype–safe linkage. These mangled names appearin the object file and the final executable file.Demangling converts these names back to theiroriginal names to make program debugging easier.

demon. Synonym for daemon.

denote. See declaration.

density. In printing, refers to the number ofcharacters per inch horizontally.

dependency line. The first line of an entry in adescription file. It contains a list of target filesfollowed by a colon and an optional list ofprerequisite files or dependencies.

1-42 Glossary

dependent. A software product that requiresanother product or update to be installed before orat the same time it is installed. Contrast withprerequisite.

dependent workstation. A workstation havinglittle or no stand–alone capability that must beconnected to a host or server in order to provideany meaningful capability to the user.

dependents. Ada–language compilation units thatwould have to be recompiled if another unit were tobe recompiled because of the compilation orderimposed by the Ada language.

depth. (1.) In Enhanced X-Windows, the number ofbits per pixel for a window or pixmap. (2.) In athree–dimensional context, the second dimension.

depth–cueing. In 3D computer graphics, varyingthe intensity of a line with depth. Typically, thepoints on the line further from the eye are darker,so the line seems to fade into the distance.

dequeue. To remove items from a queue. Contrastwith enqueue.

dereferenced pointer. In Pascal, an expressionusing the –> or @ operator used to locate adynamic variable from a pointer.

derivation. The process of deriving a C++ classfrom an existing class, called a base class.

derived class. A C++ class that inherits theproperties of a base class. You can add additionaldata members and member functions to thederived class. A derived class object can bemanipulated as if it were a base class object. Thederived class can override virtual functions of thebase class.

derived metaclass. (Or SOM–derived metaclass.)A metaclass that SOM creates automatically (ofteneven when the class implementor specifies anexplicit metaclass) as needed to ensure that, forany code that executes without method–resolutionerror on an instance of a given class, the code willsimilarly execute without method–resolution erroron instances of any subclass of the given class.SOM’s ability to derive such metaclasses is afundamental necessity in order to ensure binarycompatibility for client programs despite anysubsequent changes in class implementations.

derived type. In Ada language, a type whoseoperations and values are replicas of those of anexisting type. The existing type is called the parenttype of the derived type. See also parent type.

DES. See Data Encryption Standard.

descendant. See child.

descending key sequence. The arrangement ofdata in order from the highest value of the key fieldto the lowest value of the key field.

descriptor. (1.) In ODM, a named and typedvariable that defines a single characteristic of anobject. See also terminal descriptor, link descriptor,and method descriptor. (2.) In information retrieval,a parameter word used to categorize or indexinformation. (3.) In XOM, the means by which theclient and service exchange an attribute value andthe integers that denote its representation, type,and syntax. (4.) In XDS, a defined data structurethat is used to represent an OM attribute type anda single value. (5.) In SOM, an ID representing theidentifier of a method definition or an attributedefinition in the Interface Repository. The IRdefinition contains information about the method’sreturn type and the type of its arguments.

deselect. To cancel the selection of a button. Witha mouse, you deselect a highlighted area with theSelect (left) button. Otherwise, you can use theSelect key on the keyboard. To deselect a defaultbutton, select an alternate button in the selectionlist.

deserialize. (1.) To change from serial–by–bit toparallel–by–byte. (2.) In XDR, to change from XDRformat to a particular machine representation.

desktop. A visual representation of a group ofobjects in your system, brought together to helpyou organize your work.

destination cursor. A point or location marked bythe cursor to which data is to be pasted or inserted.

destination disk. The disk to which you areinstalling.

destructor. A special member function of a classwith the same name as the class with a ~ (tilde)preceding the name. You cannot specify argumentsor a return type for this function. A destructor”cleans up” after an object by doing such things asfreeing any storage that was dynamically allocatedwhen the object was created.

device. (1.) A mechanical, electrical, or electronicmachine that is designed for a specific purpose andthat attaches to your computer, such as a printer,plotter, or disk drive. (2.) A valuator, button, or thekeyboard. Buttons have values of 0 or 1 (up ordown); valuators (mouse, dials) return values in arange, and the keyboard returns ASCII values.

device class. Functional grouping of devices. Thegeneric name for a group of device types, forexample, all display stations belong to the samedevice class. Contrast with device type.

1-43Glossary

Device Configuration Database. Stores allinformation relevant to support the deviceconfiguration process. It consists of a PredefinedDatabase and a Customized Database. See alsoPredefined Database and Customized Database.

device definition. Information about a device thatis in the Customized Database including attributesand connection locations.

device description. Text used to give a shortdescription of the device. For example, the devicedescription for the token–ring adapter might be”Token–Ring High–Performance Adapter.”

device driver (DD). (1.) A program that operates aspecific device, such as a printer, disk drive, ordisplay. (2.) A collection of subroutines that controlthe interface between I/O device adapters and theprocessor.

device handler. The component of a device driverthat communicates directly with the hardware.Synonymous with virtual device driver.

device head. The component of a device driverthat implements the application program interfaceto a device.

device instance. When a device is defined, aCustomized Devices Object Class entry is created.This entry is considered a device instance. There isa device instance for each device defined in thesystem.

device location. Indicates the location path of adevice. This is a field in the Customized DevicesObject Class.

device manager. For complex interfaces, acollection of routines that acts as an intermediarybetween drivers and virtual machines. Forexample, supervisor calls from a virtual machineare examined by a device manager and routed tothe appropriate subordinate device drivers.

device name. (1) The logical or symbolic namereserved by the system to refer to a specific device.(2) SNA uses the operating–system device nameof the network adapter to get information thatdefines the interface. See also logical name.

device number. The reference number assignedto any external device.

device stanza. Defines a device attached to aqueue in the print spooling system. A device stanzacontains all information pertaining to the device(usually a printer) and is found in the /etc/qconfigfile.

device state. Indicates the current configurationstatus of a device instance. Possible values aredefined, available, and stopped. This is a field inthe Customized Devices Object Class.

device subclass. Distinguishes devices within thesame functional class. It is used to indicatedifferent interfaces. For example, the printer classhas three subclasses: rs232, rs422, and parallel.

device switch table. (1) A table that is used as aninterface to the device drivers. (2) A table thatcontains a pointer to the entry points for eachdevice head.

device type. The general name for a kind ofdevice sharing the same model number; forexample, 2311, 2400, 2400–1. Contrast with deviceclass.

DFT. See distributed function terminal.

DHCP. Dynamic Host Configuration Protocol. Anapplication–layer protocol that allows a machine onthe network, the client, to get an IP address andother configuration parameters from the server.

diacritic. A diacritic is a mark added to a letter toindicate a special phonetic value. Diacritics areimplemented by a nonspacing character sequence,a two–key sequence consisting of one of 13diacritics followed by an alphabetic character or aspace. The terminal device driver converts thistwo–key sequence into a single code point.

diagnostic. Pertaining to the detection andisolation of errors in programs and faults inequipment.

diagnostic aid. A tool (procedure, program, orreference manual) used to detect and isolate adevice or program malfunction or error.

diagnostic code. In X.25 communications, a1–byte code included in clear– and reset–indicationpackets that gives information about the reason forsending the packet. See also cause code.

Diagnostic Control Program. The top–levelcontrol program and configuration manager fordiagnostics. It traverses the configurationdatabase, testing resources and theirinterdependencies. It analyzes conclusions fromdiagnostic applications and generates a problemreport.

diagnostic output. Error or status messagesproduced by processes, in addition to thosemessages produced by standard output.Synonymous with error output.

dial. (1) A computer input device that allows a userto set parameter values. Dials are a type ofvaluator. See also valuator.(2) An I/O device usedto input variables by way of thumbwheels.

dial and switch box. An I/O device with 8 dials(valuators) and 32 switches. The switch box is alsocalled a ”button box” or the ”lighted programmablefunction keys (LPFKs).”

1-44 Glossary

dial–code. In BNU, a code representing atelephone number or portion of a telephonenumber.

dialing directory. In ATE, a list of telephonenumbers that can be called with AsynchronousTerminal Emulation (ATE). It is similar to a page ina telephone directory.

dialog. In an interactive system, a series of relatedinquiries and responses similar to a conversationbetween two people.

Dialog. In AIXwindows, a two–way text interfacebetween an application and its user. The interfacetakes the form of a collection of widgets andgadgets, including a DialogShell widget, aBulletinBoard widget (or a subclass of aBulletinBoard widget or some other containerwidget), plus various children, including Label,PushButton, and Text widgets.

dialog box. A window that is displayed whenfurther information is needed from the user, orwhen the system needs to display information. Aline enclosure on a structure, such as a widget orshell, that contains a specific, two–way textinterface.

dialog shell. A subclass of transient shell, thisshell is used for dialog boxes. See also dialogwidget.

dialog widget. Any of a class of widgets chosenthrough the Create menu’s Dialog submenu; dialogwidgets always have the dialog shell as theirimplicit shell. See also dialog shell.

digest. Data that has been organized into a formatthat provides for quick access to each piece ofdata.

digit. (1) A character that represents anonnegative integer. Synonymous with numericcharacter. (2) A symbol that represents one of thenonnegative integers smaller than the radix. (3)Any of the numerals from 0 through 9.

digital–to–analog converter (DAC). (1) A highlyspecialized chip that converts the digital valuescoming out of the frame buffer into the rapidlyvarying analog voltage levels that are required bythe monitor. (2) That portion of the displaysubsystem that converts pixels into colors orgrayscale.

dimension. The attribute of size given to arraysand tables.

direct addressing. (1) An addressing method thatuses an expression as an operand entry torepresent an instruction address. (2) A method ofaddressing in which the address part of aninstruction contains a direct address.

direct–bus attached. Used in relation to the fixeddisk drives attached directly to the system boardrather then through a SCSI adapter card.

direct color. (1.) In Enhanced X-Windows, a classof color map in which a pixel value is decomposedinto three separate subfields for indexing. Onesubfield indexes an array to produce red intensityvalues, the second indexes another array for blueintensity values, and the third for green intensityvalues. The RGB values can be changeddynamically. This is mutually exclusive to thePseudocolor color map color. (2.) Also DirectColor,a value.

direct connection. The attachment of a system,workstation, or other I/O device through a selectedcommunication interface and a limited–lengthcable. No modem is required.

direct–mapped cache. A cache in which exactlyone line corresponds to each possible value of thevirtual–address field that identifies the line to beinterrogated.

direct memory access (DMA). (1.) The transfer ofdata between memory and an input/output devicewithout processor intervention. (2.) General termgiven to the system facility that allows a device onthe Micro Channel bus to get direct access to thesystem or bus memory without the intervention ofthe system processor. The system–suppliedresource that provides this facility and mediates thedata transfers between the memory and devices isthe DMA controller.

direct visibility. See visibility.

directional component. In AIXwindows, a portionof a compound string that specifies a direction witha given value. The directional component iscreated with the XmStringDirectionCreatefunction.

directive. In SOM, a message (a pre–definedcharacter constant) received by a replica from theReplication Framework. Indicates a potential failuresituation.

directory. (1.) A type of file containing the namesand controlling information for other files or otherdirectories. (2.) A table of identifiers and referencesto the corresponding items of data. (3.) An indexused by a control program to locate blocks of datathat are stored in separate areas of a data set indirect access storage. (4.) Contrast with specialfile. (5.) A listing of related files arranged in a usefulhierarchy. (6.) In CDS, a logical unit for storingentries under one name (the directory name) in aCDS namespace. In addition to object entries, adirectory can contain soft links and child pointers.You can copy, delete, and control access to adirectory. Each physical instance of a directory is

1-45Glossary

called a replica. (7.) In XDS, a collection of opensystems that cooperate to hold a logical databaseof information about a set of objects in the realworld. (8.) In CDE, a collection of files and othersubdirectories. In graphical user interfaceapplications, may be called a folder.

directory ID. See directory identifier.

directory identifier (directory ID). An identifier fordistinguishing several configurations of thedirectory service within an installation.

directory mask. A pattern of characters thatcontrols which portions of a directory will beretained and which portions will not be retained.

dirty object. In SOM, a persistent object that hasbeen modified since it was last written to persistentstorage.

disable. (1.) To make nonfunctional. In interactivecommunications, to disconnect or stop asubsystem. Contrast with enable. (2.) To bring aqueue or a device attached to a queue off line sothat no print jobs get sent to it.

disabled port. In Asynchronous TerminalEmulation (ATE), a port configuration indicatingthat a port is ready to call out.

DISC. Disconnect.

discipline. Ordering method used to line up jobsfor printing, FCFS (first–come–first–served) or SJN(shortest–job–next). See alsofirst–come–first–served and shortest–job–next.

disconnect. In X.25 communications, todisconnect a port from the X.25 network.

disconnected mode (DM). In SDLC, a responsefrom a secondary station indicating that it isdisconnected and wants to be online.

discrete type. In Ada language, a type that has anordered set of distinct values. The discrete typesare the enumeration and integer types. Discretetypes are used for indexing and iteration, and forchoices in case statements and record variants.

discretionary access control. A securitymechanism that protects information fromunauthorized disclosure or modification throughowner–controlled access to files. See also accesscontrol list, base permission, and extendedpermission.

discriminant. In Ada language, a distinguishedcomponent of an object or value of a record type.The subtypes of other components, or even theirpresence or absence, may depend on the value ofthe discriminant.

discriminant constraint. In Ada language, on arecord type or private type, specifies a value foreach discriminant of the type.

discriminated union. In XDR, a C language unionthat holds several data types, with one arm of theunion being an enumeration value, or discriminant,which holds a specific object to be processed overthe system first.

disk. A storage device made of one or more flat,circular plates with magnetic surfaces on whichinformation can be stored.

disk adapter. The hardware used by a computer toaccess and control disk drives. On POWERstationsand POWERservers, disk adapters each fit into asingle Micro Channel slot, and each are controlledby software device drivers.

disk drive. The mechanism used to read and writeinformation on a disk.

disk I/O. Fixed–disk input and output.

Disk Operating System. See DOS.

disk–usage accounting. The record of thenumber of disk blocks occupied by a user’s files.Disk–usage accounting is performed by the acctdisk command.

diskette. A thin, flexible magnetic plate that ispermanently sealed in a protective cover. It can beused to store information copies from the disk oranother diskette.

diskette drive. The mechanism used to read andwrite information on diskettes.

diskless. A workstation without local file systemsor local boot images that accesses some of itsresources remotely. Diskless clients boot remotelyfrom a diskless server and use the server forremote paging.

Diskless Workstation Manager (DWM).Operating–system software that initializes andmaintains resources for diskless clients anddiskless servers. It is a group of commands, awkcommand scripts, and source code.

dispatch. To allocate processing time on a specificdevice for a job that is ready to run.

dispatch–function resolution. Dispatch–functionresolution is the slowest, but most flexible, of thethree method–resolution techniques SOM offers.Dispatch functions permit method resolution to bebased on arbitrary rules associated with an object’sclass. Thus, a class implementor has completefreedom in determining how methods invoked on

1-46 Glossary

its instances are resolved. See also dispatchmethod and dynamic dispatching.

dispatch method. In SOM, a method (such assomDispatch or somClassDispatch) that is invoked(and passed an argument list and the ID of anothermethod) in order to determine the appropriatemethod procedure to execute. The use of dispatchmethods facilitates dispatch–function resolution inSOM applications and enables method invocationon remote objects in DSOM applications. See alsoDynamic Invocation Interface, dynamic dispatching,and dispatch–function resolution.

dispatcher. In XOM, the software that implementsthe service interface functions using workspaceinterface functions.

displacement. (1.) A positive or negative numberthat can be added to the contents of a baseregister to calculate an effective address. (2.) Thedistance from the beginning of a record, block, orsegment to the beginning of a field.

display. (1.) A visual presentation of data. (2.) Topresent data visually. (3.) A computer outputscreen on which visual information is displayed.(4.) In Enhanced X-Windows, a set of one or morescreens and input devices that are driven by asingle X Server. Synonym for monitor.

display attribute. In XGSL, the following are someof the attributes associated with displays: (1.) APA(all points addressable) or character. An APAdisplay can address each pixel, while a characterdisplay addresses character–sized blocks of pixels,(2.) blink supported or not supported, (3.) color ormonochrome, and (4.) changeable color palette orfixed color palette.

display device. See display.

display list (object). In GL, also called an object.It is a sequence of drawing commands that havebeen compiled into a unit. Conceptually, a displaylist is like a macro: it can be invoked multiple timessimply by referring to its name. The object can beinstantiated at different locations, sizes, andorientations by appropriate use of thetransformation matrices. For instance, series ofpolygons arranged in the shape of a bolt can becompiled into an object. The bolt can then bedrawn multiple times by invoking its display list.

Display PostScript (DPS). Extension to X servercreated by Adobe.

display screen. The part of the display device thatdisplays information visually. Synonymous withterminal screen. See also screen.

display session. A 3270 Host ConnectionProgram 2.1 and 1.3.2 for AIX (HCON) mode of

operation during interaction with a host computerthat emulates a 3278/79 terminal display.

display station. An input/output device thatincludes a keyboard from which an operator cansend information to the system and a displayscreen on which an operator can see also theinformation sent to or received from the computer.

display symbol. A predefined printable graphicssymbol (such as, characters, numbers, mathsymbols, Greek letters, and so on) that can bedisplayed on a graphics display.

display symbol set. A set of display symbolsplaced in a table. There are up to 1024 displaysymbols. Display symbols 0 through 31 representcontrol functions and have no graphicrepresentation.

distinguished encoding. The restrictions to theBasic Encoding Rules designed to ensure a uniqueencoding of each ASN.1 value, defined in theX.500 Directory Standards (CCITT X.509).

distortion. In data communications, anundesirable change in a wave form that can occurbetween two points in a transmission system. Thesix major forms of distortion are bias, characteristic,delay, end, fortuitous, and harmonic.

distributed. The programs and computerizedsources of information that make up a computingenvironment can be physically located on differentcomputer systems, while still working together as asingle logical unit. Transaction processing systemsare easily moved to a distributed computingenvironment, because these systems traditionallyinvolve modifying a centralized source ofinformation by submitting modification orinformation requests from remote terminals.

Distributed Computing Environment (DCE). Acomputing environment in which the resources anddata may be located on different processors.

distributed file system. A file system composedof files or directories that physically reside on morethan one computer in a communications network.

distributed free space. Synonym for free space.

Distributed Function Terminal (DFT). Aworkstation that performs operations previouslyaccomplished by the processing unit, such asmanaging data links, controlling devices, andformatting data.

distributed transaction. A transaction which canupdate data in many user processes on manymachines.

distribution medium. The medium on which theoperating system software, a licensed program, or

1-47Glossary

an application program is distributed to the user.The distribution medium can be any of severaldifferent media supported by the hardware, such asstreaming cartridge tape, 9–track tape, or 3.5–inchdiskette.

dithering. In computer graphics, a technique ofinterleaving dark and light pixels so that theresulting image looks smoothly shaded whenviewed from a distance.

diversion. In text formatting, a command used tosave text for printing later in a document, such asfor footnotes.

DIX connector. A device that connects an Ethernetnetwork adapter to a standard (”thick”) Ethernetlocal area network (LAN). Its name is derived fromthe names of the principal developers of Ethernet(Digital Equipment Corporation, Intel, and Xerox).

DLC. See data link control protocol.

DLE. See data link escape character.

DLPI. Data Link Provider Interface.

DLS. Data link service.

DLS provider. In X.25 communications, the datalink layer protocol that provides the services of theData Link Provider Interface (DLPI).

DLS user. In X.25 communications, the user–levelapplication or user–level or kernel–level protocolthat accesses the services of the data link layer.

DLSAP (data–link–service access point). In X.25communications, a point at which a data linkservice (DLS) user attaches itself to a DLS providerto access data link services.

DLSAP address. In X.25 communications, anidentifier used to differentiate and locate specificDLS user access points to a DLS provider.

DM. See disconnected mode.

DMA. See direct memory access.

DMA slave. A device on the Micro Channel busthat uses the system–provided DMA facilitiesinstead of having a built–in controller. See also BusMaster.

DO loop. In FORTRAN, a range of statementscalled repetitively by a DO statement.

do statement. (1.) In C language, a loopingstatement that contains the keyword do followed bya statement (the action), the keyword while, andan expression in parentheses (the condition). (2.) Astatement used to group a number of statements ina procedure.

DO variable. In FORTRAN, a variable, specified ina DO statement, that is incremented or

decremented on each iteration of the relative DOloop and controls the number of iterations of theloop.

domain. (1.) That part of a network in which thedata processing resources are under commoncontrol. (2.) In a database, all the possible valuesof an attribute or a data element. (3.) In TCP/IP, thenaming system used in hierarchical networks. Thedomain naming system uses the DOMAIN protocoland the named daemon. In a domain system,groups of hosts are administered separately withina tree–structured hierarchy of domains andsubdomains.

domain name. A level in the hierarchy of namesused throughout the Internet.

DOS (Disk Operating System). A disk operatingsystem used on personal computers.

dot. A symbol (.) that indicates the currentdirectory in a relative path name.

dot dot. A symbol (..) in a relative path name thatindicates the parent directory.

dot matrix. A printer with wires or other means thatuses a matrix of dots for printing characters.

dotted decimal. A common notation for Internethost addresses that divides the 32–bit address intofour 8–bit fields. The value of each field is specifiedas a decimal number and the fields are separatedby periods (for example, 010.002.000.052 or10.2.0.52).

double buffer mode. In GL, a mode in which twobuffers are alternately displayed and updated. Anew image can be drawn into the back buffer whilethe front buffer (containing the previous image) isdisplayed. See also single buffer mode.

Double–Byte Character Set (DBCS). A set ofcharacters in which each character is representedin 2 bytes of storage. Languages such asJapanese, Chinese, and Korean, which containmore symbols than can be expressed in a singlebyte, are represented in this character set.

double–click. To click twice in rapid successionwithout moving the mouse pointer.

double precision. (1.) Pertaining to the use of twocomputer words to represent a number inaccordance with the required precision. (2.) Aspecification that causes a floating–point value tobe stored internally in the long format. See alsoprecision.

double–strike. A process of printing a charactertwice to create the appearance of bold type, usedfrequently with impact printers. A more flexible form

1-48 Glossary

of double–strike is emphasized printing. See alsoboldface and emphasized.

double–wide print. A print format in whichcharacters are twice as wide as they normally are.

download. To transfer data from one computer foruse on another one. Typically, users download froma larger computer to a diskette or fixed disk on asmaller computer or from a system unit to anadapter.

downstream. The direction from stream head todriver.

downward jump. For the bfs command, the act ofmoving from the current location in a file toward thebottom or end of the file.

DPS. See Display PostScript.

DR1I. Definite response 1 indicator.

DR2I. Definite response 2 indicator.

drag. To point to an object with the mouse pointer,hold down the mouse button, move the mouse, andthen release the mouse button. A method of”dragging” an object to a desired point.

DRAM. See dynamic random access memory.

drawable. In Enhanced X-Windows, a collectiveterm for both windows and pixmaps when used asdestinations in graphics operations. However, anInputOnly window cannot be used as a source ordestination drawable in a graphics operation.

drawn button. In AIXwindows, a graphic objectthat simulates a real–world button with a symbol orother image drawn on its face.

driver. The end of a stream closest to an externalinterface. The principal functions of the driver arehandling any associated device and transformingdata and information between the external deviceand stream. It can also be a pseudo–driver, notdirectly associated with a device, which performsfunctions internal to a stream, such as a multiplexeror log driver.

driving table. A table that describes all theprinter–specific information for the nroff command.

drop. In CDE, after starting the drag of an object,the act of releasing the mouse button. If the objectis dropped in an appropriate area, an action isinitiated.

drop–in. Some applications can detect that an iconhas been dropped on to their window to perform anappropriate action, such as opening a document.

drop target. In CDE, a rectangular graphic thatrepresents the drop zone in an application.

drop zone. In CDE, an area of the workspace,including the Trash Can, Print Manager, and MailerFront Panel controls, that accepts a dropped icon.Icons can be dropped on the workspace for quickaccess.

dropped folio. A page numbering style in whichthe page number is printed at the foot of the page.See also folio, blind folio, and expressed folio.

dropping locks. Releasing the locks that atransaction holds on data.

DSI. See data storage interrupt.

DSR. Data set ready; used with EIA–232 protocol.See your modem manual for more information.

DTE. See data terminal equipment.

DTR. See data terminal ready.

dummy argument. In FORTRAN, a variable withina subprogram or statement function definition withwhich actual arguments from the calling program orfunction reference are positionally associated. Seealso formal parameter.

dump. (1.) To copy the contents of all or part ofstorage onto another data medium or to an outputdevice. (2.) Data that has been dumped.

dump data. The data collected by the kernel dumpprogram. It is obtained from memory locationsused by kernel components.

dump table entry. A record in the master dumptable that identifies the location of a componentdump table. All kernel components that need tohave special data collected by the dump programneed to generate a dump table entry.

duplex. Pertains to communications data that canbe sent and received at the same time.Synonymous with full duplex and FDX. Contrastwith half duplex.

duplex connector. In a fiber channel linkenvironment, the component that terminates bothjumper cable fibers in one housing and providesphysical keying for attachment to a duplexreceptacle.

duplexed output. Output that uses both the frontand back of each sheet of paper for printing.

DWM. See Diskless Workstation Manager.

dyadic operator. Synonym for binary operator.

dynamic. A style of creating pop–up menus.

dynamic block header. A data structure used by acompiler to link dynamic variables that are in thesame heap.

1-49Glossary

dynamic connection. A connection that isestablished when needed rather than beingpredetermined or fixed.

dynamic dispatching. In SOM, methoddispatching using dispatch–function resolution; theuse of dynamic method resolution at run time. Seealso dispatch method, dispatch–function resolution,and dynamic method.

Dynamic Invocation Interface (DII). In SOM, theCORBA–specified interface, implemented inDSOM, that is used to dynamically build requestson remote objects. Note that DSOM applicationscan also use the somDispatch method for dynamicmethod calls when the object is remote. See alsodispatch method.

dynamic license. A license that specifies multiplenodelocked licenses. The license is installed at alicense server, and then the license server deriveslicense passwords (each of which specifies a singlenodelocked license) from the dynamic license. Theserver automatically installs the individual licensesat the user nodes from which the licensed productis invoked.

dynamic linking. Linking of a program in whichlibrary procedures are not incorporated into theload module but are dynamically loaded from theirlibrary each time the program is loaded.

dynamic method. A SOM method that is notdeclared in the IDL interface statement for a class

of objects, but is added to the interface at run time,after which instances of the class (or of itssubclasses) will respond to the registered dynamicmethod. Because dynamic methods are notdeclared, usage bindings for SOM classes cannotsupport their use; thus, offset method resolution isnot available. Instead, name–lookup ordispatch–function method resolution must be usedto invoke dynamic methods. (There are currentlyno known uses of dynamic methods by any SOMapplications.) See also dynamic dispatching,method, and static method.

dynamic random access memory. A storage inwhich the cells require repetitive application ofcontrol signals to retain stored data. Such repetitiveapplication of the control signals is normally calleda refresh operation.

dynamic routing. A method of setting pathsbetween hosts, networks, or both by usingdaemons that update the routing table as needed.

dynamic string. See string.

dynamic variable. A variable allocated only whenneeded. Explicit allocations and deallocations arerequired. In Pascal, the predefined proceduresNEW and DISPOSE are provided for this purpose.

dynamic window. A variable that can changedynamically within a certain window or range ofvalues.

1-50 Glossary

EEasy Install. An application used to install optionalsoftware or service updates in the form of softwarebundles.

EBCDIC. See extended binary–coded decimalinterchange code.

EBCDIC character. Any one of the symbolsincluded in the 8–bit EBCDIC set.

EC. Engineering Change level.

ECB. (1.) See event control bit. (2.) Event controlblock. (3.) Electronic codebook.

ECC. (1.) See error–checking and correction. (2.)Error correction code.

echo. (1.) A reflected signal on a communicationschannel. On a communications terminal, eachsignal is displayed twice, once when entered at thelocal terminal and again when returned over thecommunications link. This allows the signals to bechecked for accuracy. (2.) In computer graphics,the immediate notification of the current valuesprovided by an input device to the operator at thedisplay console. (3.) In word processing, to print ordisplay each character or line as it is typed in.

ECM. Entity coordination management.

ECMA. European Computer Manufacturers’Association.

edit. (1.) To add, change, delete, rearrange, ormodify the form or format of data. (2.) To check theaccuracy of information and to indicate if an error isfound.

edit buffer. A temporary storage area used by aneditor.

effective rate. The average sustained speed atwhich a device operates under real–worldconditions, when processing a representativeworkload.

effective root directory. The point where a systemstarts when searching for a file. Its path namebegins with a / (slash). The chroot subroutinecauses the directory named by the path parameterto become the effective root directory.

effective user ID. (1.) The user ID associated withthe last authenticated user or the last setuidprogram. Equal to either the real or the saved userID. (2.) The current user ID, but not necessarily theuser’s login ID. For example, a user logged inunder a login ID may change to another user’s ID.The ID to which the user changes becomes theeffective user ID until the user switches back to the

original login ID. All discretionary access decisionsare based on the effective user ID.

EGA. The Enhanced Graphics Adapter.

EGP. Exterior Gateway Protocol. The mechanismthat allows the exterior gateway of an autonomoussystem to share routing information with exteriorgateways on other autonomous systems.

EIA. Electronic Industries Association.

EIA–232D. An EIA interface standard that definesthe physical, electronic, and functionalcharacteristics of an interface line that connects acommunication device and associated workstation.It uses a 25–pin connector and an unbalanced linevoltage.

EIA–422A. An EIA interface standard that definesthe physical, electronic, and functionalcharacteristics of an interface line connecting acomputer to communications equipment. It uses abalanced line voltage for noise reduction andlonger distance capability. The system unit usesthe send and receive pins from the set of 40 pinsdefined by the EIA–422A interface.

elaborated type specifier. Typically used in C++in an incomplete class declaration or to qualifytypes that are otherwise hidden.

elaboration. In Ada language, the elaboration of adeclaration is the process by which the declarationachieves its effect (such as creating an object); thisprocess occurs during program execution.

electromagnetic compatibility. The design andtest of products to meet legal and corporatespecifications dealing with the emissions andsusceptibility to frequencies in the radio spectrum.Electromagnetic compatibility is the ability ofvarious electronic equipment to operate properly inthe intended electromagnetic environment.

electronic mail. Synonym for mail.

element. (1.) The smallest unit of data in a table orarray. (2.) In a set, an object, entity, or concepthaving the properties that define a set.Synonymous with member. (3.) In SNA, theparticular resource within a subarea that isidentified by an element address. (4.) Thecomponent of an array, subrange, enumeration, orset. (5.) In AIXwindows, an object or similar datastructure having the properties that define a class.

else clause. The part of an if statement thatcontains the keyword else followed by a statement.The else clause provides an action that is startedwhen the if condition evaluates to a value of 0(false).

1-51Glossary

em. In a specific type size, an em is the samenumber of points as there are to that specific size.See also en.

embedded blanks. Blanks that are surrounded byany other characters.

EMC. See electromagnetic compatibility.

emitter. In SOM, generically, a program that takesthe output from one system and converts theinformation into a different form. Using the EmitterFramework, selected output from the SOMCompiler (describing each syntactic unit in an IDLsource file) is transformed and formatted accordingto a user–defined template. Example emitteroutput, besides the implementation template andlanguage bindings, might include referencedocumentation, class browser descriptions, or”pretty” printouts.

emphasized. A form of double–strike printing inwhich characters are printed in multiple passes(usually two) with a slight offset, creating anartificial bold type. Emphasized printing is used tofill gaps and rough appearance in dot–matrixcharacter forms. It also prints a bold font withoutchanging the mounted character set. See alsoboldface and double–strike.

emulation. (1.) The use of programmingtechniques and special machine features to permita computing system to run programs written foranother system. (2.) Imitation. For example, whenone computer imitates the characteristics ofanother computer.

emulator. A program that causes a computer to actas a workstation attached to another system.

en. In the troff command, an en is half the size, inpoints, of an em. In the nroff command, an em andan en are identical size. See also em.

enable. (1.) To make functional. (2.) In interactivecommunications, to load and start a subsystem.Contrast with disable.

encapsulation. (1.) Hiding the internalrepresentation of data objects and implementationdetails of functions from the client program. Thisenables the end user to focus on the use of dataobjects and functions without having to know abouttheir representation or implementation. (2.) InSOM, an object–oriented programming featurewhereby the implementation details of a class arehidden from client programs, which are onlyrequired to know the interface of a class (thesignatures of its methods and the names of itsattributes) in order to use the class’s methods andattributes.

encoder/decoder. In the SOM PersistenceFramework, a class that knows how to read/write

the persistent object format of a persistent object.Every persistent object is associated with anEncoder/Decoder, and an encoder/decoder objectis created for each attribute and instance variable.An Encoder/Decoder is supplied by the PersistenceFramework by default, or an application can defineits own.

encrypt. To convert clear data into cipher text.

encryption key. A key generated by the makekeycommand to use with programs that performencryption. Its input and output are usually pipes.

end signal. In an online conference, a mutuallyagreed upon character that indicates the end of acomment by a participant. Common end signalsare o and oo.

endian. An attribute of data representation thatreflects how certain multi–octet data are stored inmemory. See also big endian and little endian.

end–to–end transit delay. In X.25communications, an optional CCITT–specifiedfacility.

enforced lock. A type of lock that a process holdson a region of a file preventing any other processfrom accessing that region with read or writesystem calls. In addition, the create command isprevented from truncating the files. See alsoadvisory lock.

enhanced graphics adapter (EGA). An adapter,such as the Enhanced Graphics Adapter, thatprovides high–resolution graphics, allowing the useof a color display for text processing as well asgraphics applications.

Enhanced X-Windows. A collection of basicfunctions for developing a variety of applicationenvironments. Toolkit functions manage Toolkitinitialization, widgets, memory, events, geometry,input focus, selections, resources, translation ofevents, graphics contexts, pixmaps, and errors.See also AIXwindows Environment.

enqueue. To place items in a queue. Contrast withdequeue.

enter. (1.) To send information to the computer bypressing the Enter key. (2.) To place a message onthe line to be transmitted from a terminal to thecomputer.

Enterprise Systems Connection. See ESCON.

entry. (1.) In FORTRAN, a language constructwithin a procedure, designating the start of theexecution sequences of the procedure. (2.) In Adalanguage, an entry is used for communicationbetween tasks. Externally, an entry is called just asa subprogram is called; its internal behavior isspecified by one or more accept statements

1-52 Glossary

specifying the actions to be performed when theentry is called. (3.) An element of information in atable, list, queue, or other organized structure ofdata or control information. (4.) A single inputoperation on a workstation.

entry class. In the SOM Emitter Framework, aclass that represents some syntactic unit of aninterface definition in the IDL source file.

entry point. (1.) An address or label of the firstinstruction performed upon entering a computerprogram, routine, or subroutine. A program mayhave several different entry points, eachcorresponding to a different function or purpose.(2.) In a routine, any place to which control can bepassed.

entry point vector (EPV). A record in which fieldsare pointers to procedures that implement theoperations defined by an interface.

entry sequence number (ESN). The numbercorresponding to the order in which the record wasentered into an entry–sequenced file. The primaryindex of an entry–sequenced file is based upon theESNs of its records. See also entry–sequenced file.

entry–sequenced file. A record–oriented file inwhich the records are stored in the order in whichthey were entered into the file. The primary indexof an entry–sequenced file is based on the entrysequence numbers (ESNs) corresponding to theorder of record insertion. Also referred to assequential file. See also entry sequence number.

enumerated scalar type. A scalar defined byenumerating the elements of the type. Eachelement is represented by an identifier.

enumeration constant. In C language, anidentifier (with an associated integer value) definedin an enumerator. You can use an enumerationconstant anywhere an integer constant is allowed.

enumeration data type. A type that representsintegers and a set of enumeration constants. Eachenumeration constant has an associated integervalue.

enumeration tag. The identifier that names anenumeration data type.

enumeration type. In Ada language, a discretetype whose values are represented by enumerationliterals which are given explicitly in the typedeclaration. These enumeration literals are eitheridentifiers or character literals.

enumerator. An enumeration constant and itsassociated value.

environment. (1.) The settings for shell variablesand paths set when the user logs in. Thesevariables can be modified later by the user. (2.) A

named collection of logical and physical resourcesused to support the performance of a function. (3.)In CDE Desktop, the set of rule files, resources,and message files that define the appearance andbehavior of a specific desktop configuration.

Environment parameter. In SOM, aCORBA–required parameter in all methodprocedures, it represents a memory location whereexception information can be returned by the objectof a method invocation. [Certain methods areexempt (when the class contains a modifier ofcallstyle=oidl), to maintain upward compatibility forclient programs written using an earlier release.]

environment variable. (1.) A variable thatdescribes the operating environment of theprocess. Common environment variables describethe home directory, command search path, theterminal in use, and the current time zone (theHOME, PATH, TERM, and TZ variables,respectively). (2.) A variable that is included in thecurrent software environment and is thereforeavailable to any called program that requests it.

EOF. End of file.

ephemeral application. An ephemeral applicationis one which does not contain any recoverabledata.

epoch. A timestamp that identifies directoryreplicas as being part of the same set.

EPOW. Emergency power off warning.

EPROM. Erasable programmable read–onlymemory.

EPV. See entry point vector or Entry Point Vector.

equivalence class. A grouping of characters orcharacter strings that are considered equal forpurposes of collation. For example, manylanguages place an uppercase character in thesame equivalence class as its lowercase form, butsome languages distinguish between accented andunaccented character forms for the purpose ofcollation.

erase. To remove text from a data medium, leavingthe medium available for recording new text. Seealso delete.

erase character. A character that indicates that theprevious character on the command line has beenerased.

error analysis facility. A program that providesinformation about the probable cause of errors.

error–checking and correction (ECC). In aprocessing unit, the detection and correction of allsingle–bit errors, plus the detection of double–bitand some multiple–bit errors.

1-53Glossary

error class. Identifies whether an error log entry isfor a hardware or software failure.

error condition. The state that results from anattempt to run instructions in a computer programthat are not valid or that operate on data that is notvalid.

error counter. A type of error entry generated bydevice driver components. Certain device driverscan generate retry operations if an operation is notsuccessful on the first attempt. They use countersto monitor the number and cause of retryoperations, and they contain algorithms that decidewhen these counters should be sent to the errorlog.

error device driver. A special file (psuedo device)driver used by the error logging facilities. Errorentries are written to the error device driver by theerrlog() subroutine and the errsave() kernelservice. Error entries are read from the error devicedriver by the error daemon process and saved inthe system error log file.

error ID. See error identifier.

error identifier (error ID). An 8–character codeused to identify a particular failure. There is aunique error identifier for each error recordtemplate.

error log. (1.) A data set or file in a product orsystem where error information is stored for lateraccess. (2.) A form in a maintenance library that isused to record error information about a product orsystem. (3.) A data set used in a processor torecord information about certain hardware andprogramming events. (4.) A record of machinechecks, device errors, and volume statistical data.

error log entry. A record in the system error logdescribing a hardware or software failure andcontaining failure data captured at the time of thefailure.

error message. An indication that an error hasbeen detected.

error output. Synonym for diagnostic output.

error record template. Describes the error class,error type, error description, probable causes,recommended actions, and failure data for an errorlog entry.

error type. Identifies whether an error log entry isfor a permanent failure, temporary failure,performance degradation, impending loss ofavailability, or undetermined failure.

ESC. See escape character.

escape character (ESC). (1.) In shellprogramming and TTY programming, the \(backslash) character, which indicates that the nextcharacter is not intended to have the specialmeaning normally assigned to it. (2.) In general, acharacter that suppresses or selects a specialmeaning for one or more characters that follow.

escape function. The code of the form ‘ESCSomething’. One type of multibyte control function.

escape sequence. (1.) A character that ispreceded by a \ (backslash) and is interpreted tohave a special meaning to the operating system.(2.) A sequence sent to a terminal to performactions such as moving the cursor, changing fromnormal to reverse video, and clearing the screen.The terminfo file defines these escape sequences.Synonymous with multibyte control. (3.)Multicharacter code specifying a string variable.See also unescaped.

ESCD console. The ESCD input/output deviceused to perform connectivity tasks at the ESCD.

ESCON (Enterprise Systems Connection). ASystem/390 I/O architecture that uses both laserand LED fiber–optic technology and the concept ofdynamic connectivity, which allows for pathsharing.

ESDI. Enhanced Small Device Interface.

ESN. See entry sequence number.

Ethernet. A 10–megabit baseband local areanetwork using CSMA/CD (carrier sense multipleaccess with collision detection). The network allowsmultiple stations to access the medium at willwithout prior coordination, avoids contention byusing carrier sense and deference, and resolvescontention by using collision detection andtransmission.

evaluation. In Ada language, the evaluation of anexpression is the process by which the value of theexpression is computed. This process occursduring program execution.

event. (1.) The enqueueing or dequeueing of anelement. (2.) An occurrence of significance to atask. (3.) In computer graphics, informationgenerated either asynchronously from a device oras the side–effect of a client request. Events aregrouped into types and are not sent to a client bythe server unless the client has issued a specificrequest for information of that type. Events areusually reported relative to a window. See alsocallback.

1-54 Glossary

event class. A number assigned to a group oftrace points that relate to a specific subject orsystem component. The defined event classes arelisted in the trace profile.

event control bit (ECB). A bit assigned to eachqueue to signal the arrival or departure of anelement.

event loop. A sequence of steps performedcyclically to accomplish a task. It must contain atleast one input (source) and an ending point.

event manager (EMan). The chief component ofthe SOM Event Management Framework thatregisters interest in various events from callingmodules and informs them through callbacks whenthose events occur.

event mask. In computer graphics, the set of eventtypes that a client requests relative to a window.

event queue. In computer graphics, a queue thatrecords changes in input devices––buttons,valuators, and the keyboard. The event queueprovides a time–ordered list of input events.

exception. (1.) In programming languages, anabnormal situation that may arise during therunning of a program, perhaps causing a deviationfrom the normal run sequence, and for whichhandling facilities exist. (2.) An abnormal conditionsuch as an I/O error encountered in processing adata set or a file. (3.) One of five types of errorsthat can occur during a floating–point exception.These are an operation that was not valid,overflow, underflow, division by zero, and inexactresults. (4.) In C++ language, any user, logic, orsystem error detected by a function that does notitself deal with the error but passes the error on toa handling routine. Passing this error is calledthrowing an exception. (5.) In Ada language, anerror situation which may arise during programexecution. To raise an exception is to abandonnormal program execution so as to signal that theerror has taken place. An exception handler is aportion of program text specifying a response tothe exception. Execution of such a program text iscalled handling the exception. Contrast withinterrupt and signal. See also handler and traphandler.

exception handler. (1.) A set of routines used todetect deadlock conditions or to process abnormalcondition processing. An exception handler allowsthe normal running of processes to be interruptedand resumed. (2.) Exception handlers are catchblocks in C++. catch blocks catch exceptions whenthey are thrown from a function enclosed in a tryblock. try blocks, catch blocks and throwexpressions are the constructs used to implementformal exception handling in C++.

exception handling. A type of error handling thatallows control and information to be passed to anexception handler when an exception occurs. tryblocks, catch blocks, and throw expressions arethe constructs used to implement formal exceptionhandling in C++.

exchange identification (XID). The ID that isexchanged with the remote physical unit when anattachment is first established.

exchange identification (XID) frame. In a logicallink control (LLC) header, the frame that conveysthe characteristics of the sending host.

exclusive lock. A type of lock in which only thetransaction holding the lock can access the data inany way. See also shared locks.

exec. To overlay the current process with anotherexecutable program. See also fork.

EXEC. Remote Command Execution Protocol.

executable. A file that can be loaded into memoryand executed as a program. An executable isproduced by the binder (ld) from one or moreobject (.o) files. The default processing ofcompilation commands includes invoking thebinder to produce an executable whose name isa.out.

executable file. A file that contains programs orcommands that perform operations on actions tobe taken.

executable program. A program that can be runas a self–contained procedure. It consists of a mainprogram and, optionally, one or more subprograms.

executable statement. A statement that causesan action to be taken by the program. For example,to calculate, to test conditions, or to alter normalsequential execution.

execute. In CDE, a file or folder (directory) accesspermission. For files, execute permission enablesthe user to run a program or shell script file. Forfolders (directories), execute permission enablesthe user to access the folder (directory) contents.

existing file. A file that has been defined and thatresides on a storage medium.

Exit button. In CDE, a Front Panel control used tolog out of the desktop.

exit value. (1.) A code sent to either standardoutput or standard error on completion of thecommand. (2.) A numeric value that a commandreturns to indicate whether it completedsuccessfully. Some commands return exit valuesthat give other information such as whether a fileexists. Shell programs can test exit values tocontrol branching and looping.

1-55Glossary

expanded name. In Ada language, a name thatdenotes an entity which is declared immediatelywithin some construct. An expanded name has theform of a selected component: the prefix denotesthe construct (a program unit; or a block, loop, oraccept statement); the selector is the simple nameof the entity.

expect–send sequence. In remotecommunications, a list of characters or signals aprogram or modem should expect to receive from aremote system, followed by the characters orsignals the program or modem should send to theremote system after it receives the expected input.The sequence can also include a subsequence thattells the program or modem what to send if it doesnot receive the expected input. See alsohandshaking and chat script.

expedited data negotiation. In X.25communications, an optional CCITT–specifiedfacility.

expedited data transfer. In X.25 communications,an optional CCITT–specified facility.

expletive. An unnecessary be–verb phrase suchas ”It is” or ”there is” used to begin a sentence orpart of a sentence.

explicit binding. A form of binding that gives theclient application control over what servermachines are involved.

explicit shell. Any of a class of shells createdmanually by the developer through the Createmenu’s Shells submenu.

exponent. A number indicating the power to whichanother number (the base) is to be raised.

exponentiation. The operation in which a value israised to a power.

export. (1.) In NCS, to provide the operationsdefined by an interface. A server exports aninterface to a client. Contrast with import. (2.) Tocopy data onto removable media.

exposure event. In Enhanced X-Windows, anevent sent to clients to inform them when contentshave been lost, as when windows are obscured orreconfigured. Servers do not guarantee thepreservation of window contents when they areobscured or reconfigured.

expressed folio. A page numbering style in whicheach page (possibly excluding the first page) isnumbered. See also folio, blind folio, and droppedfolio.

expression. (1.) A representation of a value. Forexample, variables and constants appearing aloneor in combination with operators. (2.) Inprogramming languages, a language construct for

computing a value from one or more operands,such as literals, identifiers, array references, andfunction calls. In Ada language, an expressiondefines the computation of a value. (3.) Aconfiguration of signs.

expression statement. In C language, anexpression that ends with a ; (semicolon). You canuse an expression statement to assign the value ofan expression to a variable or to call a function.

extended address. Synonym for addressextension.

extended binary–coded decimal interchangecode (EBCDIC). A code developed for therepresentation of textual data. EBCDIC consists ofa set of 256 eight–bit characters.

extended character. A character other than a7–bit ASCII character. An extended character canbe a 1–byte code point with the eighth bit set(ordinal 128 through 255). See also code page andcode point.

extended common object file format (XCOFF).The object file format for Version 3 of the operatingsystem. XCOFF combines the standard commonobject file format (COFF) with the TOC moduleformat concept, which provides for dynamic linkingand replacement of units within an object file.

extended curses. A system library(thelibcurses.c library) that contains the controlfunctions for writing data to and getting data fromthe terminal screen. It supports color, multiplewindows, and an enhanced character set.

extended family. The set of all of anAda–language compilation unit’s supporters and allof their families, including the associated bodiesand subunits. The supporters of a unit include onlythe library units required for its compilation, not theassociated bodies or subunits.

extended font. (1.) A font in which the charactersare wider than its corresponding normal font. (2.) Acollection of font sections to support languagesrequiring more than 256 graphic characters at onetime.

extended interface. Provides a set of full–functionsystem calls (the readx and writex system calls) tocommunicate with SNA Services. These callscontain an extra parameter on the call (a pointer tothe structure containing extra function requests).See also interface and limited interface.

extended permission. An access mode thatmodifies the base permissions to a file for specifiedindividuals or groups. An extended permission candeny or permit an access mode. See alsodiscretionary access control.

1-56 Glossary

extended precision constant. A processorapproximation to the value of a real number thatoccupies 16 consecutive bytes of storage and canassume a positive, negative, or zero value. Theprecision is greater that of type double precision.

extended result. An exception notification that hasdata defined in the result_ext field of thedlc_getx_arg structure.

extended selection. In CDE, to add multiple itemsto a selected set by augmenting the selectiontechnique. For example, you can add to a selectionby moving the pointer to a new item and pressingControl and the SELECT mouse buttonsimultaneously.

Extended Services. A group of optionally installedoperating system functions and programs.

extension. In Enhanced X-Windows, to extend thesystem, the named extensions can be defined forthe Core protocol, including extensions to outputrequests, resources, and event types.

extent. (1.) A continuous space on disk or diskettethat is occupied by or reserved for a particular dataset, data space, or file.

exterior gateway. A gateway on one autonomoussystem that communicates with other autonomoussystem.

external clocking. In data communications, theability of a modem to provide data clocking.

external data definition. A description of avariable appearing outside a function. It causes thesystem to allocate storage for that variable andmakes that variable accessible to all functions thatfollow the definition and are located in the same fileas the definition.

eXternal Data Representation (XDR). A standardfor the description and encoding of data; it uses alanguages to describe data formats, but thelanguage is used only for describing data and is nota programming language. Protocols such as RPCand NFS use XDR to describe their data formats.

external function. In FORTRAN, synonymous withexternal routine.

external modem. A modem that is separate fromthe unit with which it operates.

external name. (1.) A name that can be referred toby any control section or separately assembled orcompiled module; a control section name or anentry name in another module. (2.) In a program, aname whose scope is not necessarily confined toone block and its contained blocks.

external procedure. Synonymous with externalroutine.

external reference. A reference to a symboldefined as an external name in another program ormodule.

external routine. A procedure or function calledfrom outside the program in which the routine isdefined. Synonymous with external procedure.

external symbol. A symbol that is defined in a fileother than the file in which the symbol occurs. Anordinary symbol that represents an externalreference.

external variable. A variable accessible to anothercompilation unit. See also compilation unit.

extract. To obtain. For example, to extractinformation from a file.

eye coordinates. In GL, the coordinate system inwhich the viewer’s eye is located at the origin, andthus all distances are measured with respect to theeye. Viewing transformations map from worldcoordinates into eye coordinates, and projectiontransformations map from eye coordinates tonormalized device coordinates. Synonym for eyespace, viewing coordinates, and viewercoordinates. See also modeling coordinates,primitive coordinates, world coordinates, screencoordinates, and transformation.

eye space. Synonym for eye coordinates.

1-57Glossary

FF. Fahrenheit.

facilities. See optional facilities.

facilities extension. In the X.25 API, an extensionto the optional facilities field in a packet that allowsfurther, non–CCITT–specified, optional facilityinformation to be added.

factorization. An arithmetic transformation inwhich common factors are removed fromsubexpressions within an expression, and thenmultiplied by the resulting expression.

factory method. See class method.

fake target name. A control name used in amakefile file that looks like a target name, butactually tells the make command to perform someoperation differently.

family. An Ada–language library unit together withits body and subunits (if any). Not all potentialfamily members need be present; a library unit mayhave a missing optional body, and a main programprocedure may have only an implicit specification.The family of a secondary unit is that unit togetherwith any subunits.

fast select. In X.25 communications, an optionalfacility that allows inclusion of data in call–requestand clear–request packets. See also optionalfacilities.

FCC. Federal Communications Commission.

FCFS. See first–come–first–served.

FD. Full duplex. See duplex.

FDDI. Fiber–optic Distributed Data Interface. A100–Mbit/sec optical LAN interface. An ANSIstandard for a high–speed, 100–Mbit/sec,general–purpose network for the interconnection ofcomputers, networks, and peripheral equipmentusing optical fiber cable in a dual–ringconfiguration. FDDI can connect as many as 500stations with a maximum link–to–link distance of 2kilometers and a total LAN circumference of 100kilometers.

FDX. Full duplex. See duplex.

feature. A programming or hardware option,usually available at an extra cost.

fiber optics. The branch of optical technologyconcerned with the transmission of radiant powerthrough fibers made of transparent materials suchas glass, fused silica, and plastic.

field. (1.) An area in a record or panel used tocontain a particular category of data. (2.) The

smallest identifiable component of a record. Anindividually addressable subdivision of a recordcontaining a specific portion of the data in therecord. For example, a record of data about anemployee might be subdivided into fieldscontaining the employee’s name, identificationnumber, and salary. (3.) An area in a presentationspace into which the program accepts input. (4.) Inthe INed editor, an area in a structured file definedin the form used to enter and display data. Fieldsare defined using either text data paths or tree datapaths. (5.) In video, a field is one–half of a frame.Fields are drawn 60 times per second. See alsostructured field.

field of view. In GL, the extent of the area which isunder view. The field of view is defined by theviewing matrix in use.

field return. The action that moves a data cursorfrom field to field in a reverse direction, asdetermined by the panel layout.

FIFO. See first–in–first–out.

file. (1.) A collection of related data that is storedand retrieved by an assigned name. Contrast withspecial file. (2.) A sequence of records. If the file islocated in internal storage, it is an internal file; if itis on an input/output device, it is an external file.(3.) A collection of related information stored in asingle location for organizational purposes andprocessed as a unit. See also filename.

file descriptor. A small positive integer that thesystem uses instead of the file name to identify anopen file. See also shared memory ID (shmid).

file format. A description of the entries to be madein an ASCII file, such as a configuration orcustomization profile.

file index. 64 bytes of information describing a file.The file index contains the type and size of the fileand the location of the file data on the physicaldevice. This index is the same as the operatingsystem i–node. Synonym for i–node.

file manager. A program that manipulates files ordirectories.

file memory. Virtual–memory pages that arecurrently in real memory that are not part ofcomputational memory. Normally these are pagesof nonexecutable files.

file mode creation mask. See mask.

file name. (1.) A name assigned or declared for afile. (2.) The name used by a program to identify afile. See also label.

file name substitution. The process in which theshell recognizing a word (character string) that

1-58 Glossary

contains any of the *, ?, [, or { characters, or beginswith the ~ character, and replaces it with analphabetically sorted list of file names that matchthe pattern of the word. Synonymous with globbing.

file owner. The user who has the highest level ofaccess authority to a file, as defined by the file.

file pointer. An identifier that indicates a structurecontaining the file name.

file scope. A C++ name declared outside all blocksand classes has file scope and can be used afterthe point of declaration in a source file.

file server. In CDE, a host computer that storesdata files used by applications.

file spec. See file specification.

file specification (filespec). The name andlocation of a file. A file specification consists of adrive specifier, a path name, and a file name.

file suffix. In CDE, a suffix added to the end of afile name, often used in file typing or to categorizefiles for the user.

file system. The collection of files and filemanagement structures on a physical or logicalmass storage device, such as a diskette orminidisk.

file transfer. In remote communications, thetransfer of a file or files from one system to anotherover a communications link.

File Transfer Protocol (FTP). In TCP/IP, theprotocol that makes it possible to transfer dataamong hosts and to use foreign hosts indirectly.

file tree. The complete directory and file structureof a particular node, starting at the root directory. Afile tree contains all local and remote mountsperformed on directories and files.

file type. In the operating system, one of the fivepossible types of files: ordinary file, directory, blockdevice, character device, andfirst–in–first–out(FIFO or named pipe).

filename. In DOS, that portion of the file name thatprecedes the extension. See also file.

fileset. (1.) An individually installable option orupdate. Options provide specific function andupdates correct an error in, or enhance, apreviously installed option. (2.) One or moreseparately installable, logically grouped units in aninstallation package.

filetab. A kernel parameter establishing themaximum number of files that can be opensimultaneously.

fill characters. (1.) Characters used to fill fields instorage. (2.) Visual representations of enterable

character positions on the display (for example,dots in each position or vertical bars betweenpositions).

filter. (1.) A command that reads standard inputdata, modifies the data, and sends it to the displayscreen. (2.) A device or program that separatesdata, signals, or materials in accordance withspecified criteria.

filter primitive. A program that separates data inaccordance with specified criteria.

fine clipping. In GL, fine clipping masks alldrawing commands to a rectangular region of thescreen. It would be unnecessary except for thecase of character strings. The origin of a characterstring after transformation may be clipped out bygross, or 3–D, clipping, and the string would not bedrawn. By doing gross clipping with the viewportand fine clipping with the screen masks, strings canbe moved smoothly off the screen to the left orbottom. See also clipping and gross clipping.

FINGER. Name/Finger Protocol. Anapplication–level Internet protocol that provides aninterface between finger command and thefingered daemon.

firewall. A system or machine that controls theaccess between outside networks and privatenetworks.

first–come–first–served (FCFS). In general, aqueuing technique in which the next item to beretrieved is the item that has been in the queue forthe longest time. Synonym for first–in–first–out.Contrast with shortest–job–next. See alsodiscipline.

first–in–first–out (FIFO). In the operating system,a named permanent pipe. A FIFO allows twounrelated processes to exchange informationthrough a pipe connection. Synonym forfirst–come–first–served.

first–level interrupt handler (FLIH). A routine thatreceives control of the system as a result of ahardware interrupt. One FLIH is assigned to eachof the six interrupt levels.

fix number. The fix level of a program, which is anindicator of small updates that are to be built into aregular modification or release at a later time. Theversion, release, modification, and fix levelstogether comprise the program level or version of aprogram. See also program level, modificationnumber, release number, version, and versionnumber.

fixed box. (1.) A geometry managementtechnique. (2.) A type of bounding box that has afixed number of children created by the parent.

1-59Glossary

These managed children do not make geometrymanager requests.

fixed disk. (1.) A flat, circular, nonremovable platewith a magnetizable surface layer on which datacan be stored by magnetic recording. A rigidmagnetic disk used in a fixed–disk drive.(2.) Theterm fixed disk is also used loosely in the industryfor boards and cartridges containing microchips orbubble memory that simulate the operations of afixed–disk drive.

fixed–disk drive. The mechanism used to readand write information on a fixed disk.

fixed icon. An icon that is fixed on the desktop.Fixed icons are ordinarily used for files that arenecessary to use AIX Common DesktopEnvironment and therefore always appear on thedesktop, such as the Home directory.

fixed part (of a record). In Pascal, the part of arecord that is common to all instances of aparticular record type.

fixed point type. See real type.

fixed storage space. Any storage device definedduring system configuration to be an integral partof system DASD. If a fixed storage device is notavailable at some time during normal operation, theoperating system detects an error.

flag. (1.) A modifier that appears on a commandline with the command name that defines the actionof the command. A dash usually precedes a flag.(2.) An indicator or parameter that shows thesetting of a switch. (3.) A character that signals theoccurrence of some condition, such as the end of aword. (4.) An internal indicator that describes acondition to the processing unit. In the processingunit of the PC AT, flags indicate if the result of anoperation is zero, if interrupts are enabled, andother conditions. Synonymous with condition code.

flat file. (1.) A file that has no hierarchicalstructure. (2.) A one–dimensional ortwo–dimensional array. A list or table of items.

flat network. A network in which all hosts areadministered by one central authority.

flattened character. An ASCII character createdby translating an extended character to the ASCIIcharacter most like it. The code point information islost and the character cannot be retranslated to anextended character. For example, a cedillacharacter would be flattened to a plain ”c.”

FLIH. See first–level interrupt handler.

float constant. A number containing a decimalpoint, an exponent, or both a decimal point and anexponent. The exponent contains an ”e” or ”E,” an

optional sign (+ or –), and one or more digits (0through 9).

floating display. In text formatting, a block of textthat the nroff command keeps on one page.However, if there is no room for a floating displayon the current page, the nroff command sets asidethe display and finishes filling the page with the textfrom the input file that follows the display. When thepage is full, the nroff command places the displayat the top of the next page and then continues withthe text from the previous page. See also staticdisplay.

floating keep. A keep ensures that bracketed textis not broken across a page boundary, bycomparing the size of the text block against thespace remaining on the page. If it does not fit, theblock is printed at the first possible opportunity onthe following page. A fixed keep leaves theremainder of the page blank and a floating keepmoves subsequent text onto that page.

floating license. See concurrent–use license.

floating point. A way of representing real numbers(that is, values with fractions or decimals) in 32 bitsor 64 bits. Floating–point representation is useful todescribe very small or very large numbers.

floating–point constant. A constantrepresentation of a floating–point numberexpressed as an optional sign followed by one ormore digits and including a decimal point. See alsofloating–point number.

floating–point exception. See exception.

floating–point number. A real numberrepresented by a pair of distinct numerals. The realnumber is the product of the fractional part, one ofthe numerals, and a value obtained by raising theimplicit floating–point base to a power indicated bythe second numeral. See also floating–pointconstant.

floating point type. See real type.

flow control. In X.25 communications, theprocedure for controlling the data transfer rate.

flow diagram. Deprecated term for flow chart.

flyback. A movement similar to a reversing linefeed.

FM. See frequency modulation.

FM Header. Function Management Header.

focus window. Synonym for input focus.

fold. (1.) To compact data by combining parts ofthe data; for example, to transform a two–wordnumeric key by adding the numeric equivalents of

1-60 Glossary

the letters. (2.) To translate the lowercasecharacters of a character string into uppercase.See also constant folding. (3.) To place on the nextline a portion of a line that does not fit on the line.Contrast with truncate.

folder. (1.) In Message Handler, a directory ofmessages. (2.) In CDE, an icon that represents adirectory.

folio. A page numbering format that places thepage number at the outside of the running head atthe top of the page. See also blind folio, droppedfolio, and expressed folio.

font. (1.) A set of characters in a particular style.See also raster font and primitive font. (2.) InEnhanced X-Windows, a set of glyphs, usuallycharacters. The protocol does not translate orinterpret character sets. The client indicates valuesused to access the glyph arrays. A font containsadditional metric information to determineinter–glyph and inter–line spacing. (3.) A completeset of graphic characters of the same size, style,and typeface. For example, a Times 12 point font isdifferent in size from a Times 24 point font, differentin style from a Helvetica 12 point font, and differentin typeface from a Times 12 point boldface font.

font ascent. Height of a character in a specifiedfont.

font list. In AIXwindows, a list of available fontsspecified by the fontlist parameter. Also, the list offonts to be used in formatting a source document.See also font table.

font structure. A data structure that contains allthe information necessary to create a font set.

font table. A list of all fonts that have been loadedinto the system. See also font list.

font unit. Any group of characters regarded as awhole, especially for the determination of values,variables, and other data pertaining to fontcharacteristics.

footer. Text that appears at the bottom of everypage of a document, for example, a page number.

footnote. A note of reference, explanation, orcomment placed below the text of a column orpage, but within the body of the page above thefooter.

footnote text. The text within the footnote.

for statement. In programming languages, astatement that executes one or more statementsfor each of a set of values assigned to one or morevariables.

foreground. (1.) A mode of running a program inwhich the shell waits for the program specified on

the command line to complete before respondingto user input. (2.) In multiprogramming, theenvironment in which high–priority programs arerun. Contrast with background.

foreground color. A single color assigned to all ofthe graphic elements that appear in front of all thebackground graphic elements within a displayedimage. Contrast with background color.

foreground process. A process that must run tocompletion before another command is issued tothe shell. The foreground process is in theforeground process group, which is the group thatreceives the signals generated by a terminal.Contrast with background process.

foreign cell.A cell other than the one to which thelocal machine belongs. See also local cell.

foreign host. Synonym for remote host.

fork. To create and start a child process. See alsoexec.

form. A predefined INed structured file withspecially defined fields that allow you to view andedit special types of data.

formal parameter. A parameter declared in aroutine heading. It specifies what can be passed toa routine as an actual parameter. See alsoconformant string and dummy argument. For Adaprogramming, see also parameter. Contrast withactual parameter.

format. (1.) A defined arrangement of such thingsas characters, fields, and lines, usually used fordisplays, printouts, or files. (2.) The pattern thatdetermines how data is recorded. (3.) To arrangesuch things as characters, fields, and lines. (4.) Inprogramming languages, a language construct thatspecifies the representation, in character form, ofdata objects in a file. See also formatted data.

formatted data. Data that is transferred betweenmain storage and an input/output device accordingto a specified format. See also list–directed dataand format.

formatted diskette. A diskette on which track andcontrol information for a particular computersystem has been written but that may or may notcontain any data.

formatter. (1.) A computer program that preparesa source document for printing. (2.) The part of atext processor that formats input lines for printingor display on a particular type of device.

FORTRAN (FORmula TRANslation). A high–levelprogramming language used primarily for scientific,engineering, and mathematical applications.

1-61Glossary

forward difference matrix. In GL, 4x4matrix thatis iterated by adding each row to the next and thebottom row is output as the next point. Points sogenerated generally fall on a rational cubic curve.

FP. See FPU.

FPU (FP). Floating–point unit.

fragment. A unit of disk storage that is smaller thata (4KB) page.

frame. (1.) In a high–level data link control (HDLC),the sequence of contiguous bits bracketed by andincluding opening and closing flag (01111110)sequences. (2.) A set of consecutive digit time slotsin which the position of each digit time slot can beidentified by reference to a frame alignment signal.(3.) In an interlaced video monitor, a frame consistsof two fields, called ”even” and ”odd”, each of whichis one sixtieth of a second in duration. (4.) Inblock–multiplexer–channel–adapter and ESCONtransmissions, the block of data that is transferredbetween the S/370 and the workstation in oneCCW. (5.) A block of information corresponding tothe FDDI protocol which is transmitted between twoor more stations on a ring. An FDDI frame is similarto a packet.

frame buffer. A quantity of video RAM (VRAM)that is used to store the image displayed on themonitor. The frame buffer is the electronic canvason which every drawing primitive is drawn. It is oneof the last stops in the graphics pipeline, where thefinal image resides in the form of digitally codedintensities and brightnesses. These are convertedinto analog voltage signals 60 times a second andsent to the electron guns of the monitor. Thedimensions of the frame buffer can be changedwith GL. Typically, the main frame buffer might be1024 pixels vertical by 1280 pixels horizontal by 8color bits. The overlay planes might by1024x1280x2. The z–buffer is considered a framebuffer, although it is not directly visible from themonitor. (There is no direct means of displaying thecontents of the z–buffer, although this can be doneindirectly.) The size of the z–buffer is typically1024x1280x24. The cursor is a very specializedform of a frame buffer; one which can movearound. The typical cursor is 32x32x2 in size. Seealso raster.

frame burst. A group of transmitter receive framesthat are contiguous on the media.

frame level. In X.25 communications, the levelbetween the physical level and the packet level,which works according to the high–level data linkcontrol procedure (HDLC). Synonymous withdata–link level and level 2. See also level, packetlevel, and physical level.

frame–level interface. In X.25 communications,the level of the DTE/DCE interface in packet modeoperation relating to the exchange of packets withlocal error control, where packets are contained inframes. See also packet–level interface.

frame window. In X.25 communications, thenumber of frames that can be outstanding withoutacknowledgment. See also packet window andwindow.

framing error. An asynchronous transmission errorusually caused by the number of bits per characternot being set the same on the sending andreceiving workstations.

free list. A list of available blocks on each filesystem.

free–block list. See free list.

free space. Space reserved within the controlintervals of a key–sequenced data set or file, usedfor inserting new records into the data set or file inkey sequence; also, whole control intervalsreserved in a control area for the same purpose.Synonym for distributed free space.

frequency modulation (FM). Modifying thefrequency of a fixed amplitude carrier signal inaccordance with an informational signal so that itcan carry data signals.

friend class. A C++ class in which all the memberfunctions are granted access to the private andprotected members of another class. It is named inthe declaration of another class and uses thekeyword friend as a prefix to the class. Forexample, class me { on one line followed by friend class you; on the next and then //... and ending with }; makes all thefunctions in class you friends of class me .

friend function. A C++ function that is grantedaccess to the private and protected parts of aclass. It is named in the declaration of the classand uses the keyword friend as a prefix.

front and back buffers. In GL, in double buffermode, the main frame buffer bit planes areseparated into two sets––the front and backbuffers. Bits in the front buffer planes are visibleand those in the back buffer are not. Typically, anapplication draws into the back buffer and viewsthe front buffer for dynamic graphics.

Front Panel. In CDE, a centrally located windowcontaining controls for accessing applications andutilities, including the workspace switch. The FrontPanel occupies all workspaces.

Front Panel control. In CDE, an object in theFront Panel used as an interface to basic system

1-62 Glossary

services and frequently performed tasks andoperations. Controls in the default Front Panel are:Clock, Calendar, Mailer, Text Editor, Help Viewer,File Manager, Printer, Style Manager, ApplicationManager, and Trash Can. See also control.

Front Panel move handles. In CDE, an area oneach end of the Front Panel used for moving theFront Panel and for bringing it to the front of theworkspace.

frustum. In GL, a truncated, four–sided pyramid;that is, a pyramid with the point cut off. In aperspective projection, the shape of the clippingvolume is a frustum. The bottom of the frustum isreferred to the far clipping plane, the top of thefrustum is the near clipping plane, and the sidesare respectively the top, left, bottom, and rightclipping planes. In an orthographic projection, theclipping volume is a parallelepiped. See alsoclipping panes.

FTP. File Transfer Program. See also File TransferProtocol.

full backup. Backup copies of all the files on thesystem. Contrast with incremental backup.

full duplex (FDX). Synonym for duplex.

full high. Pertains to a storage device that has theoriginal height (82.5 mm or 3.25 inches), width(146 mm or 5.75 inches), and length (203 mm or8.0 inches). See also half high.

full path name. The name of any directory or fileexpressed as a string of directories and filesbeginning with the root directory. See also fullyqualified name, path name, and relative pathname.

full–screen editor. An editor that displays anentire screen at a time and that allows data to beaccessed and modified only by moving the cursorand entering commands.

fullword. Synonym for word.

fully qualified host name. A complete qualifiedname. Includes all names in the hierarchicalsequence above the structure member to which thename refers, as well as the member itself.

fully qualified name. A qualified name thatincludes all names in the hierarchical sequenceabove the structure member to which the namerefers, as well as the name of the member itself.See also full path name.

function. (1.) A specific purpose of an entity, or itscharacteristic action. (2.) A machine action such as

carriage return or line feed. (3.) A subroutine thatreturns the value of a single variable and thatusually has a single exit, such as subroutines thatcompute mathematical functions. Synonymous withprocedure. For Ada programming, see alsosubprogram.

function call. An expression that moves the pathof execution from the current function to a specifiedfunction and evaluates to the return value providedby the called function. A function call contains thename of the function to which control moves and aparenthesized list of values.

function declarator. The part of a functiondefinition that names the function, providesadditional information about the return value of thefunction, and lists the function parameters.

function definition. The complete description of afunction. A function definition contains an optionalstorage class specifier, an optional type specifier, afunction declarator, optional parameterdeclarations, and a block statement (the functionbody).

function keys. Keys that request actions but donot display or print characters. This includes thekeys that normally produce a printed character, butproduce a function instead when used with thecode key. See also character key.

function pointer. An identifier that gives thelocation of a function or procedure.

function reference. The appearance of an intrinsicfunction name or a user function name in anexpression.

function scope. C++ labels that are declared in afunction have function scope and can be usedanywhere in that function.

function subprogram. See function.

function template. Provides a blueprint describinghow a set of related individual C++ functions canbe constructed.

functional equivalence. A situation in whichdifferent algorithms for a given problem domainyield identical results.

funnelling. Forcing device drivers and kernelextensions that are not known to be MP safe to runonly on the master processor.

FX. See FXU.

FXU (FX). Fixed–point unit.

1-63Glossary

Ggadget. In AIXwindows, a windowless graphicalobject that looks like its equivalent like–namedwidget but does not support the translations,actions, or Popup widget children supplied by thatwidget.

gadget ID. In AIXwindows, a unique identificationnumber assigned to each instance of a gadgetused within a given graphical interface.

gamma correction. In GL, a logarithmicassignment of intensities to lookup table entries forshading applications. This is required since thehuman eye perceives intensities logarithmicallyrather than linearly. See also gamma ramp.

gamma ramp. In GL, a set of three lookup tables,one for each of the colors red, green, and blue,attached to the electron guns of the monitor.Entries in the gamma lookup table can be set toadjust for variations in the phosphor qualitybetween different brands of monitors. Usually, alogarithmic curve is loaded into the gamma lookuptables. See also gamma correction. The gammalookup tables are not a subset of the color maptables, but a separate entity.

gateway. (1.) An entity that operates above the linklayer and translates, when required, the interfaceand protocol used by one network into those usedby another distinct network. (2.) The network thatconnects hosts. See also active gateway. (3.) Adevice and its associated software thatinterconnect networks or systems of differentarchitectures. The connection is usually madeabove the reference model network layer. Forexample, a gateway allows LANs access toSystem/390 host computers. Contrast with bridge.

gateway host. A host that connects independentnetworks. It has multiple interfaces, each with adifferent name and address.

Gateway–to–Gateway Protocol (GGP). Theprotocol with which a gateway determinesconnectivity to networks and neighbor gatewaysand implements the shortest–path routingalgorithm.

gather. For input/output operations, to read datafrom noncontiguous memory locations to write to adevice. Contrast with scatter.

GB. See gigabyte.

GC. See graphics context.

GC caching. In Enhanced X-Windows, allowsindependent change requests to be merged intoone protocol request.

GContext. See graphics context.

GCP. Graphics Control Processor.

GCR. Group Code Recording, a magnetic taperecording format with a density of 6250 bpi.

GDA. Global Directory Agent.

GDLC. See generic data link control.

general purpose register (GPR). An explicitlyaddressable register that can be used for a varietyof purposes (for example, as an accumulator or anindex register). See also register.

generation. (1.) A means of referencing items interms of time and ancestry so that an item withoutantecedents is designated as the first (n–th)generation and subsequent derivations aredesignated as n–1, n–2, and so on. (2.) For someremote systems, the translation of configurationinto machine language.

generation number. A number used todifferentiate between the uses of the same inodefor several files or for different versions of the samefile. When a file is created, an inode is allocated forthe file, and a new generation number is stored inthe inode for that file. Any use of an inode with thewrong generation number indicates that the user’sview of the file is out–of–date, or ”stale.”

generation phase. The part of the sort programthat translates the sequence specifications intomachine language.

generic data link control (GDCL). A genericinterface definition that provides application andkernel users a common set of commands to controlDLC device managers within the operating system.Requirements for entry–point definitions, functionsprovided, and data structures for all DLC managersare specified. The following DLCs conform to thisinterface: IEEE 802.3 Ethernet, standard Ethernet,SDLC, and Token Ring.

generic interface. The interface, defined at a levelthat is independent of any particular programminglanguage.

generic network. A Network InstallationManagement (NIM) network type used to definenetworks which are not currently known by NIM tosupport network boot operations.

generic unit. In Ada language, a template eitherfor a set of subprograms or for a set of packages.A subprogram or package created using thetemplate is called an instance of the generic unit. Ageneric instantiation is the kind of declaration thatcreates an instance. A generic unit is written as asubprogram or package but with the specificationprefixed by a generic formal part which may

1-64 Glossary

declare generic formal parameters. A genericformal parameter is either a type, a subprogram, oran object. A generic unit is one of the kinds ofprogram unit. See also instance.

geometric text. Text whose character fonts aredefined by mathematical descriptions of the strokesrequired to draw the characters, rather than byraster images. Also called programmable characterset or stroke text.

geometry. In Enhanced X-Windows, (1.) Windowsize and position on the screen. (2.) The size of awidget is changed using geometry managementroutines. Synonym for layout and geometrymanagement.

geometry management. Synonymous withgeometry.

GGP. See Gateway–to–Gateway Protocol.

ghost icon. An icon that indicates that a file ismissing.

ghost instrument. In the Performance Toolbox, anempty space in the console where an instrumentused to be, usually caused when a consoledesigned for one system contains instruments notavailable on the current system. Ghost instrumentsoccupy a space and prevent a new instrument frombeing defined in that same space or otherinstruments from being moved or resized to usethe space.

ghosted. A description of an unavailable choice.Menu items are ghosted or ”grayed out” to indicatethat a standard choice is not available under thecurrent circumstances.

GID. See group number.

gigabyte (GB). 1 073 741 824 in decimal notationwhen referring to memory capacity; in all othercases, it is defined as 1 000 000 000.

GL. Graphics Library.

GLB. See Global Location Broker.

glbd. The Global Location Broker daemon.

global. (1.) In programming languages, pertainingto the relationship between a language object anda block in which the language object has a scopeextending beyond that block but contained withinan encompassing block. (2.) Pertaining toinformation defined in one subdivision of acomputer program and used in at least one othersubdivision of the program. (3.) Pertaining toinformation available to more than one program orsubroutine.

global area. (1.) A storage area used forcommunication between two or more mainprograms. (2.) An uninitialized portion of a partition

accessible by any program of a task set in thepartition at a given time. The same area may beused by other task sets that run in the samepartition.

global character. The * and ? special charactersthat can be used in a file specification to match oneor more characters. For example, placing ? in a filespecification means any character can be in thatposition.

global data. Data that can be addressed by anyprocess while in kernel mode, for example, tables,such as the open file table and process table, andother data maintained by the kernel, such as bufferpointers.

global forward substitution. An optimization inwhich the result of an assignment can bepropagated forward through a program. Forexample, the assignment B=C followed by A=B canbe replaced by A=C if B is not used elsewhere inthe program.

Global Location Broker (GLB). Part of the NCSLocation Broker. A server that maintains globalinformation about objects on a network or aninternet.

global variable. A symbol defined in one programmodule but used in other independently assembledprogram modules.

globbing. Synonym for file name substitution.

glossary window. A window that contains aglossary term.

glyph. (1.) An image, usually of a character, in afont. (2.) A graphic symbol whose appearanceconveys information; for example, the vertical andhorizontal arrows on cursor keys that indicate thedirections in which they control cursor movement.

good citizenship. A group of standardsestablished by the Inter–Client CommunicationsConventions Manual (ICCCM) that are supportedand implemented by AIXwindows WindowManager. These standards prescribe behavioramong clients in a multiclient environment to avoidcostly compatibility problems.

goto statement. In programming languages, astatement that transfers control to another point ina program.

Gouraud shading. A method of shading polygonssmoothly based on the intensities at their vertices.The color is uniformly interpolated along eachedge, and then the edge values are uniformlyinterpolated along each scan line. For realisticshading, colors should be gamma corrected.

GPR. See general purpose register.

1-65Glossary

grab. (1.) The act of selecting keyboard keys, thekeyboard, pointer buttons, the pointer, and theserver for exclusive use by a client. In general,these facilities are not intended to be used bynormal applications, but are intended for variousinput and window managers to implement variousstyles of user interfaces. See also active grab,passive grab, button grabbing, pointer grabbing,and key grabbing. (2.) A procedure by which awindow acts upon a key or button event that occursfor it or any of its descendents. This precludes thenecessity of setting up translations for all windows.

grab handles (or handles). In CDE, the smallsquares displayed at the corners and midpoints ofa selected graphic element.

grammar rules. The structure rules in a parserprogram. See also parser.

granularity. The extent to which a larger entity issubdivided. For example, a yard broken into incheshas finer granularity than a yard broken into feet.

graphic character. A character that can bedisplayed or printed.

graphical user interface. (1.) A boundarybetween two functional units that is displayed to theuser by means of fundamental drawing units suchas lines and polygons. (2.) A type of computerinterface consisting of a visual metaphor of areal–world scene, often a desktop. Within thatscene are icons, representing actual objects, thatthe user can access and manipulate with a pointingdevice. (Also called graphical interface.)

graphics. A type of data created from suchfundamental drawing units such as lines, curves,polygons, and so forth.

graphics context (GC). In Enhanced X-Windows,the storage area for various kinds of graphicsoutput, such as foreground pixel, background pixel,line width, and clipping region. Also known as ”GC”and ”GContext,” a graphics context can be usedonly with drawables that have the same root andthe same depth as the graphics context.

graphics pipeline. In GL, the sequence of stepsthat a graphics primitive goes through before itbecomes visible on the screen: transformation frommodel coordinates to NDC coordinates; 3–Dclipping (if out of bounds); perspective division;determination of color through lighting equations ordepth–cueing; transformation of NDC coordinatesto screen coordinates; 2–D clipping (by thescreenmask); rasterization (drawing into the framebuffer); and display of frame buffer.

Graphics Support Library (XGSL). Atwo–dimensional graphics application programminginterface to various output devices.

graPHIGS API. An implementation of PHIGS,based on the American National StandardsInstitute (ANSI) proposed standard, Programmer’sHierarchical Interactive Graphics System (PHIGS).

gravity. In Enhanced X-Windows, the contents ofwindows or subwindows have an attraction to alocation within the window. This determines howthe window ID is resized. See also bit gravity andwindow gravity.

gray scale. (1.) In Enhanced X-Windows, a type ofdegenerate pseudocolor where the red, green, andblue values in any given color map entry are equal,thus producing shades of gray. The gray valuescan be changed dynamically. (2.) Also GrayScale,a value. (3.) In a grayscale adapter, the differentlevels of intensity corresponding to the shades ofgray produced. See also monochrome display.

grayed. A characteristic of a command or optionthat is listed on a menu or list box but cannot bechosen.

gross clipping. In GL, also known as 3–D clippingthis is the clipping that occurs in normalized devicecoordinates, against the sides of the perspectivefrustum. All 3–D primitives undergo this clipping; inparticular, the origin of text strings (but notindividual letters) are clipped in this way. See alsoclipping, fine clipping, and clipping planes.

group. (1.) A collection of users who can shareaccess authorities for protected resources. (2.) Alist of names that are known together by a singlename. (3.) A series of records logically joinedtogether. (4.) A series of lines repeatedconsecutively as a set on a full–screen form orfull–screen panel. (5.) A set of related records thathave the same value for a particular field in allrecords.

Group Appointment. In CDE, in Calendar, anappointment for a group of people, scheduledusing the Group Appointment Editor.

group ID (GID). A number that corresponds to aspecific group name. The group ID can often besubstituted in commands that take a group nameas a value. Synonymous with group number.

group name. A name, which uniquely identifies agroup of users to the system, that contains one toeight alphanumeric characters, beginning with analphabetic, #, $, or > character.

group number. Synonym for group ID.

guard expressions. Expressions placed at thebeginning of Boolean expressions to check thatother operations can be done.

1-66 Glossary

Hhalf duplex (HD or HDX). Pertains tocommunications in which data can be sent in onlyone direction at a time. Contrast with duplex.

half high. Pertains to a storage device that hasone half the height (41.3 mm or 1.63 inches) withthe width and length the same as the full highdevice. See also full high.

half–session. A component that provides dataflow control and transmission control at one end ofa session.

halfword. A contiguous sequence of bits orcharacters that constitutes half a computer wordand can be addressed as a unit. Contrast withword.

hand tuning. The process of modifying sourcecode by hand to improve the performance of theresulting object code. Hand tuning is one aspect ofoptimization.

handle. A data structure that is a temporary localidentifier for an object. You create a handle byallocating it. You make a handle identify an objectat a specific location by binding it.

handler. A software routine that controls aprogram’s reaction to specific external events, suchas an interrupt handler. For Ada programming, seeexception.

handshaking. The process used by modems andequipment, before transmitting data, to establish anelectrical path and synchronization. See also chatscript and expect–send sequence.

hard copy. A printed copy of machine output in avisually readable form such as printed reports,listings, documents, and summaries.

hard disk. See fixed disk.

hard–disk drive. See fixed–disk drive.

hard link. A mechanism that allows the lncommand to assign more than one name to a file.Both the new name and the file being linked mustbe in the same file system.

hard return. In an Interleaf textfile, a controlcharacter created by pressing Shift–Enter thatcauses text to wrap to the next line.

hard space. In an Interleaf file, a nonbreakingspace character.

hardware. The physical equipment of computingand computer–directed activities. The physicalcomponents of a computer system. Contrast withsoftware.

hash codes. Format in which data is stored incompressed form.

hash signature. The fixed–length bit stringresulting from hashing a character string.Character strings may be compared quickly bycomparing their hash signatures.

hash table. A table of information that is accessedby way of a shortened search key (the hash value).Using a hash table minimizes average search time.

hashing. (1.) A method of transforming a searchkey into an address for the purpose of storing andretrieving items of data. (2.) Encoding a characterstring as a fixed–length bit string for comparison.The encoding may not necessarily be unique.

HCON. See 3270 Host Connection Program 2.1and 1.3.2 for AIX

HCONMRI. 3270 Host Connection Program 2.1and 1.3.2 for AIX Message Catalog.

HCONuser. A user who has been given the specialpermissions necessary to use the 3270 HostConnection Program 2.1 and 1.3.2 for AIX (HCON).See also 3270 Host Connection Program 2.1 and1.3.2 for AIX.

HD. See half duplex.

HDLC. See high–level data link control.

HDR. See header label.

HDX. See half duplex.

header. (1.) Constant text that is formatted to be inthe top margin of printed pages in a document. (2.)System–defined control information that precedesuser data. (3.) The portion of a message thatcontains control information for the message suchas destination fields, originating station, and prioritylevel. (4.) In CDE, in Mailer, the basic informationabout an electronic mail message as it appears inthe mailer container. A message header displaysthe name of the sender, subject, the date and timeit was received, and message size.

header file. A text file that contains declarationsused by a group of functions or users. Synonymouswith include file.

header label (HDR). A special set of records on adiskette describing the contents of the diskette.

header page. A separator page that precedes aprinted file or a print job.

header record. A record at the beginning of a filethat details the sizes, locations, and otherinformation that follows in the file.

heap. A collection of dynamically allocatedvariables.

1-67Glossary

HELLO. DCN Local–Network Protocol. An interiorgateway protocol designed for use withinautonomous systems.

’Hello, World’. The standalone sample programthat introduces the fundamental construct providedby Tran–C.

help. One or more display images that describehow to use application software or how to do asystem operation.

help callback. A function that calls a help.

help file. A file, separate from the source code of aprogram, that contains help definitions in a specialhelp format that Base Operating System messageservices can use.

Help Manager. In CDE, a special help volume thatlists all the online help registered on your system.

Help Viewer. In CDE, the software application thatdisplays online help.

help volume. In CDE, a complete body of helpinformation about a subject.

helper. A program used by the INed editor toprovide extra functions for a particular type of datafile.

hertz (Hz). A unit of frequency equal to one cycleper second.

heuristics. Guidelines that a system administratoruses to intervene where the two–phase commit orabort would otherwise fail.

hex. See hexadecimal.

hexadecimal (hex). Pertaining to a system ofnumbers to the base sixteen; hexadecimal digitsrange from 0 (zero) through 9 (nine) and A (ten)through F (fifteen).

hexadecimal constant. (1.) The characters 0x or0X (zero X) followed by any digits 0 through 9 anduppercase or lowercase letters A through F. (2.) Aconstant, usually starting with special characters,that contains only hexadecimal digits.

HIA. See System/370 Host Interface Adapter.

hidden file. An operating system file that is notdisplayed by a directory listing. The name of ahidden file usually begins with a period.

hidden surface. A surface of a geometric primitivethat is not visible because it is obscured by othersurfaces. See also z–buffer.

hierarchical file system. In CDE, a way toorganize data on computer systems using ahierarchy of containers, often called folders(directories) and files. In this scheme, folders maycontain other folders and files. The successive

containment of folders within folders creates thelevels of organization, which is the hierarchy.

hierarchical network. A network in which hostsare administered by a tree structure of authority.This network structure relieves the administrativeburden of the central authority.

hierarchy. A series of elements that have beengraded or ranked in some useful manner. InAIXwindows, more than 40 classes of graphicalobjects are ranked top–down from the simplest tothe most complex to determine the relative order ofinheritance of appearance resources and behaviorresources.

high–level data link control (HDLC). In datacommunications, the use of a specified series ofbits to control data links in accordance with theInternational Standards for HDLC: ISO 3309 FrameStructure and ISO 4335 Elements of Procedures.

high–order. Most significant; leftmost. Forexample, bit 0 in a register.

higher layer or level. The conceptual level ofcontrol or processing logic existing in thehierarchical structure of a station that is above thelink layer and upon which the performance of datalink functions are dependent (for example, devicecontrol, buffer allocation, station management).See also level.

highlight. To emphasize an area on the displayscreen by any of several methods, such asbrightening the area or reversing the color ofcharacters within the area.

hiragana. A graphic character set consisting ofsymbols used in one of the two common Japanesephonetic alphabets. Each character is representedby 1 byte.

history. A list of Ada debugger commands enteredrecently. The history command has a default list ofthe 20 most recently entered commands. You canuse history to re–enter a previous command, or toform a new command by editing the historyreference text.

hit. In GL, also called pick hit or select hit. A hitoccurs whenever a drawing primitive draws withinthe picking or selecting region. A hit is reportedback to the user only if the name stack haschanged since the last hit. In other words, multiplehits may occur although only one pick/select eventis reported. See also picking, picking region,selecting region, and selecting.

H&J. In C.A.T terminology, the (usually automatic)process of hyphenation and justification.

hog factor. In system accounting, an analysis ofhow many times each command was run, how

1-68 Glossary

much processor time and memory it used, and howintensive that use was.

hole in a file. Empty space in a sparse file that isleft open for future additions of data. See alsosparse file.

Hollerith constant. In FORTRAN, a string of anycharacters capable of representation in theprocessor and preceded by nH, where n is thenumber of characters in the string.

HOME. See $HOME.

home cell. See local cell.

home directory. (1.) A directory associated with anindividual user. (2.) The user’s current directoryafter login or after issuing the cd command with noargument. (3.) A parameter that supplies the fullpath name of the home directory for the transactionprogram.

home folder. In CDE, a folder where you keeppersonal files and additional directories. By default,File Manager and Terminal Emulator windows areset to the home folder when you first open them.When discussing command–line activities, may becalled the home directory.

home session. In CDE, a choice at logout todesignate a particular session, other than the oneyou are currently in, as the one you willautomatically return to at the next login. Contrastwith current session.

home–window. A window that completely displaysthe contents of the display buffer.

homogeneous coordinates. A four–dimensionalmethod of representing three–dimensional space.A point (x, y, z, w) in homogeneous coordinates isused to represent a point (X, Y, Z) inthree–dimensional space by taking X=x/w, Y=y/w,and Z=z/w. See also parametric bicubic surface.

hook ID. A unique number assigned to a specifictrace point. All trace entries include the hookidentifier of the originating trace point in the traceentry header. A hook ID is a 12–bit value. For userprograms, the hook ID may be a value from 0x010to 0x0FF. Hook identifiers are defined in the/usr/include/sys/trchkid.h file.

hooking routines. Functions that connect with thelibrary but remain outside the library; protocolextension procedures. Synonym for stub.

hop count. In the Token–Ring Network, thenumber of bridges through which a frame passeson the way to its destination.

hop count metric. (1.) In a gateway, indicates thatthe next string represents the hop count to thedestination host or network. (2.) The number ofhost–to–host connections in a route.

host. (1.) The primary or controlling computer inthe communications network. (2.) A computerattached to a network.

host ID. An identifier for a host. A host ID uniquelyidentifies a host within an address family on anetwork but does not identify the network. A hostID is not necessarily sufficient to establishcommunications with a host.

host name. (1.) A name assigned to a computerconnected to a network. The use of this term canbe ambiguous as it can refer to either the shortform name of the computer, or the fully qualifiedname of the computer. (2.) The Internet address ofa machine in the network. Also known as host ID.

hotspot. The spot associated with a cursor thatcorresponds to the coordinates reported for thepointer. A cursor has an associated hotspot, whichdefines a point in the cursor that corresponds tothe coordinates reported for the pointer.

HTML. HyperText Markup Language (HTML) is thetagging language that a web browser uses tointerpret and display documents.

Huffman coding. A character–coding technique tocompress data.

hyper–integer. An XDR standard that defines64–bit (8–byte) numbers that are the extensions ofintegers and unsigned integers.

hyperlink. In CDE, in Help text, text or a graphicyou click to display another Help topic.

hypertext. A way of presenting information onlinewith connections between one piece of informationand another. These connections are calledhypertext links. Thousands of these hypertext linksenable you to explore additional or relatedinformation throughout the online documentation.See also hypertext link.

hypertext link. A connection between one piece ofonline information and another. See also hypertext.

Hz. See hertz.

1-69Glossary

IIAR. See instruction address register.

IC. See ICU.

ICCC. Inter–Client Communications Conventions.A standard abbreviation for the manual thatcontains a detailed set of guidelines for clientapplications using the Enhanced X-Windowssystem and the AIXwindows toolkit. See alsoICCCM.

ICCCM. Inter–Client Communications Conventionsmanual. See also ICCC.

ICMP. See Internet Control Message Protocol.

icon. (1.) A picture or graphical representation ofan object on a display screen to which a user canpoint to with a device such as a mouse in order toselect a particular operation or perform a certainaction. (2.) In CDE Desktop, the visualrepresentation of a file or directory, or an objectused by the desktop, consisting of a picture on thedesktop or in a directory window.

icon box. In AIXwindows, a window used as avisual storage area for icons representingminimized windows.

Icon Editor. In CDE, the software application usedto create new icons and to modify existing icons.

icon layout policy. In AIXwindows, a specificationthat determines whether icons representingminimized windows are placed on the root windowor within an icon box.

iconify. See icon.

ICU (IC). Instruction cache unit.

ID. Identification. See identifier.

idempotent. A class of operations. An operation isidempotent if its results do not affect the results ofany operation. For example, a call that returns thetime is idempotent.

identifier (ID). (1.) A name that refers to a dataobject. An identifier contains some combination ofletters, digits, and underscores, but its firstcharacter cannot be a digit. (2.) In programminglanguages, a lexical unit that names a languageobject, such as the name of an array, record, label,or procedure. An identifier usually begins with aletter optionally followed by letters, digits, or othercharacters. (3.) A sequence of bits or charactersthat identifies a program, device, or system toanother program, device, or system. (4.) InEnhanced X-Windows, a unique value associatedwith a resource that a client program uses to name

the resource. An identifier can be used over anyconnection to name the resource.

IDL source file. In SOM, a user–written .idl file,expressed using the syntax of the InterfaceDefinition Language (IDL), which describes theinterface for a particular class (or classes, for amodule). The IDL source file is processed by theSOM Compiler to generate the binding files specificto the programming languages of the classimplementor and the client application. (This filemay also be called the ”IDL file,” the ”source file,”or the ”interface definition file.”)

idle list. A list of secondary stations on a networkthat are polled less often by the primary station dueto their inactivity.

idle time. The part of operable time during which afunctional unit is not operated.

IDP. Internet Datagram Protocol. A simple,unreliable datagram protocol, which is used tosupport the SOCK_DGRAM abstraction for theInternet Protocol family.

IEEE. Institute of Electrical and ElectronicsEngineers.

IEEE 754. Binary Floating Point Standard.

IEEE 802.3. Ethernet LAN specification.

IEEE 802.5. Token–Ring LAN specification.

IETF. Internet Engineering Task Force.

IF expression. An expression in a procedure thattests for a condition. The action performed by theprocedure depends on the result of the test.

if statement. (1.) A C language conditionalstatement that contains the keyword if followed byan expression in parentheses (the condition), astatement (the action), and an optional else clause(the alternative action). (2.) A conditional statementthat specifies a condition to be tested and theaction to be taken if the condition is satisfied.

I–field. Information field.

I–field bytes. Data within the information field of atransmit or receive sequenced data frame.

ignore. In DOS, the option to disregard the deviceerror and continue processing.

i–list. In a Base Operating System file system,blocks 2 through n compose the i–list, whichcontains structures (i–nodes) that relate a file to thedata blocks or disk. The size of the i–list dependson the size of the mounted file system. See alsoi–node and superblock.

1-70 Glossary

illegal. A violation of an architecture rule that animplementation is required to report. See alsounpredictable.

image cache. In AIXwindows, a means ofassociating an image with a name. Once thisassociation is in place, the appropriate AIXwindowssubroutines can generate pixmaps throughreferences to an .Xdefaults file (by name) andthrough an argument list (by pixmap). See alsopixmap.

image structure. The existing image in anXmInstallImage function.

immediate data. (1.) In Assembler language,actual data appearing in an instruction, as opposedto the symbolic name of some data. The data isimmediately available from the instruction andtherefore does not have to be read from memory.(2.) Data transferred during instruction run time.

immediate mode. In GL, in this mode, graphicscommands are executed immediately rather thanbeing compiled into a display list.

immediate subclass. A subclass, of a class C,having no super classes that are themselvessubclasses of C.

immediate subobject. One object that is a valueof an attribute of another.

immediate superclass. The superclass, of a classC, having no subclasses that are themselvessuperclasses of C.

immediate superobject. One object that containsanother among its attribute values.

IMPL. Initial microprogram load.

implementation (Or object implementation). InSOM, the specification of what instance variablesimplement an object’s state and what proceduresimplement its methods (or behaviors). In DSOM, aremote object’s implementation is alsocharacterized by its server implementation (aprogram).

Implementation Repository. In SOM, a databaseused by DSOM to store the implementationdefinitions of DSOM servers.

implementation statement. An optionaldeclaration within the body of the interfacedefinition of a class in a SOM IDL source file,specifying information about how the class will beimplemented (such as, version numbers for theclass, overriding of inherited methods, or type ofmethod resolution to be supported by particularmethods). This statement is a SOM–uniquestatement; thus, it must be preceded by the term

”#ifdef __SOMIDL__” and followed by ”#endif”. Seealso interface declaration.

implementation template. In SOM, a template filecontaining stub procedures for methods that aclass introduces or overrides. The implementationtemplate is one of the binding files generated bythe SOM Compiler when it processes the IDLsource file containing class interface declarations.The class implementor then customizes theimplementation, by adding language–specific codeto the method procedures.

implicit method parameter. In SOM, a methodparameter that is not included in the IDL interfacespecification of a method, but which is a parameterof the method’s procedure and which is requiredwhen the method is invoked from a client program.Implicit parameters include the requiredEnvironment parameter indicating where exceptioninformation can be returned, as well as a Contextparameter, if needed.

implicit type conversion. A type conversiongenerated by the compiler as the result of anassociation between variables of different types.For example, initializing a floating–point array tothe value of a loop counter is an implicit typeconversion from integer to floating–point.

implied DO. In FORTRAN, an indexingspecification with a list of data elements, ratherthan a set of statements, as its range. Similar to anFORTRAN DO statement, however, without usingthe word DO.

import. (1.) In NCS, to request the operationsdefined by an interface. A client imports aninterface from a server. (2.) To bring data in fromanother system. Contrast with export.

imports. In Ada language, all compilation unitsnamed in the context specification of a library unit(stated in its with clauses) and any supporting unitspecifications introduced by the compiler, forexample, the standard package SYSTEM. Theimports of a secondary unit are all the units namedin its context specification, any supporting unitrequirements introduced by the compiler; itsassociated parent unit (if any), and the bodies ofany generic specifications included among its otherimports.

in. See inch.

inaccessible. In XOM, said of an object for whichthe client does not possess a valid designator orhandle.

inactive. Describes a window that does not havethe input focus.

1-71Glossary

Inbox. In CDE, the main or default Mailercontainer. The Inbox receives all incoming mail.Messages can be moved out of the Inbox and putin various containers.

inch (in). 2.54 centimeters or 25.4 millimeters.

include file. A text file that contains declarationsused by a group of functions, programs, or users.Synonymous with header file. See also includestatement.

include statement. A computer languagepreprocessor statement that directs the processorto retrieve a specific file that contains instructionsand data the program may need. See also includefile.

incoming call. In X.25 communications, a callarriving at the data terminal equipment (DTE).

incoming–call packet. In X.25 communications, acall supervision packet transmitted by a DCE toinform a DTE of a call requested by another DTE.See also packet.

incomplete class declaration. A C++ classdeclaration that does not define any members of aclass. Until a class is fully declared, or defined, youcan only use the class name where the size of theclass is not required. Typically, an incomplete classdeclaration is used as a forward declaration.

incremental backup. The process of copying filesthat have been opened for reasons other thanread–only access since the last backup wascreated and that meet the backup frequencycriteria. Contrast with full backup.

incremental update. In SOM, a revision to animplementation template file that results fromreprocessing of the IDL source file by the SOMCompiler. The updated implementation file willcontain new stub procedures, added comments,and revised method prototypes reflecting changesmade to the method definitions in the IDLspecification. Importantly, these updates do notdisturb existing code that the class implementorhas defined for the prior method procedures.

index. (1.) A table containing the key value andlocation of each record in an indexed file. (2.) Acomputer storage position or register whosecontents identify a particular element in a set ofelements. (3.) A list of the contents of a file or adocument, together with keys or references forlocating the contents. See also base register.

index constraint. In Ada language, an indexconstraint for an array type specifies the lower andupper bounds for each index range of the arraytype.

index priority. Priority of an attribute type insearch queries.

indexed application widget. Any widget named inthe User Interface Language (UIL) that is not thechild of any other widget in the User InterfaceDefinition (UID) hierarchy.

indexed component. In Ada language, an indexedcomponent denotes a component in an array. It is aform of name containing expressions which specifythe values of the indices of the array component.An indexed component may also denote an entry ina family of entries.

indexed fields. An area in a structured data filethat contains tree data paths.

indexed instruction. An instruction that uses anindexed address.

indicator. (1.) An internal switch thatcommunicates a condition between parts of aprogram or procedure. (2.) A device that can be setto a prescribed state, usually according to theresult of a previous process or on the occurrenceof a specified condition in the equipment. Thedevice usually indicates the existence of the stateand may be used to determine the selection amongalternative processes.

indirect block. A block containing pointers to otherblocks.

industry–standard benchmark. A benchmark thathas been adopted by consensus or by some(presumably neutral) sponsoring organization asconstituting a meaningful measure of some aspectof computer–system performance. There are manycounter–examples to the assumption that animprovement in industry–standard benchmarkperformance corresponds to an improvement in theperformance experienced by users.

inferiors. In Enhanced X-Windows, all thesubwindows nested below a window.

infinity. (1.) A name for the upper boundary of theset of numbers. (2.) In binary floating–pointconcepts, a value with an associated sign that ismathematically greater in magnitude than anybinary floating point number.

information field overflow (I–field overflow).Condition that occurs when the size of theinformation field in the receive data exceeds theprimary station’s buffer capacity. Some of theinformation field is lost.

informational message. (1.) A message thatprovides information to the operator but does not

1-72 Glossary

require a response. (2.) A message that is not theresult of an error condition.

inherit. To copy resources or attributes from aparent to a child.

inheritance. (1.) In AIXwindows and EnhancedX–Windows, the passing of class resources froman object superclass downstream in the classhierarchy to an object subclass. (2.) Anobject–oriented programming technique that allowsyou to use existing classes as bases for creatingother classes. (3.) In SOM, the technique ofdefining one class (called a subclass, derivedclass, or child class) as incremental differencesfrom another class (called the parent class, baseclass, superclass, or ancestor class). From itsparents, the subclass inherits variables andmethods for its instances. The subclass can alsoprovide additional instance variables and methods.Furthermore, the subclass can provide newprocedures for implementing inherited methods.The subclass is then said to override the parentclass’s methods. An overriding method procedurecan elect to call the parent class’s methodprocedure. Such a call is known as a parentmethod call. See also subclassing.

inheritance hierarchy. In SOM, the sequentialrelationship from a root class to a subclass,through which the subclass inherits instancemethods, attributes, and instance variables from allof its ancestors, either directly or indirectly. Theroot class of all SOM classes is SOMobject.

initial program load (IPL). (1.) The initializationprocedure that causes an operating system tocommence operation. Synonymous with systemrestart and system startup. (2.) The process bywhich a configuration image is loaded into storageat the beginning or a work day or after a systemmalfunction. (3.) The process of loading systemprograms and preparing a system to run jobs.

initial program load device (IPL device). Theinput/output device, usually a fixed disk or diskette,from which the system software is loaded when themachine is turned on.

initial sequence controller. One of three controlprograms for the initial program load (IPL) ROM.The initial sequence controller accepts control afterthe hardware initialization and passes control to thecore sequence controller.

initialize. (1.) In programming languages, to setthe starting value of a data object. (2.) To setcounters, switches, addresses, or contents ofstorage to zero or other starting values at thebeginning of, or at prescribed points in, theoperation of a computer routine. (3.) To prepare foruse, such as initializing a diskette. (4.) To prepare

the system for operation. After loading the kernelinto memory, the system runs internal checks,initializes all memory and some devices, andanalyzes the root file system.

initializer. The assignment operator followed by anexpression or multiple expressions for aggregatevariables.

inline. See inline component.

inline component. A component within acomponent that has its own properties and cancontain anything a component contains. It iscreated from the same set of masters as acomponent.

inline expansion. An optimization in which thereference to a procedure is replaced with the codeof the procedure itself, to eliminate callingoverhead.

inline function. In C++, inlining is a hint to thecompiler to perform inline expansion of the body ofa function member. Functions declared and definedsimultaneously in a class definition are inline. Youcan also explicitly declare a function inline by usingthe keyword inline. Both member and nonmemberfunctions can be inlined.

inlining. See inline expansion.

i–node. The internal structure that describes theindividual files in the operating system; there is onei–node for each file. An i–node contains the node,type, owner, and location of a file. A table ofi–nodes is stored near the beginning of a filesystem. Synonym for file index. See also i–list andi–node number.

i–node number. A number specifying a particulari–node file in the file system. See also i–node.

inodetab. A kernel parameter that establishes atable in memory for storing copies of i–nodes for allactive files.

input. (1.) Data to be processed. (2.) In Pascal, apredefined standard file definition.

input data type. The type of data contained in theinput file. Examples are ASCII and PostScript.

input device. (1.) A physical device that providesdata to a computer. (2.) The device that is thesource of the software you are installing. The inputdevice can be a tape drive, CD–ROM drive,diskette drive, or a directory.

input field. (1.) An area in a display file into whichyou can type data. (2.) In computer graphics, anunprotected field on a display surface in which datacan be entered, modified, or erased.

1-73Glossary

input file. A file opened in order to allow records tobe read.

input focus. In a graphics environment, a windowdefining the scope for processing keyboard input.By default, keyboard events are sent to the clientusing the window the pointer is in. It is alsopossible to attach the keyboard input to a specificwindow. Events are then sent to the appropriateclient regardless of the pointer position.Synonymous with focus window. See also inactive.

input list. A list of variables to which values areassigned from input data.

input manager. In a graphics environment, a clientthat controls keyboard input and is usually part of awindow manager.

input mode. An open mode in which records canbe read from the file.

Input Only window. In a graphics environment, aninvisible window that can be used to control suchthings as cursors, input event generation, andgrabbing. This window cannot be used for graphicsrequests.

input redirection. The specification of an inputsource other than the standard one.

input semantics. The specified order and formatin which user input must be entered.

input stream. The sequence of operation controlstatements and data given to the system from aninput device.

input/output (I/O). (1.) Pertaining to either input,output, or both between a computer and a device.(2.) Pertaining to a device whose parts can performan input process and an output process at thesame time. (3.) Pertaining to a functional unit orchannel involved in an input process, an outputprocess, or both, concurrently or not, and to thedata involved in such a process.

input/output channel (IO channel). (1.) In a dataprocessing system, a functional unit that handlestransfer of data between internal and peripheralequipment. (2.) In a computing system, a functionalunit, controlled by a processor, that handlestransfer of data between processor storage andlocal peripheral devices.

input/output channel controller (IOCC). Ahardware component that supervisescommunication between the input/output bus andthe processor.

input/output configuration data set (IOCDS). Aconfiguration definition built by the I/O configurationprogram (IOCP) and stored on disk files associatedwith the processor controller.

input/output configuration program (IOCP). Theprogram that defines the I/O configuration datarequired by the processor complex to control I/Orequests.

input/output device number. A value assigned toa device driver by the guest operating system or tothe virtual device by the virtual resource manager.This number uniquely identifies the deviceregardless of whether it is real or virtual.

input/output file. A file opened for input andoutput use.

input/output subsystem. That part of theoperating system comprised of processes anddevice managers that provides the mechanisms fordata transfer and I/O device management andcontrol.

InputOutput window. In a graphics environment,a kind of opaque window used for input and output.InputOutput windows can have both InputOutputand InputOnly windows as inferiors.

inquiry. (1.) A request for information in storage.(2.) A request that puts a display station into inquirymode. (3.) In data communications, a request forinformation from another system.

insert cursor. The position of the cursor markingwhere new characters will be added when enteringtext.

insert mode. (1.) A keyboard operation that putsnew text within existing text at the cursor position.(2.) The source entry utility operation during whichsource statements are typed in and added as newrecords in a source member. (3.) In theToken–Ring Network, to make an attaching devicean active part of a ring.

insertion cursor position. The point at which textwill be inserted.

insertion point. In AIX Common DesktopEnvironment, the point at which text is insertedwhen you type. It usually appears as a flashingvertical line or underline.

install. (1.) To add a program, program option, orsoftware program to the system in a manner suchthat it is runnable and interacts properly with allaffected programs in the system. (2.) To connect apiece of hardware to the processor. (3.) Theprocess of connecting used when discussing theprocess of connecting something to the internalportion of the processor.

Install Icon. In CDE, an item on a subpanel usedto install icons into the Front Panel using drag anddrop.

1-74 Glossary

installation. (1.) The procedure of adding aprogram or program option to the mass storagemedium of the computer, making the programrunnable, and ensuring that the program interactsproperly with all other affected programs in thesystem. (2.) The task of adding a device driver tothe system and activating the driver so that it canbe used. (3.) The task of connecting a piece ofhardware to the processor or of adding a softwareprogram to the system.

Installation Assistant. An application used toperform system configuration tasks.

installation image. An installation image containsa copy of the software you are installing in backupformat, as well as copies of other files the systemneeds to install the software product.

installation script. A shell script or executable filecreated by the developer of an application programto install the program. The script file must followspecific guidelines in order to be compatible withthe program installation tools that are provided inthe operating system.

instance. (1.) A concrete realization of an abstractobject class. An instance of a widget or gadget is aspecific data structure that contains detailedappearance and behavioral information that is usedto generate a specific graphical object on–screenat runtime. See also widget instance and instancerecord. For Ada programming, see generic unit.(2.) An object–oriented programming termsynonymous with ”object”. An instance is aparticular instantiation of a data type. It is simply aregion of storage that contains a value or group ofvalues. For example, if a class box is previouslydefined, two instances of a class box could beinstantiated with the declaration: box box1,box2; (3.) In XOM, an object in the categoryrepresented by a class.

instance method. In SOM, a method valid for anobject instance (as opposed to a class method,which is valid for a class object). An instancemethod that an object responds to is defined by itsclass or inherited from an ancestor class.

instance record. A particular widget record thatcontains the data objects pertaining to the identityof any given widget as an instance. See alsorecord, widget record, and instance.

instance token. In SOM, a data token thatidentifies the first instance variable among thoseintroduced by a given class. ThesomGetInstanceToken method invoked on a classobject returns that class’s instance token. See alsodata token.

instance variables. (Or, instance data.) In SOM,variables declared for use within the method

procedures of a class. An instance variable isdeclared within the body of the implementationstatement in a SOM IDL source file. An instancevariable is ”private” to the class and should not beaccessed by a client program. Contrast withattribute.

instant duration locks. Locks that behave as ifthey were obtained and then immediately released.These are commonly used when a large number ofdata objects require locking, but the transactionwishes to avoid obtaining some of the necessarylocks while waiting an unknown amount of time foranother transaction to release the other requiredlocks. These are primarily useful for implementingschemes such as Jim Gray’s key–range locking(see also his Transaction Processing: Conceptsand Techniques).

instantiate. (1.) To make an instance of; toreplicate. (2.) In object–oriented programming, torepresent a class abstraction with a concreteinstance of the class. (3.) In AIXwindows, to createa specific concrete instance of that general class.(4.) To create or generate a particular instance (orobject) of a data type. For example, an instancebox1 of class box could be instantiated with thedeclaration: box box1;

instruction. A program statement that specifies anoperation to be performed by the computer, alongwith the values or locations of operands. Thisstatement represents the programmer’s request tothe processor to perform a specific operation.

instruction address register (IAR). A systemcontrol register containing the address of the nextinstruction to be run. The IAR can be accessed byway of a supervisor call in supervisor state, butcannot be directly addressed in problem state.Synonymous with program counter. See alsolocation counter.

instruction cache. A cache for providing programinstructions to the processor faster than they canbe obtained from RAM.

instruction pointer (IP). See instruction addressregister.

instruction scheduling. A compiler optimizationthat schedules instructions to the differentprocessing units of the CPU so that maximuminstruction overlap can occur.

int specifier. In C language, one of the words int,short, short int, long, long int, unsigned,unsigned int, unsigned short, unsigned shortint, unsigned long, or unsigned long int,whichdescribe the type of data a variable represents.

integer. A positive or negative whole number orzero.

1-75Glossary

integer constant. (1.) A decimal constantcontaining no decimal point. (2.) An octal orhexadecimal constant. (3.) A string of decimaldigits containing no decimal point.

integer expression. An arithmetic expression withonly integer type values.

integer type. An arithmetic data type that consistsof integer values. In Ada language, an integer typeis a discrete type whose values represent allinteger numbers within a specific range.

integral object. In the C language, a characterobject, an object having an enumeration type, or anobject having the type short, int, long, unsignedshort, unsigned int, or unsigned long.

integrity. A protection level that may be specifiedin secure RPC communications that ensures thatdata transferred between two principals has notbeen modified in transit.

intention locks. Locks used for hierarchicalresources that permit an application to avoidlocking a large data object, such as a file ofrecords, when it only needs to modify a portion ofthe data object, such as one record in a file.Obtaining the intention lock on the file indicatesthat some records in the file may be changingcurrently, but allows access to records that are notfurther locked against access.

interaction. A continuing cycle of reciprocal actionbetween a user and one or more softwareapplications through input devices (a keyboard,mouse, file server, and so on) and output devices(a display, printer, file server, and so on).

interactive. Pertaining to an activity that involvesrequests and replies, such as between a systemuser and a program or between two programs.

interactive processing. A processing method inwhich each system user action causes responsefrom the program or the system. Contrast withbatch processing.

interface. (1.) A common boundary, but not ofinternal connections. An interface can be ahardware component to link two devices or aportion of storage or registers accessed by two ormore computer programs. Synonymous withcommand interpreter. (2.) A shared boundarybetween two functional units, defined by functionalcharacteristics, common physical interconnectioncharacteristics, signal characteristics, and othercharacteristics. (3.) Hardware or software, or both,that link systems, programs, or devices. (4.)Synonymous with shell. (5.) A set of operations.The Network Computing Architecture specifies aNetwork Interface Definition Language for defining

interfaces. (6.) In SOM, the information that a clientmust know to use a class––namely, the names ofits attributes and the signatures of its methods. Theinterface is described in a formal language (theInterface Definition Language, IDL) that isindependent of the programming language used toimplement the class’s methods. See also extendedinterface and limited interface.

interface declaration. (Or interface statement.) InSOM, the statement in the IDL source file thatspecifies the name of a new class and the namesof its parent class(es). The ”body” of the interfacedeclaration defines the signature of each newmethod and any attribute(s) associated with theclass. In SOM IDL, the body may also include animplementation statement (where instancevariables are declared or a modifier is specified, forexample to override a method). See alsoimplementation statement.

Interface Definition Language (IDL). In SOM, theformal language (independent of any programminglanguage) by which the interface for a class ofobjects is defined in a .idl file, which the SOMCompiler then interprets to create animplementation template file and binding files.SOM’s Interface Definition Language is fullycompliant with standards established by the ObjectManagement Group’s Common Object RequestBroker Architecture (CORBA).

interface, extended. See extended interface.

interface icon. Any pictorial representation of aselection choice appearing within an interface.

interface, limited. See limited interface.

Interface Repository (IR). The database thatSOM optionally creates to provide persistentstorage of objects representing the major elementsof interface definitions. Creation and maintenanceof the IR is based on information supplied in theIDL source file. The SOM IR Framework supportsall interfaces described in the CORBA standard.

Interface Repository Framework. In SOM, a setof classes that provide methods whereby executingprograms can access the persistent objects of theInterface Repository to discover everything knownabout the programming interfaces of SOM classes.

interior gateway. A gateway that communicatesonly with gateways on its own autonomous system.

interlacing. A method of doubling verticalresolution by displacing odd video frames byone–half scan line.

1-76 Glossary

interlanguage call. In a program written in a givenlanguage, any reference to a procedure written in adifferent language.

intermediate data type. Any of the basic datatypes in terms of which the other, substantive datatypes of the interface are defined.

intermediate nodes. On the widget tree, widgetswith one or more children. See also widget tree.

intern. The procedure of defining an atom.

internal clocking. In data communications, dataclocking provided by an adapter.

internal data definition. A description of avariable appearing at the beginning of a block thatdirects the system to allocate storage for thatvariable and makes that variable accessible to thecurrent block.

internal data structures. The format of other datastored internally by a program or function. Used toperform type conversion on argument lists.

internal routine. A routine available only within thelexical scope in which it was declared.

international character support. Synonym fornational language support.

International Standards Organization (ISO). Aninternational body that standardizes goods andservices. For Enhanced X–Windows, standardsrelating to character sets and fonts.

Internet. (1.) A wide area network connectingthousands of disparate networks in industry,education, government, and research. The Internetnetwork uses TCP/IP as the standard fortransmitting information. (2.) Any wide areanetwork connecting more than one network.

Internet address. The numbering system used inTCP/IP Internetwork communications to specify aparticular network or a particular host on thatnetwork with which to communicate. Internetaddresses are commonly denoted in dotteddecimal form.

Internet Control Message Protocol (ICMP). Aprotocol used by a gateway to communicate with asource host, for example, to report an error indatagram. It is an integral part of Internet Protocol(IP).

Internet Protocol (IP). The protocol that providesthe interface from the higher level host–to–hostprotocols to the local network protocols.Addressing at this level is usually from host to host.

Internet Router. Enables an IP host to act as agateway for routing data between separatenetworks that use a specific adapter.

internetwork. Any wide area network connectingmore than one network.

interpreted routine. A routine that decodesinstructions written as pseudocodes andimmediately executes those instructions. See alsocompile.

interpreter. A tool that allows a program to be runimmediately, without recompiling or relinking.

interprocedural analysis. The process ofinspecting referenced procedures for informationon relationships between arguments, returnedvalues, and global data.

inter–process communication (IPC). (1.) Usedfor programs to communicate data to each otherand to synchronize their activities. Semaphores,signals, and internal message queues are commonmethods of inter–process communication. (2.) InEnhanced X-Windows, a communication path. Seealso client.

interrupt. (1.) In data communications, to take anaction at a receiving station that causes thesending station to end a transmission. (2.) To stopa process temporarily. (3.) A signal sent by an I/Odevice to the processor when an error hasoccurred or when assistance is needed to completeI/O. An interrupt usually suspends the running ofthe program that is currently running. Contrast withexception and signal.

interrupt–confirmation packet. In X.25communications, a packet used to acknowledgethe receipt of an interrupt packet. See also packet.

interrupt packet. In X.25 communications, anexpedited packet that is allowed to overtake normaldata packets (which are delivered in sequence).See also packet.

intrinsic function. In FORTRAN, a function that issupplied with the run–time environment thatperforms math, character, logical, orbit–manipulation operations.

intrinsics. In Enhanced X-Windows, a set ofmanagement mechanisms that provides forconstructing and interfacing between compositewidgets, their children, and other clients. Also,intrinsics provide the ability to organize a collectionof widgets into an application.

inverse. A matrix that results from a mathematicaloperation on a matrix such that the two matricescan be multiplied together to obtain the unit matrix.

inverse transpose. The inverse of a matrix after ithas been transposed.

inverted index. An index into a bibliographydatabase that allows for direct access. This can be

1-77Glossary

compared to the thumb cuts of a dictionary, whichallow a user to move to the exact location of theword being searched.

invocation stack. A list of programs linkedtogether as a result of programs calling otherprograms within the same job. Synonymous withprogram stack.

invoke. To start a command, procedure, orprogram.

invoke ID. An integer used to distinguish one(directory) operation from all other outstandingones.

IO. See IOU.

I/O. See input/output.

I/O channel. See input/output channel.

I/O configuration. The collection of channel paths,control units, and I/O devices that attaches to theprocessor unit.

I/O error. An error in the processing of input oroutput device data.

I/O Stream Library. A C++ class library thatprovides the facilities to deal with many varieties ofinput and output.

IOCC. See input/output channel controller.

IOCDS. I/O configuration data set.

IOT fault. A signal (SIGIOT) that abnormally endsa process.

IOU (IO). Input/output unit.

IP. See Internet Protocol.

IP address. An address in a network using theInternet Protocol. It is a 32–bit integer usuallywritten in dotted decimal notation, where eachsuccessive eight bits is translated to an integer andseparated from the other components using a dot.

IP socket. The port concatenated with the InternetProtocol (IP) address.

IPC. See inter–process communication.

IPL. See initial program load.

IPL device. initial program load device.

ips. Inches per second, a measure of tape drivespeed and performance.

ISC. See initial sequence controller.

ISO. See International Standards Organization.

ISO 7776. The ISO description ofLAPB–compatible DTE data link procedures.

ISO 8208. See X.25.

isolation level. A field in the specification of anopen file descriptor (OFD) that determines thedegree to which operations performed with thatOFD are isolated from other operations using thatOFD. Operation isolation is achieved by the use oflocks obtained internally on behalf of eachoperation. The value of this field determines howlocks are obtained and held on behalf of operationsperformed using that OFD.

ITE. In CDE, Internal Terminal Emulator. ITE allowsuse of a bitmapped display as a terminal (throughcommand–line mode from the login screen).

item. The data in one line of an indexed field.

1-78 Glossary

JJapanese Industry Standard (JIS). A standard ofcoding character sets.

Japanese Shift–In start delimiter. In SNAServices, an optional feature supported by X.21Physical Link Control.

JIS. See Japanese Industry Standard.

Java Language. A programming language basedon the C++ language and developed by SunMicrosystems. Java was developed to includemethods for Internet data manipulation. Javaapplications can be written once and run on anymachine having a Java Virtual Machine as part ofits operating system.

job. (1) A unit of work defined by a user to bedone by a system. The term ”job” sometimes refersto a representation of the job, such as a set ofprograms, files and control statements to theoperating system. (2) One or more relatedprocedures or programs grouped into a procedure,identified by appropriate job control statements.See also process.

job number. A number assigned to a job as itenters the system to distinguish the job from otherjobs.

job queue. A list of jobs waiting to be processedby the system.

journaled file system. The standard sequentialstructure of database files used in this operatingsystem.

journaling. (1) The process of recording changesmade in a physical file member in a journal. (2) Theprocess of recording information sequentially in adatabase.

jump. In the running of a computer program, adeparture from the implicit or declared order inwhich instructions are being run.

jumper. A connection on an adapter that changesthe operating characteristics of a device. Forexample, it could set up the I/O address or interrupttype of a port.

justify. To print a document with even right and leftmargins.

1-79Glossary

Kkanji. A graphic character set consisting ofsymbols used in Japanese ideographic alphabets.

katakana. A character set of symbols, usedprimarily to write foreign words phonetically,contained in one of the two common Japanesephonetic alphabets.

Kb. Kilobit.

KB. Kilobyte.

K–byte. See kilobyte.

kernel. (1.) The part of an operating system thatcontains programs for such tasks as input/output,management and control of hardware, and thescheduling of user tasks. (2.) The part of the BaseOperating System containing functions neededfrequently.

kernel device driver. See device head.

kernel dump. Synonym for system dump.

kernel mode. The state in which a process runskernel code. Contrast with user mode.

kernel parameters. Variables that specify how thekernel allocates certain system resources.Synonymous with system parameters.

kerning. The placement of characters such thattheir bounding boxes (character boxes) overlap.This allows for a more natural–looking spacingbetween characters.

key. (1.) One or more characters used to identify arecord and establish the record’s order within anindexed file. (2.) A unique identifier (of type key_t)that names the particular interprocesscommunications member. (3.) Identifies the nameof the shared library text image. (4.) An identifierwithin a set of data elements. (5.) A characterstring that matches a definition in a key table.

key click. See keyboard click.

key grabbing. In Enhanced X-Windows, keys onthe keyboard can be passively grabbed by a client.Or the keyboard can be actively grabbed by theclient when a key is pressed. See also grab, buttongrabbing, pointer grabbing, active grab and passivegrab.

key pad. A physical grouping of keys on akeyboard such as the numeric key pad and thecursor key pad.

key range. The two key fields signifying a range ofrecords to be processed sequentially. The range ofrecords is selected by specifying key values that

bound the records to be selected, or by specifyingan individual key value for which all matchingrecords should be selected in a non–unique index.

keyboard. An input device consisting of variouskeys that allows the user to input data, controlcursor and pointer locations, and to control thedialog with the workstation.

keyboard click (key click). Transient pulses orsurges on a transmission line set up by the openingor closing of keying circuit contacts.

keyboard grabbing. In Enhanced X-Windows, aclient can actively grab control of the keyboard andkey events will be sent to that client rather than theclient to which the events would normally havebeen sent.

keyboard mapping. A list, usually in a profile, thatestablishes a correspondence between each keyon the keyboard and the character displayed on adisplay screen, or action taken by a program, whenthat key is pressed. See also mapping.

keyboard send–receive. See keyboardsend–receive mode.

keyboard send–receive (KSR) mode. A mode inwhich a graphics display emulates a standardASCII terminal during both input and outputfunctions.

keyboard traversal. An X widget resource thatallows users to move the keyboard focus andactivate user interface components using a keysequence rather than a mouse.

keylock feature. (1.) A security feature in which alock and key can be used to restrict the use of thedisplay station. (2.) A program that restricts use ofthe keyboard.

keysym. An encoding of a symbol on a keycap ona keyboard.

keyword. (1.) A predefined word in a programminglanguage. A reserved word. (2.) In programminglanguages, a lexical unit that characterizes somelanguage construct. A keyword normally has theform of an identifier. (3.) A name or symbol thatidentifies a parameter. (4.) Part of a commandoperand that consists of a specific character string.

kg. See kilogram.

kill. An operating system command that stops aprocess.

kill character. Character that deletes a line ofcharacters entered after a prompt.

1-80 Glossary

kilobyte (K–byte). 1024 bytes in decimal notationwhen referring to memory capacity; in all othercases, it is defined as 1000.

kilogram (kg). One thousand grams; 2.2046pounds.

kprocs. A kernel parameter that establishes themaximum number of processes the kernel can runsimultaneously.

KSR. See keyboard send–receive mode.

KTS. Key Telephone System. A private telephonesystem requiring manual selection of outside lines.

kVA. Kilovolt–ampere, or 1000volt–amperes.

1-81Glossary

LL1 cache. The first cache accessed when astorage reference occurs.

L2 cache. The cache that is accessed, on certainRISC System/6000 models, if the L1 cache lookupresults in a cache miss. Normally, the L2 cache islarger and slower than the L1 cache, but fasterthan RAM.

label. (1.) A name in the disk or diskette table ofcontents that identifies a file. (2.) The field of aninstruction that assigns a symbolic name to thelocation at which the instruction begins. (3.) Inprogramming languages, a construction naming astatement and including an identifier. See also filename. (4.) An identifier followed by a colon, used toidentify a statement in a program. Usually thetarget of a goto or switch statement. See alsostatement label.

labeled statement. (1.) A programming languagestatement that contains one or more identifiersfollowed by a colon and a statement. (2.) Apossibly empty statement immediately preceded bya label.

LAN. See local area network.

landscape display. A rectangular display widerthan it is high. See also portrait display.

landscape left. A page orientation such that theleft side of the printed image is at the trailing edgeof the paper as it emerges from the printer.

landscape right. A page orientation such that theright side of the printed image is at the trailing edgeof the paper as it emerges from the printer.

LAP. See link–access procedures.

LAPB. Link–access procedure balanced. See alsolink–access procedures.

last line mode. A command mode in the vi editor.Enables the user to enter a command at thebottom of the screen. See also text input mode.

latency. The time from the initiation of an operationuntil something actually starts happening (forexample, data transmission begins).

layout. The arrangement of printed matter on thepage, including margins, line spacing, typespecification, header and footer information,indents, and more. Synonymous with geometry.

lb. See pound.

LC. See link control.

LCN. See logical channel number.

leaders. An evenly spaced row of dots used in atable of contents to guide the eye from the title tothe page number.

leaf. A page of text. See also page.

leaf delta. A set of changes to the source codesaved in the Source Code Control System (SCCS)file.

leaf entry. A directory entry that has nosubordinates. It can be an alias entry or an objectentry.

leap seconds. An infrequent adjustment to UTC toaccount for the irregularity of the earth’s rotation.

leased facility. Synonym for nonswitched line.

leaves. On a widget tree, widgets with no children.See also widget tree.

LED. See light–emitting diodes.

left–adjust. The process of aligning lines of text atthe left margin or at a tab setting such that theleftmost character in the line or file is in the leftmostposition.

left margin. The area on a page or screenbetween the left edge and the leftmost characterposition on the page or screen.

length specification. A source languagespecification of the number of bytes to be occupiedby a variable.

letter. An uppercase or lowercase character fromthe set A through Z.

level. (1.) The version of a software applicationprogram. (2.) See also higher layer. (3.) In X.25communications, see also physical level, packetlevel, and frame level.

level 1. Synonym for physical level.

level 2. Synonym for frame level.

level 3. Synonym for packet level.

lexical analyzer. A program that analyzes inputand breaks it into categories, such as numbers,letters, or operators.

lexical element. In Ada language, an identifier, aliteral, a delimiter, or a comment.

lexical level. The depth to which routines arenested within one another, which determines thescope of the identifiers declared within thoseroutines.

lexical scope. The portion of a program orsegment unit in which a declaration applies. Anidentifier declared in a routine is known within thatroutine and within all nested routines. If a nested

1-82 Glossary

routine declares an item with the same name, theouter item is not available in the nested routine.

library. (1.) A collection of functions, calls,subroutines, or other data. (2.) A data file thatcontains copies of a number of individual files andcontrol information that allows them to be accessedindividually. (3.) In Ada–language librarymanagement, a database that stores the variousintermediate code files produced by the compilerand records the dependency and order ofcompilation information as required by the Adalanguage specification. When compiling a unit thatdepends on other (previously compiled) units, therequired dependency information (such as thepackage specification of a unit that is included witha with clause) is obtained from the library.Similarly, when an Ada program unit is to be linked,the library specifies the set of units that must beincluded to create an executable image.

library component. In Ada language, a packagebody, package specification, subprogram body,subprogram specification, object form module, orlinked object module that resides in a library.

library list file. In Ada language, a text filecontaining the name of one or more sublibrariescomprising an Ada program library.

library unit. In Ada language, one of five syntacticentities: a subprogram declaration, a packagedeclaration, a generic declaration, a genericinstantiation, or a subprogram body in the casewhere there is no corresponding subprogramdeclaration. As the name implies, a library unitresides in the Ada program library. The significanceof library units is that they may be referenced byother independently compiled units. This referencemay either be explicit (referenced via a withclause) or implicit (such as the reference of apackage body to its specification).

license. An instance of permission to use alicensed software product or service. Sometimes, auser needs more than one license to use aproduct.

license annotation. A special data string thatmodifies the use of a license in a manner definedby the vendor of the software product.

license database. The database of licensesmaintained by a license server. The licensedatabase file–lic_db–resides in the/usr/lib/netls/conf directory.

license information. The information thatdescribes licenses. This information consists of theproduct name, the product version, the number oflicenses, the license type, the start and end datesof the licenses, the target type, the target ID, and atime stamp.

license password. A string encoded with licenseinformation for a software product.

license server daemon. A software program thatadministers licenses for software products, invokedwith the command netlsd. The netlsd commandcan be found in the /usr/lib/netls/bin directory.

licensed product. A software product that hasbeen enabled by a software vendor for use with theLicense Use Management system. Enablementallows a vendor to enforce end–user compliance totheir license agreement.

License Use Management. A run–timelicense–management application based onGradient Technologies’ Version 2.0.1 (Version1.1.2a) of the Network Licensing System. Thesystem allows software vendors to bundlecompliance mechanisms with their software. Intracking license usage, License Use Managementallows customers to easily comply with theirsoftware license agreements.

License Use Management Test Product. Theproduct used by the ls_tv tool to verify that licenseservers are working properly.

licensed program (LP). (1.) A software programthat remains the property of the manufacturer, forwhich customers pay a license fee. (2.) Aseparately priced program and its associatedmaterials that bear a copyright and are offered tocustomers under the terms and conditions of alicensing agreement.

lifetime analysis. The process of inspectingreferences to variables to determine whether thefinal assignment to a variable needs to be stored orcan be discarded.

ligature. Two (or occasionally more) charactersprinted together so they are connected.

light–emitting diodes (LED). A semiconductorchip that gives off visible or infrared light whenactivated. An LED is often used to display operatorinformation.

lighted programmable function keyboard(LPFK). An input device used primarily in graphicapplications and that has lighted keys under controlof an application program.

limited interface. A set of system calls thatprovides a limited function interface. See alsointerface and extended interface.

limited subset. A small part or simpler version of alarger set of data or programs.

limited type. In Ada language, a type for whichneither assignment nor the predefined comparisonfor equality is implicitly declared. All task types arelimited. A private type can be defined to be limited.

1-83Glossary

An equality operator can be explicitly declared for alimited type.

line. (1.) A horizontal display on a screen. (2.) Thepart of a data circuit that connects to datacircuit–terminating equipment (DCE), or to dataswitching exchange (DSE), or that connectsseveral DCEs or DSEs. (3.) A string of charactersaccepted by a system as a single block of inputfrom a workstation, such as all characters enteredbefore a carriage return. (4.) See X.25 line.

line adapter. A functional unit that converts theserial–by–bit input to a station. See alsocommunications line adapter.

line discipline. The asynchronouscommunications user interface for a TTY, whichincludes the POSIX and Berkeley line disciplinesas well as the compatibility mode of Version 2 ofthe AIX operating system.

line editor. An editor that displays data one line ata time and that allows data to be accessed andmodified only by entering commands.

line height. The vertical measurement of a line oftext, measured from the bottom of one line to thebottom of the next line. Line height is usuallyexpressed in points.

line number. For the Ada–language debugger, aline relative to the Ada compilation that containsthe specified compilation unit.

line of memory. The section of memory thatcorresponds to a cache line, which corresponds toa single virtual–memory address tag.

line pacing. The sending of a line followed by awaiting interval before continuing transmission. Seealso pacing.

line printer. A printer that prints output, one line ofcharacters at a time, as a unit. Output of lineprinters is in constant–width characters.

line speed. (1.) The rate at which data istransmitted from one point to another over atelecommunication line. (2.) The number of binarydigits that can be sent over a telecommunicationline in one second, expressed in bits per second(bps). Synonym for speed.

line switching. Synonym for circuit switching.

linear interpolation. A method of approximatingdata values by assuming that they lie along astraight line. Typically, the two end data points areknown. For example, if A is the value at a, and B isthe value at b, and a<t<b, then the value C at t is(from the two–point formula): B – A divided by b –a, multiplied by t – D, added to A.

linefeed. An ASCII character that causes an outputdevice to move forward one line.

linestyle. The pattern used to draw a line. Alinestyle might be solid or broken into a pattern ofdashes.

linewidth. The width of a line in pixels.

link. (1.) In the file system, a connection betweenan i–node and one or more file names associatedwith it. (2.) In data communications, a transmissionmedium and data link control component thattogether transmit data between adjacent nodes.(3.) In programming, the part of a program thatpasses control and parameters between separateportions of the computer program. (4.) Tointerconnect items of data or portions of one ormore computer programs, such as linking objectprograms by a linkage editor or linking data itemsby pointers. (5.) See X.25 link. (6.) See hypertextlink.

link–access procedures (LAP or LAPB). In X.25communications, the link level elements used fordata interchange between a DCE and a DTEoperating in user classes of service 8 to 11, asspecified in CCITT Recommendation X.1. LAPB isa duplex, asynchronous, symmetric protocol, usedin point–to–point communication. See also LAPB.

link address. An address assigned at initializationthat identifies a channel or control unit and allows itto send and receive frames and perform I/Ooperations. A set of computers sharing a networkthat does not include bridges of wide area networklinks.

link anchor. The reference point giving thelocation of a particular link.

link control (LC). See logical link control.

link descriptor. In ODM, a named variable of typelink used to define a relationship between anobject in an object class and an object in anotherobject class. See also descriptor.

link–editing. To create a loadable computerprogram by means of a linkage editor.

link level. See frame level.

link station. The part of data link control that isresponsible for the transfer of data on a singlelogical link.

link target. See target.

link trace. A sequential log of events that occur onthe link. This log can help determine the source ofa recurring error.

1-84 Glossary

linkable. The state of an Ada–language programwhen all its compilation–unit dependencies havebeen resolved. To produce an executable file, thecompiler does not need to do any translation ofAda source; it only needs to call the linkage editor.

linkage editor. A program that resolvescross–references between separately compiledobject modules and then assigns final addresses tocreate a single relocatable load module. If a singleobject module is linked, the linkage editor simplymakes it relocatable.

linker. See linkage editor.

LIS. Logical IP Subnet. An LIS is comprised ofsome number of ATM stations. LISs are analogousto traditional LAN segments.

LISP. A programming language designed for listprocessing and used extensively for artificialintelligence problems.

LISP code. Program instructions written in theLISP programming language.

LISP mode. For text editors, a mode in whichsymbols used in the LISP programming language,such as ( (left parenthesis) and ]] (double rightbracket), are treated as symbols, not as editorcommands.

list. (1.) A data object consisting of a collection ofrelated records. (2.) An ordered set of data.

list–directed. In FORTRAN, an input/outputspecification that uses a data list instead of aFORMAT specification.

list–directed data. In FORTRAN, data that istransferred between main storage and an I/Odevice according to the length and type of variablesin the I/O list. See also formatted data.

list fields. See indexed fields.

listen. In the X.25 API, to be prepared to receiveincoming calls that satisfy criteria specified in anentry in the routing list, through a specified X.25port.

listen identifier. In the X.25 API, an identifier usedto listen for and receive an incoming call.

listening. Programs waiting for networkcommunication on a given socket are listening onthat socket. See also socket and port.

literal. (1.) A symbol or a quantity in a sourceprogram that is itself data, rather than a referenceto data. (2.) In programming languages, a unit thatdirectly represents a value. For example, 14represents the integer 14. (3.) In Ada language, aliteral represents a value literally, that is, by meansof letters and other characters. A literal is either a

numeric literal, an enumeration literal, a characterliteral, or a string literal.

literal string. A string that does not containpattern–matching characters and can therefore beinterpreted just as it is. Contrast with regularexpression.

little endian. An attribute of data representationthat reflects how multi–octet data are stored inmemory. In little endian representation, the lowestaddressed octet of a multi–octet data item is theleast significant. See also endian and big endian.

little endian order. The method of storage inwhich integer values are stored least significantbyte first. See also big endian order.

LLB. See Local Location Broker.

llbd. The local location broker daemon.

LLC. See logical link control.

LMS. Line monitoring system.

LNS. See LU network services component.

load. (1.) To transfer programs or data fromstorage into an area of memory where the programcan be run or where the data can be manipulated.(2.) To place a diskette into a diskette drive. (3.) Toinsert paper into a printer. See also call.

load level. The balance of work betweenprocessing units, channels, or devices.

load module. See run file.

load–store bound. Where the delay in a series ofcomputations is caused by the amount of data thatmust be loaded into registers or stored back intomemory.

loader. A program that reads run files into mainstorage so that the files can be run.

local. (1.) Pertaining to a device, file, or systemthat is accessed directly from your system, withoutthe use of a communications line. Contrast withremote. (2.) Pertaining to information that isdefined and used only in one subdivision of acomputer program.

local address. The address specified for thecurrent network or host. The local address isusually referred to as the local host address or thelocal network address to differentiate the two types.

local area network (LAN). (1.) A network in whichcommunications are limited to a moderate–sizedgeographic area (1 to 10 km) such as a singleoffice building, warehouse, or campus. A localnetwork services a facility without the use ofcommon carrier facilities, although they may beinterconnected using common carriers. A local

1-85Glossary

network depends upon a communications mediumcapable of moderate to high data rate (1 to 20 Mbytes per second), and normally operates with aconsistently low error rate. (2.) A data network inwhich serial transmission is used for direct datacommunication among data stations.

local cell. The cell to which the local machinebelongs. See also foreign cell.

local echo. On a communications workstation, asituation in which each signal is displayed twice,once when entered at the local workstation andagain when returned over the communications link.

local host. In TCP/IP, the host on the network atwhich a particular operator is working.Synonymous with current host.

local listen. A link station at the local node that iswaiting for an incoming call from a remote station.

Local Location Broker (LLB). (1.) Part of theNCS Location Broker. A server that maintainsinformation about objects on the local host. TheLLB also provides the Location Broker forwardingfacility. (2.) A service that provides an interface tothe global location broker from the License UseManagement server. The LLB daemon (llbd) hasno information about network–wide services. It runscontinuously in the background to intercept andforward information to the glbd. See also LocationBroker and Location Broker Client Agent.

local name. A name that is meaningful and usableonly from within the cell where the entry exists. Thelocal name is a shortened form of a global name.Local names begin with the prefix /.: and do notcontain a cell name.

local pacing. Pacing generated by the localsystem in an attempt to control the output from theremote system that is input to the local system.See also pacing.

local scope. A name declared in a block has localscope and can only be used in that block.

local storage. A device accessed directly (withouttelecommunications) from the user’s system,where information can be retained and laterretrieved.

local variable. A symbol defined in one programmodule or procedure that can only be used withinthat program module or procedure.

locale. A subset of a user’s environment thatdefines conventions for a specified culture, such astime formatting, numeric formatting, monetaryformatting, and character classification, conversion,and collation.

locality of reference. The degree to which arunning program makes use of a compact range ofaddresses for instructions and/or data.

Location Broker. In NCS, a set of softwareincluding the Local Location Broker, the GlobalLocation Broker, and the Location Broker ClientAgent. The Location Broker maintains informationabout the locations of objects. See also broker,Local Location Broker, and Location Broker ClientAgent.

Location Broker Client Agent. Part of the NCSLocation Broker. Programs communicate withGlobal Location Brokers and with remote LocalLocation Brokers using the Location Broker ClientAgent. See also Local Location Broker andLocation Broker.

location code. A path from the adapter in theprocessor through the signal cables and fan outbox, if there is one, to the device or workstation.The code consists of four fields of information:Drawer, Slot, Connector, and Port.

location counter. A counter in the assembler thatdenotes the next byte available for code allocation.The location counter assigns storage addresses toprogram statements. See also instruction addressregister.

locator. In computer graphics, an input device thatprovides coordinate data; for example, a mouse,tablet, or thumb wheel.

locator resolution. The density of points on alocator device.

locator sample rate. The rate of input from alocator device. Synonymous with sample rate.

lock. A mechanism with which a resource isrestricted for use by the holder of the lock. See alsorecord lock.

LOCK. See Lock Service.

Lock button. In CDE, a Front Panel control usedto lock the screen.

lock file. In multiprocess applications, a system fileon disk that the sharing processes use to controltheir access to shared data or devices.

Lock Service (LOCK). The component of EncinaBase that enables transactions to lock resourcesbefore accessing or modifying them.

log. (1.) To record. For example, to record allmessages on the system printer. (2.) A list ofmessages, such as an error log. (3.) A collection ofmessages or message segments placed in an

1-86 Glossary

auxiliary storage device for accounting or datacollections purposes.

log file. (1.) The text file that records messagesand errors from the license server, and sometimesfrom licensed products, which resides in the/usr/lib/netls/conf directory. (2.) In Ada language,a file that contains a record of your commands andcomments and the debugger’s responses. This logcan be used for later analysis, for documentingprogram behavior, or for making comparisons afterprogram modification.

log force. An action that causes all pending logrecords to be written to permanent storage. A logforce is usually associated with committing atransaction, and ensures that the log recordsassociated with that transaction are actuallypresent in the log. Until a log force is done, theserecords might only be stored in memory and might,therefore, be vulnerable to system failures.

log force groups. A logical association of the logrecords associated with different processes.Grouping the log records associated with allprocesses spawned by a specific transactionprovides a convenient way to ensure that all of thelog records associated with any processes actingon behalf of a specific transaction can be referredto with a single expression or operation.

log in. (1.) To begin a session at a display station.(2.) The act of gaining access to a computersystem by entering identification and authenticationinformation at the workstation.

log off. To end a session with a computer systemat a display station.

log on. See log in.

log out. See log off.

log record. A predefined structure into which thelog data is formatted. Records have a specific sizeand format, and contain a certain set of relatedinformation. A log record can be identified by its logsequence number (LSN).

log volume. An abstract representation of diskspace that is used for storage by the Encina logserver. There are two types of log volumes:permanent and archival. Permanent volumes canbe stored on file or disk devices. Archival volumescan only be stored on file devices. Internal logserver data and log file groups must be stored onpermanent volumes. Log archive groups must bestored on archival volumes. See also volume,logical volume, and physical volume.

logarithm. A mathematical operation related to thebase of a numbering system.

logger. (1.) A functional unit that records eventsand physical conditions, usually with respect totime. (2.) A program that enables a user entity tolog in (for example, identify itself, its purpose, andtime of entry) and log off with the correspondingdata. This enables the appropriate accountingprocedures to be carried out in accordance with theoperating system.

logical channel. In X.25 communications, ameans of two–way simultaneous transmissionsacross a data link, comprising associated send andreceive channels. A logical channel can representthe path that data travels from its origin to thenetwork or from the network to its destination. Seealso channel.

logical channel number (LCN). An umber thatuniquely identifies a logical channel.

logical constant. A constant with a value of true orfalse.

logical device. (1.) A file for conducting input oroutput with a physical device. (2.) A file formapping user I/O between virtual and real devices.

logical expression. An expression consisting oflogical operators, relational operators, or both thatcan be evaluated to a value of either true or false.

logical link. The logical connection between anapplication on the S/370 and an application on theworkstation.

logical link control (LLC). In a local area network,the protocol that governs the assembling oftransmission frames and their exchange betweendata stations, independently of the medium accesscontrol protocol. See also medium access control.

logical name. A name assigned to a device thatdistinguishes it from all other device instances inthe system. It is the name used to refer to aparticular device. For example, ”tok0” can refer to atoken–ring adapter. This is the same as ”devicename,” which is a field in the Customized DevicesObject Class. See also device name.

logical network. A subnetwork of machines set upto function as a whole and separate network. Alogical network usually functions as a subnetworkof a larger physical network.

logical operation. An operation that follows therules of Boolean logic.

logical operator. A symbol that represents anoperation, such as AND, OR, or NOT, on logicalexpressions.

logical partition (LP). (1.) One to three physicalpartitions (copies). The number of logical partitions

1-87Glossary

within a logical volume is variable. (2.) A fixed–sizeportion of a logical volume. A logical partition is thesame size as the physical partitions in its volumegroup. Unless the logical volume of which it is apart is mirrored, each logical partition correspondsto, and its contents are stored on, a single physicalpartition. See also logical volume.

logical primary. A primary that can have a value oftrue or false.

logical resource. A software construct, such as alock or a buffer, that is required for the execution ofa program and is in limited supply.

logical storage. A conceptual storage layout inwhich an application maps first into logicaladdresses, which are then mapped into realaddresses by control blocks.

logical type. A data type that contains the valuesof true and false.

logical unit (LU). (1.) A type of networkaddressable unit that enables end users tocommunicate with each other and gain access tonetwork resources. (2.) In SNA, a port throughwhich an end user accesses the SNA network tocommunicate with another user, and through whichthe end user accesses the functions provided bysystem services control points (SSCPs). An LU cansupport at least two sessions, one with an SSCPand one with another LU, and may be capable ofsupporting many sessions with other LUs.

Logical Unit Type 1 (LU1). An SNA session thatsupports communication between an applicationand multiple input/output devices. Thiscommunication could occur in an interactive orbatch environment.

Logical Unit Type 2 (LU2). An SNA session thatuses a 3270 device data stream to supportcommunication between an application and adisplay.

Logical Unit Type 3 (LU3). An SNA session thatuses a 3270 device data stream to supportcommunication between an application and aprinter.

Logical Unit Type 6.2 (LU6.2). (1.) An SNAsession between two applications in a distributeddata processing environment. (2.) The LU typeused for SNA advanced program–to–programcommunications (APPC). See also peer–to–peercommunications.

logical volume (LV). (1.) A collection of physicalpartitions organized into logical partitions allcontained in a single volume group. Logicalvolumes are expandable and can span severalphysical volumes in a volume group. (2.) A set oflogical partitions, each of which is stored on one or

more physical partitions from one or more of thephysical volumes of a given volume group. Alogical volume has a device name (of the form/dev/hdn) and contains a single file system. Seealso log volume, migration installation, logicalpartition, and volume group.

Logical Volume Manager (LVM). Manages diskspace at a logical level. It controls fixed–diskresources by mapping data between logical andphysical storage and by allowing data to spanmultiple disks and to be discontiguous, replicated,and dynamically expanded.

login directory. The directory you access whenyou first log in to the system.

login name. A string of characters that uniquelyidentifies a user to the system.

login session. The period of time during which auser of a workstation can communicate with aninteractive system, usually the elapsed timebetween log in and log off.

login shell. The shell that is started when a userlogs into the computer system. The login shell for aparticular user is determined by the entry in the/etc/passwd file for that user. See also shell.

long. (1.) In ODM, a terminal descriptor type usedto define a variable as a signed 4–byte number.See also terminal descriptor. (2.) A signed 4–bytenumber.

long constant. A 4–byte integer constant followedby the letter ”l” or ”L.”

long queue status. Synonym for long status.

long status. A detailed, multiline status thatcontains more information about each job than thenormal short status. Synonymous with long queuestatus.

loop. (1.) A sequence of instructions performedrepeatedly until an ending condition is reached. (2.)A closed unidirectional signal path connecting inputand output devices to a system.

loop collapse. In nested array–processing loops,an optimization that collapses the nested loops intoa single loop with an iteration count that is theproduct of the iteration counts of the original loops,and that adjusts array indices appropriately.

loop defactorizing. An optimization that removesan invariant factor from a loop that sumscalculations into a scalar. The summation scalarcan be multiplied by the factor on exit from theloop.

loop elimination. A form of loop unrolling in whichthe loop is completely unrolled, and references to

1-88 Glossary

loop index within the unrolled loop are replaced byconstant values.

loop fusion. An optimization that takes the bodiesof loops with identical iteration counts and fusesthem into a single loop.

loop nest reordering. An optimization thatchanges the order of loops within a loop nest, toachieve stride minimization or to eliminate datadependencies.

loop overhead. The CPU time used by a loop thatcannot be attributed to computations within theloop.

loop peeling. An optimization that improves theperformance of a loop that maps an array to acylindrical coordinate system.

loop rerolling. An optimization that transformsuser–unrolled loops into their original, unrolledequivalents, so that other optimizations can beattempted.

loop unrolling. An optimization that increases thestep of a loop, and duplicates the expressionswithin a loop to reflect the increase in the step. Thiscan improve instruction scheduling and memoryaccess time.

looping statement. A statement that runs anynumber of times, depending on the value of aspecified expression.

low–order. Least significant; rightmost. Forexample, in a 32–bit register (0 through 31), bit 31is the low–order bit.

LP. See licensed program.

LPFK. See lighted programmable functionkeyboard.

LPM. Lines per minute. The number of lines aprinter can print in one minute.

LPR. Line Printer Server.

LQ. Letter quality.

LRU. Least recently used.

ls_admin. In License Use Management, thesoftware program used to modify a license serverdatabase, invoked with the command ls_admin,which is located in the /usr/lib/netls/bin directory.

ls_rpt. In License Use Management, the softwareprogram that reports on the history of licenseserver events, invoked with the command ls_rpt,which is located in the /usr/lib/netls/bin directory.

ls_stat. In License Use Management, the softwareprogram that reports on the status of licenses,invoked with the command ls_stat, located in the/usr/lib/netls/bin directory.

ls_tv. In License Use Management, the networklicense server daemon test and verification tool,invoked with the command ls_tv, located in the/usr/lib/netls/bin directory.

lsb. Least significant bit

LSB. Least significant byte.

LU. See logical unit.

LU1. See Logical Unit Type 1.

LU2. See Logical Unit Type 2.

LU3. See Logical Unit Type 3.

LU6.2. See Logical Unit Type 6.2.

LU, dependent. A logical unit that cannot start aconversation but must wait for the host system tostart the conversation.

LU, independent. A logical unit that can start aconversation with another logical unit.

LU–LU session. In SNA Services, a sessionbetween two logical units (LUs) of the same typethat supports communication between two endusers, or between an end user and an LU servicescomponent.

LU network services component (LNS). Beginsand ends LU–LU sessions in response to requestsfrom the resource manager and from the remoteLU. It also activates and deactivates CP–LUsessions.

lvalue. (1.) An expression that represents a dataobject that can be both examined and altered. (2.)The left–hand part of an expression.

LV. See logical volume.

LVM. See Logical Volume Manager.

1-89Glossary

Mm. See meter.

MAC. (1.) See medium access control. (2.)Mandatory Access Control.

machine execution state. A state that indicatesthe machine is shut down, booting, or running. Thisstate is one of two machine states.

machine instruction. (1.) A binary number thatdirects the operation of a processor. Compilers andassembler convert source instructions to machineinstructions. (2.) An instruction of a machinelanguage. Synonym for computer instruction andcomputer language.

machine language. A language that can be useddirectly by a computer without intermediateprocessing. The final output of the compilationprocess is a load module containing machinelanguage instructions. Synonym for computerlanguage.

machine object. An entry in the NetworkInstallation Management database that representsa machine configuration.

machine state. A state that identifies the machineexecution state and control state for each machine.

machine word. Synonym for word. See alsocomputer language.

macro. (1.) A label that is declared at the start of aprogram or file. The label can then be used torepresent the values assigned to the label in thedeclaration. (2.) A name or label used in place of anumber of other names. (3.) The sequence ofinstructions or statements that a macrogeneratorruns when replacing a macro instruction. (4.) A setof statements defining the name of, format of, andconditions for generating a sequence of assemblerstatements from a single source statement. (5.) Aseries of Ada–language debugger commands thatexecute in sequence when you call the macro. Withthe macro option, you can define and manipulatenew debugger commands. See also routine,statement function, and subroutine.

macro call. A single instruction that, whenexecuted, causes the execution of a predefinedsequence of instructions in the same sourcelanguage.

macro instruction. See macro call and macro.

macro processor. A program that converts macroinstructions into specified values.

magic number. A numeric or string constant in afile that indicates the file type.

mail. Correspondence in the form of messagestransmitted between workstations over a network.Synonymous with electronic mail.

mail box. A storage location in a network to whichmessages for a user are sent.

mail drop. The file into which messages are firstreceived.

Mailer. In CDE, an application that enables you tosend, receive, and compose electronic mailmessages.

mailer. The program that does the actual deliveryof mail.

mailer container. In CDE, the electronic mail boxand filing system that contains all mail messages.Once a message is put in a container, you candisplay, modify, delete, print, include, forward, andreply to it.

Mailer control. In CDE, the Front Panel controlused to start the Mailer software application.Dropping a file on the control loads the file into theMailer Compose window.

main. In FORTRAN, the default name given to amain program if one was not supplied by theprogrammer.

main function. A function that has the identifiermain. Each C language program must haveexactly one function named main. This function isthe main program of a C language program.

Main Panel. In CDE, the portion of the Front Panelexcluding the subpanels.

main program. (1.) The first program unit toreceive control when a program is run. Contrastwith subprogram. (2.) A program that performsprimary functions, passing control to routines andsubroutines for the performance of more specificfunctions.

main storage. (1.) Program–addressable storageor memory from which instructions and other datacan be loaded directly into registers for subsequentrunning or processing. Synonymous with systemmemory. (2.) The part of internal storage into whichinstructions and other data must be loaded forrunning or processing. (3.) The part of theprocessing unit where programs are run.

mainframe. A large computer, particularly one towhich other computers can be connected so thatthey can share facilities the mainframe provides.The term usually refers to hardware only.

maintenance analysis procedure (MAP).Documentation used by customer engineers andby service representatives to repair equipment. A

1-90 Glossary

MAP contains yes/no questions and proceduresthat direct the user to the failing part of theequipment.

maintenance level update. The service updates(fixes and enhancements) that are necessary toupgrade the Base Operating System (BOS) or anoptional software product to the current releaselevel. See also service update.

maintenance mode. State in which a product orsystem can be serviced. Synonymous with servicemode.

maintenance system. A special version of theoperating system that is loaded from diskette andused to perform system management tasks.

major device number. A system identificationnumber for each device or type of device. Themajor device, minor device, and channel numbersuniquely identify a hardware device. See alsominor device number.

managed children. In Enhanced X-Windows,children in which the managed field has a value ofTrue can have their layout (geometry) changed sothat they can be repositioned and resized.

managed window. See managed children.

manager. See device manager.

Manager class. In AIXwindows, a metaclass thatprovides the resources and functionality toimplement certain features, such as a keyboardinterface and traversal mechanism. It is built fromthe Core, Composite, and Constraint classes.

mangling. The encoding, during compilation, ofC++ identifiers such as function and variablenames to include type and scoping information.The linker uses these mangled names to ensuretype–safe linkage.

manual call. In data communications, a line typethat requires the operator to place a call over aswitched line. Contrast with auto–call.

manual dialing. In making an ATE connection,dialing the number manually over a telephone line.

map. See mapping.

MAP. See maintenance analysis procedure.

mapped. In Enhanced X-Windows, a window issaid to be mapped if a map call has beenperformed on it.

mapped conversation. A temporary connectionbetween an application program and an advancedprogram–to–program communication (APPC)session in which the system provides all theprotocol information. It allows the two programs toexchange data records of any length and in any

format specified by the transmission programs.Only LU6.2 sessions allow mapped conversation; itis used primarily for application transactionprograms. Contrast with basic conversation.

mapped file. (1.) A file that can be accessedthrough direct memory operations instead of beingread from disk each time it is accessed. (2.) A fileon the fixed disk that is accessed as if it is inmemory.

mapping. (1.) In Enhanced X-Windows, a windowon which a map call has been performed. Mappingmakes a window visible if there are no obscuring oroccluding windows. (2.) A list, usually in a profile,that establishes a correspondence between itemsin two groups. For example, a keyboard mappingcan establish what character is displayed when acertain key is pressed. See also keyboard mappingand profile.

margin. Left and right border of text on a screen orhardcopy page.

mark block. In Pascal, a dynamic block headerthat designates a subheap within a heap.

marker. (1.) A visual symbol within anon–interactive pane indicating the location of thecursor when the pane was last interactive. (2.) Incomputer graphics, a glyph with a specifiedappearance that is used to identify a particularlocation.

marshal. In NCS, to copy data into a RemoteProcedure Call (RPC) packet. Stubs performmarshalling. Contrast with unmarshal. See alsostub.

mask. (1.) A pattern of characters that controls thekeeping, deleting, or testing of portions of anotherpattern of characters or bits, usually through anAND or OR operation. (2.) To apply a mask.

master. The only machine in the NIM environmentthat has permission to remotely executecommands on other NIM clients.

master dump table. A structure containing dumptable entries generated by kernel components. Thedump program uses this table to locate datastructures that should be included in a dump.

master file. (1.) A collection of permanentinformation, such as a customer address file. (2.) Afile that is used as an authority in a given job andthat is relatively permanent, even though itscontents may change.

master processor. The first processor started atboot time in a multiprocessor system.

master server. In a network installationenvironment, the server that has permissions to

1-91Glossary

execute commands on all other machines in theenvironment. The master server is designed tomanage the network, client, and resource objectsin the network installation database.

matrix. (1.) A rectangular array of elementsarranged in rows and columns that can bemanipulated based on matrix algebra rules. (2.) Incomputers, a logic network in the form of an arrayof input and output leads with logic elements joinedat some of their intersections. (3.) By extension, anarray of any number of dimensions.

matrix stack. In GL, a stack of matrices withhardware and software support. The top matrix onthe stack is the current transformation matrix, andall points passed through the graphics pipeline aremultiplied by that matrix. It is a concatenation of thecurrent modeling and viewing transformations. Seealso current transformation matrix.

maximum transfer unit (MTU). (1.) The maximumnumber of bytes that an Internet Protocol (IP)datagram can contain. (2.) The largest amount ofdata that can be transmitted in a single frame for aparticular network interface.

Mb. Megabit.

MB. Megabyte.

M–bit. In X.25 communications, the bit in a datapacket that indicates that there is more data tofollow in another data packet (when a message istoo large for one packet).

mbuf. A small (256–byte) buffer provided by thembuf management facility to the various layers ofcommunication software in AIX.

M–byte. See megabyte.

MC. See MCU.

MCU (MC). Memory control unit.

medium access control. In a local area network,the protocol that governs communication on thetransmission medium without concern for thephysical characteristics of the medium. However, ittakes into account the topological aspects of thenetwork, to enable the exchange of data betweendata stations. See also logical link control.

megabyte (MB). Loosely, one million bytes. Whenreferring to semiconductor memory capacity, two tothe twentieth power; 1 048 576 in decimal notation.When referring to media device storage, amegabyte is ten to the sixth power (1 000 000).

megahertz (MHz). A unit of measure of frequency.One megahertz equals 1 000 000 hertz.

member. (1.) A data object in a structure, a union,or a library. (2.) Synonym for element. (3) A C++data object or function in a structure, union or

class. Members can also be classes,enumerations, bit fields and type names.

member function. C++ Operators and functionsthat are declared as members of a class. Amember function has access to the private andprotected data members and member functions ofan object of its class. Member functions are alsocalled methods.

memory. (1.) Program–addressable memory fromwhich instructions and other data can be loadeddirectly into registers for subsequent running orprocessing. (2.) Memory on electronic chips.Examples of memory are random access memory,read–only memory, or registers. See also storage.

memory deallocation. To free up memory that hasbeen previously allocated for a specific purpose.

memory dump. The means by which the computersystem records its state at the time of a failure.

memory image. The logical layout of the parts of aprocess in memory.

memory leak. A software bug in which theprogram allocates memory, loses track of it, andthen allocates some more. If the program islong–running, it can eventually tie up largeamounts of real memory and paging space.System performance gradually deteriorates; theprogram that finally fails due to lack of resourcemay not be the culprit. Memory leaks in kernelextensions that allocate pinned memory may beparticularly costly.

memory load control. A VMM facility, added inAIX Version 3.2, that detects memoryover–commitment and temporarily reduces thenumber of running processes, thus avoidingthrashing.

memory over–commitment. A condition in whichthe number of virtual–memory pages being usedby the currently running programs exceeds thenumber of real–memory page frames available tohold them. If the over–commitment is large orsustained, system performance suffers.

menu. A displayed list of items from which anoperator can make a selection.

menu bar. A rectangular area at the top of theclient area of a window that contains the titles ofthe standard pull–down menus for that application.

menu cursor. In AIXwindows, the cursor definedfor a particular menu. Each type of cursor isidentified by an ID number.

menu pane. The physical window containing apop–up menu listing a group of options to bechosen by the user. See also pane.

1-92 Glossary

menu system. An interactive interface that listsrelated software options in a manner that expeditesreview and selection by the user.

message. (1.) Information from the system thatinforms the user of a condition that may affectfurther processing of a current program. (2.) Anerror indication, or any brief information that aprogram writes to standard error or a queue. (3.)Information sent from one user in a multiuseroperating system to another. (4.) A general methodof communication between two processes. (5.) Agroup of characters and control bit sequencestransferred as an entity. (6.) One or more linkedblocks of data or information, with associatedSTREAMS control structures containing a messagetype. Messages are the only means ofcommunicating within a stream.

message control block. In the X.25 API, thestructure used to indicate what type of packet hasarrived and to point to the structure that containsthe packet information.

message queue. A linked list of messagesconnected to a QUEUE.

message queue ID (msqid). An identifier assignedto a message queue for use within a particularprocess. It is similar in use to a file descriptor of afile.

message type. A defined set of values identifyingthe contents of a message.

metaclass. (1.) In AIXwindows and EnhancedX-Windows, an object class that does notinstantiate widgets or gadgets but is capable ofpassing a unique set of inheritable resources to thesubclasses beneath it in the class hierarchy. Eachinstance of a widget subclass has the featurescommon to that widget class and exports thesefeatures to child widgets of that class. Included inthis class are Core, Composite, Constraint,Primitive, Button, Manager, MenuMgr, andMenuPane. (2.) In SOM, a class whose instancesare classes. In SOM, any class descended fromSOMClass is a metaclass. The methods a classinherits from its metaclass are sometimes calledclass methods (in Smalltalk) or factory methods (inObjective–C) or constructors. See also classmethod.

metaclass incompatibility. In SOM, a situationwhere a subclass does not include all of the classvariables or respond to all of the class methods ofits ancestor classes. This situation can easily arisein OOP systems that allow programmers toexplicitly specify metaclasses, but is not allowed tooccur in SOM. Instead, SOM automaticallyprevents this by creating and using derivedmetaclasses whenever necessary.

metadata. The structural data associated with thefile system, such as the organization of directories,inode tables, and links. Metadata is not datasupplied by a user; it is information about thestructure of user data.

meter (m). A linear measurement that equals1.0936 yards, 3.2808 feet, or 39.3696 inches.

method. (1.) In Enhanced X-Windows, thefunctions or procedures that a widget itselfimplements. (2.) In ODM, executable codeassociated with an object and defined as the valueof a method descriptor for the object. The methodcan be a command, program, or shell script. Seealso method descriptor. (3.) An object–orientedprogramming term synonymous with memberfunction. (4.) In SOM, a combination of a procedureand a name, such that many different procedurescan be associated with the same name. Inobject–oriented programming, invoking a methodon an object causes the object to execute aspecific method procedure. The process ofdetermining which method procedure to executewhen a method is invoked on an object is calledmethod resolution. (The CORBA standard uses theterm ”operation” for method invocation). SOMsupports two different kinds of methods: staticmethods and dynamic methods. See also staticmethod and dynamic method.

method descriptor. In ODM, a named variable oftype method used to define a method or operationto associate with an object. The method can be anyexecutable code such as a command, program, orshell script. See also method and descriptor.

method ID. In SOM, a number representing azero–terminated string by which SOM uniquelyrepresents a method name. See also somId.

method procedure. In SOM, a function orprocedure, written in an arbitrary programminglanguage, that implements a method of a class. Amethod procedure is defined by the classimplementor within the implementation template filegenerated by the SOM Compiler.

method prototype. In SOM, a method declarationthat includes the types of the arguments. Based onmethod definitions in an IDL source file, the SOMCompiler generates method prototypes in theimplementation template. A class implementoruses the method prototype as a basis for writingthe corresponding method procedure code. Themethod prototype also shows all arguments andtheir types that are required to invoke the methodfrom a client program.

method resolution. In SOM, the process ofselecting a particular method procedure, given amethod name and an object instance. The process

1-93Glossary

results in selecting the particularfunction/procedure that implements the abstractmethod in a way appropriate for the designatedobject. SOM supports a variety ofmethod–resolution mechanisms, including offsetmethod resolution, name–lookup resolution, anddispatch–function resolution.

method table. In SOM, a table of pointers to themethod procedures that implement the methodsthat an object supports. See also method token.

method token. In SOM, a value that identifies aspecific method introduced by a class. A methodtoken is used during method resolution to locatethe method procedure that implements theidentified method. The two basicmethod–resolution procedures are somResolve(which takes as arguments an object and a methodtoken, and returns a pointer to a procedure thatimplements the identified method on the givenobject) and somClassResolve (which takes asarguments a class and a method token, andreturns a pointer to a procedure that implementsthe identified method on an instance of the givenclass). See also method table.

MHz. See megahertz.

MIB Variable. A managed object that is defined inthe Management Information Base (MIB). Themanaged object is defined by a textual name and acorresponding object identifier, a syntax, an accessmode, a status, and a description of the semanticsof the managed object. The MIB Variable containspertinent management information that isaccessible as defined by the access mode.

Micro Channel architecture. The I/O channelused on the POWERstation and POWERserversystem units.

microdocument. A document within a frame thathas its own properties and shares components withthe main document.

migration installation. An installation method forupgrading AIX Version 3.2 or later to the currentrelease while preserving the existing root volumegroup. This method preserves the /usr, /tmp, /var,and / (root) file systems, as well as the root volumegroup, logical volumes, and system configurationfiles. Migration is the default installation method for,and can only be used on, an AIX Version 3.2 orlater machine. See also root volume group andlogical volume.

mil. A measurement of thickness: 1/1000 inch.

millisecond. A measurement of time: 1/1000 of asecond.

minimally consistent. Said of an object thatsatisfies various conditions set forth in the definitionof its class.

minor device number. A number that specifiesvarious types of information about a particulardevice. For example, a number that distinguishesbetween several printers of same type. See alsomajor device number.

mirroring. The creation of a mirror image of aprimitive.

mixed string. A string consisting of a mixture ofDBCS characters and single–byte characters.

mm. (1.) A package of macros for manuscriptpreparation that supports the eqn and troffcommands or the neqn and nroff commands andfeatures annotation, footnoting, indexing, andtables by supporting the tbl command. (2.)Millimeter.

mnemonic. (1.) A symbol chosen to help the userremember the significance of the symbol. (2.) Thefield of an assembler instruction that contains theacronym or abbreviation for a machine instruction.(3.) In CDE, a single, underlined character in acommand. The mnemonic indicates that you canchoose the command by typing that letter.Mnemonics are used most commonly in menucommands; however, other buttons may also havemnemonics.

mnemonic overstrike. A nonstandard charactercreated by printing one character on top of anotherto represent a nonprinting character.

modal. The state in which a secondary windowreceives keyboard or pointer input that it does notpass on to its associated window.

modal dialog. In AIXwindows, a Dialog widgetthat interrupts the work session to solicit input fromthe user.

modal interaction. The communication betweenseparate modes or functions.

modal pop–up. In Enhanced X-Windows, awindow that normally is not visible to the windowmanager and available only after the manager isturned off. This pop–up disables user–eventprocessing except for events that occur in thedialog box.

mode. (1.) A method of operation. (2.) In SNA datacommunications, the set of rules and protocols tobe used for a session. (3.) In the M–Video CaptureAdapter, a method of operation such as live oroverlay capture. (4.) For Ada programming, seeparameter.

1-94 Glossary

model number. In Ada language, an exactlyrepresentable value of a real type. Operations of areal type are defined in terms of operations on themodel numbers of the type. The properties of themodel numbers and of their operations are theminimal properties preserved by allimplementations of the real type.

modeless dialog. In AIXwindows, a Dialog widgetthat solicits input from the user but does notinterrupt the work session.

modeless pop–up. In Enhanced X-Windows, awindow that is normally visible and is controlled bythe window manager.

modeling coordinates, modeling space. In GL,the coordinate system in which all drawingprimitives do their drawing. The user can select theposition and orientation of the modeling space withregard to the world space by means of translations,rotations, scales, or generalized transformations.The relation between modeling coordinates andworld coordinates is determined by the modelingmatrix. Modeling coordinates are a usefulconceptual device when drawing complex orrepetitive scenes. For instance, a paper clip can bedefined once in modeling coordinates, and thendrawn hundreds of times by moving the modelingcoordinates around in world space. See also eyecoordinates, screen coordinates, worldcoordinates, and transformation.

modem (modulator–demodulator). A device thatconverts digital data from a computer to an analogsignal that can be transmitted on atelecommunication line, and converts the analogsignal received to digital data for the computer.

modem eliminator. A device that connects aworkstation directly to a computer port through awired connector with a specific pin arrangement.When two devices both function as DTEs (dataterminal equipment), the cable that connects themmust transmit send and receive signals using amodem eliminator. Synonymous with null modem.

mode name. (1.) The name of an entry in the loginmode table. (2.) In SNA, identifies the set of rulesand protocols to be used for the session.

mode word. An i–node field that describes thetype and state of the i–node.

modification number. The modification level of aprogram, which is an indicator of changes that donot affect the external interface of the program. Theversion, release, modification, and fix levelstogether comprise the program level, fix number,release number, and version number.

modifier. (1.) Word or quantifier used to change aninstruction causing the execution of an instruction

different from the original one. Consequently, thesame instruction, successively changed by amodifier, can be used repetitively to carry out adifferent operation each time it is used. (2.) InSOM, any of a set of statements that control how aclass, an attribute, or a method will beimplemented. Modifiers can be defined in theimplementation statement of a SOM IDL sourcefile. The implementation statement is aSOM–unique extension of the CORBA specification. [User–defined modifiers can also bespecified for use by user–written emitters or tostore information in the Interface Repository, whichcan then be accessed via methods provided by theInterface Repository Framework.]

modifier key. In CDE, a key that when pressedand held along with another key or mouse buttonchanges the meaning of the second key or mouseclick. Control, Alt, and Shift are examples.

modifier keys. In Enhanced X-Windows, keyssuch as Shift, Shift Lock, Control, Alt, Caps Lock,and Meta.

modulation. Changing the frequency or size ofone signal by using the frequency or size ofanother signal.

modulator–demodulator. See modem.

module. (1.) A discrete programming unit thatusually performs a specific task or set of tasks.Modules are subroutines and calling programs thatare assembled separately, then linked to make acomplete program. (2.) In programming languages,a language construct that consists of procedures ordata declarations and that interact with other suchconstructs. (3.) A packaged functional hardwareunit designed for use with other components. (4.)Synonym for program unit. (5.) See also run file.(6.) Software that performs functions on messagesas they flow between stream head and driver. Amodule is the STREAMS counterpart to thecommands in a shell pipeline except that a modulecontains a pair of functions that allow independentbidirectional (downstream and upstream) data flowand processing. (7.) In SOM, the organizationalstructure required within an IDL source file thatcontains interface declarations for two (or more)classes that are not a class–metaclass pair. Suchinterfaces must be grouped within a moduledeclaration. See also object module.

MOM. See monitor mode.

mond. See monitor scheduling daemon.

monitor. (1.) A device that observes and verifiesoperations of a data processing system. (2.) Afunctional unit that observes and records selectedactivities for analysis within a data processing

1-95Glossary

system. Possible uses are to show significantdepartures from the norm or to determine levels ofutilization or particular functional units. (3.)Synonym for display.

monitor mode (MOM). A mode in which anapplication program can directly access the displayadapter.

monitor scheduling daemon. A process that runson an application server and provides clients withlinks to processing agents as needed

monochrome. A special case of static gray inwhich there are only two color map entries. Somemonochrome adapters can display shades of grayin the Gray Scale Adapter.

monochrome display. A display device that hasonly one color. See also gray scale.

more–data bit. See M–bit.

mount. To make a file system accessible.

mouse. A hand–held locator that a user operatesby moving it on a flat surface. It allows the user toselect objects and scroll the display screen bypressing buttons.

mouse button 1. On a mouse, the leftmost buttonwhen configured for right–handed use; therightmost button when configured for left–handeduse. Mouse button 1 is primarily used for selection,and is the default button for the ”click” instruction.

mouse button 2. On a three–button mouse, themiddle button. On a two–button mouse, the rightbutton if configured for right–handed use or the leftbutton if configured for left–handed use. Mousebutton 2 has two modes: Transfer and Adjust.

mouse button 3. On a mouse, the rightmostbutton when configured for right–handed use; theleftmost button when configured for left–handeduse. Mouse button 3 activates pop–up menus.

mouse pointer. A symbol on the screen (such asan arrow or hand) that follows the movement of themouse as the user moves it.

mouse scaling. The distance the cursor movesrelative to the mouse movement. The scaling factoris either 1:1 or 2:1.

mouse threshold. An operating system parameterthat determines the amount of horizontal or verticalmouse movements required to move the cursor onthe screen.

ms. A package of macros for manuscript andthesis preparation that features automatic footnotenumbering and bibliography capabilities.

msb. Most significant bit.

MSB. Most significant byte.

MS–DOS. Microsoft Disk Operating System.

msqid. See message queue ID.

MTU. See maximum transfer unit.

multibyte control. One of the two types of controlsvalid in a character stream data. Synonym forescape sequence.

multicast address. A multicast address, for FDDI,is an address with the high order bit in thehigh–order byte of the address set. This type ofaddress allows a user to have multiple stations ona ring set to the same address. If a packet is sentto a multicast address, all stations with thataddress receive the packet. A multicast address issometimes referred to as a group address.

multidrop. (1.) Stations connected to a multipointchannel at one location. (2.) A networkconfiguration in which there are one or moreintermediate nodes on the path between a centralnode and an endpoint node.

multihomed machine. A machine that has morethan one configured network adapter and morethan one host name.

multihomed server. A server that has more thanone network interface running.

multiline. More than one communications line.

multimode optical fiber. A graded–index orstep–index optical fiber that allows more than onebound mode to propagate. Contrast withsingle–mode optical fiber.

multiple inheritance. An object–orientedprogramming technique implemented in C++through derivation, in which the derived classinherits members from more than one base class.

multiplex. To interleave or simultaneously transmittwo or more messages on a single channel.

multiplexed device. (1.) A device that takesseveral input signals and combines them into asingle output signal so that each of the inputsignals can be recovered. (2.) A device capable ofinterleaving events of two or more activities orcapable of distributing events of an interleavedsequence to the respective activities.

multiplexer. See multiplexed device.

multipoint. Pertaining to communication amongmore than two stations over a singletelecommunications line.

multipoint link. A circuit that interconnects severalstations.

multitasking. A mode of operation that providesfor concurrent performance or interleaved

1-96 Glossary

processing of two or more tasks. Synonym fortasking.

multiuser mode. A mode of operation that enablestwo or more users to use the services of aprocessor within a given period of time. The usageis usually serial unless otherwise specified.

mutex. Jargon for mutual exclusion lock. Use ofthis type of lock excludes all threads other than thelock holder from any access whatsoever to thelocked resource.

mutual exclusion mechanism. A means forpreventing two separately executing pieces of code

from interfering with each other’s use of a particulardata object. For example, if one thread is executinga function that modifies a shared data structure,then the application may need to prevent otherthreads from attempting to read the datasimultaneously, before the modifications arecomplete.

MVS. Multiple Virtual Storage.

MVS/TSO. A type of operating system used on aSystem/370 computer.

mwm. AIXwindows window manager. See alsowindow manager.

1-97Glossary

Nn. See en.

NA. Not applicable.

name. (1.) A sequence of 1 to 250 alphanumericcharacters, the first of which must be alphabetic,that identifies a data object. (2.) In Ada language, aname is a construct that stands for an entity: it issaid that the name denotes the entity, and that theentity is the meaning of the name. See alsodeclaration and prefix. (3.) In C++, a name iscommonly referred to as an identifier. However,syntactically, a name can be an identifier, operatorfunction name, conversion function name,destructor name, or qualified name. See alsosymbolic name.

name–lookup method resolution. Similar to themethod resolution techniques employed byObjective–C and Smalltalk. In SOM, it issignificantly slower than offset resolution.Name–lookup resolution, unlike offset resolution,can be used when the name of the method to beinvoked is not known until run time, or the methodis added to the class interface at run time, or thename of the class introducing the method is notknown until run time.

name resolution. The process of translating(resolving) a symbolic name into its more efficientInternet address.

name server. A host that provides name resolutionfor a network. Name servers translate symbolicnames assigned to networks and hosts into theefficient Internet addresses used by machines.

name string. A character string that identifies oneof a variety of objects such as an icon, a resource,or a font.

named common. In FORTRAN, a separatecommon block consisting of variables and arraysand given a name.

named pipe. A pipe that an application opens byname in order to write data into or read data fromthe pipe. By convention, named pipes are placed inthe /dev directory and are treated as special files.Using a named pipe facilitates communicationbetween a sending process and a receivingprocess.

naming scope. See scope.

NaN. See not–a–number.

national language support. Conversionsubroutines for languages other than AmericanEnglish that translate between various character

sets and date and time string formats. Synonymouswith international character support.

national terminal number (NTN). In X.25communications, the 1– to 12–digit number thatfollows the country code in the network useraddress.

natural or social science format. The style ofbibliography entry favored by writers in the naturaland social sciences.

navigation keys. In CDE, the keyboard keys usedto move the current location of the cursor. Theseinclude the arrow keys (with or without the Controlkey); the Tab key (with or without the Control orShift keys); the Begin and End keys (with or withoutthe Control key); and the Page Up and Page Downkeys.

NCA. See Network Computing Architecture.

NCCF. See Network Communications ControlFacility.

NCK. See Network Computing Kernel.

NCS. See Network Computing System.

NCS cell. A logical concept of grouping togetherone or more machines in an NCS network. Anynode belonging to an alternate cell may only havetheir license requests satisfied by License UseManagement servers in that cell. Nodes outside thecell may not make license requests to servers inanother cell. Two types of cells, default andalternate, are used to provide two ways ofaccessing License Use Management servers.

NDC. See normalized device coordinates.

negative response. In data communications, areply indicating that data was not received correctlyor that a command was incorrect or unacceptable.

negotiation. In X.25 communications, the processby which two DTEs establish the packet size,packet window size, and throughput class to beused during a call procedure. Contrast withvalidation.

neighbor gateway. One of the peers acquired byan exterior gateway. All exterior gateways do notcommunicate with all other exterior gateways.Instead, they acquire neighbors through which theycommunicate.

nest. (4.) To incorporate a structure or structuresinto a structure of the same kind. (5.) To placesubroutines or data in other subroutines or data ata different hierarchical level. Therefore, thesubroutines can be run as recursive subroutines orso that the data can be accessed recursively. (6.) Aself–contained software element that completely

1-98 Glossary

encompasses a similar software element is said tohave that similar element ”nested” within it.Examples include software loops (the nested loop)nested within larger loops (the nesting loop) andsubmenus nested within menus.

nested class. A C++ class defined within thescope of another class.

nested DO. In FORTRAN, a DO loop or DOstatement in which the range is entirely containedwithin the range of another DO loop.

nested transaction. A transaction begun withinthe scope of another transaction. These are alsoreferred to as subtransactions.

NETASCII. Eight–bit ASCII with the first bit alwaysset high, for error checking.

NetBios. Network Version of Basic Input/OutputSystem.

NetLS. See License Use Management.

netlsd. The command used to invoke the networklicense server daemon.

network. A collection of data processing productsthat are connected by communication lines forinformation exchange between locations.

network adapter. Circuitry that allows devices tocommunicate with other devices on the network.

network address. (1.) The part of an addressindicating a specific network. A complete addressfor a machine on a network consists of the networkaddress and the host address. (2.) In NCS, aunique identifier (within an address family) for aspecific host on a network or an internet. Thenetwork address is sufficient to identify a host, butdoes not identify a communication end point withinthe host.

network boot image. A boot image that supportsstandalone, diskless, and dataless machines.

Network Communications Control Facility(NCCF). A licensed program that serves as a basefor command processors that can monitor, control,and improve the operation of a network.

Network Computing Architecture (NCA). A set ofprotocols and architectures that support distributedcomputing.

Network Computing Kernel (NCK). Thecombination of the RPC runtime library and theLocation Broker, which contain the necessarypieces required to run distributed applications.

Network Computing System (NCS). A set ofsoftware tools developed by Apollo Computer Inc.that conform to the Network ComputingArchitecture. These tools include the Remote

Procedure Call runtime library and the LocationBroker. NCS is the underlying communicationsprotocol used by License Use Management totransmit licensing transactions between clients andservers. Messages are broadcast from clients tothe NCS–managed network.

Network File System (NFS). A distributed filesystem that enables users to access files anddirectories located on remote computers and treatthose files and directories as if they were local.NFS is independent of machine types, operatingsystems, and network architectures through theuse of remote procedure calls (RPC).

Network Information Center (NIC). Thepublication distribution center for DARPA TCP/IPinformation.

Network Installation Management (NIM). Anenvironment that provides installation andconfiguration of software within a network interface.

network interface. The software that formatspackets at the network layer into packets thatspecific network adapters can understand andtransmit.

Network License System. See License UseManagement.

network management. The conceptual controlelement of a data station that interfaces with all ofthe layers of that data station and is responsible forthe setting and resetting control parameters,obtaining reports of error conditions, anddetermining if the station should be connected to ordisconnected from the medium.

network mask (netmask). A 32–bit mask used toidentify the most local portion of a local areanetwork (LAN).

network object. An entry in the NetworkInstallation Management database that representsa local area network.

network protocol. A communications protocolfrom the Network Layer of the OSI networkarchitecture, such as the Internet Protocol (IP).

network provider. In X.25 communications, theorganization, often a PTT, that provides a publicnetwork.

network state. A state that indicates either that thenetwork object can participate in NIM operations oran error in the definition of the network object.

network terminating unit (NTU). In X.25communications, the point of access to thenetwork.

Network Time Protocol (NTP).Internet–recommended time standard.

1-99Glossary

network user . A kernel–level protocol oruser–level application that accesses the services ofthe network layer.

network user address (NUA). In X.25communications, the X.121 address containing upto 15 binary code digits.

network user identification (NUI). (1.) The facilitythat enables the transmitting DTE to provide billing,security, or management information on a per–callbasis to the DCE. (2.) The NUI can identify anetwork user independent of the port being used.See also address.

new. In C++, a keyword identifying a free storeallocation operator. The new operator may be usedto create class objects.

new installation. An installation method usedwhen the fixed disk or disks you are installing BOSonto are empty. A hard disk is considered empty ifit does not contain any data or if it contains datanot in a volume group.

new–line character (NL). A control character thatcauses the print or display position to move downone line. This character is represented by ’\n’ in theC language. Usually a carriage return is implicitlyassociated with an NL.

new–process image. A new program laid over thecurrent program by the exec subroutine.

next. The dialog management action fordependent workstations that causes the nextportion of a data object to be presented.

NFS. See Network File System.

NIC. See Network Information Center.

nice value. A number that is used to bias thepriority of a process. A higher number results in alower priority.

nickname. Synonym for alias.

NIM. See Network Installation Management.

NIM routing. The information that defines whichnetworks in the NIM environment can communicatewith each other and which gateways they use tofacilitate that communication. NIM routing is usedto represent the TCP/IP routine that exists for theLANs in the overall network environment.

NIS. Network Information Service. A distributeddatabase that allows you to maintain consistentconfiguration files throughout your network.

NL. See new–line character.

node. (1.) A computer connected to a network. (2.)An end point of a link, or a junction common to twoor more links in a network. Nodes can beprocessors, controllers, or workstations, and they

can vary in routing and other functional capabilities.(3.) In Systems Network Architecture the portion ofa hardware component, along with its associatedsoftware components, that implements thefunctions of the seven architectural layers (SNA).(4.) In a tree structure, a point at which subordinateitems of data originate.

node ID. A unique string of characters thatidentifies the node on a network.

node verification. An additional level of securitybeyond that provided by the network addressingscheme. Node verification helps to ensure that aconnection reaches the correct remote station. It isavailable on LU6.2 connections only. See alsoBIND password.

nodelock file. The text file at a user node (ratherthan at a license server node) where nodelockedlicenses are added. The nodelock file is located inthe /usr/lib/netls/conf directory.

nodelocked license. A type of license locked to aspecific node so that the product may only be usedat that node. The license server does notadminister nodelocked licenses.

nodes. Systems connected in a network to form amonitor cell.

no–input zone. Synonym for dead zone.

noise. (1.) A disturbance that affects a signal andpotentially distorts the information carried by thatsignal. (2.) Random variations of the characteristicsof any entity, such as voltage, current, or data.(3.)A random signal of known statistical propertiesof amplitude, distribution, and spectral density.

nolock lock. A dummy lock mode that is usedwhen a lock mode must be supplied, but whenactually locking the data is not required. Functionsspecifying this lock mode can read data even whenit is currently locked by other operations ortransactions, enabling dirty reads to be performed.This type of lock is operationally consistent, whichmeans that using it to lock and read a value willreturn an actual value that was correct at somemoment in time, but is not transactionallyconsistent.

nondeterministic program. A program whoseresults cannot be determined by analyzing thesource code. A program that does not initializevariables before their first use is nondeterministic,because the value of an uninitialized variable canchange between runs of the program.

nonexecutable program unit. In FORTRAN, ablock data subprogram.

nonexecutable statement. A statement thatdescribes the characteristics of a program unit,

1-100 Glossary

data, editing information, or statement functions,but does not cause any action to be taken.

non–extended result. An exception notificationthat does not have any data defined in theresult_ext file of the dlc_getx_arg structure.

non–printing character. Synonym for controlcharacter.

non–productive. Data traffic on the media that isonly made up of repetitive control information anddoes not contain end user data.

non–return–to–zero (NRZ). A binary code systemin which a signal condition must be sustained forthe full time interval and does not revert to astandby or quiescent state between signalelements. Using NRZ permits the maximum datasignaling rate on the channel, which should betwice the band width, according to Nyquist’stheorem.

nonspacing character. See diacritic.

nonspacing character sequence. For accentedcharacters, a two–part sequence consisting of avalid diacritic followed by an alphabetic characteror a space. The system converts the sequence intoa single code point that results in the alphabeticcharacter with the specified diacritic mark.

nonswitched line. (1.) A connection betweencomputers or devices that does not have to beestablished by dialing. (2.) A dedicated line.Synonym for leased facility. Contrast with switchedline.

nonswitched network. On a network, aconnection between computers or devices thatdoes not have to be established by dialing.

nonterminal symbol. The structure that the parserrecognizes.

nonvolatile random access memory (NVRAM).Random access memory (storage) that retains itscontents after the electrical power to the machine isshut off. A specific part of NVRAM is set aside foruse by the system ROS for the boot device list.

nonzero. A value that is not equal to zero.

normal attachment stop. See normal stop.

normal mode. See multiuser mode.

normal port. A port that is asynchronous andallows users to log in. No outgoing use of the portis allowed while it is enabled.

normal stop. One of two ways to stop anattachment. (The other way is a forced stop.) If theattachments or any of their connections are in apending state, SNA Services rejects the normalstop attachment action.

normalized device coordinates (NDC). In GL,coordinates in the range from –1 to 1. All primitivesthat draw within the unit cube are visible on thescreen (unless masked by the screen mask). Seealso transformation and unit cube.

not–a–number (NaN). In binary floating–pointcomputations, a value, not interpreted as amathematical value, that contains a mask state anda sequence of binary digits.

notify flag. A parameter that indicates whether areply is required at that point in an event loop.

nroff. A typesetting utility originally designed todrive Teletype model 37 printing workstations. Itnow drives a wide variety of backspacing andnon–backspacing tty–type line printers andtty–emulating printers.

NRZ. See non–return–to–zero.

NS. Network Systems. Also, Network Services.

NSA. Next station addressing.

NSI. Name Service Interface.

NTN. See national terminal number.

NTP. See Network Time Protocol.

NTSC. A national television industry broadcastingstandard as defined by the National TelevisionStandard Committee used in the USA, Canada,Japan, and other countries. A video display andtiming format that is the American broadcaststandard. Most video tape recorders record andplay back NTSC signals. Specialized hardware isrequired to convert from RGB monitor outputs to anNTSC signal. See also PAL and SECAM.

NTSC signal. A signal as defined by the NationalTelevision Standard Committee. Also calledcomposite video.

NTU. See network terminating unit.

NUA. See network user address.

NUI. See network user identification.

NUL. See null character.

NUL character. In XPG4 system interface, acharacter with all bits set to zero.

null. Empty, having no value, containing nothing.

NULL. In the C language, a pointer guaranteed notto point to a data object.

null character (NUL). (1.) The hex 00 characterused to represent the absence of a printed ordisplayed character. (2.) A control character usedto accomplish media–fill or time–fill that can beinserted into or removed from a sequence ofcharacters without affecting the meaning of the

1-101Glossary

sequence. (3.)A control character used to delimit astring of characters.

null character string. Two consecutive singlequotation marks that specify a character stringconsisting of characters.

null modem. See modem eliminator.

null signal. A signal parameter of 0 (zero).

null statement. A statement that consists of asemicolon.

null–terminated. Having a zero byte at the end. Inthe C language, character strings are stored thisway internally.

numeric. Pertaining to any of the digits 0 through9.

numeric character. See digit.

numeric constant. A constant that expresses aninteger, real, or complex number.

numeric error. A situation where the result of areal or integer expression exceeds a compiler’slimits (or limits imposed by the programminglanguage) for such expressions.

numeric literal. A numeric character or string ofcharacters whose value is implicit in the charactersthemselves. For example, 777 is literal as well asthe value of the of the number 777. A numericliteral can contain any of the numeric digits 0through 9, a plus or minus sign, and a decimalpoint. Contrast with character literal.

NURBS. (Non–Uniform Rational B–spline). Aparametric surface that can be trimmed withnonuniform rational B–spline curves and piecewiselinear curves. See also trimming loops.

NVRAM. See nonvolatile random access memory.

1-102 Glossary

OO. Organization.

object. (1.) In the NIM environment, an entry in theNIM database that represents a machine, network,or resource. (2.) In Enhanced X-Windows, asoftware abstraction consisting of private data andprivate and public routines that operate on theprivate data. Users of the abstraction can interactwith the object only through calls to the publicroutines of the objects. (3.) In ODM, an instance ormember of an object class, conceptually similar toa structure that is a member or an array ofstructures. See also object class. (4.) In Pascal,synonymous with data object. (5.) In GL,synonymous with display list. A sequence ofdrawing commands that have been compiled into aunit. Conceptually, a display list is like a macro; itcan be invoked multiple times simply by referring toits name. The object can be instantiated at differentlocations, sizes, and orientations by appropriateuse of the transformation matrices. For instance,series of polygons arranged in the shape of a boltcan be compiled into an object. The bolt can thenbe drawn multiple times by invoking its display list.(6.) In NCS, an entity that is manipulated bywell–defined operations. Disk files, printers, andarray processors are examples of objects. Objectsare accessed though interfaces. Every object has atype. (7.) In Ada language, an object contains avalue. A program creates an object either byelaborating an object declaration or by evaluatingan allocator. The declaration or allocator specifies atype for the object: the object can only containvalues of that type. See also constant and variable.(8.) In C++, a region of storage. An object iscreated in C++ when a variable is defined or new isinvoked. An object is destroyed when it goes out ofscope. (9.) In XDS, anything in some ‘‘world,’’generally the world of telecommunications andinformation processing or some part thereof, that isidentifiable (can be named) and for which the DIBcontains some information. (10.) In XOM, any ofthe complex information objects created,examined, modified, or destroyed by means of theinterface. (11.) In SOM, an entity that has state (itsdata values) and behavior (its methods). An objectis one of the elements of data and function thatprograms create, manipulate, pass as arguments,and so forth. An object is a way to encapsulatestate and behavior. Encapsulation permits manyaspects of the implementation of an object tochange without affecting client programs thatdepend on the object’s behavior. In SOM, objectsare created by other objects called classes. (12.) InCDE, any logical piece of data that has associated

behavior. For example, in File Manager, files,folders, actions, and applications are all consideredobjects. Each type of object has specific associatedactions. Typically, each object is represented as anicon. See also type UUID .

object adapter (OA). In SOM, a CORBA termdenoting the primary interface a serverimplementation uses to access ORB functions; inparticular, it defines the mechanisms that a serveruses to interact with DSOM, and vice versa. Thisincludes server activation/deactivation, dispatchingof methods, and authentication of the principalmaking a call. The basic object adapter describedby CORBA is defined by the BOA (basic objectadapter) abstract class; DSOM’s primary objectadapter implementation is provided by the SOMOA(SOM Object Adapter) class.

object class. In ODM, a stored collection ofobjects with the same definition, conceptuallysimilar to an array of structures. See also object,terminal descriptor, and class.

Object Class Table (OCT). A recurring attribute ofthe directory schema with the description of theobject classes permitted.

object code. (1.) Instructions that are able to berun by a machine, usually generated by a compilerfrom source code written in a higher–levellanguage (such as C language). For programs thatmust be linked, object code consists of relocatablemachine code. (2.) Output from a compiler orassembler that is itself executable machine code oris suitable for processing to produce executablemachine code. Contrast with source code.

Object Data Manager (ODM). A data managerintended for the storage of system data. The ODMis used for many system management functions.Information used in many commands and SMITfunctions is stored and maintained in the ODM asobjects with associated characteristics.

object definition. See class.

object file. (1.) A member file in an object library.(2.) The primary output of a compiler or assembler,which can be processed by the binder (ld) toproduce an executable file. The names of objectfiles normally end in .o.

object handle. In graphical files, the start point ofan arc or lines object.

object identifier. A value (distinguishable from allother such values) that is associated with aninformation object. (X.208)

object implementation. See implementation.

object instance. See instance and object.

1-103Glossary

object library. An area on a direct access storagedevice used to store object programs and routines.

object management. The creation, examination,modification, and deletion of potentially complexinformation objects.

object module. (1.) A portion of an object programsuitable for input to a linkage editor. (2.) A set ofinstructions in machine language produced by acompiler from a source program. See also module.

object–oriented programming. A programmingapproach based on the concepts of dataabstraction and inheritance. Unlike proceduralprogramming techniques, object–orientedprogramming concentrates not on how somethingis accomplished but instead on what data objectscomprise the problem and how they aremanipulated.

object program. A fully compiled or assembledprogram that is ready to be loaded into thecomputer. Synonymous with target program.

object reference. In SOM, a CORBA termdenoting the information needed to reliably identifya particular object. This concept is implemented inDSOM with a proxy object in a client process, or aSOMDObject in a server process. See also proxyobject, server object, and SOMDObject.

object request broker (ORB). See ORB.

object space. The space in which a graphicsobject is defined. A convenient point is chosen asthe origin and the object is defined relative to thispoint. When an object is rendered by a call to thecallobj subroutine, it is rendered in modelingcoordinates, and the object space becomes (forthat moment) the same as the modeling space.

object type. In CDE, a desktop mechanism usedto associate particular data files with theappropriate applications and actions. Object typingdefines the criteria for typing the file (such as nameor contents), the appearance (the icon used in FileManager), and the behavior of the object (forexample, what happens when you double–click it).

object UUID. A UUID that identifies a particularobject. Both the RPC runtime library and theLocation Broker in NCS use object UUIDs toidentify objects. See also Universal UniqueIdentifier (UUID).

obscure. In Enhanced X-Windows, (1.) A state ofbeing for a window. A window is obscured ifanother window is in front of it making the obscuredwindow partially viewable. Window B is obscuredby window A if both are viewable InputOutputwindows and A is higher in the global stackingorder and the rectangle defined by the outsideedges of A intersects the rectangle defined by the

outside edges of B. Window borders are includedin the calculation, and a window can be obscuredand yet still have visible regions. (2.) An action onewindow does to another when it partially obstructsthe viewing of the other. Window A obscureswindow B if both are viewable InputOutputwindows, A is higher in the global stacking order,and the rectangle defined by the outside edges ofA intersects the rectangle defined by the outsideedges of B. Contrast with widget visibility.

occlude. In Enhanced X-Windows, (1.) A state ofbeing for a window. A window is occluded if theview of it is completely obstructed by anotherwindow. Window B is occluded by window A if bothare mapped, A is higher in the global stackingorder, and if no part of the border of B is viewable.A fine distinction exists between ”occlude” and”obscure.” Window borders are included in thecalculation. InputOnly windows never obscureother windows but can occlude other windows. (2.)An action one window does to another when itcompletely obstructs the view of the other. Contrastwith widget visibility.

OCS. On–Card Sequencer.

OCT. See Object Class Table.

octal. (1.) A base–eight numbering system. (2.)Pertaining to a fixed–radix numeration having aradix of eight.

octal constant. The digit 0 (zero) followed by anydigits 0 through 7.

octet. (1.) A group of 8 bits (also known as a byte).(2.) Pertaining to a selection, condition, or choicethat has eight potential values or states. See alsooctet string.

octet string. A string made up of octets. See alsooctet.

ODM. See Object Data Manager.

off–hook. Activated, with regard to a telephoneset. On a public switched system, a data set thatautomatically answers is said to go off–hook.Contrast with on–hook.

offline. (1.) Pertaining to the operation of afunctional unit when it is not under the direct controlof a computer. (2.) Neither controlled directly by norcommunicating with the computer. Contrast withonline.

offset. (1.) In Pascal, the selection mechanism inthe SPACE data type; an element is selected byplacing an integer value in brackets. The origin ofSPACE is based on zero. (2.) In publications, theindentation of all lines of a block of text followingthe first line.

1-104 Glossary

offset method resolution. The default mechanismfor performing method resolution in SOM, becauseit is the fastest (nearly as fast as an ordinaryprocedure call). It is roughly equivalent to the C++”virtual function” concept. Using offset methodresolution requires that the name of the method tobe invoked must be known at compile time, thename of the class that introduces the method mustbe known at compile time (although not necessarilyby the programmer), and the method to be invokedmust be a static method.

OIDL. The original language used for declaringSOM classes. The acronym stands for ObjectInterface Definition Language. OIDL is stillsupported by SOM release 2, but it does notinclude the ability to specify multiple inheritanceclasses.

OM. See XOM.

on–hook. Deactivated, in regard to a telephoneset. A telephone not in use is ”on–hook.” Contrastwith off–hook.

On Item help. In CDE, when you choose On Itemfrom the Help menu, the cursor changes to aquestion mark and you can obtain informationabout a particular command, operation, dialog box,or control by clicking that object.

On Item Help control. In CDE, Front Panel controlused to access item help information on the FrontPanel.

one–copy serializable. The consistency propertyof the SOM Replication Framework which statesthat the concurrent execution of methods on areplicated object is equivalent to the serialexecution of those same methods on anonreplicated object.

one–way channel. In X.25 communications, alogical channel that allows incoming calls only oroutgoing calls only. Contrast with two–way channel.

ones complement. The diminished radixcomplement in the pure binary numeration system.The ones complement is derived by replacing all ofthe zeros with ones and all of the ones with zerosin a binary number. In a ones complement system,the ones complement of a number n is –n. Seealso twos complement.

online. (1.) Being controlled directly by or directlycommunicating with the computer. Contrast withoffline. (2.) Pertaining to the operation of afunctional unit when under the direct control of acomputer.

op code. See operation code.

opaque. See opaque data type.

opaque data structure. A data structure usedinternally by one functional unit of code butexported for limited external use in anotherfunctional unit of code. The external uses mustavoid accessing the structure’s components ormaking assumptions about its constitution.

opaque data type. In XDR, bytes of a fixed sizethat are not interpreted as they pass through thedata streams between computers.

opaque structure. A data item or data type whosestructure is hidden from the code that is handling it.

open. To make a file available to a program forprocessing. Contrast with close.

Open Systems Interconnection (OSI). (1.) Theinterconnection of open systems in accordancewith specific ISO standards. (2.) The use ofstandardized procedures to enable theinterconnection of data processing systems.

operand. (1.) An instruction field that representsdata (or the location of data) to be manipulated oroperated upon. Not all instructions require anoperand field. (2.) An identifier, constant, orexpression that is grouped with an operator. (3.) Anentity on which an operation is performed. (4.)Information entered with a command name thatdefines the data on which a command processoroperates and that controls the running of thecommand processor.

operating system (OS). A set of programs thatcontrol how the system works. Controls the runningof programs and provides such services asresource allocation, scheduling, input and outputcontrol, and data management.

operation. (1.) A specific action (such as add,multiply, or shift) that the computer performs whenrequested. (2.) In NCS, a procedure through whichan object is accessed or manipulated. An operationis defined syntactically by its name and itsparameters but not by its implementation. (3.) InAda language, an operation is an elementaryaction associated with one or more types. It iseither implicitly declared by the declaration of thetype, or it is a subprogram that has a parameter orresult of the type.

operation code (op code). A numeric code thattells the processor which operation to perform.

operation logging. In the SOM ReplicationFramework, a technique for maintainingconsistency among replicas of a replicated object,whereby the execution of a method that updatesthe object is repeated at the site of each replica.

1-105Glossary

operator. (1.) A symbol (such as +, –, or *) thatrepresents an operation (in this case, addition,subtraction, multiplication). (2.) A person whooperates a device. (3.) In Ada language, anoperator is an operation which has one or twooperands. A unary operator is written before anoperand; a binary operator is written between twooperands. This notation is a special kind of functioncall. An operator can be declared as a function.Many operators are implicitly declared by thedeclaration of a type (for example, most typedeclarations imply the declaration of the equalityoperator for values of the type).

operator function. An overloaded C++ operatorthat is either a member of a class or takes at leastone argument that is a class type or a reference toa class type.

optimization. The process of achieving improvedrun–time performance or reduced code size of anapplication. Optimization can be performed by acompiler, by a preprocessor, or throughhand–tuning of source code.

optimize. To improve the speed of a program or toreduce the use of storage during processing.

optimized unit. An Ada–language compilation unitthat has been processed by one or more of thecompiler’s optimizing phases. Some source–levelinformation is unavailable to the debugger when itexamines the unit. You can use an optimized unit inthe same contexts as the correspondingunoptimized unit. Optimized and unoptimized unitscan be mixed within an Ada program.

option. (1.) An item of either hardware or softwarethat may be purchased in addition to the basicsystem. An option can include cables, an adapter,a warranty, and other items. (2.) A specification in astatement that can influence the running of thestatement. (3.) An installable unit of a softwarepackage. Software product options are separatelyinstallable units that can operate independentlyfrom other options of that software package.

option button. In CDE Desktop, adiamond–shaped button that allows you to selectfrom a number of options.

optional facilities. In X.25 communications,facilities that may or may not be offered by thenetwork provider to which customers choosewhether or not to subscribe. See also closed usergroup, fast select, reverse charging, andthroughput–class negotiation.

optional software. Also referred to as optionalsoftware products. Software that is notautomatically installed on your system when youinstall the Base Operating System (BOS). Optionalsoftware can be products packaged and sold with

BOS. Optional software can also be separatelypurchased software products that are speciallyordered and not sold as part of BOS. In eithercase, BOS must be installed on your system beforeyou can install optional software.

ORB (object request broker). In SOM, a CORBAterm designating the means by which objectstransparently make requests (that is, invokemethods) and receive responses from objects,whether they are local or remote. With SOMobjectsDeveloper Toolkit and Runtimes, this functionality isimplemented in the DSOM Framework. Thus, theDSOM (Distributed SOM) system is an ORB. Seealso BOA (basic object adapter) class and SOMOA(SOM object adapter) class.

ordinal number. One of the counting numbers,used to indicate position.

ordinal type. A type in which members can becounted to indicate position.

ORed. Having the logical OR operation performed.

organization. Data that associates a named set ofusers who can be granted common access rightsthat are usually associated with administrativepolicy. Also, the third field of a subject identifier.

orphaned files. Files that cannot be reached bythe fsck command.

orthographic projection. A representation inwhich the lines of a projection are parallel.Orthographic projections lack perspectiveforeshortening and its accompanying sense ofdepth realism. Because they are simple to draw,orthographic projections are often used bydraftsmen. See also perspective projection.

OS. See operating system.

OS/2. Operating System/2.

OSF. Open Software Foundation.

OSI. See Open Systems Interconnection.

OSPF. Open Shortest Path First routing protocol.

OSS. OSI Session Service.

OU. Organizational Unit.

outgoing call. In X.25 communications, a callbeing made to another data terminal equipment(DTE).

output. (1.) The result of processing data. (2.)Pertaining to a functional unit or channel involvedin an output process, or to the data or involved insuch a process. (3.) Data transferred from storageto an output device. (4.) In Pascal, a predefinedstandard file definition.

1-106 Glossary

output buffer. In Enhanced X-Windows, an areaused by the Xlib library to store requests.

output device. A physical device that a computeruses to present data to a user. Synonymous withoutput unit.

output file. (1.) A file that a program opens so thatit can write to that file. (2.) A file that contains theresults of processing.

output handler. The program module responsiblefor distributing data generated by a process orsubprocess.

output list. A list of variables from which valuesare written to a file or device.

output mode. An open mode in which records canbe written to a file.

output redirection. The specification of an outputdestination other than the standard one.

output stream. Messages and other output datathat an operating system or a processing programdisplays on output devices.

output unit. Synonym for output device.

overflow. (1.) That portion of an operation’s resultthat exceeds the capacity of the intended unit ofstorage. (2.) In a register, the loss of one or moreof the leftmost whole–number digits because theresult of an operation exceeded the size of theregister.

overflow condition. (1.) A condition that occurswhen a portion of an operation’s result exceeds thecapacity of the intended unit of storage. (2.) Acondition that occurs when the overflow line on apage has been printed or passed.

overflow line. The line specified as the last line tobe printed on a page.

overlay. (1.) To write over (and therefore destroy)an existing file. (2.) A program segment that isloaded into main storage, replacing all or part of apreviously loaded program segment. (3.)Repeatedly using the same areas of internalstorage during different states of a program. (4.) InDPS, a collection of predefined data such as lines,shading, text, boxes, or logos that can be mergedwith variable data while printing on a page. (5.) Inthe M–Video Capture Adapter, the replacement ofspecified pixels of one source with pixels fromanother source such as memory pixels overlaid onlive images.

overlay planes. One or more bit planes in adisplay buffer that are used to create visual data(text, graphics, and so on) that overlays the visualdata in the frame buffer in a nondestructivemanner. Rather than a background color, overlayplanes are transparent.

overloading. (1.) In Ada language, an identifiercan have several alternative meanings at a givenpoint in the program text: this property is calledoverloading. For example, an overloadedenumeration literal can be an identifier thatappears in the definitions of two or moreenumeration types. The effective meaning of anoverloaded identifier is determined by the context.Subprograms, aggregates, allocators, and stringliterals can also be overloaded. (2.) In C++, acapability that allows you to redefine functions andmost standard C++ operators when the functionsand operators are used with class types.

override. (1.) A parameter or value that replaces aprevious parameter or value. (2.) To replace aparameter or value. (3.) In SOM, the technique bywhich a class replaces (redefines) theimplementation of a method that it inherits fromone of its parent classes. An overriding method canelect to call the parent class’s method procedure aspart of its own implementation. (Such a call isknown as a parent method call.)

overscan. A characteristic of display monitorswhere a number of lines and horizontal pixelsdelivered to the monitor exceed the visible displayspace of the screen.

overstriking. A method of generating specialcharacters by typing one character and then,without moving the print head to the next characterposition, typing the second character on top of thefirst.

overwrite. To record into an area of storage so thatthe data that was previously stored there isdestroyed.

overwrite mode. A form of system operation thatreplaces existing characters with characters typedat the keyboard.

owner. The user who has the highest level ofaccess authority to a data object or action, asdefined by the object or action; usually the creatorof the object.

ownership. The creator or namer of an entity.

1-107Glossary

Ppacing. (1.) A technique used by a receivingcomponent to control the rate of transmission bysending a component to prevent overrun. (2.) A filetransfer protocol required by some systems. Itcontrols data transmission by waiting for aspecified character, or waiting a specified numberof seconds between lines. This protocol preventsthe loss of data when the block size is too large ordata is sent too quickly for the system to process.See also line pacing, local pacing, receive pacing,and remote pacing.

pacing response. In SNA Services, an indicatorthat signifies the readiness of a receivingcomponent to accept another pacing group. Theindicator is carried in a response header (RH) forsession–level pacing, and in a transmission header(TH) for virtual–route pacing.

pack loop. A loop that packs active cells of asparse array into successive cells in another array,so that the resulting array contains no empty cellsbetween its first and last active cells.

package. (1.) An installable unit of a softwareproduct. Software product packages are separatelyinstallable units that can operate independentlyfrom other packages of that software product. (2.)In Ada language, specifies a group of logicallyrelated entities, such as types, objects of thosetypes, and subprograms with parameters of thosetypes. It is written as a package declaration and apackage body. The package declaration has avisible part, containing the declarations of allentities that can be explicitly used outside thepackage. It may also have a private part containingstructural details that complete the specification ofthe visible entities, but which are irrelevant to theuser of the package. The package body containsimplementations of subprograms (and possiblytasks as other packages) that have been specifiedin the package declaration. A package is one of thekinds of program unit. See also private part.

package closure. The set of classes that need tobe supported to be able to create all possibleinstances of all classes defined in the package.

packet. In data communications, a sequence ofbinary digits, including data and control signals,that is transmitted and switched as a compositewhole. The data, call control signals, and errorcontrol information are arranged in a specificformat. See also call–accepted packet,call–connected packet, call–request packet,clear–confirmation packet, clear–indication packet,clear–request packet, data packet, incoming–callpacket, interrupt packet, interrupt–confirmation

packet, reset–request packet, reset–confirmationpacket, address field, and restart–confirmationpacket.

packet assembler/disassembler (PAD). In X.25communications, equipment used for connectingasynchronous (start/stop) devices to an X.25network.

packet header. In X.25 communications, controlinformation at the start of the packet; the contentsof the packet depend on the packet type.

packet level. In X.25 communications, the packetformat and control procedures for the exchange ofpackets containing control information and userdata between the data terminal equipment (DTE)and the data circuit–terminating equipment (DCE).Synonymous with level 3. See also level, framelevel, datalink level, and physical level.

packet–level interface. In X.25 communications,the level of the DTE/DCE interface in packet modeoperation relating to the exchange of data andsignaling, where this information is contained inpackets. See also frame–level interface.

packet mode operation. Synonym for packetswitching.

packet size. In X.25 communications, in thecontext of data packets, refers to the length of theuser data.

packet switching. Routing and transferring databy addressing packets so that a channel isoccupied only during packet transmission. Oncompletion of the transmission, the channel isavailable for transfer of other packets. Synonymouswith packet mode operation. See also circuitswitching.

packet window. In X.25 communications, thenumber of packets that can be outstanding withoutacknowledgment. See also frame window andwindow.

packing. In AIXwindows and EnhancedX-Windows, the grouping of children objects withina parent container object. If the children are closelypacked, the common distance between theirborders is minimal; if they are loosely packed, thecommon distance border–to–border is maximized.

pad. (1.) To fill unused positions in a field withdummy data, usually zeros or blanks. (2.) A deviceused to introduce transmission loss into a circuit. Itcan be inserted to introduce loss or matchimpedances.

padding. Bytes inserted in the data stream tomaintain alignment of the protocol requests onnatural boundaries. Padding increases the ease ofportability to some machine architectures.

1-108 Glossary

page. (1.) A block of instructions, data, or both. (2.)The number of lines that can fit into a window. (3.)In a virtual storage system, a fixed–length blockthat has a virtual address and is transferred as aunit between real storage and auxiliary storage.(4.) A contiguous 4096–byte portion of avirtual–memory segment. The offset of each pagefrom the beginning of the segment is an integralmultiple of 4096. See also leaf.

page cluster. A type of memory buffer that isconstructed from a full memory page (normally4096 bytes).

page fault. (1.) A program interruption that occurswhen an active page refers to a page that is not inmemory. (2.) An interrupt that occurs when theprocessor attempts to access a virtual–memorypage that is not in real memory.

page frame. (1.) In real storage, a storage locationhaving the size of a page. (2.) An area of mainstorage that contains a page. (3.) A4096–contiguous–byte portion of real memory thatis used to hold a virtual–memory page.

page frame table. A table, contained in realmemory, that contains the real memory locations ofall currently defined pages.

pagination. (1.) The process of adjusting text to fitwithin page margins. (2.) In word processing, theautomatic arrangement of text according to apreset number of page layout parameters.

paging. (1.) The action of transferring instructions,data, or both between real storage and externalpage storage. (2.) Moving data between memoryand a mass storage device as the data is needed.(3.) In System/370 virtual storage systems, theprocess of transferring pages between real storageand external page storage.

paging device. A disk device used to store pagesof memory that are not currently in real memory.

paging space. Disk storage for information that isresident in virtual memory but is not currently beingaccessed.

paint. In computer graphics, to shade an area of adisplay image.

PAL. (1.) Programmable array logic. (2.) A nationaltelevision industry broadcasting standard used inEurope and some other countries. See also NTSCand SECAM.

PAL signal. A phase analog lock signal, alsocalled composite video. The European standard forcomposite video.

palette. (1.) Location for building customizedcomponents and parenting them with othercomponents. Subsequently, components can be

reused by copying and moving them to otherinterfaces. (2.) In CDE, a range of graphicallydisplayed choices, such as colors or collections oftools, that you can select in an application.

pane. On a display screen, the inner portion of awindow used to present information to the user. Awindow can consist of one or more panes. Seealso menu pane.

panel. (1.) A set of logically related informationdisplayed on the screen for the purpose ofcommunicating information to or from a computeruser. (2.) A group of one or more panes that aretreated as a unit. The panes of a panel aredisplayed together, erased together, and usuallyrepresent a unit of information to a person usingthe application. A panel is represented on thedisplay as a rectangular area tiled (completelyfilled) with panes.

panning. (1.) In computer graphics, the viewing ofan image that is too large to fit on a single screenby moving from one part of the image to another.(2.) Progressively translating an entire displayimage to give the visual impression of lateralmovement of the image.

paragraph. (1.) Text that is separated from othertext by blank lines. (2.) In word processing, one ormore sentences that maybe preceded by orfollowed by an appropriate indicator.

parallel channel. Communications protocolbetween controller and mainframe processors.

parallel device. A device that can perform two ormore concurrent activities. Contrast with serialdevice.

parallel processing. The condition in whichmultiple tasks are being performed simultaneouslywithin the same activity. Contrast with serialprocessing.

parallel transmission. (1.) Transmitting all bits ofa character simultaneously. (2.) In datacommunication, the simultaneous transmission of anumber of signal elements that constitute the sametelegraph or data signal.

parameter. (1.) Information that the user suppliesto a panel, command, or function. (2.) A variablethat is given a constant value for a specifiedapplication. (3.) Data passed between programs orprocedures. (4.) In Ada language, a parameter isone of the named entities associated with asubprogram, entry, or generic unit, and used tocommunicate with the corresponding subprogrambody, accept statement or generic body. A formalparameter is an identifier used to denote thenamed entity within the body. An actual parameteris the particular entity associated with the

1-109Glossary

corresponding formal parameter by a subprogramcall, entry call, or generic instantiation. The modeof a formal parameter specifies whether theassociated actual parameter supplies a value forthe formal parameter, or the formal supplies avalue for the actual parameter, or both. Theassociation of actual parameters with formalparameters can be specified by namedassociations, by positional associations, or by acombination of these. See also formal parameterand mode.

parameter block. A block of memory that containsspecific parameters for an ioctl operation.

parameter declaration. Description of a value thata function receives. A parameter declarationdetermines the storage class and the data type ofthe value.

parametric bicubic surface. A surface defined bythree equations. The x equation is: x(u,v) =a11u3v3 + a12u3v3 + a13u3v + a14u3 + a21u2v3+ a22u2v2 + a23u2v + a24u2 + a31uv3 + a32uv2 +a33uv + a34u + a41v3 + a42v2 + a43v + a44. Theequations for y and z are similar. The points on abicubic patch are defined by varying theparameters u and v from 0 to 1. If one parameter isheld constant and the other is varied from 0 to 1,the result is a cubic curve. If w(u,v)=1 for all u,v, thebicubic surface is called ”ordinary,” but if w(u,v)varies as a function of u,v, then the surface iscalled ”rational.” See also homogeneouscoordinates.

parametric component. In AIXwindows, a simplemechanism that delivers all the functionsnecessary for most applications, yet is easier andless time consuming to build.

parametric cubic curve. A curve defined by theequation: x(t) = axt3 + bxt2 + cxt + dx; y(t) = ayt3 +byt2 + cyt + dy; z(t) = azt3 + bzt2 + czt + dz; w(t) =awt3 + bwt2 + cwt + dw. Where x, y, z, and w arecubic polynomials. The parameter t typically variesbetween 0 and 1. Such a curve is consideredrational only if a(w), b(w), or c(w) is not equal to 0;otherwise, it is simply an ordinary parametric curve.See also B–spline cubic curve, Bezier cubic curve,and cardinal spline cubic curve.

parent. (1.) A process that has spawned a childprocess using the fork primitive. (2.) Pertaining to asecured resource, either a file or library, whoseuser list is shared with one or more files or libraries.Contrast with child. (3.) In AIXwindows andEnhanced X-Windows, a graphical object thatcontrols one or more smaller graphical objectsattached to it. The smaller graphical objects arecalled children, and they are automatically deletedwhen their parent is deleted. (4.) In Ada language,the associated specification of a package body or

subprogram body. The parent of a subunit is thebody in which it was declared.

parent class. In SOM, a class from which anotherclass inherits instance methods, attributes, andinstance variables. A parent class is sometimescalled a base class or superclass.

parent device. A hierarchical location term. Itindicates what device the device you areconcerned with connects to. For example, theparent device of an SCSI disk might be an SCSIadapter.

parent directory. The directory one level abovethe current directory. See also parent folder.

parent folder. In CDE, a folder that containssubfolders and files. When discussingcommand–line activities, this may be called theparent directory. See also subfolder.

parent ID. The character sequence identifying thegraphical object that controls smaller graphicalobjects, called children.

parent method call. In SOM, a technique wherean overriding method calls the method procedureof its parent class as part of its ownimplementation.

parent type. For Ada programming, see derivedtype.

parent window. In Enhanced X-Windows, thewindow that controls the size and location of itschildren. If a window has children, it is a parentwindow.

parity bit. A binary digit (bit) appended to a groupof binary digits to make the sum of all digits in thegroup either always odd (odd parity) or alwayseven (even parity).

parity check. A test to determine whether thenumber of ones (or zeros) in an array of binarydigits is odd or even.

parity error. A transmission error that occurs whenthe received data does not have the parityexpected by the receiving system. This error isusually caused by the sending and receivingsystems having different parity settings.

parse. (1.) In systems with time sharing, to analyzethe operands entered with a command and createa parameter list for the command processor fromthe information. (2.) Before a command lineinterpreter can convert an operating–systemcommand into an executable form of machinecode, the command must be broken down intoeasily coded elements, or ”parsed”, by theinterpreter.

1-110 Glossary

parser. A program that interprets user input anddetermines what to do with the input. See alsogrammar rules.

participant. An application is a participant in atransaction when it either initiates the transaction orreceives a request on behalf of that transaction.

partition. (1.) A logical division of storage on afixed disk. (2.) A fixed–size division of storage.

partner. In data communications, the remoteapplication program or the remote computer.

Pascal. A high–level, general–purposeprogramming language. Programs written in Pascalare block–structured, consisting of independentroutines.

pass–by–CONST. In Pascal, theparameter–passing mechanism by which theaddress of a variable is passed to the calledroutine. The called routine is not permitted tomodify the formal parameter. Synonymous withpass–by–read–only–reference.

pass–by–read–only–reference. Synonym forpass–by–CONST.

pass–by–read/write–reference. Synonym forpass–by–VAR.

pass–by–value. In Pascal, the parameter–passingmechanism by which a copy of the value of theactual parameter is passed to the called routine. Ifthe called routine modifies the formal parameter,the corresponding actual parameter is not affected.

pass–by–VAR. In Pascal, the parameter–passingmechanism by which the address of a variable ispassed to the called routine. If the called routinemodifies the formal parameter, the correspondingactual parameter is also changed. Synonymouswith pass–by–read/write–reference.

pass–through function. The ability to pass datathrough a program transparently, without alteration.

pass–through mode. The mode of use providedby the VM/Pass–ThroughFacility, which allows VMdisplay station users to interactively access a VMsystem, including the one to which the terminal isattached. It also allows users to access non–PVMsystems that support Remote 3270 BinarySynchronous Communication (BSC) displaystations and 4300 processors having the RemoteOperator Console Facility (ROCF). A user canaccess, log on to, and use another system in adefined network as though the user’s local terminalwere directly connected to that system. PVMactivities become transparent to the user oncelogged on to the target system.

passive gateway. A gateway that does notexchange routing information. Its routing

information is contained indefinitely in the routingtables and is included in any routing informationthat is transmitted. Contrast with active gateway.

passive grab. In Enhanced X-Windows, grabbinga key or button is a passive grab. The grabbecomes an active grab when the key or button isactually pressed. Contrast with active grab. Seealso grab, button grabbing, pointer grabbing, andkey grabbing.

password. (1.) A string of characters known onlyto the user and the system. The user must specifythe correct password to gain access to a systemand the data stored with it. (2.) A string encodedwith information about a software vendor (vendorpassword) or about a software product (productpassword).

password security. The process of requiring auser to enter a password to log in to a system.

patch. A parametric bicubic surface.

path. (1.) In SNA, the series of path controlnetwork components traversed by the informationexchanged between two network addressable units(NAUs). A path consists of a series of path controlelements, data link control elements, and links. (2.)In a network, any route between any two nodes.(3.) In a database, a sequence of segmentoccurrences from the root segment to an individualsegment. (4.) In the InfoExplorer program, the listof articles you followed to get to the article that iscurrently displayed. (5.) In CDE, a text string thatspecifies the hierarchical location of a folder(directory).

path list. The structure, or the correspondingparameter, containing the full path name for a file.

path name. A file name specifying all directoriesleading to the file. See also full path name andrelative path name.

pattern. (1.) A regular expression or series ofregular expressions that define the search pattern.(2.) In GL, a 16x16, 32x32, or 64x64 array of bitsdefining the texturing of polygons on the systemdisplay.

pattern–action. When the awk command finds apattern in an input data file that matches a line inthe program file, it performs the associated actionon that line.

pattern address. Reference to a line by a stringcontained within the line, rather than by anumerical or symbolic address. A pattern addresscan be a character string or a regular expression.See also symbolic address.

pattern matching. Specifying a pattern ofcharacters that the system should find.

1-111Glossary

pattern–matching character. Special characterssuch as * (asterisk) or ? (question mark) that canbe used in a file specification to match one or morecharacters. For example, placing a ? in a filespecification means that any character can be inthat position. Synonymous with wildcard.

pattern strings. Strings of regular expressionscomposed of special pattern–matching characters.The pattern strings can be used in addresses tospecify lines and, in some subcommands, portionsof a line.

PBX. Private Branch Exchange. A privatetelephone system that performs automaticselection of outside lines.

PC. Personal computer.

PCI. Programmed Control Interrupt.

PCM. Physical Connection Management.

PCS. See programmable character set.

PDN. See public data network.

PE. Phrase Encoded, a magnetic tape recordingformat with a density of 1600 bpi.

peak rate. The maximum speed at which a devicecould operate under ideal conditions, if its designerwere choosing the workload.

peer–to–peer communications. Pertaining todata communications between two nodes that haveequal status in the interchange. Either node canbegin the conversation. See also Logical Unit Type6.2.

peer trust. A type of trust relationship establishedbetween two cells by means of a secret key sharedby mutual authentication surrogates maintained bythe two cells. A peer trust relationship enablesprincipals in the one cell to communicate securelywith principals in the other.

pel. See picture element.

pending. Waiting, as in an operation that ispending.

pending state. A condition of a server program inwhich it has received a request for an action (start,stop, or suspend) but has not yet performed thataction.

PEP. Packet Exchange Protocol. A datagramservice that is implemented by a user–level library,using IDP datagram sockets.

per–process data area. In kernel mode, a portionof the user process stack segment. This area ispaged with the process and it contains processinformation such as the current directory of filesopened by the process or input in I/O mode. This

information occupies the top of the stack segment.See also user block and user structure.

peripheral device. With respect to a particularprocessing unit, any equipment that cancommunicate directly with that unit.

peripheral unit. See peripheral device.

permanence. A basic property of transactionprocessing systems. This term means that once atransaction has committed, the modifications madeto data by that transaction must be permanent.Subsequent transactions requesting the datamodified by a previous transaction must alwayssee the new data. These changes must bepreservable even in the event of a system failure.

permanent error. An error that cannot beeliminated by retrying an operation.

permanent link. A connection below a multiplexerthat can exist without having an open controllingstream associated with it.

permanent storage. A storage device whosecontents cannot be modified.

permanent virtual circuit (PVC). In X.25communications, a virtual circuit that has a logicalchannel permanently assigned to it at each DTE.Call–establishment protocols are not required.Contrast with switched virtual circuit. See alsovirtual circuit.

permission. The modes of access to a protectedobject.

permission code. A three–digit octal code or anine–letter alphabetic code that indicates accesspermissions. The access permissions are read,write, and run. See also access permission.

permission field. One of the three–characterfields within the permissions column of a directorylist. The permission field indicates the read, write,and run permissions for the file or directory owner,for the group, and for all others.

permissions. Codes that determine how the filecan be used by any users who work on the system.In CDE Desktop, a set of flags that determine auser’s access to files and directories, which youcan see using the Properties... command on theFile menu.

persistence. In Display PostScript (DPS), aspecified character set that is used for allsubsequent text segments in a compound stringuntil a new character set is encountered.

persistent data. Data which retains its valueacross multiple runs of transactional applications,regardless of system failures or restarts.

1-112 Glossary

persistent object. In SOM, an object whose statecan be preserved beyond the termination of theprocess that created it. Typically, such objects arestored in files.

persistent segment. A segment whose pageshave permanent locations on disk, rather thantemporary slots in the paging space.

perspective projection. A technique used toachieve realism when drawing primitives. In aperspective projection, the lines of projection meetat the viewpoint; thus, the size of a primitive variesinversely with its distance from the sourceprojection. The farther a primitive or part of aprimitive is from the viewer, the smaller it will bedrawn. This effect, known as perspectiveforeshortening, is similar to the effect achieved byphotography and by the human visual system. Seealso orthographic projection.

peta. Two to the fiftieth power.

PEX. A protocol for supporting three–dimensionalgraphics.

PEXlib. A programmer’s interface to the PEXprotocol.

PFM. See program fault management.

phase. (1.) One of several stages of file systemchecking and repair performed by the fsckcommand. (2.) A distinct part of a process in whichrelated operations are performed. (3.) A part of asort and merge program, such as sort phase andmerge phase. (4.) A part of a data call.

phase modulation. Altering the phase of a carriersignal to convey data signals.

PHIGS. See Programmers’ Hierarchical InteractiveGraphics System.

phototypesetter. A typesetting machine thatoperates by projecting light through film matrices ofthe type characters upon light–sensitive paper orfilm.

physical block. See block.

physical data block. See block.

physical device. See device.

physical file. (1.) An indexed file containing datafor which one or more alternative indexes havebeen created. (2.) A database file that describeshow data are to be presented or received from aprogram and how data are actually stored in thedatabase. A physical file contains one recordformat and one or more members.

physical layer. The lowest layer of network designas specified by the ISO Open SystemInterconnection (OSI) reference model. This layer

is responsible for interfacing with the medium,detecting and generating signals on the medium,and converting and processing signals receivedfrom the medium and from the data link layer. Seealso physical level.

physical level. In X.25 communications, themechanical, electrical, functional, and proceduralmedia used to activate, maintain, and deactivatethe physical link between the data terminalequipment (DTE) and the data circuit–terminatingequipment (DCE). Synonymous with level 1. Seealso level, frame level, data–link level, packet level,and physical layer.

physical network. A network of machines linkedby physical network cabling, modems, or otherhardware. A physical network can contain one orseveral logical networks.

physical partition (PP). The smallest unit ofdisk–space allocation for a logical volume. Thephysical partition is contiguous space on a physicalvolume. A fixed–size portion of a physical volume.One or more physical partitions constitute theunderlying physical storage medium for a logicalpartition.

physical unit (PU). In SNA, a set of programs thatcontrol the actual physical hardware associatedwith a node.

physical volume (PV). (1.) The portion of a singleunit of storage accessible to a single read/writemechanism; for example, a drum, a disk pack, orpart of a disk storage module. (2.) A read–writefixed disk physically attached to a computer. Theactual storage space provided by a singlefixed–disk drive. See also log volume.

picking. In computer graphics, a method forfinding out what primitives are being drawn nearthe cursor on the display screen. See also hit,picking region, selecting, and selecting region.

picking region. A rectangular volume around thecursor that is sensitive to picking events. If adrawing primitive draws within this volume, a pickevent is reported. The width and height of theregion can be set by the user. If the z–buffer isenabled, the depth of the region is the entirez–buffer. See also hit, selecting, picking, andselecting region.

picture. A pixmap used for displaying CDEDesktop icons, background patterns, and controls.

picture element (pel). (1.) In computer graphics,the smallest element of a display space that can beassigned color and intensity independently. (2.) Apoint in the frame buffer or on the display. See alsopixel.

1-113Glossary

PID. See process ID.

piecewise linear curve. A list of coordinate pairsin the parameter space for the Non–UniformRational B–Spline (NURBS) surface. These pointsare connected with straight lines to form a path.

pin. (1.) An area of memory reserved for certainfunctions. (2.) One of the connectors in an adapterplug.

PIO. See programmable input/output operation.

PIP. See Program Initialization Parameters.

pipe. (1.) To direct the data so that the output fromone process becomes the input to another process.The standard output of one command can beconnected to the standard input of another with thepipe operator ( | ). Two commands connected inthis way constitute a pipeline. (2.) A one–waycommunication path between a sending processand a receiving process. See also pipeline.

pipeline. (1.) A direct, one–way connectionbetween two or more processes. (2.) A serialarrangement of processors or a serial arrangementof registers within a processor. Each processor orregister performs part of a task and passes resultsto the next processor. Several parts of differenttasks can be performed at the same time. (3.) Toperform processes in a series. (4.) For increasedprocessing speed, to start the running of aninstruction sequence before the previousinstruction sequence is completed. See also pipe.

pipeline options. In GL, variables that control theflow of processing in the graphics pipeline. Forinstance, lighting is a pipeline option. If lighting isturned on, the color of a primitive is obtained byevaluating the lighting equations. If lighting isturned off, the last color specified is used. Otherpipeline options are the back–facing flag, theshade–model flag, the depth–cueing flag, thepicking flag, the color–mode (color index or RGB)flag, the z–buffer flag (enables or disables drawingto the z–buffer), and so on. See also attribute.

pitch. A unit of width of typewriter type, based onthe number of times a letter can be set in a linearinch. For example, 10–pitch type has 10 charactersper inch.

pixel. A rectangular picture element. The smallestelement used to compose an image, a single dot. Adisplay screen is composed of an array of pixels. Ina black–and–white system, pixels are turned onand off to form images. In a color system, eachpixel has three components: red, green, and blue.The intensity of each component can be controlled.See also picture element.

pixel map. A three–dimensional array of bits. Apixel map can be thought of as a two–dimensional

array of pixels, with each pixel being a value fromzero to 2 to the N –1, with N as the depth of thepixel map. Synonym for pixmap.

pixel value. In Enhanced X-Windows, the numberof bit planes used in a particular window or pixmap.For a window, a pixel value indexes a color mapand derives an actual color to be displayed. A pixelis an N–bit value, where N is the number of bitplanes (the depth) used in a particular window orpixmap.

pixmap. (1.) Synonym for pixel map. (2.) InAIXwindows and Enhanced X-Windows, a datatype to which icons (originally created as bitmaps)are converted. Once this conversion takes place,the appropriate AIXwindows subroutines cangenerate pixmaps through references to an.Xdefaults file (by name) and through an argumentlist (by pixmap). See also image cache.

placeholder. An object, component or file that onlyexists to mark the position of an intended entity.

plaintext. The input to an encryption function orthe output of a decryption function. Decryptiontransforms ciphertext into plaintext.

plane. When a pixmap or window is thought of as astack of bitmaps, each bitmap is called a plane orbit plane.

plane mask. (1.) Determines which of the displayadapter storage places are modified by the outputfunctions. (2.) In Enhanced X-Windows, a bit maskrestricting graphics operations to affect a subset ofbit planes. It is stored in a graphics context.Graphics operations can be restricted to affect onlya subset of bit planes of a destination.

platen. The support mechanism for paper on aprinter, commonly cylindrical, against which printingmechanisms strike to produce an impression.

playing back. In Encina, the actions of theRecovery Service when a TP system usingrecoverable data is restarted. When started, theRecovery Service plays back log records fortransactions that have prepared but which were notactually committed, guaranteeing that the state ofthat recoverable data reflects the recordsmaintained by the TP system.

PList. An array of pointers with a suite ofoperations for adding and removing elements invarious ways.

plotter. A hard copy device, attached to the systemwith cables, that prints two–dimensional graphsand charts.

plug. A device that connects the wires of anelectrical circuit to an electrical source. The plug isdesigned to be inserted into a jack.

1-114 Glossary

PMF. Parameter management frame.

PMP. See Preventive Maintenance Package.

PMR. See Problem Management Record.

point. (1.) A unit of typesetting measure equal to0.01384 inch (0.3505 mm), or about 1/72 of aninch. There are 12 points per pica. (2.) In CDE, tomove the mouse until the pointer rests on aparticular screen element or area.

point–handle. A point within a graphic object.

point–to–point link. A switched or nonswitchedlink that connects a single remote link station to anode or to another station.

pointer. (1.) A variable that holds the address of adata object. (2.) A physical or symbolic identifier ofa unique target. (3.) In computer graphics, thedevice attached to the cursor and tracked on thescreen.

pointer grabbing. In Enhanced X-Windows, aclient can actively grab control of the pointer so thatbutton and motion events will be sent to that clientrather than the client to which the events normallywould have been sent. See also grab, buttongrabbing, and key grabbing.

pointer to member. Used to access the address ofnonstatic members of a C++ class.

pointer type. A data type that defines variablescontaining addresses and, sometimes, otherinformation about variables.

pointing. Positioning the pointing cursor on adisplayed object. The action of lining up the mousepointer so that the pointer lies on top of something.

pointing device. In Enhanced X-Windows, adevice with effective dimensional motion, usually amouse. One visible cursor is defined by the Coreprotocol, and it tracks whatever pointing device isattached as the pointer.

polar coordinates. A coordinate system in whichpositions are measured as a distance from theorigin and an angle from some reference direction(usually, counterclockwise from the x–axis).

poll. (1.) In data communications, an interrogationthat determines whether a station is ready totransmit information. (2.) To run a pollingsequence.

polled I/O devices. Devices (keyboard, mouse,button, dials) whose current values are read by theuser process.

polling. (1.) On a multipoint connection or apoint–to–point connection, the process wherebydata stations are invited, one at a time, to transmitdata. (2.) Interrogation of devices so as to avoid

contention, determine operational status, ordetermine readiness to send or receive data.

polyline. In computer graphics, a sequence ofadjoining lines.

polymarker. In computer graphics, a sequence ofmarkers. The definition of the marker includesspecific attributes such as color, style, width,height, pattern, and origin.

polymorphic functions. Functions that can beapplied to objects of more than one data type. C++implements polymorphic functions in two ways:overloaded functions (calls are resolved at compiletime); and virtual functions (calls are resolved atrun–time).

polymorphism. An object–oriented programmingfeature that may take on different meanings indifferent systems. Under various definitions ofpolymorphism, (a) a method or procedure call canbe executed using arguments of a variety of types,or (b) the same variable can assume values ofdifferent types at different times, or (c) a methodname can denote more than one methodprocedure. The SOM system reflects the thirddefinition (for example, when a SOM classoverrides a parent class definition of a method tochange its behavior). The term literally means”having many forms.”

pop. A term used when a module that isimmediately below the stream head is removed.

pop–down. In Enhanced X-Windows, an actionreferring to a type of widget that closes when apointer button is released.

pop up. (1.) In Enhanced X-Windows, a box on thedisplay screen that displays information or asksyou to make choices. (2.) In Enhanced X-Windows,an action referring to a type of widget that opensautomatically when a pointer button is held downwithin certain windows. (3.) To use a widget tocreate a window outside the window hierarchydefined by the widget tree.

pop–up cascade. In Enhanced X-Windows,several spring–loaded pop–ups emanating insuccession from one modal pop–up.

pop–up child. In Enhanced X-Windows, a child onthe pop–up list.

pop–up list. A list of pop–up children stored in awidget.

pop–up menu. (1.) Synonym for popup. (2.) InAIXwindows, a type of MenuPane widget thatappears as the result of some user action (usuallyclicking a mouse button) and then disappears whenthe action is completed. (3.) The interface definitionfor translation actions. (4.) In CDE, a menu that,

1-115Glossary

when requested, is displayed next to the objectwith which it is associated. Pop–up menus areusually displayed by clicking mouse button 3 orpressing Shift+F10.

pop–up widget. In Enhanced X-Windows, awindow child of the root that is attached to itswidget parent differently than the normal widget; apop–up widget is not geometrically constrained byits parent widget.

pop–up window. Any window that opensautomatically when activated. See also pop–up.

popdown. In AIXwindows, the manner in which atype of MenuPane widget disappears suddenly(pops down) in the display when some user action(usually clicking a mouse button) is completed.

popup. In AIXwindows, the manner in which a typeof MenuPane widget appears suddenly (pops up)in the display as the result of some user action(usually clicking a mouse button). Synonym forpop–up menu. See also pop–up window.

POR. See power–on reset.

port. (1.) A part of the system unit or remotecontroller to which cables for external devices(display stations, terminals, or printers) areattached. The port is an access point for data entry(input) to or exit from (data output) a computersystem. (2.) An entrance to or exit from a network.(3.) To make the programming changes necessaryto allow a program that runs on one type ofcomputer to run on another type of computer. (4.)In NCS, a specific communications end point withina host. A port is identified by a port number. Seealso socket and listening.

portability. The characteristic that determineswhether a source program can be compiled andrun on computers of different architectures withoutrequiring recoding.

portable character set. In the XPG4 systeminterface, the collection of characters present in alllocales supported by XSI–conformant systems: OrABCDEFGHIJKLMNOPQRSTUVWXYZ

abcdefghijklmnopqrstuvwxyz

0123456789!#%^&*()_+–={}[] :”~;’‘<>?,.|\/@$

Also included are the alert, backspace, tab,newline, vertical–tab, form–feed, carriage–return,space characters, and the null character, NUL.

portable file name character set. In the XPG4system interface, the set of characters from whichportable file names are constructed. For a filename to be portable across implementations of theXPG4 and ISO POSIX–1 standard, it must consistonly of the following characters:ABCDEFGHIJKLMNOPQRSTUVWXYZ

abcdefghijklmnopqrstuvwxyz

0123456789._–

The last three characters are the period,underscore, and hyphen characters, respectively.The hyphen must not be used as the first characterof a portable file name. Uppercase and lowercaseletters retain their unique identities betweenconforming implementations. In the case of aportable path name, the slash character can alsobe used.

Portable Operating System Interface ForComputer Environments (POSIX). An IEEEstandard for computer operating systems.

portrait display. A rectangular display that is tallerthan it is wide. See also landscape display.

portrait upside–down. A page orientation suchthat the top of the printed image is at the trailingedge of the paper as it emerges from the printer.

POS registers. Programmable Option Selectregisters. A set of registers that allow the softwareto automatically configure devices on the MicroChannel bus at the time the machine is turned on.These registers allow the setup software (which isrun at the time the machine is turned on) toautomatically identify the adapter and to set upvarious parameters on the adapter such as itsstarting address and interrupt level.

position. (1.) Any location in a string that may beoccupied by an element and that is identified by aserial number. (2.) The location of a character in aseries, as in a record, a displayed message, or acomputer printout.

position (within an attribute). The ordinal positionof one value relative to another.

position (within a string). The ordinal position ofone element of a string relative to another.

positional association. In Ada language,specifies the association of an item with a positionin a list, by using the same position in the text tospecify the item.

positional parameter. (1.) A shell facility thatassigns values from the command line to variablesin a program. (2.) A parameter that must appear ina specified location relative to other positionalparameters.

POSIX. See Portable Operating System InterfaceFor Computer Environments.

post. The action required to make a pop–up orpull–down menu appear. This action is normally aclick or button press on one of the mouse buttons.

POST. See power–on self–test.

1-116 Glossary

post processor. A computer program that effectssome final computation or organization. In textformatting, a postprocessor command translatesthe output of the nroff and troff commands for useon certain printers, typesetters, orphototypesetters.

posted event. A notification sent to the DLC by itsattached device handler by way of the e_postsystem call.

PostScript. A graphics language used to driveoutput of text and graphics. Trademark of AdobeSystems, Inc.

pound (lb). Unit of measurement for weight equalto 16 ounces or 454 grams.

power factor. The ratio of power consumed to thevolt amps (apparent power).

power–on light. The light on the operator panelthat indicates that the DC power in the system unitis functioning.

power–on reset (POR). A key sequence thatrestarts the operating system (or other program)without turning off the electrical power of thesystem.

power–on self–test (POST). A series of internaldiagnostic tests activated each time the systempower is turned on.

power requirement. The actual power consumedby a computer system, measured in watts.

power source. The minimum acceptable rating ofthe electrical circuit providing power to a computersystem, measured in volt amps (kVA).

PPA (physical point of attachment). The point atwhich a system attaches itself to a physicalcommunications medium.

PPA identifier. An identifier of a particular physicalmedium over which communication occurs.

P(R). In X.25 communications, the packet receivesequence number.

pragma. In Ada language, conveys information tothe compiler.

precedence. (1.) The priority system for groupingdifferent types of operators with their operands. (2.)In programming languages, an order relationdefining the sequence of the application ofoperators within an expression.

precision. (1.) A measure of the ability todistinguish between nearly equal values. See alsosingle precision and double precision. (2.) Thedegree of discrimination with which a quantity isstated. For example, a three–digit numeraldiscriminates among 1000 possibilities. (3.) In GL,

the number of digits that are printed or displayed.(4.) The number of straight line segments used toapproximate one segment of a spline.

preconnected file. A unit or file that was definedat installation time. For example, standard inputand standard output are preconnected files.

Predefined Connection Object Class. Specifiesthe kind of connections that can be made to adevice and where.

predefined convention. In FORTRAN, the impliedtype and length specification of a data item basedon the initial character of its name, when no explicitspecification is given. The initial characters Ithrough N imply type integer of length 4; the initialcharacters A through H, O through Z, $, and _imply type real of length 4.

predefined database. Contains configuration datafor all possible devices supported by the system.See also Device Configuration Database andCustomized Database.

Predefined Devices Object Class. Representseach device type, as determined by class,subclass, and type. The Predefined Devices ObjectClass contains basic information about the devices,such as device method names and how to accessthe information contained in the other objectclasses.

predicate. Boolean logic term denoting a logicalexpression that determines the state of somevariables. For example, a predicate can be anexpression stating that ”variable A must have thevalue 3.” The control expression used inconjunction with condition variables is based upona predicate. Use a condition variable to wait forsome predicate to become true, for example, towait for something to be in a queue.

preferential CUG. In X.25 communications, thedefault closed user group.

prefix. In Ada language, used as the first part ofcertain kinds of name. A prefix is either a functioncall or a name. See also name.

preinstalled. Software that is installed by themanufacturer and ready to use.

premultiplication. In GL, matrix multiplication onthe left. If a matrix M is premultiplied by a matrix T,the result is TM.

preprocessor. (1.) A functional unit that effectspreparatory computation or organization. (2.) Inemulation, a program that converts data from theformat of an emulated system to the formataccepted by an emulator. (3.)A program thatexamines the source program for preprocessorstatements, which are then run, resulting in the

1-117Glossary

alteration of the source program. (4.)A programthat modifies, and possibly optimizes, sourceprograms before they are processed by a compiler.

preprocessor statement. In C language, astatement that begins with the # (pound sign) andcontains instructions that the preprocessorinterprets.

prerequisite. A software product or a serviceupdate that must be installed before anothersoftware product or service update is installed. Ifyou attempt to install software products or serviceupdates without the required prerequisite software,a system message displays the names of requiredprerequisite software. Contrast with dependent.

presentation address. An unambiguous namethat is used to identify a set of presentation serviceaccess points. Loosely, it is the network address ofan OSI service. See also address.

Presentation Service Access Point (PSAP).Address of an OSI communications partner. Itaddresses an application in a computer.

presentation space. An array that contains thedata and attributes associated with a window.

preservation installation. An installation methodused when a previous version of BOS is installedon your system and you want to preserve the userdata in the root volume group. However, thismethod overwrites the /usr, /tmp, /var,and /(root)file systems, so any user data in these directoriesis lost. System configuration must be done afterdoing a preservation installation.

Preventive Maintenance Package (PMP). Amaintenance level update for your system. A PMPincludes updates for the Base Operating System(BOS) and for each optional software product thatis installed on your system.

primary. An irreducible unit of data. For example, asingle constant, variable, or array element.

Primary Enterprise Systems ConnectionManager. In multiple ESCM environments, thesource of ESCM commands.

primary expression. An identifier, parenthesizedexpression, function call, array elementspecification, structure member specification, orunion member specification.

primary group. In concurrent groups, the groupthat is assigned to the files that you create.

primary language. The primary locale you wantyour system to use for screen information.

primary navigation article. The general, top–levelunit of software documentation.

primary representation. The form in which theservice supplies an attribute value to the client.

primary selected text. A text group selected as aprimary target or destination, especially textselected within a text field that can be passed to afunction. Also, the first block of text specified in afunction or statement. See also primary selection.

primary selection. In AIXwindows, the textselected in a widget. The primary selection has avalue retrieved by the XmTextGetSelectionfunction. See also primary selected text.

primary slow poll. A technique used by primarylink stations to reduce nonproductive polling of asecondary link station.

primary station. (1.) On a point–to–point channel,the station that gains control of the channel first.On a multipoint channel, the station controllingcommunications. (2.) In high level data link control(HLDC), the part of a data station that supports theprimary control functions of the data link, generatescommands for transmission, and interpretsreceived responses. (3.) In SNA, the station on anSDLC data link that is responsible for control of thedata link. There can be only one primary station ona data link. All traffic over the data link is betweenthe primary station and a secondary station.

prime file. In Pascal, a file containing precompileddeclarations in the internal table format of thePascal compiler. Prime files are used to initializethe internal tables of the compiler beforecompilation begins.

primitive. A drawing command, such as arc, line,circle, polygon, or charstr. Such commands arecalled primitives because they are not made up ofsmaller parts, and because they are the basicpieces out of which more complex scenes can becomposed. Also used to describe the figurescreated by drawing commands.

Primitive. In Enhanced X-Windows, the Primitiveclass provides the resources and functionality forthe low–level widgets that are managed by themanager class. Primitive class widgets cannothave normal child widgets but they can havepop–up child widgets.

primitive coordinates. The space in which aprimitive is defined. A convenient point is chosenas the origin and the primitive is defined relative tothis point. Synonym for primitive space. See alsoeye coordinates, screen coordinates, and worldcoordinates.

primitive font. A font in which characters aredefined as primitives. Like all other primitives,

1-118 Glossary

primitive font characters can be scaled and rotated.See also raster font and font.

primitive space. Synonym for primitivecoordinates.

primitive widget. In Enhanced X-Windows, awidget that instantiates its own children of a knownclass and does not expect external clients to do so.Primitive widgets do not have general geometrymanagement methods. Primitive widgets thatinstantiate children are responsible for alloperations requiring downward traversal belowthemselves. See also widget.

principal identifier. The name used to identify aprincipal uniquely.

Print Manager. In CDE, a software application thatshows all the printers on your system.

print queue. A file containing a list of the names offiles waiting to be printed.

print server. In CDE, a host computer to whichone or more printers are connected, or the UNIXprocess that manages those printers.

printer. A device externally attached to the systemunit, used to print system output on paper.

Printer control. In CDE, the Front Panel controlused to start the Printer software application.Dropping a file on the control displays a dialog boxyou can use to print the file to the default printer.

Printer Jobs. In CDE, a software application thatprovides information about jobs on a single printer.

printer session. A 3270 Host Connection Program2.1 and 1.3.2 for AIX (HCON) mode of operationduring interaction with a host computer thatemulates a 3286/87 printer.

printing device. Any printer or other device thatprints, such as a typewriter–like device or a plotter.

printout. Information from the computer producedby a printer.

priority. (1.) A rank assigned to a task thatdetermines its precedence in receiving systemresources, the CPU in particular. (2.) The relativesignificance of one job to other jobs in competingfor allocation of resources. The importance orurgency of a process.

priority number. A number that establishes therelative priority of printer requests.

priority value. A number maintained by thescheduler for each process that indicates thepriority of that process. The smaller the priorityvalue of the process, the higher its priority.

privacy. A protection level that may be specified insecure RPC communications and that encryptsRPC argument values.

private. A private member of a C++ class is onlyaccessible to member functions and friends of thatclass.

private object. (1.) In XDS, an OM object createdin a workspace using the object managementfunctions. (2.) In XOM, an object that isrepresented in an unspecified fashion.

private part. For Ada programming, see package.

private type. In Ada language, a type whosestructure and set of values are clearly defined, butnot directly available to the user of the type. Aprivate type is known only by its discriminants (ifany) and by the set of operations defined for it. Aprivate type and its applicable operations aredefined in the visible part of a package, or in ageneric formal part. Assignment, equality, andinequality are also defined for private types, unlessthe private type is limited.

privileged instructions. System controlinstructions that can only run in the processor’sprivileged, or supervisor, state. Privilegedinstructions generally manipulate virtual machinesor the memory manager and are not usedordinarily by application programmers. See alsoprivileged state.

privileged state. A hardware protection state inwhich the processor can run privileged instructions.Contrast with unprivileged state. See alsoprivileged instructions.

privileged user. A user logged into an accountwith root user authority.

problem determination. The process of identifyingthe source of a problem. Often this processidentifies programs, equipment, datacommunications facilities, or user errors as thesource of the problem.

problem determination procedure. A prescribedsequence of steps aimed at recovery from, orcircumvention of, problem conditions.

Problem Management Record (PMR). A numberassigned by a support center to a reportedproblem.

problem state. (1.) One of two virtual machineprotection states that run in the unprivileged stateof the processor. User–written applicationprograms typically run in the problem state. (2.) Astate during which the processing unit cannot runinput/output and other privileged instructions.

1-119Glossary

procedure. (1.) See shell procedure. (2.) In aprogramming language, a block, with or withoutformal parameters, that is initiated by means of aprocedure call. (3.) The description of the actionstaken to solve a problem. (4.) A set of relatedcontrol statements that cause one or moreprograms to be performed. (5.) Synonym forfunction. (6.) For Ada programming, seesubprogram.

procedure address. The location of a particularprogram procedure in the AIXwindows Toolkit.

process. (1.) A sequence of actions required toproduce a desired result. (2.) An entity receiving aportion of the processor’s time for running aprogram. (3.) An activity within the system that isstarted by a command, a shell program, or anotherprocess. When a program is running, it is called aprocess. (4.) In a computer system, a unique, finitecourse of events defined by its purpose or by itseffect, achieved under given conditions. (5.) Anyoperation or combination of operations on data. (6.)In the operating system, the current state of aprogram that is running. This includes a memoryimage, the program data, variables used, generalregister values, the status of opened files used,and the current directory. Programs running in aprocess must be either operating system programsor user programs. See also job.

process accounting. An analysis of how eachprocess uses the processing unit, memory, and I/Oresources.

process concurrency. The degree to which agiven process has multiple dispatchable threads atall times.

process group. Each process in the system is amember of a process group that is identified by aprocess group ID. This grouping permits thesignaling of related groups of processes. A newlycreated process joins the process group of itscreator.

process ID (PID). A unique number assigned to aprocess that is running.

process image. See new–process image.

process lock. Allows the calling process to lock orunlock both its text and data segments intomemory.

process pacing. See pacing.

process table. A kernel data structure thatcontains relevant information about all processes inthe system.

processing agent. A thread within an applicationserver that handles remote procedure calls fromclients.

processing unit. A functional unit within acomputer that is responsible for a certain aspect ofprocessing.

processor affinity. The degree to which a threadis likely to be dispatched to the same physicalprocessor on which it last ran.

product. A software product is made up ofsoftware packages that are separately installable.

product ID. An integer that identifies a vendor’slicensed software product; by means of productIDs, the license server distinguishes amongproducts of the same vendor.

product password. A string encoded withinformation about licenses for a software product.Product passwords are of two types: licensepasswords and compound passwords.

profile. (1.) A file containing customized settingsfor a system or user. (2.) Data describing thesignificant features of a user, program, or device.(3.) In security, a description of the characteristicsof an entity to which access is controlled. (4.) Adescription of the control available to a particularnetwork operator. See also customization profileand mapping.

program. (1.) A file containing a set of instructionsthat conform to a particular programming languagesyntax. (2.) A sequence of instructions suitable forprocessing by a computer. Processing can includethe use of an assembler, compiler, interpreter, ortranslator to prepare the program for running, andto run it. (3.) In programming languages, a logicalassembly of one or more interrelated modules. InAda language, a program is composed of anumber of compilation units, one of which is asubprogram called the main program. Execution ofthe program consists of execution of the mainprogram, which may invoke subprograms declaredin the other compilation units of the program. (4.)To design, write, and test computer programs.

program assertion. A mathematical statementused in attempts to verify program corrections. Inthe graphics operating system, the assertsubroutine tests program assertions.

program counter. A register in the processing unitthat guides the computer through the program.Synonym for instruction address register.

1-120 Glossary

program fault management (PFM). A subsystemof NCS that allows a user to set up cleanuproutines when an application does not successfullycomplete.

Program Initialization Parameters (PIP). Datapassed to a program when it starts running. Thisdata modifies the actions taken by that program orthe environment in which that program runs.

program level. The version, release, modification,and fix levels of a program. See also fix number,modification number, release number, version,background, and version number.

program stack. Synonym for invocation stack.

program temporary fix (PTF). A temporarysolution to, or bypass of, a defect in a currentrelease of a licensed program.

program text. The part of a program that is able tobe run. See text.

program–text segment. A virtual–memorysegment that contains the executable instructionsof an application program. A program–textsegment is identified by the occurrence of aninstruction–cache miss in that segment.

program unit. A main program or a subprogram.In Ada programming, a program unit is any one ofa generic unit, package, subprogram, or task unit.Synonymous with module. See also segment unit.

programmable character set (PCS). A geometrictext font. Synonymous with stroke text. See alsogeometric text.

programmable input/output operation. Thetransfer of data between the processor and an I/Odevice or memory address space as part of an I/Oinstruction. The I/O instruction designates theaddress of the control logic, the command to beperformed and the processor register location intoor from which the data is transferred.

programmable terminal. (1.) A user workstationthat has computational capabilities. (2.) Aworkstation that can be programmed to performeduser–determined functions.

programmatic interface. In AIXwindows, anapplication created in such a manner that it willoperate in a multiclient environment with otherapplications running concurrently. Clientscommunicate with the window manager throughXlib calls or libraries built upon Xlib.

Programmers’ Hierarchical Interactive GraphicsSystem (PHIGS). An ANSI and ISO standard.PHIGS defines an application programminginterface designed for interactive two–dimensional

and three–dimensional graphics applications usingretained data structures.

PROM. Programmable read–only memory.

prompt. A displayed symbol or message thatrequests information or operator action.

propagation time. The time necessary for a signalto travel from one point to another on acommunications line.

property. (1.) In Enhanced X-Windows, the name,type, data format, and data associated with awindow. By using properties, clients and a windowmanager share information, such as resize hints,program names, and icon formats. It is ageneral–purpose naming mechanism for clients.The protocol does not interpret properties. (2.)Public information (that is, information available toany client) that is associated with a window.

property list. In Enhanced X-Windows, the list ofproperties that are defined for a particular window.

protected. A protected member of a C++ class isaccessible to member functions and friends of thatclass, or member functions and friends of classesderived from that class.

protected field. A displayed field in which a usercannot enter, modify, or erase data.

protection. An arrangement for restricting accessto or use of all or part of a computer system.

protection level. The degree to which securenetwork communications are protected.

protocol. (1.) In SNA and SNA Services, themeaning of, and the sequencing rules for, requestsand responses used for managing a network,transferring data, and synchronizing the states ofnetwork components. (2.) A set of semantic andsyntactic rules that determines the behavior offunctional units in achieving communication. (3.) Amutually agreed–upon mechanism forcommunicating between clients to accomplishcertain actions.

protocol boundaries. The set of SNA verbssupported by SNA Services LU6.2.

protocol family. A set of related communicationsprotocols; for example, the Department of DefenseInternet Protocols. All members of a protocol familyuse a common addressing mechanism to identifyend points. Synonymous with address family. Seealso socket address.

protocol port. A unique host identifier used bytransport protocols to specify a destination within ahost.

1-121Glossary

prototype file. The first file in a new file systemthat contains tokens. These include the name ofthe bootstrap program, the size of the created filesystem, and the specifications of the root file.

proxy object. In DSOM, a SOM object in theclient’s address space that represents a remoteobject. The proxy object has the same interface asthe remote object, but each method invoked on theproxy is overridden by a dispatch method thatforwards the invocation request to the remoteobject. Under DSOM, a proxy object is createddynamically and automatically in the clientwhenever a remote method returns a pointer to anobject that happens to be remote. See also objectreference.

pruning. In GL, eliminating the drawing of parts ofthe display list because a bounding box test showsthat they are not visible. See also culling.

P(S). In X.25 communications, the packet sendsequence number.

PSAP. See Presentation Service Access Point.

PSDN (packet–switching data network) . APSDN is an interconnecting set of switching nodesthat enables subscribers to exchange data using astandard protocol and packet–switchingtechnology. Such a network carries messagesdivided into packets over circuits that are shared bymany network users. A single physical line into anoffice can handle many concurrent connections.

pseudo device. A software–based device; forexample, a pty device.

Pseudo–PostScript. A graphics language, similarto PostScript, used to drive output of text andgraphics.

pseudo terminal (PTY). A special file in the /devdirectory that effectively functions as a keyboardand display device to software that uses theBerkeley line discipline. A pseudo terminal consistsof a pair of character devices, referred to as the”master” and ”slave.” The slave device (/dev/pts) ismanipulated by another process through themaster half (/dev/ptc) of the pseudo terminal.

pseudocolor. In Enhanced X-Windows, (1.) Aclass of color map in which a pixel value indexesthe color map entry to produce independent red,green, and blue values. That is, the color map isviewed as an array of triples (RGB values). TheRGB values can be changed dynamically. This ismutually exclusive to the direct color color mapclass. (2.) Also PseudoColor, a value.

PSN. See public switched network.

PSTN. See public switched telephone network.

PTF. See program temporary fix.

PTN. See public telephone network.

PTT. Post, Telegraph, and Telephone authority.

PTY. See pseudo terminal.

PU. See physical unit.

public. A public member of a C++ class isaccessible to all functions.

public data network (PDN). A communicationscommon carrier network providing datacommunications services over switched ornonswitched lines.

public directory. In BNU, the directory(/var/spool/uucppublic) that is open to all BNUusers. The public directory is used to transfer filesand programs among systems linked by BNU orother versions of the UNIX–to–UNIX Copy Program(UUCP).

public node. Any node that does not run Monitorsystem components or servers. For example, clientapplications run on public nodes.

public switched network (PSN). Acommunications service through which users canbe connected by dialing specific service addressnumbers.

public switched telephone network (PSTN). Acommunications common carrier network thatprovides voice and data communications servicesover switched lines.

public telephone network (PTN). Acommunications common carrier network thatprovides voice and data communications servicesover switched or nonswitched lines.

puck. A device used to select a particular locationon a tablet.

pull installation. In the Network InstallationManagement environment, an installation that isinitiated from a target.

pulldown. The manner in which a MenuPanewidget gives the appearance of being ”pulleddown” from a MenuBar widget as the result ofsome user action (usually clicking a mouse button).

pulldown menu. A type of MenuPane widget thatgives the appearance of being ”pulled down” froma MenuBar widget as the result of some useraction (usually clicking a mouse button).

pure virtual function. A virtual function is declaredpure by replacing the function definition with ’=0;’.

purported name. A construct that is syntactically aname, but that has not yet been shown to be avalid name.

1-122 Glossary

push. A term used when a module is inserted in astream immediately below the stream head.

push button. A rounded–corner rectangle with textinside. Push buttons are used in dialog boxes foractions that occur immediately when the pushbutton is selected.

push installation. In the Network InstallationManagement environment, an installation that isinitiated from a machine other that the target.

push permissions. Permissions that enableremote execution of commands.

pushable module. A module between the streamhead and the driver. A driver is a non–pushablemodule and a stream head includes anon–pushable module.

PUT. Program update tape.

PUT 2.0 or PUT 2.1. In SNA, a peripheral node thathas limited addressing and path control routingcapabilities. A PUT 2.0 node depends on subareanodes (PUT 4 and PUT 5) to translate between itslocal addressing and network addressing. PUT 2.0does not support the full capabilities of LU6.2; PUT2.1 does. SNA Services operates only as either aPUT 2.0 or a PUT 2.1 peripheral node.

PUT 4 or PUT 5. A subarea node that providesnetwork–wide addressing and control data flowwithin a subarea (the subarea node and allperipheral nodes connected to it). PUT 4 does notcontain an SSCP component; PUT 5 does. SNAServices cannot perform the functions of a PUT 4or a PUT 5 subarea node.

PVC. See permanent virtual circuit.

1-123Glossary

QQ–bit. In X.25 communications, the bit in a datapacket that can be set by the sending DTE toqualify the user data in some way that ismeaningful to the receiving DTE.

qdaemon. The daemon process that maintains alist of outstanding jobs and sends them to thespecified device at the appropriate time.

QIC. Quarter–inch cartridge.

QID. Queue identifier.

QLLC. See qualified logical link control.

qualified class name. Any class name or classname qualified with one or more :: (scope)operators.

qualified expression. In Ada language, anexpression preceded by an indication of its type orsubtype. Such qualification is used when, in itsabsence, the expression might be ambiguous (forexample as a consequence of overloading).

qualified logical link control (QLLC). A data linkcontrol protocol that enables SNA–to–SNAcommunications over an X.25 network.

qualified name. (1.) A name made unique by theaddition of one or more qualifiers. (2.) A data nameexplicitly accompanied by a specification of theclass to which it belongs in a specifiedclassification system. (3.) In C++, used to qualify anonclass type name such as a member by its classname.

qualified type name. Used to reduce complexclass name syntax by using typedefs to representqualified class names.

qualifier. (1.) A unique name used to identifyanother name. (2.)A modifier that makes a nameunique. (3.) All names in a qualified name otherthan the rightmost, which is called the simplename.

qualifier bit. See Q–bit.

quality of service negotiation. An optionalCCITT–specified facility.

quantization. The subdivision of the range ofvalues of a variable into a finite number ofnonoverlapping, but not necessarily equal intervals.Each interval is represented by an assigned value.

quantum. A subrange in quantization.

quark. In Enhanced X-Windows, synonym forstring.

query. (1.) The action of searching data fordesired information. (2.) In data communications,the process by which a master station asks a slavestation to identify itself and to give its status. (3.) Ininteractive systems, an operation at a workstationthat elicits a response from the system. (4.) Arequest for information from a file based on specificconditions.

queue. (1.) A line or list formed by items waiting tobe processed. (2.) To form or arrange in a queue.

queue device. A logical device definingcharacteristics of a physical device attached to aqueue.

queue element. A block of data or an item in aqueue.

queue stanza. Defines a queue for one or moredevices to which jobs can be queued.

queued I/O devices. Devices (keyboard, mouse,button, dials) whose changes are recorded in theevent queue.

quiet system. A system on which no processesare running other than the process whoseperformance is being timed, and from which allcommunications devices have been disconnected.

quit. A key, command, or action that tells thesystem to return to a previous state or stop aprocess.

quote. To mask the special meaning of certaincharacters, causing the characters to be takenliterally.

QWERTY keyboard. A keyboard having thestandard keyboard layout. The term is derived fromthe sequence of the first six keys in the first row ofalphabetic keys. See also AZERTY keyboard.

1-124 Glossary

Rrace condition. For the signal subroutine, thecondition in which the signal occurs while the signalaction is set to the SIG_DFL value, and thesignal–catching function has not yet establisheditself as the catcher for this signal.

radio box. Special configuration of toggle buttonswithin a row column manager widget.

radio button. Indicates a fixed set of choices. Onlyone of the buttons in the set can be selected at atime. A circle with text beside it. The circle ispartially filled when a choice is selected.

radio frequency interference. A signal (noise)that is radiated or conducted from one electroniccircuit or device the may cause incorrect operationinterference in another electronic circuit or device.An electronic circuit or device can be an emitter ofelectromagnetic interference (EMI) or susceptibleto electromagnetic interference.

raise. To make the stacking order of a windowhigher.

raising an exception. For Ada programming, seeexception.

RAM. Random access memory. Specifically, thememory used for system memory. Sometimes thismemory is referred to as main storage.

random access. An access mode in which recordscan be read from, written to, or removed from a filein any order.

random file access. Location of a record thatmatches a specific index key value. Randomaccess of the records in a file requires that the filehave a unique index and that each record have aunique index key value.

range. In Ada language, a contiguous set of valuesof a scalar type. A range is specified by giving thelower and upper bounds for the values. A value inthe range is said to belong to the range.

range constraint. In Ada language, a rangeconstraint of a type specifies a range, and therebydetermines the subset of the values of the type thatbelong to the range.

range of a DO loop. Those statements thatphysically follow a DO statement, up to andincluding the final statement specified by the DOstatement.

range of records. Multiple records to beprocessed sequentially. A range of records isselected by specifying key values that bound therecords to be selected, or by specifying an

individual key value for which all matching recordsshould be selected in a nonunique index.

raster. The area of the video display that iscovered by sweeping the electron beam of thedisplay horizontally and vertically. Normally theelectronics of the display sweep each linehorizontally from top to bottom and return to the topduring the vertical retrace interval. See also framebuffer.

raster font. A font in which the characters aredefined directly by the raster bit map. See also fontand primitive font.

raster graphics. Computer graphics in which adisplay image is composed of an array of pixelsarranged in rows and columns.

raster mosaics. An area in annotated text fontsthat contains a definition for each character in thefont.

raster subsystem. That part of the systemconcerned with an image after it has beentransformed and scaled to screen coordinates. Itincludes scan conversion and display.

raw device. A device that treats data I/O as acontinuous stream, without consideration for thedata’s logical structure. For example, I/O for fixeddisks and streaming tapes occurs in units of bytesthat have no relationship to characters.

raw I/O. Character–oriented access to a blockdevice not utilizing in–core buffers.

raw tape device. See raw device.

RC. Routing control.

RCM. (1) See real–time control microcode. (2)Rendering Context Manager.

RCS. See Revision Control System.

RD. Receive Data used with EIA–232 protocol.

read access. An access right that grants the abilityto view CDS data.

read–only file. Pertaining to file system mounting,a condition that allows data to be read but notcopied, printed, or modified.

Read Only Storage (ROS) menus. The menusdisplayed by system ROS on a target. Informationused in booting the target is provided by the user tothe ROS menus.

read queue. A message queue in a module ordriver containing messages moving upstream.Associated with input from a driver.

readers and writers. In the SOM ReplicationFramework, different processes can access the

1-125Glossary

same replicated object in different modes. A”reader” is a process that does not intend to updatethe object, but wants to continually watch the objectas other processes update it. A ”writer” is a processthat wants to update the object, as well ascontinually watch the updates performed by others.

real constant. A string of decimal digits thatexpresses a real number. A real constant mustcontain either a decimal point, a decimal exponent,or both.

real device. The actual device hardware.

real group ID. For each user, the group ID definedin the password file.

real memory. The active physical memory on anysystem. Contrast with virtual memory.

real number. (1.) A number that contains adecimal point and is stored in fixed–point orfloating–point format. (2.) A number that can berepresented by a finite or infinite numeral in afixed–radix numeration system.

real operation. Any operation on Adafloating–point or fixed–point values.

real page number. This field in the translationcontrol word (TWC) contains the real page addressthat the bus address is mapped to in systemmemory.

real storage. Storage directly accessible to theprocessor from which instructions can be run andfrom which instructions can fetch data.

real time. (1.) The time elapsed between theloading of a program and its completion. (2.)Pertaining to the processing of data by a computerin connection with another process outside thecomputer, according to time requirements imposedby the outside process. (3.) Used to describesystems that operate in conversational mode andprocesses that can be influenced by humanintervention while in progress. (4.) Pertaining to anapplication, such as a process control system or acomputer–assisted instruction system, in whichresponse to input is fast enough to affectsubsequent input.

real–time control microcode (RCM). In X.25communications, the microcode that runs on theX.25 Interface Co-Processor/2 to provide controlfunctions.

real–time system. A system that receives andprocesses data so the data or result is available forimmediate use.

real type. (1.) An arithmetic data type that canapproximate the values of real numbers. (2.) InAda language, a real type is a type whose valuesrepresent approximations to the real numbers.

There are two kinds of real type: fixed point typesare specified by absolute error bound; floating pointtypes are specified by a relative error boundexpressed as a number of significant decimaldigits.

real user ID. (1.) Identifies the user who wasauthenticated the last time the login command orsu command was used. (2.) For each user, theuser ID that is specified in the /etc/passwd file.

realm. A cell, considered exclusively from the pointof view of security; this term is used in Kerberosspecifications.

rebinding. Reestablishing a communicationschannel for making remote procedure calls afterthat channel has been closed.

reboot. To reinitialize the execution of a programby repeating the initial program load (IPL)operation.

REC. See Lock Service.

receive. In X.25 communications, to take anincoming packet (such as an incoming–call packetor a data packet) from the buffer.

receive pacing. In SNA, the pacing of messageunits that a component is receiving. Contrast withsend pacing. See also pacing.

receive time out. In data communications, acondition that occurs when no data is received in agiven period of time.

recognized private operating agency (RPOA). Aprivate X.25 network that can optionally beselected by the user at call setup time to carry theX.25 traffic.

Recommendation X.25. See X.25.

record. (1.) In programming languages, anaggregate that consists of data objects, possiblywith different attributes, that usually have identifiersattached to them. (2.) A set of data treated as aunit. (3.) A collection of fields treated as a unit. Seealso class record, widget record, and instancerecord.

record lock. A lock that prevents some or all of afile from being written to or read. See also lock.

record name. A data name for a record describedin a record description entry.

record type. (1.) The classification of records in afile. (2.) In Ada language, a value of a record typeconsists of components are usually of differenttypes or subtypes. For each component of a recordvalue or record object, the definition of the recordtype specifies an identifier that uniquely determinesthe component within the record.

1-126 Glossary

recording instrument. In Performance Toolbox,an instrument with the ability to show the statisticsfor a system resource over a period of time.Recording instruments typically have a time scalewith the current time to the right. The values plottedare moved to the left as new readings are received.Types of graphs used to plot these recordingsinclude line, area, skyline, and bar graphs. Contrastwith state instrument.

recoverable data. Data whose values persistacross system shutdowns and failures. Changesmade to recoverable data are permanentregardless of system problems. Logging changesto recoverable data is the most common methodused to ensure permanence. The changes to thatdata recorded in the log can always be replayed tobring that data to a valid state.

recovery procedure. (1.) An action performed bythe operator when an error message appears onthe display screen. This action usually permits theprogram to continue or permits the operator to runthe next job. (2.) The method of returning thesystem to the point where a major system erroroccurred and running the recent critical jobs again.(3.) A process in which a specified data stationattempts to resolve conflicting erroneous conditionsarising during the transfer of data.

rectangle. A rectangle specified by [x,y,w,h]has an infinitely thin outline path with corners at[x,y][x+w,y][x+w,y+h] and [x,y+h] . InXGSL , when a rectangle is filled, the lower–rightedges are not drawn. For example, if w=h=0,nothing would be drawn; if w=h=1, a single pixelwould be drawn.

recurring attribute. An attribute with severalattribute values.

recursion. (1.) Using a function to define itself. (2.)Performing an operation in several steps, with eachstep using the output of the preceding step.

redirect. To divert data from a process to a file ordevice to which it would not normally go.

redirecting control. Transferring an operation to aspecified client. Used when window managers orclient programs enforce window layout policy toprevent attempts to change the size or position of awindow.

redispatch stub. In SOM, a procedure,corresponding to a particular method, which hasthe same signature as the method’s procedure butwhich invokes somDispatch to dispatch themethod. The somOverrideMtab method can beused to replace the procedure pointers in a class’smethod table with the corresponding redispatchstubs. This is done when overriding somDispatchto customize method resolution so that all static

method invocations will be routed throughsomDispatch for selection of an appropriatemethod procedure. (Dynamic methods have noentries in the method table, so they cannot besupported with redispatch functionality.)

Reduced Instruction Set Computer (RISC). Aclass of computer designs that uses a relativelysmall set of frequently used instructions thatexecute in one cycle.

reentrant service. A service that is safe to callfrom multiple threads in parallel. If a service isreentrant, there is no burden placed on callingroutines to serialize their access or take otherexplicit precautions. See also thread–serial service,and thread–synchronous service.

refer. A bibliographic preprocessor for the nroffand troff commands. ”Refer” is designed forliterature citations, and it supports data entry,indexing, sorting, retrieval, printing, citations, andeither footnote or endnote numbering.

reference bit. A bit in each page frame table entrythat denotes that the corresponding page has beenaccessed (either read from or written to) since thelast time the operating system cleared the page.

reference count. In an i–node, a record of the totalnumber of directory entries that refer to the i–node.

reference data. In SOM, application–specific datathat a server uses to identify or describe an objectin DSOM. The data, represented by a sequence ofup to 1024 bytes, is registered with DSOM when aserver creates an object reference. A server canlater ask DSOM to return the reference dataassociated with an object reference. See alsoobject reference.

reference monitor. Code that controls access toan object.

reference widget. The parent widget thatsearched for children satisfied the search criteria.

refresh rate. The rate at which the monitor isrefreshed. A 60 Hz monitor is redrawn 60 times persecond. Synonymous with vertical retrace.

region. An area within a bitmap, a pixmap, ascreen, or a window.

Region. An arbitrary set of pixel locations. The Xliblibrary provides subroutines for manipulatingregions. The opaque type Region is defined in the<X11/Xutil.h> header file.

register. (1.) A storage device having a specifiedstorage capacity such as a bit, byte, or computerword, and that is usually intended for a specialpurpose. See also general purpose register. (2.) InNCS, to make an interface known to the RPC runtime library and, thereby, available to clients

1-127Glossary

through the RPC mechanism. The rpc_$registercall registers an interface. (3.) In NCS, to enter anobject and its location in the Location Brokerdatabase. The lb_$register call registers an objectwith the Location Broker. A program can useLocation Broker lookup calls to determine thelocation of a registered object.

registration. The creation of an object in thenetwork installation database that uniquelyidentifies a client, network, or resource in thenetwork installation environment to the masterserver.

Registry database. A database of informationabout persons, groups, organizations, andaccounts.

regular expression. (1.) A set of characters, metacharacters, and operators that define a string orgroup of strings in a search pattern. (2.) A stringcontaining wildcard characters and operations thatdefine a set of one or more possible strings.Contrast with literal string. See also collatingelement and subpattern.

reject. To cause portions of applied updates frombecoming permanent parts of the product, basedon the results of a test period. When you reject anapplied service update, the update’s files aredeleted and the software vital product data(SWVPD) information is changed to indicate thatthe update is no longer on the system. Theprevious version of the software, if there is one, isrestored and becomes the active version of thesoftware. Contrast with apply and commit.

relational expression. (1.) A logical statement thatdescribes the relationship (such as greater than orequal) of two arithmetic expressions or data items.(2.) An expression that consists of an arithmeticexpression followed by a relational operator,followed by another arithmetic expression, and thatcan be reduced to a value that is true or false.

relational operator. (1.) The reserved words orsymbols used to express a relational condition or arelational expression. (2.) An operator thatcompares two operands and yields a Booleanvalue.

relational transformation. A transformation thatchanges an arithmetic relational expression into thenegation of its logical complement. For example, arelational transformation of A>B is NOT(A<=B).

relative address. (1.) An address specified relativeto a base address. (2.) An address counted relativeto a symbol. When a program is relocated, theaddresses themselves change, but the relativeaddresses remain the same.

relative directory. A directory whose name beginswith a ./ (dot and a slash).

Relative Distinguished Name (RDN). A set ofAttribute Value Assertions (AVAs), each of which istrue, concerning the distinguished values of aparticular entry.

relative drawing commands. In computergraphics, commands that draw relative to thecurrent graphics position as opposed to beingdrawn at absolute locations.

relative file. A file organized as an array offixed–length slots. Records can be inserted in thefirst free slot found from the beginning or end of thefile, or can be explicitly positioned in a certain slotin the file, identified by its relative slot number(RSN).

relative path name. The name of a directory or fileexpressed as a sequence of directories followed bya file name, beginning from the current directory.Relative path names do not begin with a / (slash)but are relative to the current directory. See alsopath name and full path name.

relative record number. A number that expressesthe location of a record in relation to a baseposition in the file containing it.

relative slot number (RSN). The number of theslot occupied by a record in a relative file. The RSNis part of the user’s data record. Each record in arelative file contains a field that holds its RSN.

relative time. A discrete time interval that isusually added to or subtracted from an absolutetime.

release number. The release level of a program,which is an indicator of changes to the externalprogramming interface of the program. Theversion, release, modification, and fix levelstogether comprise the program level or version of aprogram. See also fix number, modificationnumber, version number, program level andversion.

release update package. A set of selectiveenhancements, filesets, and new versions ofoptional software products available since the lastrelease of the operating system. Also included is amaintenance level package for each softwarepackage.

reliable stream delivery. A type of packet deliverythat allows an application program on one machineto connect to an application program on anothermachine. The stream actually contains manypackets of data that are sent one at a time to thereceiving machine.

1-128 Glossary

relocatable. (1.) A value, expression, or addressthat does not have to be changed when theprogram is relocated. (2.) Attribute of a set ofcodes whose address constants can be altered tomake up for a change in origin.

remote. Pertaining to a system or device that isaccessed through a communications line. Contrastwith local.

remote access data processing. Synonym forteleprocessing.

remote connection. A communications linkbetween the local system and a remote system ordevice.

remote host. Any host on the network except theone at which a particular operator is working.Synonymous with foreign host.

remote job entry (RJE). Submission of a jobthrough an input unit that has access to a computerthrough a data link.

remote login. Initiating a session on a system thatis accessed through a communications line.

remote pacing. Pacing generated by the remotesystem attempting to control the output of the localsystem. See also pacing.

remote print. Issuing print jobs to one machine(client) to print on another machine (server) on anetwork.

remote procedure call (RPC). The calling of aremote operation between processes on differenthosts or on the same host.

Remote Procedure Call run–time library. The setof rpc_$ system calls that NCS provides toimplement a remote procedure call mechanism.

Remote Statistics Interface (RSi). InPerformance Toolbox, the Manager API whichallows an application program to access statisticsfrom remote nodes (or the local host) through anetwork interface.

remote system. A system that is connected toyour system through a communication line.

remote transaction program name (RTPN). Thename of a transaction program at the other(remote) end of a conversation.

removable storage device. Any storage devicedefined during system configuration to be anoptional part of the system DASD. A removablestorage device can be removed from the systemanytime during normal operation.

remove. For a software option, the deletion of theoption and all of its applied or committed updatesfrom the system. The software vital product data

(SWVPD) information is changed to indicate thatthe option has been removed from the system.Depending on the option, system configurationinformation is also cleaned up, although this is notalways complete. If a previous version, release, orlevel of the option is on the system, the system willnot restore the previous version. Only an optionwith its updates can be removed. Updates cannotbe removed by themselves. Contrast with commit.

renaming declaration. In Ada language, declaresanother name for an entity.

render. To create an image on a visual displayfrom data that describes the scene.

rendezvous. In Ada language, the interaction thatoccurs between two parallel tasks when one taskhas called an entry of the other task, and acorresponding accept statement is being executedby the other task on behalf of the calling task.

repage fault. A page fault on a virtual–memorypage that is known to have been read from disk”recently.”

reparent. When a widget is moved betweeninterface windows, it is reassigned to the parentwidget in the new location, and automaticallyacquires the inheritable attributes of the newparent.

repeat factor. In GL, the magnification with whichthe linestyle pattern is used.

repetitive tiling operation. In XGSL, an operationthat consists of repeatedly copying a 16x16–pixeltile rectangle (pointed to by the tile pixel map dataaddress) to fill a rectangle area of a size specifiedby the H and W parameters of this call. The formatdefined in the flags field of the tile pixel mapstructure defines the format of the tile data.

replica. In SOM, when an object is replicatedamong a set of processes (using the ReplicationFramework), each process is said to have a replicaof the object. From the view point of any applicationmodel, the replicas together represent a singleobject.

reply. (1.) A response to an inquiry. (2.) In SNA, arequest unit sent only in reaction to a receivedrequest unit. For example, Quiesce Complete is thereply sent after receipt of Quiesce At End of Chain.(3.) In Enhanced X-Windows, the way informationrequested by a client program is sent back to theclient. Both events and replies are multiplexed onthe same connection. Most requests do notgenerate replies; some generate multiple replies.

representation clause. In Ada language, a clausethat directs the compiler in the selection of themapping of a type, an object, or a task onto

1-129Glossary

features of the underlying machine that executes aprogram. In some cases, representation clausescompletely specify the mapping; in other cases,they provide criteria for choosing a mapping.

request. (1.) A directive, by means of a basictransmission unit, from an access method thatcauses the network control program to perform adata–transfer operation or auxiliary operation. (2.)In SNA, a message unit that signals initiation of anaction or protocol. (3.) In Enhanced X-Windows, acommand to the server to send a single block ofdata over a connection. (4.) In text formatting, arequest is a built–in command recognized by theformatters.

requester. A display station or interactivecommunications session that requests a programto be run.

required list. In Enhanced X-Windows, an orderedlist containing a subset of the installed color maps.

required parameter. A parameter having no valueautomatically supplied. The user must provide avalue.

required value. Synonym for required parameter.

requisite. A software product or a service updatethat must be installed with another softwareproduct or service update. If you attempt to installsoftware products or service updates without therequired requisite software, a system messagedisplays the names of required requisite software.

reserved character. A character or symbol thathas a special (non–literal) meaning unless quoted.

reserved word. A word that is defined in aprogramming language for a special purpose, andthat must not appear as a user–declared identifier.

reset. (1.) To cause a counter to take the statecorresponding to a specified initial number. (2.) Toput all or part of a data processing device back to aprescribed state. (3.) On a virtual circuit,reinitialization of data flow control. (4.) To return adevice or circuit to a clear state. (5.) In X.25communications, to reinitialize the flow of controlon a virtual circuit, which eliminates all data thatmay be in transit for the virtual circuit at the time ofresetting.

reset cause. See cause code.

reset collision. See collision.

reset–confirmation packet. In X.25communications, a packet transmitted by the dataterminal equipment (DTE) to inform the datacircuit–terminating equipment (DCE) that a resetoperation has been processed. See also packet.

reset diagnostic. See diagnostic code.

reset packet . A packet used to reset a virtualcircuit at the interface between the data terminalequipment (DTE) and the data circuit–terminatingequipment.

reset–request packet. In X.25 communications, apacket used for the resetting of a virtual circuit atthe DTE/DCE interface. See also packet.

resize border. In CDE, a control used to changethe size of a window or a pane in a window.

resolution. The process or capability of makingthe individual parts of objects on screendistinguishable, especially regarding fontgeneration. The number of dots that can bedisplayed on the screen. Used to determine theclarity of a graphic image.

resolver routine. A kernel process used to resolvesymbolic host names into Internet addresses. Themethod the routine uses to resolve names dependson whether the local network is organized as a flatnetwork or as a hierarchical network.

resource. (1.) In NIM, any file, directory, filesystem, or device that is required to perform a NIMoperation. (2.) In Enhanced X-Windows, items suchas windows, pixmaps, cursors, fonts, graphicscontexts, and color maps are known as resources.Each has a unique identifier associated with it fornaming purposes. The lifetime of a resource isbounded by the lifetime of the connection overwhich the resource was created. (3.) In EnhancedX-Windows, a named piece of data in a widget thatcan be set by a client, by an application, or by userdefaults. (4.) In AIXwindows and EnhancedX-Windows, a unique characteristic of appearanceor behavior that is associated with one specificclass of graphical object. Resources can be passeddownward (inherited) by each subclass that isdownstream from a higher–level class in the classhierarchy.

resource database. The database assembled fora particular combination of display, host, andapplication. It can contain information from severalsources.

resource identifier (rid). In Enhanced X-Windows,an integer returned to an application program thatidentifies a resource that has been allocated for theprogram’s use.

resource manager. A component that managesapplication data. Resource managers communicatewith application servers.

1-130 Glossary

resource object. A resource used in the NetworkInstallation Management environment thatrepresents a file or directory.

resource outage. The inability to obtain thenecessary resources, such as links, buffers, orcontrol block storage.

resource pair. See resource value.

resource state. A state that indicates that theresource is either available or unavailable for use.

resource string. A parameter, such as a part ofthe program name, that identifies an application’sresources.

resource value. Resources determine a widget orwindow’s operation and attributes, such as colorand behavior. The resource is associated with avalue list that gives the specific values for eachresource. See also attribute.

resource value string. A parameter containing thedefault value to be used if a specific resource hasnot been set.

response. (1.) An answer to an inquiry. (2.) InSNA, a message unit that acknowledges receipt ofa request; a response consists of a responseheader (RH), a response unit (RU), or both.

response time. (1.)The time it takes for a datacommunications system to respond to a request.For example, if you enter a customer number on aworkstation keyboard, response time begins whenyou press the last key and ends when the firstcharacter of your answer is displayed at theworkstation. (2.) The time from the initiation of anoperation until its initiator has enough informationto proceed.

restart–confirmation packet. In X.25communications, a call supervision packettransmitted by a DCE to confirm that the link hasbeen restarted. See also packet.

restart–indication packet. In X.25communications, a call supervision packettransmitted by a DCE to indicate to a DTE that arestart–request has been received.

restart–request packet. In X.25 communications,a call supervision packet transmitted by a DTE torequest that a link be restarted.

restore. To return to an original value or image; forexample, to restore a library from diskette.

restricted response. In X.25 communications,when restricted response is specified for afast–select call, the call must be cleared; it may notbe accepted.

restricted shell. Shell providing controlled, limitedaccess to specified users.

result. An entity produced by an operation.

retransmit. To repeat the transmission of amessage or segment of a message.

retrieval time. The time interval required to locatedata in storage and read it for subsequentprocessing.

retry. To try the operation that caused the deviceerror message again.

return code. (1.) A value that is returned to aprogram to indicate the results of an operationissued by that program. (2.) A code used toinfluence the running of succeeding instructions.Synonymous with return value.

return statement. A programming languagecontrol statement that contains the word returnfollowed by an optional expression and asemicolon.

return value. Synonym for return code.

reverse charging. In X.25 communications, anoptional facility that allows a DTE to request thatthe cost of a call it makes be charged to the calledDTE. See also optional facilities.

reverse video. A form of highlighting a character,field, or cursor by reversing the color of thecharacter, field, or cursor with its background. Forexample, changing a red character on a blackbackground to a black character on a redbackground.

Revision Control System (RCS). Managesmultiple revisions of text files. Designed to controlfrequently revised text, such as programs, formletters, and papers. It features automaticidentification, storage, logging, retrieval, andmerging of file revisions. See also Source CodeControl System.

revision text. See version identifier.

rewind. To select an earlier item, rather than thenext or current item, from an argument list.

RFC. Request for comments.

RFI. See radio frequency interference.

RGB color. A color value scale that is composed ofthe primary values (red, green, and blue).

RGB mode. A configuration of the hardware thatallows values stored in the frame buffer to beinterpreted as packed RGB values. The valuesfound in the frame buffer are passed directly to the

1-131Glossary

red, green, and blue guns of the display monitor.The values are not passed through the color mapfirst. (However, each color is sent individuallythrough the gamma ramp to make a final correctionto its intensity.) See also color map mode.

RGB signal. Red/green/blue signal.

RGB value. The set of red, green, and blueintensities that compose a color is that color’s RGBvalue.

RGBA value. In GL, the set of red, green, blue,and alpha intensities that compose a color. Alphavalues are available only on machines havingalpha bitplanes.

RIC. Realtime interface coprocessor.

rid. See resource identifier.

right–hand rule. If the right hand is wrappedaround the axis of rotation, the fingers curl in thesame direction as positive rotation, and the thumbpoints in the same direction as the axis of rotation.A right–handed rotation is counter–clockwise.

right margin. The area between the rightmost textcharacter and the right edge of the display orpaper.

ring. (1.) A method used to distribute data in aLAN. (2.) In FDDI, two or more stations connectedby a physical medium wherein information ispassed sequentially between active stations, eachstation is turn examining or copying and repeatingthe information, finally returning it to the originatingstation. See also ring network.

ring buffer. An application–defined buffer in whichmonitor mode input is placed. An application placesdata from input devices in the buffer. The ringbuffer mechanism dramatically shortens the inputdata path from the input device to the application.

ring network. (1.) A network in which every nodehas two branches connected to it. (2.) A networkconfiguration in which devices are connected byunidirectional transmission links to form a closedpath. See also ring.

RIP. See Routing Information Protocol.

RISC. See Reduced Instruction Set Computer.

RJE. See remote job entry.

RMT. Ring management.

RNR frame. In X.25 communications, areceive–not–ready frame. Contrast with RR frame.

RNR packet. In X.25 communications, areceive–not–ready packet. Contrast with RRpacket.

rolled back. Undoing any modifications performedon behalf of a transaction which does not complete(is aborted). Any changes made by a transactionwhich is aborted, for whatever reason, must beundone. Once a transaction is rolled back, noevidence that the transaction was ever attemptedremains outside of records in the transactionprocessing system’s log. See also abort.

roller ball. The sphere inside a mechanical mousethat contacts a desktop or other hard surface.

ROM. Read–only memory.

Roman font. The ordinary type style. In manytypefaces, this is the default font, governing mosttext. It most often is used to turn off italics orboldface.

Roman numerals. Numbers formed fromtraditional combinations of Roman letters, eitheruppercase (I, II, III, IV, and so on) or lowercase (i,ii, iii, iv, and so on). See also Arabic numerals.

root. (1.) The user name for the system user withthe most authority. (2.) In Enhanced X-Windows,(a.) The screen on which the window is created.The root of a pixmap or GContext is the same asthe root of the drawable used when the pixmap orGContext was created. The root of a pixmap orgraphics context is the same as the root ofwhatever drawable was used when the pixmap orgraphics context was created. The root of a windowis the root window under which the window wascreated. (b.) On the widget tree, the Shell widgetreturned by the XtInitialize orXtCreateApplicationShell subroutine. (3.) InAIXwindows, the Shell widget is the root of thewidget tree hierarchy that is maintained within anygiven application interface. See also widget tree.

root device. The device on which the root filesystem resides.

root directory. The directory (/) that contains allother directories in the system.

root file system. The basic file system, onto whichall other file systems can be mounted. The root filesystem contains the operating system files that getthe rest of the system running.

root segment. (1.) In an overlay operation, thepart of a program that must remain in main storagewhen other overlay segments are run; the firstsegment of a program with overlays. The rootsegment remains in main storage at all times whilethe program is being run. (2.) In a hierarchicaldatabase, the highest segment in the treestructure.

1-132 Glossary

root user. The person who has unrestricted abilityto access and modify any part of the operatingsystem, usually the user who manages the system.See also root user authority.

root user authority. The unrestricted ability toaccess and modify any part of the operatingsystem, usually associated with the user whomanages the system. See also root user.

root volume group (rootvg). A volume groupcontaining the Base Operating System (BOS). Seealso migration installation.

root window. In a graphics environment, eachscreen has a root window covering it. This windowcannot be reconfigured or unmapped, butotherwise performs like any other window. A rootwindow has no parent.

ROS. Remote Operation Service.

ROSE. Remote Operation Service Elements.

rotation. In computer graphics, the transformationof a primitive by rotating it about an axis. See alsotransformation.

route. A path defined for sending data across anetwork.

routine. A set of statements in a program causingthe system to perform an operation or a series ofrelated operations. See also macro and subroutine.

routing. (1.) The assignment of the path by whicha message will reach its destination. (2.) In SNA,the forwarding of a message unit along a particularpath through a network as determined byparameters carried in the message unit, such asthe destination network address in a transmissionheader. (3.) In X.25 communications, the processby which a packet gets to the intended user.

Routing Information Protocol (RIP). A variant ofthe XeroxNS Routing Information Protocol, used tomaintain current kernel routing table entries.

routing list. The list that associates user nameswith network user addresses and other information,for the purpose of directing incoming X.25 calls.

routing table. The table holding a list of validpaths through which hosts can communicate withother hosts. The routing table can hold static routesand dynamic routes.

row. A horizontal arrangement of characters orother expressions.

row column manager. A widget that containstoggle buttons or push buttons. It updates itsproperty that accounts for menu history, whichallows it to determine which toggle button wasselected last.

row–major order. A way of storing array elementssuch that the rightmost subscript varies mostrapidly as memory–adjacent elements areaccessed.

RPC. See remote procedure call.

rpm. Revolutions per minute.

RPN. See real page number.

RPOA. See recognized private operating agency.

RPQ. Request for Price Quotation.

RR. (1.) Resource Record (DNS). (2.) Round Robin(scheduling).

RR frame. In X.25 communications, areceive–ready frame. Contrast with RNR frame.

RR packet. In X.25 communications, a packetused by a DTE or by a DCE to indicate that it isready to receive data packets within the window.Contrast with RNR packet.

RS–232C. See EIA–232D.

RS–422A. See EIA–422A.

RSi. See Remote Statistics Interface.

RTI. Response type indicator.

RTPN. See remote transaction program name.

RTS. Ready to Send used with EIA–232 Protocol.

rubber–band outline. A window with a moveableoutline.

rule file. A file containing rules determining theappearance and behavior of CDE Desktop.

run. (1.) A performance of one or more jobs orprograms. (2.) To cause a program, utility, or othermachine function to be performed.

run file. The output of the linkage editor. Aprogram file in a format that is suitable for beingloaded into main storage and run. See alsomodule.

run–time algorithm selection. An optimizationtechnique in which the parameters to an operationare evaluated to determine which of severalequivalent algorithms will perform the operationmost efficiently.

run–time checks. Error checking that occurs whilean Ada program runs. If an error is detected, theprogram raises an exception.

run–time environment. A collection of subroutinesand shell variables that provide commonly usedfunctions and information for system components.

run–time monitor. The part of the Monitor thatmanages transactional client and server

1-133Glossary

applications that take input from users and servicerequests.

running state. The condition of a machine whenusers can login and use the machine.

RW lock. Abbreviation for read shared/writeexclusive lock. Any number of threads can hold thelock simultaneously for reading, but if a threadholds the lock for writing, all other threads areexcluded from reading or writing the lockedresource.

1-134 Glossary

SS–connector. The type of connector used withsuper–video. Similar to the Y/C connector. It is a4–pin–min din–type connector.

S–video. Super–video. Used to improve the qualityof a video image, a technique that maintainsseparate Y/C signals before recording on magnetictape or displaying on a monitor.

SABM. See set asynchronous balanced mode.

SAK. See secure attention key.

sample rate. Synonym for locator sample rate.

SAP. See service access point.

SAS. Single–attachment station. A station thatconnects only to the primary ring by way of a wiringconcentrator or connects to one other SAS in aback–to–back wiring configuration.

sash. In CDE, a box on a separator or split bar thatenables you to increase or decrease the size of awindow pane using the mouse. You can navigate tothe sash using the keyboard.

satisfy. For Ada programming, see constraint andsubtype.

saved user ID. The user ID that is acquired whenrunning a setuid program. The saved user ID is thesame as the owner of the file that ran. If the file thatran was not setuid, the saved user ID is set to theeffective user ID of the parent.

saveset. A list of window clients that should not bedestroyed when a connection is closed and shouldbe remapped or unmapped. Usually used bywindow managers to avoid lost windows if themanager is ended abnormally.

scalability. The ability of a workload to benefit froma multiprocessor environment.

scalar. An arithmetic object or enumerated object.

scalar type. A type that defines a variablecontaining a single value at run time. Contrast withstructured type. In Ada programming, an object orvalue of a scalar type does not have components.A scalar type is either a discrete type or a real type.The values of a scalar type are ordered.

scale. Increments of measure used by the nroffand troff commands. All supported scales areconverted for the typesetter into a scale calledmachine units (u).

scale factor. (1.) A number indicating the positionof the decimal point in a real number. (2.) Anumber used as a multiplier in scaling.

scaling. (1.) In computer graphics, enlarging orreducing all or part of a display image bymultiplying the coordinates of the image by aconstant value. (2.) In programming, indicating thenumber of digit positions in object code to beoccupied by the fractional portion of a fixed–pointor floating–point constant. (3.) In GL, uniformstretching of a primitive along an axis.

scaling factor. The throughput of a workload on amultiprocessor divided by the throughput of thatworkload on a comparable uniprocessor (not on asingle–processor SMP system).

scan. (1.) To examine sequentially, part by part.(2.) To search records for a specified characterstring or syntax error.

scan code. Raw input from the keyboard.

scan conversion. The process of generating pixelinformation into the frame buffer from anapplication program.

scanline. (1.) A list of pixel or bit values viewed asa horizontal row (all values have the same ycoordinate). The values are ordered by increasingthe x coordinate. As part of an image, the nextscanline is ordered by increasing the y coordinate.(2.) A visible line produced on a display by onehorizontal sweep of the electron beam of a cathoderay tube.

scanline order. An image represented byscanlines ordered by increasing the y coordinate.

scanned image. An image that is examinedsequentially, part by part.

scatter. For input and output operations, to readdata from a device and locate it in noncontiguousmemory addresses. Contrast with gather.

SCCS. See Source Code Control System andRevision Control System.

SCCS delta. A set of changes made to an SCCSfile. Creating a new delta saves only the changesmade.

SCCS identification (SID). In SCCS, a numberassigned to each version of a program.

scheduling policy. The set of rules that governwhen a thread will lose control of the CPU andwhich thread will get control next.

scope. (1.) That part of a source program in whicha variable can communicate its value. (2.) Theportion of a program within which a declarationapplies. For Ada programming, see declaration.(3.) In SOM, that portion of a program within whichan identifier name has ”visibility” and denotes aunique variable. In SOM, an IDL source file forms a

1-135Glossary

scope. An identifier can only be defined once withina scope; identifiers can be redefined within anested scope. In a .idl file, modules, interfacestatements, structures, unions, methods, andexceptions form nested scopes.

scope operator (::). Defines the scope for the rightargument in C++. If the left argument is blank, thescope is global. If the left argument is a classname, then the scope is within that class.

scratch file. A file, usually used as a work file, thatexists temporarily, until the end of the program thatuses it.

screen. (1.) See display screen. (2.) In theextended curses library, a special type of windowthat is as large as the workstation screen. (3.) InEnhanced X-Windows, a server can provideseveral independent screens that typically havephysically independent monitors (display screens).This is the expected configuration when there isonly a single keyboard and pointer shared amongthe screens. A screen structure contains theinformation about that screen and is linked to thedisplay structure.

screen capture. The storage of a screen displayas a text or graphics file on disk.

screen coordinates. The coordinate system thatdefines the display screen. In GL, distances aremeasured in units of pixels, and the origin is in thelower left–hand corner. On most systems thescreen size is 1024 pixels high by 1280 pixelswide. The viewport defines the mapping fromnormalized device coordinates to screencoordinates. Synonymous with screen space. Seealso eye coordinates, primitive coordinates,modeling coordinates, world coordinates, andtransformation.

screen lock. In CDE, a function that locks theworkstation screen, barring further input until thevalid user password is entered.

Screen Saver. In CDE, a choice that, after aspecified time period, switches off the workstationdisplay or varies the images that are displayed,thereby prolonging the life of the screen.

screen space. Synonym for screen coordinates.

screenmask. In GL, a rectangular area of thescreen to which all drawing operations are clipped.It is normally set equal to the viewport and to thewindow. A screenmask is useful for characterclipping. See also clipping.

script file. In the Ada debugger, a file that containsa series of commands that can be used to drive thedebugger. Script files are useful for debugginglarge, complex programs when you may not be

able to complete a debugging session in onesitting.

scroll. To move text vertically or horizontally inorder to view information that is outside the displayor pane boundaries.

scroll bar. The horizontal and vertical bars in theborder of a directory window that allow you to scrollthe files to see what is beyond the border of thewindow. A graphical device consisting of a slider,scroll area, and scroll arrows. A user changes theview by sliding the slider up or down in the scrollarea or by pressing one of the scroll arrows. Thiscauses the view to scroll up or down in the windowadjacent to the scroll bar.

scroll region. In AIXwindows, the rectangularportion of a ScrollBar widget that contains twoarrows and a slider.

scrolled list. A list that is scrolled. See also scroll.

scrolled text. Text that is scrolled. See also scroll.

scrolling. The horizontal or vertical movement ofgraphic or text information presented on a displayscreen.

SCSI Adapter. See Small Computer SystemsInterface Adapter.

sdb. See symbolic debugger.

SDLC. See synchronous data link control.

SDLC primary station. A station that hasresponsibility for the data link. It issues commandsto secondary stations.

SDLC secondary station. A station that respondsto requests from another station (the primarystation) and has little control over data linkoperations.

SDT. See static debugger trap.

seal. To encrypt a record containing several fieldsin such a way that the fields cannot be modifiedwithout either knowledge of the encryption key orleaving evidence of tampering.

search. The action of scanning a set of dataelements to locate all instances of a particular item,such as a text string or a file name.

search loop. An array–processing loop used toperform a table lookup or to find exceptional valueswithin an array.

SECAM. A national television industrybroadcasting standard used in France, USSR, andsome other countries. See also NTSC and PAL.

second–level interrupt handler (SLIH). Adevice–dependent routine that handles the

1-136 Glossary

processing of an interrupt from a specific adapter.An SLIH is called by the first–level interrupt handler(FLIH) associated with that interrupt level.

secondary key. A key field of a record that definesa secondary index.

secondary representation. A second form, analternative to the primary representation, in whichthe client may supply an attribute value to theservice.

secondary station. A data station that runs datalink control functions as instructed by the primarystation. It interprets received commands andgenerates responses for transmission.

secondary unit. In Ada language, the body of alibrary unit (such as a subprogram body, packagebody, generic body, or subprogram body) or asubunit. All compilation units that are not libraryunits are secondary units. Secondary units are notsubject to reference by other independentlycompiled units and can be thought of as thehidden implementation of a library unit or separatedeclaration.

secondary window. A window of short durationsuch as a dialog box. The window is only displayedfor a short time, usually just long enough to conveysome information or get some operationaldirections.

section. In the vi editor, text that follows a sectionheading as defined by the sect= option.

sector. (1.) The smallest amount of informationthat can be written to or read from a disk ordiskette during a single read or write operation. (2.)On disk or diskette storage, an addressablesubdivision of a track used to record one block of aprogram or data.

secure attention key (SAK). A key sequence thatends all processes associated with a terminal toprovide a trusted path for secure communicationwith the TCB. The SAK sequence is Ctrl–x followedby Ctrl–r.

secure node. A node that is capable of runningone or more application servers and one or moreMonitor system components, normally a highlytrusted machine.

security. The protection of data, systemoperations, and devices from accidental orintentional ruin, damage, or exposure.

seek pointer. A data structure that contains theoffset of the current location in a character file ordevice.

segment. (1.) A contiguous area of virtual storageallocated to a job or system task. A programsegment can be run by itself, even if the whole

program is not in main storage. (2.) Virtual memoryis divided into segments that arelinearly–addressable spaces of one or more4KB–byte pages up to a maximum size of 2 to the28th power bytes. (3.) The information that can beaddressed via a single, unique segment–registervalue (256MB). (4.) A portion of a computerprogram that can be run as an entity without theentire program being maintained in systemmemory. (5.) A group of display elements. (6.) InEnhanced X-Windows, one or more lines that aredrawn but not necessarily connected at the endpoints.

segment flag. The segflag parameter of thefp_open kernel service that indicates whether thepath parameter is located in user space or in kernelspace.

segment registers. Registers in the system thathold the actual addresses of the memory segmentscurrently in use.

segment unit. In Pascal, an independentlycompilable piece of code containing routines linkedwith the program unit. See also program unit.

segmentation fault. A memory addressingexception. Occurs when a memory location isreferenced that has not been allocated to thereferencing process. An out–of–bounds arrayreference or incorrect use of a pointer can cause asegmentation fault.

segmenting of BIUs. An optional function of pathcontrol that divides a basic information unit (BIU)received from transmission control into two or morepath information units (PIUs). The first PIU containsthe request header of the BIU and usually part ofthe response unit (RU). The remaining PIU or PIUscontain the remaining parts of the RU.

select. (1.) To choose a button on the displayscreen. (2.) To place the cursor on an object (nameor command) and press the Select (left) button onthe mouse or the Select key on the keyboard. (3.)To indicate the item or items the next commandyou choose will affect. The item may be highlightedto confirm your selection. Selecting does notactually carry out the command.

selected component. In Ada language, a nameconsisting of a prefix and of an identifier called theselector. Selected components are used to denoterecord components, entries, and objectsdesignated by access values; they are also usedas expanded names.

selecting. In GL, a method for finding whatprimitives are being drawn in a given volume inthree–dimensional space. See also hit, selectingregion, picking, and picking region.

1-137Glossary

selecting region. In GL, a rhomboid–shapedvolume in world coordinates that is sensitive toselecting events. If a drawing primitive draws withinthis region, a select event is reported. See also hit,selecting, picking, transformation, and pickingregion.

selection. (1.) Addressing a workstation or acomponent on a selective calling circuit. (2.) Theprocess by which a computer requests a station tosend it a message. (3.) See also addressing. (4.) InEnhanced X-Windows, an indirect property of adynamic type maintained by the client (the owner)but belonging to the user. It is not private to aparticular window subhierarchy or a particular setof clients. When a client asks for the contents of aselection, it specifies a target type. This target typecan be used to control the transmittedrepresentation of the contents.

selection area. In AIXwindows, a portion of aRowColumn widget over which the mouse pointercan be placed to select other widgets.

selection criteria. In the select subroutine, thereadlist, writelist, and exceptlist parametervalues that specify what to check for reading,writing, and exceptions.

selection range. See key range.

selector. (1.) In Pascal, the term in a CASEstatement that, once evaluated, determines whichof the possible branches of the CASE statementare processed. (2.) For Ada programming, seeselected component.

semantic. The relationships of characters orgroups of characters to their meanings,independent of the manner of their interpretationand use.

semantic error. A compile–time error caused byincorrect definition of constants and identifiers. Seealso syntax error.

semaphore. (1.) Entity used to control access tosystem resources. Processes can be locked to aresource with semaphores if the processes followcertain programming conventions. (2.) Provides ageneral method of communication between twoprocesses that is an extension of the features ofsignals.

semaphore ID (semid). An integer that points to aset of semaphores and a data structure thatcontains information about the semaphores.

semid. See semaphore ID.

send pacing. In SNA, the pacing of message unitsthat a component is sending. Contrast with receivepacing.

sense code. A value sent or received, or anegative response to indicate what error occurred.

sentence. In the vi editor, text that is separatedfrom other text by a . (period), ! (exclamation point),or ? (question mark) followed by two spaces.

separator. A punctuation character that separatesparts of a command or file, or that delimitscharacter strings.

sequential access. (1.) An access method inwhich records are read from, written to, or removedfrom a file based on the logical order of the recordsin the file. (2.) The facility to obtain data from orenter data into a storage device so that the processdepends on the location of the data and on areference to data previously accessed.

sequential file access. The location of a range ofrecords through key values and the subsequentprocessing of them in some order related to thosekey values. The index of the file need not beunique.

sequential I/O model. A model of the operatingsystem for all accesses to system networkresources. When SNA supports this model, itsimplifies access to the network, allows programsto be designed for portability, and allows programsto use network resources through redirection.

serial device. A device that performs functionssequentially, such as a serial printer that prints onecharacter at a time. Contrast with parallel device.

serial port. A port used for a serial device. Seealso serial device.

serial processing. Pertaining to the sequential orconsecutive running of two or more processes in asingle device, such as a channel or processingunit. Contrast with parallel processing.

serial transmission. Transmitting each bit of adata character separately over the same electricalpath.

serializability. A basic property of transactionprocessing systems, this refers to the idea that theexchange and modification of information bytransactions must be able to be synchronized andappear as though multiple, simultaneoustransactions are actually a series of sequentialrequests. Data being changed by a transaction, orupon which a transaction depends, must beshielded from other transactions until the firsttransaction completes.

serialize. (1.) To change from parallel–by–byte toserial–by–bit. (2.) In XDR, to convert a particularmachine representation to XDR format.

1-138 Glossary

server. (1.) An application program that usuallyruns in the background (daemon) and is controlledby the System Program Controller. (2.) On anetwork, the computer that contains the data orprovides the facilities to be accessed by othercomputers on the network. (3.) A program thathandles protocol, queuing, routing, and other tasksnecessary for data transfer between devices in acomputer system. (4.) In Enhanced X-Windows,provides the basic windowing mechanism. Ithandles IPC connections from clients,de–multiplexes graphics requests onto screens,and multiplexes input back to clients. (5.) In NCS, aprocess that exports one or more interfaces to oneor more objects, and whose procedures can beinvoked from remote hosts. (6.) In DSOM, aprocess, running in a distributed environment, thatexecutes the implementation of an object. DSOMprovides a default server implementation that candynamically load SOM class libraries, create SOMobjects, and make those objects accessible toclients. Developers can also writeapplication–specific servers for use with DSOM.

server grabbing. When a client seizes the serverfor exclusive use to prevent processing requestsfrom other client connections until the grab iscomplete. This is typically a transient state for suchthings as rubber–banding and pop–up menus or torun requests indivisibly.

server object. In DSOM, every server has anobject that defines methods for managing objectsin that server. These methods include objectcreation, object destruction, and maintainingmappings between object references and theobjects they reference. A server object must be aninstance of the class SOMDServer (or one of itssubclasses). See also object reference andSOMDObject.

server reporting. A protocol for servers to reportto the cell manager contact by previously unknownclients, for the purpose of registration.

service access point (SAP). In the Ethernetlogical link profile, the address for the transactionprogram on the local system. This address is ahexadecimal value.

service controls. A group of parameters, appliedto all directory operations, that direct or constrainthe provision of the service.

service mode. Synonym for maintenance mode.

service request number (SRN). A group ofnumbers used by service technicians to determinethe failing area of the system.

service transaction program. (1.) A program thatprovides a function internal to SNA Services. (2.) Atransaction program implemented by a transaction

processing system. Service transaction programsperform such functions as providing access toremote data bases and remote queues. See alsoapplication transaction program and transactionprogram.

service update. Software that corrects a defect inor adds new function to the Base OperatingSystem (BOS) or to an optional software product.See also maintenance level update.

session. (1.) The period of time during whichprograms or devices can communicate with eachother. (2.) A name for a type of resource thatcontrols local LUs, remote LUs, modes, andattachments. (3.) In network architecture, anassociation of facilities that establish, maintain, andrelease connections for communication betweenstations. (4.) The period of time during which theuser of a workstation can communicate with aninteractive system, usually elapsed time betweenlogin and logoff. (5.) In SNA, a logical connectionbetween two network addressable units (NAUs)that can be activated, tailored to provide variousprotocols, and deactivated as requested. (6.) Inremote communications, a period ofcommunication with a remote system or hostsystem.

session date. The date associated with a session.See also creation date and system date.

session key. Used in Kerberos specifications. Seealso conversation key.

session–level pacing. In SNA, a flow controltechnique in which a receiving half–sessioncontrols the data transfer rate (the rate at which itreceives request units). It is used to preventoverloading a receiver with unprocessed requests,when the sender can generate requests faster thanthe receiver can process them.

Session Manager. In CDE, a software applicationthat controls saving sessions, restoring sessions,screen locking and unlocking, and the use ofscreen savers. When a session is saved, the stateof the desktop environment (location of icons, sizeand location of open windows, open/closed statusof applications, current color palette, and so on) ispreserved so that it can be restored at the nextlogin.

session profile. For the 3270 Host ConnectionProgram 2.1 and 1.3.2 for AIX, a profile describingthe characteristics of a session between a clientsystem and a System/370 host computer. See also3270 Host Connection Program 2.1 and 1.3.2 forAIX and profile.

session records. In the accounting system, arecord (produced from log in and log off records) of

1-139Glossary

time connected and line usage for connecteddisplay stations.

session server. In CDE, a system that providesnetworked sessions. Session files reside on thesession server and are used whenever you log into a system on the network.

set. In NCS, to associate an allocated RemoteProcedure Call (RPC) handle with a specific socketaddress. See also bind.

set–associative cache. A cache in which two orfour (or more) lines correspond to each possiblevalue of the virtual–address field that identifies theline to be interrogated during cache lookup.

set associativity. An aspect of cache design thatdetermines how many cache lines can beassociated with a given memory location. A cachethat is four–way set associative can contain a givenmemory location in one of four cache lines. Seealso cache line.

set asynchronous balance mode (SABM). A linkcontrol frame.

set flags. Flags that can be put into effect with theshell set command.

set–group–ID mode bit. In setting file accesspermissions, sets the effective and saved groupIDs of the process to the group ID of the file onexecution.

set–user–ID mode bit. In setting file accesspermissions, sets the effective and saved user IDsof the process to the owner ID of the file onexecution.

setgid. See set–group–ID mode bit.

setuid. See set–user–ID mode bit.

severity code. A code that indicates how seriousan error condition is.

shadow. A darkened area below a window and toits right, or above it and to its left, which representsthe shadow a window might cast.

shadow color. The shaded area around or behinda dialog box.

shadow widget. An opaque pointer to a structurecreated each time a widget is created; it identifiesthe widgets in the interface. Also called swidget.

shadowing. In the SOM Emitter Framework, atechnique that is required when any of the entryclasses are subclassed. Shadowing causesinstances of the new subclass(es) (rather thaninstances of the original entry classes) to be usedas input for building the object graph, withoutrequiring a recompile of emitter framework code.

Shadowing is accomplished by using the macroSOM_SubstituteClass.

shared library. A library created by the ldcommand that contains at least one subroutine thatcan be used by multiple processes. Programs andsubroutines are linked as before, but the codecommon to different subroutines is combined inone library file that can be loaded at run time andshared by many programs. A key to identify theshared library file is left in the header of eachsubroutine.

shared locks. Shared locks are a type of lock inwhich multiple transactions can simultaneously locka data item for reading. See also exclusive lock.

shared memory. An area of memorysimultaneously accessible to more than onecooperating process.

shared memory ID (shmid). An identifier assignedto the shared segment for use within a particularprocess. See also file descriptor.

shared port. A port used by communicationsapplications (for example, UUCP) to ensureexclusive access to a port.

Shared Product Object Tree (SPOT). (1.) Aversion of the /usr file system that diskless clientsmount as their own /usr directory. (2.) For NIM, a/usr file system or an equivalent file system that isexported by servers in the NIM environment forremote client use.

shell. (1.) A software interface between a user andthe operating system of a computer. Shellprograms interpret commands and userinteractions on devices such as keyboards,pointing devices, and touch–sensitive screens andcommunicate them to the operating system. (2.)Software that allows a kernel program to run underdifferent operating system environments. (3.) Thecommand interpreter that provides a user interfaceto the kernel. See also shell program andcommand interpreter. Synonymous with interface.(4.) A shell is a command interpreter that acts asan interface between users and the operatingsystem. A shell can contain another shell nestedinside it, in which case, the outer shell is the parentshell and the inner shell is the child. (5.) InAIXwindows, Shell widgets are top–level widgetsthat are internal and cannot be instantiated, butthey provide the necessary interface with thewindow manager. See also shell widget.

shell box. A geometry management techniquewhere a type of bounding box can have only onechild that is exactly the same size as the shell.

1-140 Glossary

shell command names. Operating–systemcommands.

shell control command. A command that enablesthe user to pass control to various parts of a shellprocedure, or to control how a procedure ends.

shell procedure. A series of commands, combinedin a file, that carry out a particular function whenthe file is run or when the file is specified as a valueto the sh command. Synonymous with shell script.

shell program. A program that accepts andinterprets commands for the operating system.Synonym for shell.

shell prompt. The character string on thecommand line indicating that the system canaccept a command (typically the $ character).

shell script. Synonym for shell procedure.

shell variables. Facilities of the shell program forassigning variable values to constant names.

shell widget. In Enhanced X-Windows, holds thetop–level widgets that communicate directly withthe window manager. These widgets do not haveparents. Synonymous with shell. See also widget.

shielded twisted pair. A transmission medium oftwo twisted conductors with a foil or braid shield.

Shift–Japanese Industrial Standard (SJIS). Anencoding scheme consisting of single bytes anddouble bytes used for character encoding. Becauseof the large number of characters in Japanese andother Asian languages, the 8–bit byte is notsufficient for character encoding.

shmid. See shared memory ID.

short. In ODM, a terminal descriptor type used todefine a variable as a signed 2–byte number. Seealso terminal descriptor.

short circuiting. The evaluation of Booleanexpressions with AND and OR such that the rightoperand is not evaluated if the result of theoperation can be determined by evaluating the leftoperand. The evaluation of the expression isalways from left to right.

short status. Status output in abbreviated form(short form) from the spooling subsystem.

shortest–job–next (SJN). A method of queueingjobs where the shortest jobs are printed first.Contrast with first–come–first–served. See alsodiscipline.

sibling. Children of the same parent window.

SiCounter. In Performance Toolbox, a value that isincremented continuously. Instruments show thedelta (change) in the value between observations,

divided by the elapsed time, representing a rateper second.

SID. SCCS identification. The name assigned to adelta.

side effect. An undesirable result caused byaltering the values of nonlocal variables by aprocedure or function.

sign–off. To end a session at a display station.

sign–on. To begin a session at a display station.

signal. (1.) A simple method of communicationbetween two processes. One process can informthe other process when an event occurs. (2.) Inoperating system operations, a method ofinter–process communication that simulatessoftware interrupts. Contrast with exception andinterrupt.

signal handler. A subroutine called when a signaloccurs.

signal mask. Defines the set of signals currentlyblocked from delivery to a process.

signal stack. An alternate stack on which signalsare to be processed.

signature. In SOM, the collection of typesassociated with a method (the type of its returnvalue, if any, as well as the number, order, and typeof each of its arguments).

signed. Information is digitally signed byappending to it an enciphered summary of theinformation. This is used to ensure the integrity ofthe data, the authenticity of the originator, and theunambiguous relationship between the originatorand the data.

Simple Mail Transfer Protocol (SMTP). Aprotocol, typically used over a network, in which theobjective is to transfer mail. SMTP is used by thesendmail command to accept and receive mail.

simple name. For Ada programming, seedeclaration and name.

simultaneous peripheral operation online. Seespooling.

single buffer mode. . In GL, a mode in which theframe buffer bitplanes are organized into a singlelarge frame buffer. This frame buffer is the onecurrently displayed and is also the one in which alldrawing occurs. See also double buffer mode.

single–byte control codes. ASCII codes 0through 31 (0x00 through 0x1f) and delete (0x7f).

single–mode optical fiber. An optical fiber inwhich only the lowest–order bound mode (whichcan consist of a pair of orthogonally polarized

1-141Glossary

fields) can propagate at the wavelength of interest.Contrast with multimode optical fiber.

single–precision. (1.) The use of one computerword to represent a number, in accordance with therequired precision. (2.) The specification thatcauses a floating–point value to be stored in theshort format. See also precision.

single–processor SMP. A system designed tohandle two or more processors, running the SMPversion of the operating system, which has beenconfigured with a single processor. Contrast withuniprocessor.

single–shift control. In codepage switching,control codes that shift to another page for a singlecharacter; nonlocking shifts.

SiQuantity value. In Performance Toolbox,represents a level, such as memory used oravailable disk space. The actual observation valueis shown by instruments.

sister class object. In SOM, a duplicate of a classobject that is created in order to save a copy of theclass’s original method table before replacing themethod table to customize method resolution. Thesister class object is created so that some originalmethod procedures can be called by thereplacement method procedures.

size. The screen management action that changesthe size of a window.

size field. In an i–node, a field that indicates thesize, in bytes, of the file associated with the i–node.

SJIS. See Shift–Japanese Industrial Standard.

SJN. See shortest–job–next.

skew. The time difference between two clocks orclock values.

SLA. Serial Link Adapter. See also SOCC.

sleeping process. A process that is waiting forinput or output to complete, time slices, an event tooccur, or signals from other processes. When aprocess is sleeping, it can be paged out of memory.

slider. (1.) In AIXwindows, a small interactivegraphical object connected to an XmScrollBar barwidget. The slider controls the vertical or horizontalmovement of text information or graphics acrossthe display screen. (2.) A control that uses a trackand arm to set a value from among the availablevalues. The position of the arm (or a separateindicator) gives the currently set value.

SLIH. See second–level interrupt handler.

SLIP. Serial Line Interface Protocol. The protocolthat TCP/IP uses when operating through a serialconnection.

slot. A long electrical socket inside the system unitinto which an electronic circuit board (card) isinstalled.

slow list. A list of secondary stations on amultidrop network that, due to their inactivity, arepolled less often by the primary station.

small caps. See caps.

Small Computer Systems Interface Adapter(SCSI Adapter). An adapter that supports theattachment of various direct–access storagedevices and tape drives to the system unit.

small word. In the vi editor, a contiguous set ofalphanumeric characters bounded on at least oneend with a character that is not a blank, a tab, or anew–line indicator. For example, in the word isn’t,the two sets of characters isn and t are smallwords. Contrast with big word.

SMIT. System Management Interface Tool.

SMP. See symmetrical multiprocessor system.

SMP efficient. Avoidance in a program of anyaction that would cause functional or performanceproblems in an SMP environment. A program thatis described as SMP efficient is generally assumedto be SMP safe as well. An SMP–efficient programhas usually undergone additional changes tominimize incipient bottlenecks.

SMP exploiting. Adding features to a program thatare specifically intended to make effective use ofan SMP environment. A program that is describedas SMP exploiting is generally assumed to be SMPsafe and SMP efficient as well.

SMP safe. Avoidance in a program of any action,such as unserialized access to shared data, thatwould cause functional problems in an SMPenvironment. This term, when used alone, usuallyrefers to a program that has undergone only theminimum changes necessary for correctfunctioning in an SMP environment.

SMT. Station management.

SMTP. See Simple Mail Transfer Protocol.

SNA. See System Network Architecture.

SNA network. The part of a user–applicationnetwork that conforms to the formats and protocolsof System Network Architecture (SNA). It enablesreliable transfer of data among end users andprovides protocols for controlling the resources ofvarious network configurations. The SNA networkconsists of network addressable units (NAUs),boundary–function components, and the pathcontrol network.

SNBU. See switched network backup.

1-142 Glossary

SNMP. Simple Network Management Protocol. Aprotocol used by network hosts to exchangeinformation in the management of networks. SNMPnetwork management is based on the client–servermodel that is widely used in TCP/IP–based networkapplications.

SNOBOL. A programming language designed forstring processing and pattern matching.

SOCC. Serial Optical Channel Converter. A220–Mbit/sec optical point–to–point link.

social science format. See natural or socialscience format.

socket. (1.) A unique host identifier created by theconcatenation of a port identifier with a TCP/IPaddress. (2.) A port identifier. (3.) A 16–bit portnumber. (4.) In NCS, a port on a specific host; acommunications end point that is accessiblethrough a protocol family’s addressing mechanism.A socket is identified by a socket address. See alsosocket address, port, and listening.

socket address. A data structure that uniquelyidentifies a specific communications end point. Asocket address consists of a port number and anetwork address. It also specifies the protocolfamily. See also protocol family.

Sockets class. A SOM class that provides acommon communications interface to DistributedSOM, the Replication Framework, and the EventManagement Framework. The Sockets classprovides the base interfaces (patterned afterTCP/IP sockets); the subclasses TCPIPSockets,NBSockets, and IPXSockets provide actualimplementations for TCP/IP , Netbios, and NetwareIPX/SPX, respectively.

software. Programs, procedures, rules, and anyassociated documentation pertaining to theoperation of a system. Contrast with hardware.

software configuration. The processing requiredto make installed software ready to use.

software installation. The process of restoringsoftware from external media to a local file system.The software can require further processing, orconfiguration, before it is ready to use.

software keyboard. A table mapping a rawkeystroke to a display symbol, predefined functionor string. Software keyboards that are shipped withthe operating system are associated withlanguages (U.S. English, U.K. English, Danish,Japanese, and so on).

software keyboard map. A table that maps akeystroke to a character or to a predefined functionsuch as a tab.

Software Vital Product Data (SWVPD).Information that uniquely defines system,hardware, software, and microcode elements of aprocessing system.

SOM. See System Object Model.

SOM Compiler. A tool provided by the SOM Toolkitthat takes as input the interface definition file for aclass (the .idl file) and produces a set of bindingfiles that make it more convenient to implementand use SOM classes.

SOM–derived metaclass. See derived metaclass.

SOMClass. One of the three primitive class objectsof the SOM run–time environment. SOMClass isthe root (meta)class from which all subsequentmetaclasses are derived. SOMClass defines theessential behavior common to all SOM classobjects.

SOMClassMgr. One of the three primitive classobjects of the SOM run–time environment. DuringSOM initialization, a single instance (object) ofSOMClassMgr is created, calledSOMClassMgrObject. This object maintains adirectory of all SOM classes that exist within thecurrent process, and it assists with dynamic loadingand unloading of class libraries.

SOMDObject. The SOM class that implements thenotion of a CORBA ”object reference” in DSOM. Aninstance of SOMDObject contains informationabout an object’s server implementation andinterface, as well as a user–supplied identifier. Seealso object reference.

somId. In SOM, a pointer to a number thatuniquely represents a zero–terminated string. Suchpointers are declared as type somId. In SOM,somId’s are used to represent method names,class names, and so forth. See also method ID.

SOMOA (SOM object adapter) class. In DSOM, aclass that dispatches methods on a server’sobjects, using the SOM Compiler and run–timesupport. The SOMOA class implements methodsdefined in the abstract BOA class (its base class).See also BOA class and ORB (object requestbroker).

SOMObject. One of the three primitive classobjects of the SOM run–time environment.SOMObject is the root class for all SOM(sub)classes. SOMObject defines the essentialbehavior common to all SOM objects.

somSelf. In SOM, within method procedures in theimplementation file for a class, a parameterpointing to the target object that is an instance of

1-143Glossary

the class being implemented. It is local to themethod procedure.

somThis. In SOM, within method procedures, alocal variable that points to a data structurecontaining the instance variables introduced by theclass. If no instance variables are specified in theSOM IDL source file, then the somThis assignmentstatement is commented out by the SOM Compiler.

sort. To rearrange some or all of a group of items,based upon the contents or characteristics of thoseitems.

source. (1.) A system, a program within a system,or a device that makes a request to a target.Contrast with target. (2.) In advancedprogram–to–program communications, the systemor program that starts jobs on another system.

source code. The input to a compiler orassembler, written in a source language. Contrastwith object code.

Source Code Control System (SCCS). A programfor maintaining version control for the source filesof a developing program. It stores the changesmade to a file instead of the changed file, thusallowing several versions of the same file to exist inthe system. See also Revision Control System.

source documents. Verbal information producedconcurrently with the original software, by theoriginal development company.

source file. A file that contains source statementsfor such items as high–level language programsand data description specifications. A filecontaining input data or commands.

source module. See source program.

source program. A computer program expressedin a source language.

source statement. A statement written in aprogramming language.

space. (1.) A site intended for storage of data,such as a location in a storage medium. (2.) Abasic unit of area, usually the size of a singlecharacter. (3.) One or more space characters. (4.)In a neutral circuit, an impulse that causes the loopto open or causes absence of signal. In a polarcircuit, it causes the loop current to flow in adirection opposite to that for a mark impulse. Aspace impulse is equal to a binary zero.

sparse array. An array in which few of the definedcells are used.

sparse file. A file that is created with a lengthgreater than the data it contains, leaving empty

spaces for future addition of data. See also hole ina file

SPC. See System Program Controller.

special character. A character other than a letteror number. For example, *, +, and % are specialcharacters.

special file. Used in the operating system toprovide an interface to input/output devices. Thereis at least one special file for each deviceconnected to the computer. Contrast with directoryand file. See also block file and character specialfile.

specific. The attribute types that may appear in aninstance of a given class, but not in an instance ofits superclasses.

specification statement. In FORTRAN, one of theset of statements that provide the compiler withinformation about the data used in the sourceprogram and how to allocate storage.

specifiers. Used in C++ declarations to indicatestorage class, fundamental data type, and otherproperties of the object or function being declared.

speed. The baud rate. Synonym for line speed.

SPI. Stub programming interface. A private RPCruntime interface whose routines are unavailable toapplication code.

spill area. A storage area used to save thecontents of registers.

Spmi. See System Performance MeasurementInterface.

spool file. (1.) A disk file containing output that hasbeen saved for later printing. (2.) Files used in thetransmission of data among devices.

spooler. A synonym for the queueing system thatpertains to its use for queueing print jobs.

spooling (simultaneous peripheral operationonline). (1.) The use of auxiliary storage as abuffer storage. This reduces processing delayswhen transferring data between peripheralequipment and the processors of a computer. (2.)Reading and writing input and output streams onan intermediate device in a format convenient forlater processing. (3.) Performing a peripheraloperation such as printing while the computer isbusy with other work.

SPOT. See Shared Product Object Tree.

SPP. Sequence packet protocol. The primarytransport–layer protocol in the Xerox NetworkSystems. It provides reliable, flow–controlled,

1-144 Glossary

two–way transmission of data for an applicationprogram. It is a byte–stream protocol used tosupport the SOCK_STREAM abstraction. The SPPprotocol uses the standard Network System (NS)address formats.

spring–loaded pop–up. A kind of widget, such asa menu, that is not visible to the window manager.The spring–loaded pop–up disables user–eventprocessing except for events that occur in themenu.

SRC. System Resource Controller.

SRF. Standard record format.

SRN. See Service request number.

SRT. See Structure Rule Table.

SSCP. See system services control point.

stack. (1.) An area in storage that storestemporary register information and returnaddresses of subroutines. (2.) A list constructedand maintained so that the last data element storedis the first data element retrieved. (3.) In kernelmode, an area that is paged with the user process.The kernel maintains a stack for each process. Itsaves the process information such as the callchain and local variables used by the kernel for theuser process.

stack buffer. A storage area that stores retrievabledata in sequence. The last text stored is the firsttext removed.

stack overflow. An error condition in DOS thatresults from an insufficient number of stack frames,which are used by DOS to handle hardwareinterrupts.

stack pointer. A register providing the currentlocation of the stack.

stack traceback. The calling sequence thatindicates the path taken by a process to get to itscurrent location.

stacked tape. A bootable tape with multiplesoftware images.

stacking order. The relationship between siblingwindows that stack on top of each other.

stage. One of a series of steps to enter a gedsubcommand that typically ends with < cr >(carriage return). Each subcommand consists of asubset of stages, including command line, text,points, pivot, and destination.

standalone. A machine in the network installationenvironment that accesses all required resourceslocally.

standalone shell. A limited version of the shellprogram used for system maintenance.

standalone system. See standalone workstation.

standalone workstation. A workstation that canperform tasks without being connected to otherresources such as servers or host systems.

standard error (STDERR). The place where manyprograms place error messages.

standard input (STDIN). The primary source ofdata going into a command. Standard input comesfrom the keyboard unless redirection or piping isused, in which case standard input can be from afile or the output from another command.

Standard I/O Board. The Standard I/O Boardprovides a group of I/O functions that are basic tomost system units. Common standard I/O functionsare keyboard, tablet, speaker, mouse, serial port,parallel port and diskette adapter.

standard output (STDOUT). The primarydestination of data coming from a command.Standard output goes to the display unlessredirection or piping is used, in which casestandard output can be to a file or anothercommand.

standard screen. In the extended curses library, amemory image of the screen to which the routinesmake changes.

standout mode. The general–purpose highlightingmechanism used by the terminfo structure.

stanza. A group of lines in a file that together havea common function or define a part of the system.Stanzas are usually separated by blank lines orcolons, and each stanza has a name.

start method. Takes the device from the stoppedstate to the available state. The start methodapplies only to devices that support the optionalstopped state.

start–stop. Asynchronous transmission in which agroup of signals representing a character ispreceded by a start element and followed by a stopelement. See also asynchronous transmission.

startup set. A grouping of application servers thatcan be thought of as a single unit for administrationpurposes.

state. (1.) A state in which the circuit remains untilapplication of a suitable pulse. (2.) One of theseparate, restartable portions into which therunacct command (the main daily accounting shellprocedure) breaks its processing. (3.) In SOM, thedata (attributes, instance variables and theirvalues) associated with an object. See alsobehavior.

state information. Information about the currentstate of the appearance and behavior of a widget

1-145Glossary

or gadget. This information is recorded within eachindividual widget and gadget and updated asnecessary.

state instrument. In Performance Toolbox, a stateinstrument shows the latest statistics for a systemresource, optionally as a weighted average. Whileit does not show the statistics over time, somestate instruments collect this data in case you wantto change the instrument to a recording instrument.Types of graphs used to plot these recordingsinclude state bar, state light, pie chart, andspeedometer. Contrast with recording instrument.

statement. (1.) An instruction in a program orprocedure. (2.) In programming languages, alanguage construct that represents a step in asequence of actions or a set of declarations. Seealso block statement. In Ada language, a statementspecifies one or more actions to be performedduring the execution of a program.

statement function. In FORTRAN, a name,followed by a list of dummy arguments, that isequated to an arithmetic, logical, or characterexpression, and that can be substituted for theexpression throughout the program. See alsomacro.

statement function definition. In FORTRAN, astatement that defines a statement function. Itsform is a statement function followed by = (equalsign) followed by an arithmetic, logical, or characterexpression.

statement label. In FORTRAN, a numbercontaining one to five decimal digits that is used toidentify a statement. A statement label is usuallyused to transfer control, define the range of a DOloop, or refer to a FORMAT statement. See alsolabel.

statement number. See statement label.

static. (1.) A style of creating pop–ups. (2.) In C++,a keyword used for defining the scope and linkageof variables and functions. For internal variables,the variable has block scope and retains its valuebetween function calls. For external values, thevariable has file scope and retains its value withinthe source file. For class variables, the variable isshared by all objects of the class and retains itsvalue within the entire program.

static binding. Binding that occurs at compilationtime based on the resolution of overloadedfunctions.

static debugger trap (SDT). A trap instructionplaced in a predefined point in code that calls thedebug program. The trap instruction causes aprogram check when run and, as a result of theprogram check, the debug program is activated.

static display. In text formatting, when the nroffcommand finds a block of text in the input file thathas been specified as a static display, it places thetext on the current page only if there is room for theentire block. If there is not enough room, the nroffcommand starts a new page and places the blockof text there. See also floating display.

static linking. Linking of a program in which libraryprocedures are incorporated into the load module,instead of being dynamically loaded from theirlibrary each time the program is run.

static memory. Allocated memory of fixed size.

static method. In SOM, any method that can beaccessed through offset method resolution. Anymethod declared in the IDL specification of a classis a static method. See also method and dynamicmethod.

static routing. A method of setting paths betweenhosts, networks, or both by manually enteringroutes into the routing table. Static routes are notaffected by routing daemons and must be updatedmanually.

static variable. A variable that is allocated as soonas a program starts running and that remainsallocated until the program stops. Normal scopingrules apply to the variable. Contrast with automaticvariable.

station. (1.) A computer or device that can send orreceive data. (2.) An input or output point of asystem that uses telecommunication facilities, suchas one or more systems, computers, workstations,devices, and associated programs at a particularlocation that can send or receive data over atelecommunication line. (3.) A location on a deviceat which an operation is performed. (4.) In FDDI,an addressable logical and physical attachment ina ring capable of transmitting, receiving, andrepeating information. (5.) In SNA, a link station.

statistic line. In Performance Toolbox, the lines ina list that represent a specific value. Contrast withcontext line.

status. (1.) The current condition or state of aprogram or device. For example, the status of aprinter. (2.) The condition of the hardware orsoftware, usually represented in a status code. (3.)In Enhanced X-Windows, many Xlib subroutinesreturn a success status. If the subroutine does notsucceed, however, its values are not disturbed.

STDERR. See standard error.

STDIN. See standard input.

STDOUT. See standard output.

steal (a page frame). The act (by the VirtualMemory Manager) of reallocating a real–memory

1-146 Glossary

page frame that contains a virtual–memory pagethat is being used by a currently executingprogram.

sticky bit. An access permission bit that causes anexecutable program to remain on the swap area ofthe disk. Only someone with root authority can setthe sticky bit. This bit is also used on directories toindicate that only file owners can link or unlink filesin that directory.

stipple. A bitmap used to tile a region. A stipplepattern serves as an additional clip mask for a filloperation with the foreground color.

stop bit. (1.) In start–stop transmission, a signal atthe end of a character that prepares the receivingdevice for reception of a subsequent character. (2.)A signal to a receiving mechanism to wait for thenext signal.

stop method. Takes the device from the availablestate to the stopped state. The stop method appliesonly to devices that support the optional stoppedstate.

stop record. In Performance Toolbox, a specialtype of value record which signals that recordingwas stopped for a set of statistics and gives thetime it happened. This allows programs using therecording file to distinguish between gaps in therecording and variances in the recording interval.

stopped state. Allows a device to be madeunavailable but still have its device driver loadedand bound in the kernel and still be known by thedevice driver.

storage. (1.) The location of saved information. (2.)In contrast to memory, the saving of information onphysical devices such as disk or tape. See alsomemory. (3.) A unit into which recorded text can beentered, retained, and processed, and from whichit can be retrieved. (4.) The action of placing datainto a storage device.

storage class specifier. A storage class keyword.One of the following C++ keywords: auto, register,static, or extern.

storage device. (1.) A functional unit for storingand retrieving data. (2.) A facility into which datacan be retained.

store. To place information in a storage device (inmemory or onto a diskette, fixed disk, or tape), sothat it is available for retrieval and updating.

stream. (1.) Sequential input or output from anopen file descriptor. (2.) A continuous stream ofdata elements being transmitted, or intended fortransmission, using a defined format. (3.) All datatransmitted through a data channel in a single reador write operation. Synonym for data stream. (4.)

The kernel aggregate created by connectingSTREAMS components, resulting from anapplication of the STREAM mechanism. Theprimary components are a stream head, a driver,and zero or more pushable modules between thestream head and driver. A stream forms a fullduplex processing and data transfer path in thekernel, between a user process and a driver. Astream is analogous to a shell pipeline except thatdata flow and processing are bidirectional.

stream buffer. A C++ stream buffer is a bufferbetween the ultimate consumer and the I/O StreamLibrary functions that format data. It is implementedin the I/O Stream Library by the streambuf classand the classes derived from streambuf.

stream collection. A method of collecting auditingdata that writes audit records to a circular bufferwithin the kernel. The data can be displayed, orprinted to provide a paper audit trail, or convertedinto bin records.

stream editor. The sed command, which modifieslines from a specified file, according to an editscript, and writes them to a standard output.

stream end. The end of the stream furthest fromthe user process. The stream end contains thedriver.

stream head. The end of the stream closest to theuser process. The stream head provides theinterface between the stream and the userprocess. The principal functions of the stream headare processing STREAMS–related system calls,and bidirectional transfer of data and informationbetween a user process and messages inSTREAMS’ kernel space.

streaming tape device. See streaming tape drive.

streaming tape drive. A magnetic tape unit thatstores large amounts of data and is designed tomake a nonstop dump or restore of magnetic diskswithout using interblock gaps.

STREAMS. A kernel mechanism that supportsdevelopment of network services and datacommunication drivers. It defines interfacestandards for character input and output within thekernel, and between the kernel and user level. TheSTREAMS mechanism comprises integralfunctions, utility routines, kernel facilities, and a setof structures.

strength reduction. An optimization that replacesan arithmetic operation with a functionallyequivalent arithmetic optimization of lesserstrength. For example, 4*2 can be transformed into4+4.

1-147Glossary

strict type checking. Checking data types forcompliance with the rules of C language morestrictly than the C compiler, such as with the lintprogram.

stride. The relationship between the layout of anarray’s elements in memory and the order in whichthose elements are accessed. A stride of 1 meansthat memory–adjacent array elements areaccessed on successive iterations of anarray–processing loop. A stride of N means that foreach array element accessed, N–1memory–adjacent elements are skipped overbefore the next accessed element.

string. (1.) A linear sequence of entities such ascharacters or physical elements. Examples ofstrings are alphabetic string, binary element string,bit string, character string, search string, andsymbol string. (2.) In Pascal, an object of thepredefined type STRING. (3.) The form of dataused in programming languages for storing andmanipulating text. In C language code, a string istreated as a one–dimensional array of type char.

string constant. Characters enclosed in doublequotation marks.

string register. A register that holds a definedstring value to be called by a token. See alsotoken.

string value. Value of specified string. InAIXwindows, the value of a string that identifies aText widget.

stroke text. Synonym for programmable characterset and geometric text.

structure. A variable that contains an orderedgroup of data objects. Unlike an array, the dataobjects within a structure can have varied datatypes.

Structure Rule Table (SRT). A recurring attributeof the directory schema with the description of thepermitted structures of distinguished names.

structure tag. The identifier that names a structuredata type.

structured field. A mechanism that permitsvariable length data to be encoded for transmissionin the data stream. See also field.

structured file. (1.) A special type of INed file thatcontains specialized data, such as informationabout the structure of the data in the file, andhistory information about changes that have beenmade to the file. Structured files can containhierarchical data that is displayed and edited byusing forms. (2.) In Encina, a file with dataorganized into a specific format that is usuallyrecord–oriented.

structured file system. The collection of datamanaged by a single structured file server (SFS).All access to a structured file system is through asingle server, using a special type of file descriptor(OFD) that identifies the file system and itsorganization.

structured programming. A technique fororganizing computer programs in hierarchicalmodules, making programs easier to debug,modify, and replace. Typically, all modules have asingle entry point and a single exit point. Control ispassed downward through the structure withoutunconditional branches to higher levels of thestructure.

structured type. Any of several data types thatdefine variables having multiple values; forexample, records and arrays. Each value is acomponent of the structured type. Contrast withscalar type.

stub. (1.) In NCS, a program module that transfersremote procedure calls and responses between aclient and a server. Stubs perform marshalling,unmarshalling, and data format conversion. Bothclients and servers have stubs. The compilergenerates client and server stub code from aninterface definition. See also marshal. (2.) Hookingfunctions used as extensions to the protocol togenerate protocol requests for EnhancedX-Windows. Synonym for hooking routines. (3.)The RPC calls produced by the compiler when aninterface is defined. Two sets of stubs areproduced, client stubs and server stubs. Theapplication code calls the stub, and the RPCmechanism translates this into a call to theappropriate function on the remote machine.

stub procedures. Method procedures in theimplementation template generated by the SOMCompiler. They are procedures whose bodies arelargely vacuous, to be filled in by the implementor.

Style Manager. In CDE, the software applicationused to customize some of the visual elements andsystem device behaviors of the workspaceenvironment, including colors and fonts, andkeyboard, mouse, window, and session start–upbehaviors.

stylus. A device used to select a particular locationon a tablet.

subaddress. In X.25 communications, theunallocated digits at the end of the nationalterminal number (NTN). If the network providerallocates all digits to the NTN, there can be nosubaddress.

subarea node. In data communications, a nodethat uses network addresses for routing, andwhose routing tables are affected by changes in

1-148 Glossary

the configuration of the network. Subarea nodescan provide boundary function support forperipheral nodes.

subchannel. A logical communications pathdefined in S/370 architecture to perform transfersto a given device.

subclass. (1.) A class of widgets that inheritsresources from a higher class. (2.) In SOM, a classthat inherits instance methods, attributes, andinstance variables directly from another class,called the parent class, base class, superclass, orindirectly from an ancestor class. A subclass mayalso be called a child class or derived class.

subclassing. In SOM, the process whereby a newclass, as it is created (or derived), inherits instancemethods, attributes, and instance variables fromone or more previously defined ancestor classes.The immediate parent class(es) of a new classmust be specified in the class’s interfacedeclaration. See also inheritance.

subcommand. A request for an operation that iswithin the scope of work requested by a previouslyissued command.

subcomponent. In Ada language, either acomponent, or a component of anothersubcomponent.

subdirectory. In the file system hierarchy, adirectory contained within another directory.

subfolder. In CDE, a folder contained withinanother folder (sometimes called the parent folder).When discussing command–line activities, this maybe called a subdirectory.

subheap. In Pascal, part of a heap delimited by acall to MARK. Subheaps are treated in a stack–likemanner within a heap.

subhost. A communications system that controlsattached workstations in addition to communicatingwith another (usually higher–level) system.

subject identifier (SID). A string that identifies auser or set of users. Each SID consists of threefields in the form person.group.organization. In anaccount, each field must have a specific value; in aACL entry, one or more fields may be a wildcard.

submenu. A menu accessed from another menuby a ––> symbol. A related menu that can only bereached from a main menu. In AIXwindows, oneexample of a submenu is an XmCascadeMenuwidget that appears from the side of anXmPopupMenu widget when the mouse pointer isdragged sideways across a main menu item.

subnet. One of a group of multiple logical networkdivisions of a single network, such as can be

created by the TCP/IP Interface Program.Synonymous with subnetwork.

subnet address. The subdivided part of the localhost address, which has been reserved forindicating the subnet. Subnet addressing allows anautonomous system made up of multiple networksto share the same Internet network address.

subnet address mask. A bit mask used by a localsystem to determine whether a destination is onthe same network as the source or if thedestination can be reached directly through one ofthe local interfaces.

subnetwork. Synonym for subnet.

subobject. An object that is in a subordinaterelationship to a given object.

subpanel. In CDE, an extension of the Front Panelthat slides up providing access to additionalelements. Subpanels usually contain groups ofrelated elements.

subpattern. A discrete element of a regularexpression.

subprocess. A process initiated by anotherprocess. Control is transferred back to the mainprocess after the subprocess finishes running.

subprogram. (1.) A program called by anotherprogram, such as a subshell. (2.) In FORTRAN, aprogram unit that has a FUNCTION,SUBROUTINE, or BLOCK DATA statement as itsfirst statement. Contrast with main program. (3.) InAda language, a subprogram is either a procedureor a function. A procedure specifies a sequence ofactions and is invoked by a procedure callstatement. A function specifies a sequence ofactions and also returns a value called the result,and so a function call is an expression. Asubprogram is written as a subprogramdeclaration, which specifies its name, formalparameters, and (for a function) its result; and asubprogram body which specifies the sequence ofactions. The subprogram call specifies the actualparameters that are to be associated with theformal parameters. A subprogram is one of thekinds of program unit. See also function andprocedure.

subrange scalar type. In Pascal, a type thatdefines a variable whose value is restricted tosome subset of values of a base scalar type. Seealso base scalar type.

subroutine. (1.) A sequenced set of statements orcoded instructions that can be used in one or morecomputer programs and at one or more points in acomputer program. (2.) A routine that can be partof another routine. See also routine. (3.) A request

1-149Glossary

by an active process for a service by the systemkernel. See also macro.

Subroutine ID. A unique identification numberassociated with each subroutine included in anapplication.

subroutine switch table. Contains the address forthe specific handler routine that handles thesubroutine.

subscribe. In X.25 communications, to a rent anX.25 line, specifying the required facilities.

subscript. (1.) An integer or variable whose valueselects a particular element in a table or an array.(2.) Characters printed one–half line below thenormal printing line.

subscript declarator. In an array definition ordeclaration, the bracketed expressions followingthe array name. Specifies the number of elementsin an array dimension.

subscript quantity. In FORTRAN, a component ofa subscript. A subscript quantity is an integer orreal constant, variable, or expression.

subserver. A system resource or program that isdirectly controlled by a server program runningunder control of the System Program Controller.

subset. (1.) A set each element of which is anelement of a specified other set. (2.) A variant formof a programming language with fewer features ormore restrictions than the original language. (3.) Intelecommunications, a subscriber set such as atelephone.

subshell. An instance of the shell program startedfrom an existing shell program.

substring. A contiguous subportion of a string.

subsystem. (1.) A secondary or subordinatesystem, usually capable of operating independentlyor synchronously with a controlling system. (2.) Thepart of communications that handles therequirements of the remote system, isolating mostsystem–dependent considerations from theapplication program.

subtree. A lower–level directory structure.

subtype. (1.) An IOCINFO ioctl variable thatidentifies the kind of DLC being queried. (2.) In Adalanguage, a subtype of a type characterizes asubset of the values of the type. The subset isdetermined by a constraint on the type. Each valuein the set of values of a subtype belongs to thesubtype and satisfies the constraint determining thesubtype.

subunit. For Ada programming, see body.

subwidget. In AIXwindows and EnhancedX-Windows, a widget class directly beneath ahigher widget class in a widget–gadget hierarchy.

suffix. (1.) A character string attached to the endof a file name that helps identify its file type. (2.) Acode dialed by a caller who is already engaged in acall. (3.) A part of a file name, added at the end,separated from other suffixes or the base file nameby some punctuation, such as a period (.).

superblock. In a file system layout, refers to Block1, which is used to keep track of the file systemand is the most critical part of the file system. Itcontains information about every allocation ordeallocation of a block in the file system. See alsoi–list.

superclass. In AIXwindows and EnhancedX-Windows, a class of widgets that passesinheritable resources down the hierarchy to a lowersubclass. See also widget record.

superclient. A diskless client with read and writepermission and root access to the remoteresources used by other clients. A superclientinstalls and maintains optional software of Version3.2 of the operating system on a non–Version 3.2diskless server.

superobject. An object that is in a superiorrelationship to a given object.

superscalar. The capability to execute multipleinstructions in a given clock cycle.

superuser. See root user.

superuser authority. See root user authority.

supervisor. The part of the operating systemcontrol program that coordinates the use ofresources, and maintains the flow of processingunit operations.

supervisor call (SVC). An instruction thatinterrupts the program being run and passescontrol to the supervisor so it can perform aspecific service indicated by the instruction.

supporters. In Ada language, all the compilationunits required by the language to allow a unit to becompiled. This consists of the unit’s imports, theirimports, and so on.

surface characteristics. Characteristics of thestyle of a written document: readability, sentencelength and structure, word length and usage, verbtype, and sentence openers.

suspended state. (1.) A state in which theresource is temporarily not receiving a request. Astart action request returns the resource to the

1-150 Glossary

state it was in prior to being suspended. (2.) Asoftware state in which a task is not dispatched bythe system and is not contending for the processor.

SVC. See switched virtual circuit and Supervisorcall.

swap interval. In GL, the amount of elapsed timebetween frame buffer swaps. The system waits atleast the amount of time specified by the swapinterval subroutine before honoring a request toexchange the front and back buffers. The swapinterval is measured in units of vertical retraces,which occur every 30th of a second on mostsystems. The swap interval is useful in achievingsmooth–flowing animation.

swapping. (1.) Temporarily removing an active jobfrom main storage, saving it on disk, andprocessing another job in the area of main storageformerly occupied by the first job. (2.) In a systemwith virtual storage, a paging technique that writesthe active pages of a job to auxiliary storage andreads pages of another job from auxiliary storageinto real storage.

swidget. See shadow widget.

switch. A command–line option.

switch expression. (1.) The expression that islocated between the keyword switch and the bodyof a switch statement. (2.) In C language, thecontrolling expression of a switch statement.

switch table. The table used by the file system tolocate the entry points of a character device.

switched line. In data communications, aconnection between computers or devicesestablished by dialing. Contrast with nonswitchedline.

switched network backup (SNBU). In datacommunications, a technique that provides aswitched line connection when a nonswitched linefails.

switched virtual circuit (SVC). In X.25communications, a virtual circuit that is requestedby a virtual call. It is released when the virtual callis cleared. Contrast with permanent virtual circuit.See also virtual circuit.

SWVPD. See Software Vital Product Data.

symbol. In the SOM Emitter Framework, any of a(standard or user–defined) set of names (such as,className) that are used as placeholders whenbuilding a text template to pattern the desiredemitter output. When a template is emitted, thesymbols are replaced with their correspondingvalues from the emitter’s symbol table. Othersymbols (such as, classSN) have values that areused by section–emitting methods to identify major

sections of the template (which are correspondinglylabeled as ”classS” or by a user–defined name).

symbol table. See parse.

symbolic address. A unique line address, such as. (period) or $ (dollar sign), used in place of a linenumber address to identify location of data. Seealso pattern address.

symbolic debugger (sdb). A tool that aids in thedebugging of programs written in certain high–levellanguages.

symbolic link. Type of file that contains the pathname of and acts as a pointer to another file ordirectory.

symbolic name. A unique name used to representan entity such as a file or a data item. See alsoname.

symmetrical multiprocessor (SMP) system. Asystem containing multiple processors that areessentially identical and perform identical functions.

SYN. See synchronization character.

synchronization character (SYN). In binarysynchronous communications, the transmissioncontrol character that provides a signal to thereceiving station for timing.

synchronous. (1.) Two or more processes thatdepend upon the occurrences of specific eventssuch as common timing signals. (2.) Occurring witha regular or predictable time relationship orsequence.

synchronous data link control (SDLC). (1.) Aform of communications line control usingcommands to control the transfer of data over acommunications line. Contrast with binarysynchronous communication. (2.) A disciplineconforming to subsets of the advanced datacommunications control procedures (ADCCP) ofthe ANSI and the HDLC of the InternationalOrganization for Standardization. It managessynchronous, code–transparent, serial–by–bitinformation transfer over a link connection.Transmission exchanges can be duplex orhalf–duplex over switched or nonswitched links.The configuration of the link connection may bepoint–to–point, multipoint, or loop.

synchronous transmission. (1.) In datacommunications, a method of transmission inwhich the sending and receiving of characters iscontrolled by timing signals. Contrast withasynchronous transmission. (2.) Data transmissionin which the time of occurrence of each signalrepresenting a bit is related to a fixed time base.

syntax. (1.) The grammatical rules for constructinga command, statement, or program. (2.) In XOM:

1-151Glossary

(a.) An OM syntax is any of various categories intowhich the object management specificationstatically groups values on the basis of their form.These categories are additional to the OM type ofthe value. (b.) A category into which an attributevalue is placed on the basis of its form.

syntax diagram. A diagram for a command thatdisplays how to enter the command on thecommand line.

syntax error. A compile–time error caused byincorrect syntax. See also semantic error.

syntax template. A lexical construct containing anasterisk from which several attribute syntaxes canbe derived by substituting text for the asterisk.

system. The computer and its associated devicesand programs.

System/370 Host Interface Adapter (HIA). Anadapter that allows the attachment of aPOWERstation or POWERserver to a 5088Graphics Control Unit.

system address list. The address list, controlledby the system manager, that all users on thesystem can use with the xtalk command to makeoutgoing X.25 calls. See also address list and useraddress list.

System Application Architecture FORTRAN(SAA FORTRAN). A superset of the ANSI X3.p –1978 FORTRAN 77 standard.

system board. The main circuit board in thesystem unit that supports a variety of basic systemdevices, such as a keyboard, a mouse, and soforth. The system board also supplies other basicsystem functions.

system call. A call by a program to an operatingsystem subroutine.

system console. A console, usually equipped witha keyboard and display screen, that is used by anoperator to control and communicate with asystem. Synonymous with console.

system customization. Specifying the devices,programs, and users for a particular dataprocessing system. Contrast with configuration.See also customization.

system date. The date assigned by the systemuser during setup and maintained by the system.See creation date and session date.

system dump. A copy from storage of selecteddata areas. Synonymous with kernel dump.

system image. The representation of a program(and its related data) as it exists at the time itresides in system memory.

system management. The tasks involved inmaintaining the system in good working order andmodifying the system to meet changingrequirements.

System Management Interface Tool (SMIT). Aset of menu–driven services that facilitate theperformance of such system tasks as softwareinstallation and configuration, device configurationand management, problem determination, andstorage management. SMIT is provided in both acharacter–based curses interface and anAIXwindows–based graphical user interface.

system memory. Synonymous with main storage,but used in hardware to refer to semiconductormemory (modules).

system menu. In AIXwindows, the pulldown in thetop left–hand corner of a window that allows usersto restore, move, size, minimize, and maximize thewindow. It also allows users to exit the applicationor to close a window. Also causes the appearanceof a dialog box to contain a list of the activeapplications. With the optional split windowtechnique, the user views many parts of the sameobject at one time.

System Network Architecture (SNA). (1.) Anarchitecture for controlling the transfer ofinformation in a data communications network. (2.)The description of the logical structure, formats,protocols, and operating sequences for transmittinginformation units through, and controlling theconfiguration and operation of networks.

system node. In the hierarchy of device locations,this is the highest node. Every hardware device willlead back to the system node if you follow theconnection path. For example, an SCSI disk isconnected to an SCSI adapter that is connected toa bus that is connected to the system node.

System Object Model (SOM). Object–orientedprogramming technology for building, packaging,and manipulating binary class libraries.

system parameters. Synonym for kernelparameters.

System Performance Measurement Interface(Spmi). In the Performance Toolbox, the Agent APIthat allows an application program to registercustom performance statistics about its ownperformance or that of some other systemcomponent. Once registered, the custom statisticsbecome available to any consumer of statistics,local or remote. Also permits applications to accessstatistics on the local system without using thenetwork interface. Such applications are calledlocal data–consumer programs.

1-152 Glossary

system profile. A file containing the default valuesused in system operations.

System Program Controller (SPC). A systemprogram that controls the operation of otherapplication programs that run in the background(daemons).

system prompt. Synonym for command line. Thesystem prompt is the symbol that appears at thecommand line of an operating system. The systemprompt indicates that the operating system is readyfor the user to enter a command.

System Resource Controller (SRC). A set ofcommands and subroutines used to create andcontrol subsystems. The SRC controls subsystemprocesses using a common command line and theC interface. The SRC is useful when you need acommon method to start, stop, and collect statusinformation on processes.

system restart. Synonym for initial program load.

system ROS. The piece of system microcode thatis responsible for loading a boot image.

system services control point (SSCP). In SNA,the focal point within an SNA network for managingthe configuration, coordinating network operatorand problem determination requests, and providingdirectory support and other the session services fornetwork end users. Multiple SSCPs, cooperating aspeers, can divide the network into domains ofcontrol, with each SSCP having a hierarchicalcontrol relationship to the physical units and logicalunits within its domain.

system startup. Synonym for initial program load.

system time. The amount of time that theoperating system spends providing services to anapplication. System time includes time spent by theoperating system allocating storage or devices toyour program, and time spent processing operatingsystem calls your program makes.

system unit. The part of the system that containsthe processing unit.

system user. A person, device, or system thatuses the facilities of a computer system.

1-153Glossary

Ttab. To move a cursor to a preset location on adisplay screen.

tab group. In AIXwindows, a means of organizingXmPrimitive widgets into groups for more efficienttraversal within and between groups.

table. An array of data in which each item can beunambiguously located by means of one or morevalues.

tablet. A special flat surface with a mechanism forindicating positions on it. A tablet is normally usedas a locator.

tablet origin. A point on a tablet to which all otherlocations on the tablet correspond. The origin iseither the lower–left corner or the center of thetablet.

tabulating window. In Performance Toolbox, aspecial form of window that tabulates the values ofan instrument as data is received and can alsocalculate a line with a weighted average for eachvalue.

tag. (1.) In GL, a marker in the display list used asa location for display list editing. (2.) In Interleaf,the alphanumeric name of an autonumberreference. This name can be assigned by Interleafor by the writer; but it must match the autonumberof the component it is referencing.

tag field. In Pascal, the field of a record thatdefines the structure of the variant part. See alsovariant part.

tag–in. A control line bus that passes signals fromthe control unit to the host on the System 360/370Parallel Channel Interface.

tag–out. A control line bus that passes signalsfrom the host to the control unit on the System360/370 Parallel Channel Interface.

Tagged Input Format File (TIFF). A graphics fileformat using bitmaps.

tape drive. A mechanism for moving magnetictape and controlling its movement.

target. (1.) A system, a program within a system,or a device that interprets, rejects, or satisfies, andreplies to requests received from a source.Contrast with source. (2.) The node at which apassword is to be installed. If the passwordspecifies a single nodelocked license, the target isthe node licensed to run the product. If thepassword specifies multiple nodelocked licenses(that is, a compound password for nodelockedlicenses), or licenses of any other type, then the

target is a node running the license serverdaemon. (3.) For NIM, the client you are installing.

target file. A file created by the make program thatcontains a completed program.

target object. (Or receiver.) In SOM, the objectresponding to a method call. The target object isalways the first formal parameter of a methodprocedure. For SOM’s C–language bindings, thetarget object is the first argument provided to themethod invocation macro, _methodName.

target program. Synonym for object program.

task. (1.) A basic unit of work to be performed.Some examples include a user task, a server task,and a processor task. (2.) A process and theprocedures that run the process. (3.) In amultiprogramming or multiprocessing environment,one or more sequences of instructions treated by acontrol program as an element of work to beaccomplished by a computer. (4.) In Ada language,a task operates in parallel with other parts of theprogram. It is written as a task specification (whichspecifies the name of the task and the names andformal parameters of its entries), and a task bodywhich defines its execution. A task unit is one ofthe kinds of program unit. A task type is a type thatpermits the subsequent declaration of any numberof similar tasks of the type. A value of a task type issaid to designate a task. (5.) A C++ task is alightweight, nonpreemptive routine that you canuse to simulate the operation of programs. Tasksare nonpreemptive because only a single task isexecuting at any one time. Tasks are lightweightbecause less time and space are required to createa task than a true operating–system process.

task ID. In Ada language, analphabetic label oridentification for a task. This label is determined bythe debugger TASKS option. A task ID is assignedto each task that has not terminated.

Task Library. A C++ class library that provides thefacilities to write programs that are made up oftasks.

tasking. Synonym for multitasking.

tbl. A preprocessor that formats tables for the nroffand troff commands.

TCB. See trusted computing base.

TCP. See Transmission Control Protocol.

TCP/IP. See Transmission Control Protocol/InternetProtocol.

TCW. Translation control word.

TD. Transmit Data used with EIA–232 Protocol.

1-154 Glossary

telecommunication. The transmission of controlsignals and information between computer systemsat two or more locations over telecommunicationlines, or between a computer system and remotedevices.

teleprocessing. Processing data that is receivedfrom or transmitted to a remote location by way ofcommunication channels. Synonym for remoteaccess data processing.

Telnet. In TCP/IP, the protocol that opens theconnection to the system.

template. (1.) A representation of a keyboard thatincludes functions not engraved on the keyboard.(2.) Each command line stored in the buffer. (3.) Inenhanced edit mode, a special character bufferassociated with the terminal. (4.) In Mailer, anASCII file you can create for conveniently includingfrequently typed information, such as your nameand electronic mail address, in your mailmessages. (5.) A family of C++ classes or functionswith variable types.

template class. A C++ class instance generatedby a class template.

template function. A C++ function generated by afunction template.

temporary error. An error that requires anoperation to be retried a number of times before itis successfully completed.

temporary scalar. In a source–level optimization,a scalar that is used to temporarily hold thecontents of an array element or the result of acomputation to eliminate logically redundant storesand loads of that element or result.

term. An expression that is a subportion of anotherexpression, usually composed of other subportionsby means of addition or subtraction.

terminal. (1.) A device, usually equipped with akeyboard and a display device, capable of sendingand receiving information over a communicationsline. See also workstation. (2.) In a system orcommunications network, a point at which data caneither enter or leave. (3.) In curses and extendedcurses, a special screen that represents what theworkstation’s display screen currently looks like.The terminal screen is identified by a windownamed curscr, which the user does not accessdirectly. Instead, users make changes to the stdscrwindow (or a user–defined screen) and then therefresh (or wrefresh) window to update theterminal.

Terminal. In CDE, in the Front Panel, an item inthe Personal Applications subpanel used to open aterminal window.

terminal application. An application running at aworkstation (terminal).

terminal descriptor. In ODM, a named variable oftype short, long, binary, char, or vchar used todefine the basic data types in an ODM object classdefinition. See also short, long, binary, char,descriptor, vchar, and object class.

terminal emulator. A program that allows a devicesuch as a microcomputer or personal computer toenter and receive data from a computer system asif it were a particular type of attached terminal.

terminal mapping. To translate between astandard character set and a terminal–specificcharacter set.

terminal screen. Synonym for display screen.

terminator. The part of the program product thatperforms the action necessary to end a job orprogram.

test mode. Mode employed in testing a new userinterface, in which the compiled application is usedto drive the interface. Allows building, modifying,testing, and refining operations without having tocompile, link, and debug.

text. (1.) A type of data consisting of a set oflinguistic characters (letters, numbers, andsymbols) and formatting controls. (2.) The portionof a program that is able to be run. (3.) In kernelmode, contains kernel program code that runs. It isread only by a user process. (4.) In ASCII and datacommunications, a sequence of characters treatedas an entity when preceded by one start–of–textand ended by one end–of–text communicationcontrol character. See also program text. (5.) Inword processing, information intended for humanviewing that is presented in a two–dimensionalform, such as data printed on paper or displayedon a screen. (6.) The part of a message that is notthe header or control information.

text buffer. A text storage area.

text cursor. A cursor that indicates where to type acharacter. The text cursor is controlled by thekeyboard.

Text Editor. In CDE, the software application usedto create and edit documents.

text field. In CDE, a rectangular area in a windowwhere information is typed. Text fields withkeyboard focus have a blinking text insertioncursor.

text formatting program. A program thatdetermines the manner in which data will be placedon a page.

1-155Glossary

text indicators. Symbols at the bottom of the INedwindow to show directions the user can scroll toview additional portions of the file.

text input mode. Mode in which typed charactersare interpreted by an editor as text entered into afile. See also command mode and last line mode.

text lock. Allows the calling process to lock orunlock its text segments into memory.

text string. A sequence of characters(alphanumeric or special) defined by the user.

text widget. A text editor for customizing userinterfaces and programmatic interfaces.

text wrap. See word wrap.

textport. In GL, a region on the display screenused to present textual output from graphical ornongraphical programs.

texture. A pattern used to fill rectangles, convexpolygons, arcs, and circles.

tftp. See Trivial File Transfer Protocol.

thermal output. The heating load that a computersystem places on the cooling system of thebuilding, measured in British Thermal Units (BTU).

this. A C++ keyword that identifies a special typeof pointer that references the class object in amember function.

thrashing. A condition, caused by a high level ofmemory over–commitment, in which the system isspending all of its time writing out virtual–memorypages and reading them back in. The applicationprograms make no progress because their pagesdon’t stay in memory long enough to be used.Memory load control is intended to avoid or stopthrashing.

thread. The dispatchable entity in AIX Version 4.Each thread represents the current execution stateof a single instance of a program. Each user threadruns in the environment provided by a specificprocess, but multiple threads may share theresources owned by that process.

thread–serial service. A reentrant system serviceis thread–serial if it blocks the current thread andall other threads that attempt to call the sameservice or other related services until the first callreturns. See also reentrant service.

thread–synchronous service. A reentrant systemservice is thread–synchronous if it blocks only thecurrent thread and allows other threads to executethe same operation during the block. See alsoreentrant service.

threaded application. An application thatperforms its function by simultaneously using

multiple execution paths (threads of control) withina single address space.

threshold. (1.) A logic operator with the propertythat if P is a statement, Q is a statement, R is astatement, and so on, then the threshold of P, Q, R,and so on, is true if at least N statements are true,and false if less than N statements are true. N is aspecified nonnegative integer called the thresholdcondition. (2.) In computer graphics, a level abovewhich all gray–scale image data can berepresented as white and below which allgray–scale image data can be represented asblack.

throughput. The number of workload operationsthat can be accomplished per unit of time.

throughput–class negotiation. In X.25communications, an optional facility that allows aDTE to negotiate the speed at which its packetstravel through the packet switching network. Seealso optional facilities.

throw expression. An argument to the exceptionbeing thrown.

TIC. Transfer in channel.

ticket. An application–transparent mechanism thattransmits the identity of an initiating principal to itstarget. A simple ticket contains the principal’sidentity, a session key, a timestamp, and otherinformation, sealed using the target’s secret key. Aprivilege ticket contains the same information as asimple ticket, and also includes a privilege attributecertificate. A ticket–granting ticket is a ticket to theticket–granting service; a service ticket is a ticketfor a specified service other than theticket–granting service.

TIDL. Transactional Interface Definition Language.

tie–down resistor. A resistor used to hold theinput to a logic function or gate to the low level.One end of the resistor is connected to ground orthe appropriate negative voltage.

tie–up resistor. A resistor used to hold the input toa logic function or gate to the high level. One endof the resistor is connected to the appropriatepositive voltage.

TIFF. See Tagged Input Format File.

tile. (1.) A pixmap. (2.) To fill a region with apixmap. (3.) To replicate a pixmap in twodimensions.

time slice. The interval between scheduled checksby the CPU scheduler to see if a different threadshould be dispatched. Unscheduled checks mayoccur as a result of interrupts or system calls.

1-156 Glossary

time stamp. (1.) A time value expressed inmilliseconds, typically since the last server reset.Time–stamp values wrap around usually after 49.7days. The server, once given its current time, isrepresented by timestamp T and always interpretstime stamps from clients by treating half of thetime–stamp space as being earlier in time than T,and half the time–stamp space as being later intime than T. One timestamp value, represented bythe constant CurrentTime, is never generated bythe server. This value is reserved for use inrequests to represent the current server time. (2.)Information added to a record or other form of datathat shows the date and time at which a computerprocessed that record or data. (3.) An integer thatdescribes the date and time at which a set oflicenses was created. (4.) Records the date andtime when an Ada–language compilation unit waslast modified.

TIMED. Timed Server Protocol. A protocol used tosynchronize a host’s time with the time of otherhosts.

timeslicing. A mechanism by which runningthreads are preempted at fixed intervals. Thisensures that every thread is allowed time toexecute.

timing loop. A loop placed around code whoseperformance is to be timed, such that the timingloop increases the number of executions of thecode within it to a time that can provide ameaningful performance measurement.

title bar. The bar that appears across the top of awindow and that contains a file name or title. It canbe used for moving or activating the window.

TLB. See translation lookaside buffer.

TLB miss. A memory delay that occurs when amemory location is referenced and the page thatcontains that memory location does not have anentry in the appropriate transition lookaside buffer(instruction or data).

TLI. Transport Layer Interface.

TOD. Time of day.

toggle. (1.) A switching device such as a togglekey on a keyboard. (2.) Pertaining to any devicehaving two stable states. (3.) To switch betweentwo modes on a computer or network.

toggle button. In AIXwindows and EnhancedX-Windows, a graphical object that simulates areal–world toggle switch; it switches sequentiallyfrom one optional state to another.

token. (1.) The smallest independent unit ofmeaning of a program as defined by either theparser or the lexical analyzer. A token can contain

data, a language keyword, an identifier, or otherparts of a language syntax. (2.) In the m4command, any string of letters and digits that them4 command recognizes. (3.) A type of macro thatthe typesetting preprocessor replaces with anassigned string value. See also string register. (4.)In a local area network, the symbol of authoritypassed among data stations to indicate the stationtemporarily in control of the transmission medium.

token numbers. Nonnegative integers thatrepresent the names of tokens.

token ring. A type of local area network that wasdeveloped under the auspices of the IEEE 802.5Subcommittee. A token access procedure usedwith a sequential (ring) topology.

Toolkit. In AIXwindows and Enhanced X-Windows,a collection of C language data structures andsubroutines that collectively expedite thedevelopment of graphical user interfaces forcompatible applications written in C language.

top–down. An approach to problem solving thatstarts at the highest level of abstraction andproceeds toward the lowest level.

top–level. In AIXwindows and EnhancedX-Windows, pertaining to the widget classes at thetop level of a widget–gadget hierarchy.

top–level transaction. A transaction that does notexecute within the scope of another transaction. Inother words, a top–level transaction is the root of atransaction family, even if it is the only transactionin the family tree.

top–level widget. In AIXwindows and EnhancedX-Windows, widget classes that are at or near thetop level of the object class hierarchy, which isknown as the Core class.

top–level window. In AIXwindows and EnhancedX-Windows, the main window that contains allother windows associated with a client application.

top shadow. In AIXwindows, an arrow band oflighter color across the top of a rectangulargraphical object (a widget or gadget) that creates athree–dimensional appearance when the object ismanipulated.

topic tree. In CDE, in a general help dialog box, anexpandable and contractible list of topics that canbe selected to display help information.

topological sort. A sorting file that sorts anunordered list of ordered pairs.

tower. A set of physical address and protocolinformation for a particular server. CDS uses thisinformation to locate the system on which a serverresides and to determine which protocols are

1-157Glossary

available at the server. Tower values are containedin the CDS_Towers attribute associated with theobject entry that represents the server in the cellnamespace.

TPN. See transaction program name.

trace. (1.) To record data that provides a history ofevents occurring in the system. (2.) A record of therunning of a computer program. It exhibits thesequences in which the instructions were run. (3.)To monitor system performance or aid indebugging programs.

trace daemon. Reads from the trace device driverand writes to the trace log file.

trace entry. Data recorded from a trace event.

trace ID. A unique identifier for a traced event.

trace log. A file where trace events are recorded.

trace table. A storage area that contains a recordof the performance of computer programinstructions.

trace template. Used by the trace formatter todetermine how the data contained in trace entriesshould be formatted.

traceback. For the Ada debugger, a listing of theroutines that are in the call chain above the codeyou are debugging. For example, if you set abreakpoint within an Ada procedure and request acall traceback, you see a list of all the proceduresthat called your Ada procedure, in the order inwhich they called it. All the calling procedures inthe call chain are listed up to, but not including, theoperating system calling the original highest levelroutine.

track. (1.) A circular path on the surface of a fixeddisk or diskette on which information ismagnetically recorded and from which recordedinformation is read. (2.) The path on a datamedium associated with a single reading or writingcomponent as the data medium moves past thecomponent.

trailer. The portion of a message that containscontrol information. Trailers are used by the VAXTrailer Encapsulation Protocol. Trailerencapsulation allows the receiving host to receivedata on a page–aligned boundary, which is arequirement for utilizing a page–mapped virtualmemory environment.

trailer page. A trailer page that follows a printedfile or a print job.

TRAN. Distributed Transaction Service.

transaction. (1.) An exchange between aworkstation and a program, two workstations, ortwo programs that accomplish a particular action or

result. Some examples are the entry of acustomer’s deposit and the updating of thecustomer’s balance. (2.) In a batch or remote batchentry, a job or job step.

transaction family. Nested transactions that havea common ancestor belong to the same transactionfamily. All members of a transaction family committogether and drop their locks simultaneously.

transaction ID. See transaction identifier.

transaction identifier. A unique identifier assignedto each transaction, used to identify all actionsassociated with that transaction.

transaction program. A program that processestransactions in an SNA network. The two kinds oftransaction programs are application transactionprograms and service transaction programs. Seealso conversion, application transaction program,and service transaction program.

transaction program name (TPN). The name ofan application program that uses datacommunications to send or receive data to or fromanother application program.

transactional RPC. transactional remoteprocedure call.

transcript. In remote communications, a file thatcontains the written record of commands you enteron the remote system and the remote system’sresponse to those commands.

transfer. To send data to one place and to receivedata at another place.

transformation. In GL, a four–by–four matrix thathelps determine the location wherethree–dimensional drawing will occur, the positionof the viewpoint (the viewer’s ”eye”), and theamount of the scene encompassed and visible.Transformations occur at four points within thegraphics pipeline: (1.) Modeling transformation,which maps modeling coordinates into worldcoordinates. All drawing primitives specify positionsthat are presumed to be positions in modelingcoordinates. Modeling transformation can be usedto move the thing being drawn. (2.) Viewingtransformation, which maps from world coordinatesto viewer coordinates. The origin of the viewercoordinate system can be thought of as thelocation of the viewer’s ”eye,” and viewingtransformations can be used to move the ”eye”around in world coordinates. (3.) Projectiontransformation, which defines the boundaries of theclipping region. A projection transformation mapsviewer coordinates to normalized devicecoordinates, and the clipping plane boundaries areat x = +/–w,y = +/–w, z= +/–w. Projectiontransformations can be used to define what region

1-158 Glossary

of the world is visible on the screen. (4.) Viewport,or NDC to DC transformation. The viewporttransformation is not a full–fledged four–by–fourtransformation matrix; only three of the diagonalelements in the matrix can be changed. Theviewport determines the mapping from normalizeddevice coordinates to screen (device) coordinates.By default viewports are the same size as thewindow, although this can be adjusted. See alsonormalized device coordinates, modelingcoordinates, rotation, eye coordinates, screencoordinates, selecting region, viewing matrix, worldcoordinates, clipping, and current transformationmatrix.

transient. A program or subroutine that does notreside in main storage.

transit delay. In X.25 communications, the time ittakes a packet to travel from one DTE to the other.

translation. (1.) The movement of something by acertain distance. (2.) In computer graphics, themoving of a display image in a straight line fromone location to another. See also transformation.

translation lookaside buffer (TLB) . A table in theCPU that contains cross–references between thevirtual and real addresses of recently referencedpages of memory.

translation table. (1.) A table that specifies themapping of events or event sequences toprocedure names. (2.) A string containing a listtranslating the events to procedure calls.

translation table list. See translation table.

translations. Action procedures that are called foran event or sequence of events.

transmission control characters. Specialcharacters included in a message to controlcommunication over a data link. For example, thesending station and the receiving station usetransmission control characters to exchangeinformation. The receiving station usestransmission control characters to indicate errors indata it receives.

Transmission Control Protocol (TCP). Acommunications protocol used in ARPA Internetand any network following the U.S. Department ofDefense standards for inter–network protocol.Provides a reliable host–to–host protocol betweenhosts in packet–switched communicationsnetworks and in interconnected systems of suchnetworks. It assumes that the Internet Protocol isthe underlying protocol.

Transmission Control Protocol/InternetProtocol (TCP/IP). An industry–standard,nonproprietary communication protocol suite thatallows connectivity between equipment from

different manufacturers. Its development wasfunded by the Department of Defense AdvancedResearch Projects Agency. A communicationssubsystem that allows you to set up local area andwide area networks.

transmission services (TS). In SNA, aspecification in a session activation request fortransmission control (TC) protocols to be supportedby a particular session (such as session–levelpacing the usage of session–level requests). Eachtransmission services request defined is identifiedby a number.

transmit burst. A group of transmit packets thatare sent without an intervening receive or time–outoperation.

transparent. (1.) In communications, pertaining totransmissions that cannot interfere with data linkcontrol, regardless of format or content.Transparent transmissions are unrecognized bydata link controls. (2.) In data transmission,pertaining to information that the receiving programor device does not recognize as transmissioncontrol characters. (3.) Pertaining to operations ordata that are of no significance to the user.

transparent binding. A form of binding that allowsthe client application to bind to any available serverexporting the desired interface

transparent mode. A method of binarysynchronous text transmission in which onlytransmission control characters preceded by thedata link escape(DLE) character are processed astransmission control characters.

Transport Layer. A network service that providesend–to–end communications between two parties,while hiding the details of the communicationsnetwork. The TCP and ISO TP4 transport protocolsprovide full–duplex virtual circuits on which deliveryis reliable, error free, sequenced, and duplicatefree. UDP provides no guarantees (theconnectionless RPC protocol provides someguarantees on top of UDP).

transport protocol. A communications protocolfrom the Transport Layer of the OSI networkarchitecture, such as the Transmission ControlProtocol (TCP) or the User Datagram Protocol(UDP).

trap. An unprogrammed, hardware–initiated,conditional jump to a specific address. It occurs asa result of an error or certain other conditions. Arecord is made of the location from which the jumpoccurred.

trap handler. A user–defined trap routine usedwhen a trap occurs. See also exception.

1-159Glossary

Trash Can. In CDE, a container for deleted files orfolders.

traversal. See keyboard traversal.

tree delta. A SCCS file that has a trunk, withchanges identified by a release and level, and withone or more branches with deltas identified by anSID.

tree structure. A hierarchical calling sequence thatconsists of both a root segment and one or morelevels of the segments called by way of the rootsegment.

tree view. In CDE, a view of a folder or files thatincludes all lower–level folders in the search path.

triangular array. A two–dimensional array in whichactive elements are found only on one side of ahypothetical axis delineated by the first and lastelements of the array.

trimming loops. In GL, a set of oriented closedcurves used to set the boundaries of a NURBSsurface. See also NURBS.

Trivial File Transfer Protocol. Transfers filesbetween hosts using minimal protocol.

troff. A phototypesetting utility originally designedto support a Graphics Systems phototypesettingmachine, but now capable of supporting a varietyof phototypesetters.

true color. In Enhanced X-Windows, (1.) Adegenerate case of direct color in which thesubfields in the pixel value directly encode thecorresponding RGB values. That is, the color maphas predefined read–only RGB values. The valuesare typically near–linear increasing ramps. (2.) AlsoTrueColor, a value. (3.) Refers to the use of 24–bitsper pixel direct RGB, where there are 8 bits (256levels) of red, 8 bits (256 levels) of green, and 8bits (256 levels) of blue, for a total of 256*256*256or 16,777,216 different combinations of red, green,and blue intensities. The number of differentcolored pixels that can then be simultaneouslydisplayed is only limited by the number of pixelsdisplayable from the frame buffer.

truncate. (1.) To end a computational process inaccordance with some rule; for example, to end theevaluation of a power series at a specified term.(2.) To remove the beginning or ending elements ofa string. (3.) To drop data that cannot be printed ordisplayed in the line width specified or available.Contrast with fold. (4.) To shorten a field orstatement to a specified length.

trust peer. A characterization of one cell withrespect to another with which the cell maintains amutual authentication surrogate.

trusted computing base (TCB). The part of thesystem that contains all the elements that supportthe security policy of the system. The trustedcomputing base includes all hardware, microcode,and software that protect information on thesystem.

trusted device. An IPL device such as a fixed diskor diskette drive, where the IPL ROM code can findan IPL record and IPL code.

trusted environment. A clean environment inwhich all untrusted processes have been killedorder to ensure security for communicationsbetween the user and the operating system.

trusted path. See trusted environment.

trusted process. A process in which a particularstandard of security has been met.

try block. A C++ block in which a known exceptionis passed to a handler.

TS. See transmission services.

TSO Time Sharing Option.

tty. In the operating system, any device that usesthe termio standard terminal device interface. ttydevices typically perform input and output on acharacter–by–character basis.

tty device. See tty.

tuning. See hand tuning.

turnaround. Changing a communications line fromtransmit mode to receive mode, or from receivemode to transmit mode.

twist. A rotation around the line of sight.

two and one–half dimension. See 2–1/2dimension.

two–way channel. In X.25 communications, alogical channel that allows both incoming andoutgoing calls. Contrast with one–way channel.

twos complement. The radix complement in thepure binary numeration system. The twoscomplement is derived by taking the onescomplement and then adding one to the resultingnumber. In a twos complement system, the twoscomplement of a number n is –n. See also onescomplement.

type. (1.) In Enhanced X-Windows, an arbitraryatom used to identify the data. A type is solely forthe benefit of clients and is not interpreted by theserver. Enhanced X-Windows predefines typeatoms for many frequently used types. Clients alsocan define new types. (2.) In Pascal, see data type.(3.) In NCS, a class of object. All objects of a

1-160 Glossary

specific type can be accessed though the sameinterface or interfaces. (4.) In Ada language, a typecharacterizes both a set of values, and a set ofoperations applicable to those values. A typedefinition is a language construct that defines atype. A particular type is either an access type, anarray type, a private type, a record type, a scalartype, or a task type. (5.) In XOM, a category intowhich attribute values are placed on the basis oftheir purpose.

type compatibility. See compatible types.

type conversion. A routine or set of routines thatenables an application to change a specified stringof data from one declared type to another. InAIXwindows programming, type conversion isperformed on strings using conversion informationcontained in the MRM database.

type declaration. The specification of the typeand, optionally, the length of a variable or functionin a specification statement.

type definition. A definition of a name for a datatype.

type identifier. The name given to a declared type.See also type specifier.

type regrouping. An optimization that involvesreodering mixed–type expressions so that allvariables of a given type are grouped together.

type specifier. A name of a data type. See alsotype identifier.

type style. The form of characters of a given size,style, and design within the set of the same font.

type UUID. (1.) A UUID that permanently identifiesa particular type. Both the RPC run time library andthe Location Broker use type UUIDs to specifytypes. (2.) In DCE RPC, the UUID that identifies aparticular type of object and an associatedmanager. See also object and Universal UniqueIdentifier UUID.

typematic key. A key that, when held down,repeats its function multiple times.

1-161Glossary

UUA. See unnumbered acknowledge.

UART. See Universal AsynchronousReceive/Transmit.

ublock. See user block.

UCT. See Universal Coordinated Time.

UDP. See User Datagram Protocol.

UDP/IP. User Datagram Protocol/Internet Protocol.

UFS. See UNIX File System.

UI. See unnumbered information frame.

UID. See user number and AIXwindows UserInterface Definition.

UIL. See AIXwindows User Interface Language.

ultimate consumer. The target of data in an inputand output operation. An ultimate consumer can bea file, a device, or an array of bytes in memory.

ultimate producer. The source of data in an inputand output operation. An ultimate producer can bea file, a device, or an array of bytes in memory.

umask. The file–mode creation mask. The defaultpermissions that are set automatically when a file iscreated. These defaults can be changed byincluding an appropriate umask command in thesystem profile.

unary expression. An expression that containsone operand.

unary operator. An operator that represents anoperation on one operand. Contrast with binaryoperator.

unblocked. In an Enterprise Systems ConnectionDirector, the attribute that, when set, establishescommunications capability for a specific port.Contrast with block.

unconditional branch. A branch that is takenevery time it is encountered.

unconfigure. (1.) Indicates that a user is taking adevice from the available (configured) state to thedefined state. This is accomplished by running theunconfigure method for a device. The device statusfield in the Customized Devices Object Class wouldreflect this action. (2.) To take out of use by thecurrent computer system.

undefine. (1.) Indicates that a user is taking adevice instance out of the system. This isaccomplished by running the undefine method forthe device. All information for the device in theCustomized Database is purged by this operation.

(2.) To cause a command to no longer recognizedby the current computer system.

underlying editor. A large editor program, such asvi, of which another editor program, such as vedit,is a limited subset.

unescaped. In an expression, a character that isnot preceded by an escape sequence and istherefore interpreted as a control character. Seealso escape sequence.

unformatted file. A file displayed with data that isnot arranged with particular characters.

unidirectional printing. A printing method inwhich the print head on the printer prints only whileit moves in one direction, instead of also printingwhile it moves in the opposite direction. Thismethod of printing usually produces higher–qualityprint output.

union. A variable that can hold any one of severaldata types, but only one data type at a time.

union tag. The identifier that names a union datatype.

uniprocessor. A system containing a singleprocessor. As used in this book, the phrase”comparable uniprocessor” means a systemdesigned to have only a single processor, with thesame CPU–clock speed and cache capacity as theSMP system being discussed, running auniprocessor version of the operating system.Contrast with single–processor SMP system.

unit. (1.) In FORTRAN, a means of referring to afile to use input/output statements. A unit can beconnected or not connected to a file. If connected,it refers to the file. The connection is symmetric;that is, if a unit is connected to a file, the file isconnected to the unit. (2.) See also compilable unit.(3.) For Ada programming, synonym forcompilation unit.

unit cube. In GL, a volume defined by thefollowing planes: x = –1, x = 1, y=–1, y = 1, z = –1,z=1. See also normalized device coordinates.

unit identifier. In FORTRAN, the number thatspecifies an external unit or internal file. Thenumber can be one of the following: (1.) an integerexpression whose value must be zero or positive,(2.) an * (asterisk) that corresponds to unit 5 forinput or unit 6 for output, or (3.) the name of acharacter array, character array element, orcharacter substring for an internal file.

Universal Asynchronous Receive/Transmit. Acircuit used in asynchronous data communicationapplications to provide all the necessary logic torecover data in a serial–in parallel–out fashion and

1-162 Glossary

to transmit data in a parallel–in serial–out fashion.It is usually full–duplex, that is, it can transmit andreceive simultaneously with the option to handlevarious data work length.

Universal Coordinated Time (UCT). The newstandard term for worldwide time–telling that hasthe same meaning as Greenwich Mean Time.

Universal Unique Identifier (UUID). A 128–bitvalue used for identification. NCS uses UUIDs toidentify cells, interfaces, objects, and types. TheUUID for a cell, generated by the uuid_gen tool, iscompletely unique, having been created based onthe unique system ID of the workstation and a timestamp. Once generated, the cell UUID is placed inthe glb_obj.txt file. See also object UUID and typeUUID.

UNIX File System (UFS). A section of the UNIXfile tree that is physically contained on a singledevice or disk partition and that can be separatelymounted, dismounted, and administered.

UNIX–to–UNIX Copy Program (UUCP). (1.) Agroup of commands, programs, and files, presenton most UNIX systems, that allows the user tocommunicate with another UNIX system over adedicated line or a telephone line. See also BasicNetworking Utilities. (2.) The command (uucp) thatstarts file copying from one or more sources to asingle destination.

unmanaged widget. A widget whose size cannotbe changed.

unmapped window. A window that is not visibleon the screen.

unmarshal. In NCS, to copy data from a RemoteProcedure Call packet. Stubs performunmarshalling. Contrast with marshal.

unnumbered acknowledge (UA). A link controlframe.

unnumbered information (UI) frame. A frame inunnumbered format, used to transfer unnumberedcontrol functions.

unpredictable. A violation of an architecture rulethat an implementation is not required to report.Results can include an error report from a threadscall, the operating system, or the hardware; a hangor deadlock of the program; or an incorrectoperation of the program without indication of error.See also illegal.

unprivileged state. A hardware protection state inwhich the processor can only run unprivilegedinstructions. The processor’s unprivileged statesupports the virtual machine’s operating systemstate and problem state. Contrast with privilegedstate.

unreachable code. Code that cannot be reachedduring program execution. Unreachable code isdetected and removed as part of optimization.

unused subprograms. In Ada language,subprograms unused only within the context of aspecific program or set of units. For example, aprogram might call only a small subset ofsubprograms in a utility package. The remaininguncalled (unreachable) subprograms constituteunreachable code in the context of that program.

unviewable. Pertaining to a mapped window withan unmapped ancestor.

update. (1.) The procedure of modifying a programor program option that exists on the mass storagemedium of a computer, making the programexecutable, and ensuring that the modifiedprogram interacts properly with all other affectedprograms in the system. (2.) An improvement forsome part of the system. (3.) To add, change, ordelete items. (4.) To modify a master file withcurrent information according to a specifiedprocedure.

update propagation. An immediate attempt toapply a change to all replicas of the CDS directoryin which the change was just made. An updatepropagation delivers changes in a more efficientand timely way than a skulk, which is the periodicdistribution of a whole collection of changes.

update script. A shell script or executable filecreated by the developer of an application programto update the program. The script file must followspecific guidelines to be compatible with theprogram update tools that are provided in theoperating system.

Update Timestamp (UTS). An attribute thatidentifies the time at which the most recent changewas made to any attribute of a particular CDSname. For directories, the UTS reflects changesmade only to attributes that apply to the directoryas a whole (not one of its replicas).

upgrade. Software that fixes a defect in apreviously released software product.

upgrade locks. Locks used instead of read locksthat announce the potential need to also modify theprotected data. If an application obtains a read lockand possibly a write lock to the same data, anupgrade lock is less likely to deadlock.

upload. To transfer data from one computer toanother. Typically, users upload from a smallcomputer to a larger one.

upstream. The direction from driver to streamhead.

1-163Glossary

usage bindings. The language–specific bindingfiles for a class that are generated by the SOMCompiler for inclusion in client programs using theclass.

use clause. In Ada language, a clause thatachieves direct visibility of declarations that appearin the visible parts of named packages.

use–once license. In License Use Management, atype of license administrated by the license serverthat can be used for a single instance of invoking aproduct or of using a service. The license serverdecrements the number of use–once licenses eachtime the product is used.

user. (1.) The name associated with an account.(2.) Anyone requiring the services of a computingsystem.

user account. See account.

user address list. The address list that anindividual can use with the xtalk command to makeoutgoing X.25 calls. See also address list andsystem address list.

user area. The parts of main storage and diskavailable to the user.

user block. A data structure maintained by thekernel that contains system information about auser process, such as its real and effective userIDs, the list of open file descriptors, andsignal–handling settings. The user structure(defined in the /usr/include/sys/user.h header file)specifies the exact information that is kept in theuser block. See also per–process data area.

User Datagram Protocol (UDP). A packet–levelprotocol built directly on the Internet Protocol layer.UPD uses application–to–application programsbetween host systems.

user data segment. In kernel mode, the virtualmemory segment that contains user data, whichconsists of initialized data variables.

user–defined variable. A shell variable to whichthe user assigns a character string as a value.

user file. A text file that specifies the users whomay (or may not) use licensed software products.

user ID. See user identification.

user identification (user ID). (1.) One to eightalphanumeric characters, beginning with analphabetic, #, $, or > character, that identifies auser. This string of characters limits the functionsand information the operator can use. Often, theuser ID can be substituted in commands that take auser’s login name as a value. See also user

number. (2.) A parameter that specifies the user IDunder which the application or transaction programruns. Contrast with user name.

user interface. The hardware, software, or both bywhich a user communicates with a system,program, or device. Examples are a keyboard,mouse, command language, or windowingsubsystem.

user mode. A mode in which a process is carriedout in the user’s program rather than in the kernel.Contrast with kernel mode.

user name. A string of characters that uniquelyidentifies a user to the system. Contrast with useridentification.

user number (UID). A number that uniquelyidentifies a user to the system. It is the internalnumber associated with a user ID. See also useridentification (user ID).

user profile. A file in the user’s home directorynamed .profile that contains shell commands thatset initial user–defined characteristics and defaultsfor the login session.

user space. The address space seen by a processin user mode. See also user structure.

user structure. In kernel mode, the data area thatcontains information that must be accessible whilea process runs. One user structure is allocated foreach active process. See also per–process dataarea and user block.

user time. The amount of time a program isrunning in the CPU. Does not include timeassociated with operating system services providedto the program, the program’s I/O time, or time inwhich other processes preempt the program’s useof the CPU.

USOC–RJ11. A miniature telephone jack.

UTC. See Universal Coordinated Time.

utility. (1.) A service. In programming, a programthat performs a common service function. (2.) Thecapability of a system, program, or device toperform the functions for which it is designed.

UTS. See Update Timestamp.

UUCP. See UNIX–to–UNIX Copy Program.

UUCP login ID. A login name, provided with theBasic Networking Utilities (BNU), that has completeaccess to all BNU files and directories. See alsoBasic Networking Utilities.

UUID. See Universal Unique Identifier.

1-164 Glossary

VV. Volt.

V.24. The 24th CCITT recommendation in the Vseries, listing the definitions for interchange circuitsbetween a DTE and a DCE.

V.35. The 35th CCITT recommendation in the Vseries, defining data transmission at 48 kilobits persecond using 60–180 kHz group band circuits.

v–node. Virtual i–node. An object in a file systemthat represents a file. Unlike an i–node, there is noone–to–one correspondence between a v–nodeand the file system; multiple v–nodes can refer to asingle file (a single i–node). V–nodes are used tocommunicate between the upper half of the filesystem (the logical file system) and the file systemimplementations (such as the journaled file system,the network file system, and the CD–ROM filesystem).

valid. (1.) Allowed. (2.) True, or conforming to anappropriate standard or authority.

validation. In X.25 communications, the processby which the receiving DTE accepts the packetsize, packet window size, and throughput classsent by the sending DTE, on the conditions thatthey are valid. Contrast with negotiation.

valuator. (1.) An input device that provides a scalevalue; for example, a thumb wheel or apotentiometer. (2.) In GL, an input/output devicethat returns a value in a range. For example, amouse is logically two valuators: the x position andthe y position. See also dial.

value. (1.) A set of characters or a quantityassociated with a parameter or name. (2.) Inprogramming, the contents of a variable or astorage location. (3.) A specific occurrence of anattribute, such as blue for the attribute color. (4.) Aquantity assigned to a constant, variable,parameter, or symbol. (5.) In XOM, an arbitrarilycomplex information item that can be viewed as acharacteristic or property of an object. See alsoattribute value.

value logging. In the SOM ReplicationFramework, a technique for maintainingconsistency among replicas of a replicated object,whereby the new value of the object is distributedafter the execution of a method that updates theobject.

variable. (1.) A name used to represent a dataitem whose value can change while the program isrunning. Contrast with constant. (2.) Inprogramming languages, a language object thatcan take different values at different times. (3.) A

quantity that can assume any of a given set ofvalues. (4.) For Ada programming, see object.

variable length field. A field of varying length thatcontains data prefaced by an internal, opaque fieldproviding the length of the field.

variable substitution. The ability to change anddisplay the values of variables in a string, replacinga name of a variable with the value it represents.

variant part. In Pascal, the part of a record thatcan vary from one instance of the record toanother. The variant part consists of alternatesequences of fields that share the same physicalstorage. In Ada language, a variant part of a recordspecifies alternative record components,depending on a discriminant of the record. Eachvalue of the discriminant establishes a particularalternative of the variant part. See also tag field.

VC. See virtual circuit.

vchar. In ODM, a terminal descriptor type used todefine a variable as a variable–length,null–terminated string. See also terminal descriptor.

VCI. Virtual channel identifier in an ATM network.

VDD. See virtual device driver.

vector. (1.) An array of one dimension. (2.) Aquantity usually characterized by an ordered set ofnumbers. (3.) In computer graphics, a directed linesegment.

vector graphics. (1.) Graphics for which thedisplay images are generated from coordinates, asopposed to an array of pixels. (2.) The mostcommon class of graphics, where all vector outputconsists of lines and curves drawn point–to–pointby the output unit as ordered by the computer.

vector product. Another term for the vector crossproduct. If a = (a1, a2, a3) and b = (b1, b2, b3) aretwo three–dimensional vectors, the vector producta times b = (a2b3–b2a3, a3b1–b3a1, a1b2–b1a2).

vendor ID. In License Use Management, theidentifier of a vendor of licensed products. Bymeans of vendor IDs, license servers candistinguish among any number of vendorsestablished in a network. Vendor IDs are anLicense Use Management–specific usage ofNetwork Computing System Universal UniqueIdentifiers (UUIDs).

vendor password. In License Use Management, astring encoded with information about a vendorthat, together with a vendor ID, establishes thevendor of a licensed product in a license database.

verify. (1.) To confirm the correctness. (2.) Todetermine whether a transcription of data or otheroperation has been accomplished accurately. (3.)

1-165Glossary

In software installation, the verify procedureinstructs the system to verify the software you areinstalling. The system confirms that your softwarefiles are the correct length and contain the correctnumber of digits and characters. If any errors arereported, it might be necessary to install thesoftware product again. The verification processcan add a significant amount of time to theinstallation process.

Versatile Message Transfer Protocol (VMTP). Aprotocol that provides datagram communicationservice at the user level. Unlike most programs thatuse UDP/IP, programs using VMTP do not have toimplement time out, retransmission, or estimationof network delays because the VMTP protocolprovides end–to–end datagram delivery.

version. A particular instance of an applicationprogram or licensed program. The version, release,modification, and fix levels of a program. Theversion, release, modification, and fix levelstogether comprise the program level or version of aprogram. A new version of a program usually hassignificant new code or functions compared to theprevious version. See also fix number, programlevel, modification number, release number, andversion number.

version control. The process by which thecontents of each revision of software, hardware, ordocumentation are accounted for.

version identifier. In License Use Management, astring that identifies a version of a product; bymeans of version identifiers, the license serverdistinguishes among different versions of aproduct.

version number. The version level of a program,which is an indicator of the hardware and basicoperating system upon which the programoperates. The version, release, modification, andfix levels together comprise the program level orversion of a program. See also fix number,modification number, release number, version andprogram level.

vertical retrace. (1.) The rate at which the monitoris refreshed. A 60 Hz monitor is redrawn 60 timesper second. Synonymous with refresh rate. (2.)The action of moving the electron beam from thebottom to the top of the screen.

vertical retrace period. The amount of elapsedtime between retraces of the screen. All videomonitors use an electron beam to sweep thephosphors at the face of the monitor. Because thephosphors glow for only a brief period of time, theentire screen must be reswept periodically by theelectron beam. On most monitors, this is done 30

times per second (30 Hz). Thus, the vertical retraceperiod is 1/30 second.

vhandle. An identifier for each object in VEOS.vhandles are used in graphics programming toidentify software objects specified in VEOS. Thevhandle can exist longer than the object that itidentifies. After a software object such as a swidgetis destroyed, the vhandle for that object remainsdefined.

video lookup table (VLT). A colormapimplemented in hardware.

view–data paradigm. A SOM ReplicationFramework construct similar to theModel–View–Controller paradigm in SmallTalk. The”view” object contains only presentation–specificinformation, while the ”data” object contains thestate of the application. The ”view” and ”data” areconnected by means of an ”observation” protocolthat lets the ”view” be notified whenever the ”data”changes.

viewable. Pertaining to a mapped window whoseancestors are all mapped; not necessarily visible.Graphics requests can be performed on a windowwhen it is not viewable, but output will not beretained unless the server is maintaining backingstore.

viewer coordinates. Synonym for eyecoordinates.

viewing coordinates. Synonym for eyecoordinates.

viewing matrix. In GL, a matrix used to describethe location of the viewer (the virtual eye lookingupon a scene) in relation to the world. See alsofield of view, transformation, and world coordinates.

viewport. In GL, the mapping from normalizeddevice coordinates to device coordinates. Theviewport maps the unit cube x/w = +/–1, y/w = +/–1,z/w = +/–1 to the screen space, as measured inpixels. The viewport is the last transformation in thegraphics pipeline. The viewport can be smaller orlarger than the window and smaller or larger thanthe screenmask, although in most applications, it isthe same size.

virtual address. The address of a location invirtual storage. A virtual address must be translatedinto a real address for the data or instruction itaddresses to be accessible to the CPU.

virtual call facility . In data communications, auser facility in which a call–setup procedure and acall–clearing procedure determine a period ofcommunication between two data terminalequipment (DTEs) in which user data is transferred

1-166 Glossary

in the network in the packet mode of operation. Alluser data is delivered from the network in the orderit is received by the network. It is the packetnetwork equivalent of a dialed line.

virtual circuit (VC). In X.25 communications,those facilities provided by a network that give theappearance to the user of an actual connection.See also switched virtual circuit and permanentvirtual circuit.

virtual device. A device that appears to the useras a separate entity, but is actually a shared portionof a real device.

virtual device driver (VDD). Synonym for devicehandler.

virtual file system (VFS). A remote file systemthat has been mounted so that it is accessible tothe local user.

virtual function. A C++ member function that isdeclared with the keyword virtual. Theimplementation that is executed when you make acall to a virtual function depends on the type of theobject for which it is called. This is determined atrun time.

virtual key binding. In AIXwindows, theuser–designed key definitions.

virtual memory. Addressable space that appearsto be real storage. From virtual storage,instructions and data are mapped into real storagelocations. The size of virtual storage is limited bythe addressing scheme of the computer systemand by the amount of auxiliary storage available,not by the actual number of system memorylocations. Contrast with real memory. Synonymouswith virtual storage.

virtual mount point. The directory or file in the filetree where another file system is mounted. Forexample, if /dev/hd9 is mounted on /fred , then/fred is the virtual mount point.

virtual printer. A view of a printer that refers onlyto the high–level data stream (such as ASCII orPostScript) that the printer understands. It does notinclude any information about how the printerhardware is attached to the host computer or theprotocol used for transferring bytes of data to andfrom the printer.

virtual printer definition. A set of attributes valuesthat describe a particular data stream for aparticular printer.

virtual storage. Synonym for virtual memory.

Virtual Storage Extended (VSE). An operatingsystem that is an extension of DOS. A VSE systemconsists of licensed VSE/Advanced Functions

support plus all programs required to meet the dataprocessing needs of the user. Together with thehardware it controls, VSE forms a complete dataprocessing system. Its current version is calledVSE/ESA.

Virtual Storage Extended/Enterprise SystemsArchitecture(VSE/ESA). The VSE operatingsystem operating in an ESA environment. ESA isan extension to the System/370 architecture andincludes an advanced addressability feature thatprovides access registers.

Virtual Storage Extended/System Product(VSE/SP). A licensed program providing VSEoperating system support.

Virtual Telecommunication Access Method(VTAM). A licensed program that controlscommunication and data flow in an SNA network. Itprovides single–domain, multiple–domain, andinterconnected network capability, and alsosupports application programs and subsystems.

visibility. In Ada language, at a given point in aprogram text, the declaration of an entity with acertain identifier is said to be visible if the entity isan acceptable meaning for an occurrence at thatpoint of the identifier. The declaration is visible byselection at the place of the selector in a selectedcomponent or at the place of the name in a namedassociation. Otherwise, the declaration is directlyvisible, that is, if the identifier alone has thatmeaning.

visible. (1.) A region of a window that is mappedand not occluded on the screen by another window.(2.) Visibility of C++ identifiers is based on scopingrules and is independent of access.

visible part. For Ada programming, see package.

VLSI. Very large scale integration.

VLSI circuit. Very large scale integrated circuit.

VLT. See video lookup table.

VM. Virtual machine.

VM/CMS. A type of operating system used on aSystem/370 computer.

VMTP. See Versatile Message TransactionProtocol.

VOL. See Volume Service.

Vol ID. See Volume ID.

volatile attribute. The keyword volatile located ina definition, declaration, or cast. It causes the Clanguage compiler to place the value of the dataobject in storage and to reload this value at eachreference to the data object.

1-167Glossary

volatile register. In a C language program, aregister whose value on entry need not bepreserved when the called routine returns.

volume. (1.) A certain portion of data, together withits data carrier, that can be handled conveniently asa unit. (2.) The level of sound of the system. (3.)The physical storage location of a file system. Seealso log volume.

volume group (VG). A set of one or more physicalvolumes from which space can be allocated to oneor more logical volumes. A collection of 1 to 32physical volumes (read–write fixed–disk drives) ofvarying size and type. See also logical volume.

Volume ID (Vol ID). A series of characters,recorded on the diskette, used to identify thediskette to the user and to the system.

volume label. An area on tape or disk that is usedto identify the tape volume and its owner.

Volume Service (VOL). The component of EncinaBase that addresses storage.

VPD. See Software Vital Product Data (SWVPD).

VPI. Virtual path identifier in an ATM network.

VRAM. Video random–access memory.

VSE. See Virtual Storage Extended.

VSE/ESA. See Virtual StorageExtended/Enterprise Systems Architecture.

VSE/SP. See Virtual Storage Extended/SystemProduct.

VTAM. See Virtual Telecommunication AccessMethod.

VTL. Vendor Technology Logic.

1-168 Glossary

WWAN. See wide area network.

WAN links. Communications connections betweengroups of computers that are spread across a largegeographical distance. Modem connections, T1lines, and satellite hookups are some commonexamples. See also wide area network.

water mark. A limit value used in flow control.Each queue has a high–water mark and alow–water mark. The high–water mark valueindicates the upper limit related to the number ofbytes contained on the queue. When thecharacters in a queue reach the high–water mark,STREAMS causes another queue that attempts tosend a message to this queue to become blocked.When the characters in this queue are reduced tothe low–water mark value, the other queue isunblocked by STREAMS.

Web–based System Manager. A graphical userinterface (GUI) tool for managing AIX systems.Based on the OO (Object Oriented) model,Web–based System Manager enables users toperform administration tasks by manipulating iconsrepresenting objects in the system, as analternative to learning and remembering complexAIX commands.

well–known host name. A conventional nameassociated with an Internet Protocol address on aparticular network (for example, the nameserverand timeserver servers).

well–known port. A conventional port assignmentused by hosts that support the same protocols,whether or not the hosts are on the same network.Synonymous with contact port.

while statement. A C language looping statementthat contains the keyword while followed by anexpression in parentheses (the condition) and astatement (the action).

white space. Space characters, tab characters,and new–line characters.

wide area network (WAN). A network thatprovides data communication capability ingeographic areas larger than those serviced bylocal area networks. A network that includescomputers spread across a large geographicaldistance, usually involving several cities, states, orcountries.

wide band channel. A communications channelthat has a greater bandwidth than a voice channel;

therefore, it is capable of transmitting data at highspeeds. Synonym for broadband channel.

widening. An expansion of the size of a value (forexample, short to int) by padding bits located tothe left of the value with a copy of the sign bit.

widget. (1.) The fundamental data type of theEnhanced X-Windows Toolkit. (2.) An objectproviding a user–interface abstraction; for example,Scrollbar widget. It is the combination of anEnhanced X-Windows (or subwindow) and itsassociated semantics. Logically, it is a rectanglewith associated input and output semantics,although some can be input–only or output–only.Each widget belongs to one widget class. A widgetimplements procedures through its widget classstructure. See also composite widget, core widget,primitive widget, and shell widget. (3.) A widget is agraphic device capable of receiving input from thekeyboard and the mouse and communicating withan application or another widget by means of acallback. Every widget is a member of only oneclass and always has a window associated with it.

widget class. The general group that a specificwidget belongs to, otherwise known as the widgettype. Physically, it is a pointer to a structure.Synonymous with widget type. See also class.

widget gravity. Synonym for window gravity.

widget hierarchy. Synonymous with widget tree.

widget ID. A unique identification numberassociated with each widget instantiated in aninterface.

widget instance. A specific widget object asopposed to a general widget class. It is composedof a data structure containing instance–specificvalues and another data structure containinginformation applicable to all widgets of that class.See also instance.

widget menu. A menu that allows the user toperform any number of actions, such as cutting,copying, and pasting, to selected widgets.

widget programmer. A programmer who addsnew widgets to the Enhanced X-Windows (or other)Toolkit.

widget record. A collection of related data objects,such as variables and parameters, associated withany given widget. See also instance record, record,class record, and superclass.

widget tree. (1.) The symbolic structure forEnhanced X-Windows Toolkit code. The basicelement is a widget class. See also leaves,intermediate nodes, and root. (2.) A widget tree is a

1-169Glossary

hierarchy of widgets within a specific clientapplication. The Shell widget is the root of thewidget tree. Widgets with no children of any kindare leaves of the tree. Synonymous with widgethierarchy.

widget type. Synonym for widget class.

widget visibility. Contrast with obscure andocclude.

wildcard. Special characters such as * (asterisk) or? (question mark) that can be used to match one ormore characters. Synonymous withpattern–matching character.

window. (1.) In AIXwindows, rectangular area ofthe screen that can be moved about, placed on topof or pulled under other windows, or iconized bythe user. (2.) In GL, all drawing inside the windowis done by the GL process that created thatwindow, and is totally under the control of thatprocess. However, the drawing of the windowborders together with the windowplacement/iconization, is under the control of thewindow manager; for example, the AIXwindowsWindow Manager. For most simple GL programs,the viewport and screenmask are set to the samesize as the window. Do not confuse an AIXwindowssubroutine with the GL window subroutine, whichdefines a frustum in world space. See also clippingand current window. (3.) In curses and extendedcurses, the internal representation of what aportion of the display may look like at some point intime. Windows can be any size, from the entiredisplay screen to a single character. (4.) In datacommunications, the number of data packets aDTE or DCE can send across a logical channelbefore waiting for authorization to send anotherdata packet. The window is the main mechanism ofpacing, or flow control, of packets. See also framewindow and packet window. (5.) In the INed editor,an area within the display screen that can besubdivided into a collection of contiguous panesused to present data to the user.

window gravity. The attraction of a subwindow tosome part of its parent. Window gravity causessubwindows to be automatically repositioned,relative to an edge, corner, or center of a windowwhen resized. Synonymous with widget gravity.See also gravity.

window icon. In CDE, a minimized window.

window ID. A unique identification numberassociated with each newly opened window in anAIXwindows or Enhanced X-Windows environment.

window manager. In CDE Desktop, the programthat displays and controls windows on your screen.Software that manages the multiple windowsassociated with AIXwindows and Enhanced

X-Windows. In a graphics environment, the clientthat manipulates windows on a screen andprovides much of the user interface. See alsomwm.

Window Manager. In CDE, the softwareapplication that provides users with the capability tomanipulate windows on the workspace; forexample, opening, resizing, moving, and closingwindows.

Window menu. In CDE, the menu displayed bychoosing the Window menu button. The menuprovides choices that manipulate the location orsize of the window, such as Move, Size, Minimize,and Maximize.

Window menu button. In CDE, the control at theupper left corner of a window, next to the title bar.Choosing it displays the Window menu.

wire frame. A graphics surface–drawing techniquein which the edges and contours of a primitive arerepresented by simple lines.

with clause. For Ada programming, seecompilation unit.

word. (1.) A contiguous series of 32 bits (fourbytes) in storage, addressable as a unit. Theaddress of the first byte of a word is evenly divisibleby four. Synonymous with fullword, machine word,and computer word. Contrast with halfword. (2.) Acharacter string considered as a unit for a givenpurpose.

word wrap. In word processing, a feature thatautomatically moves text to the next line if the textdoes not fit within the margins.

work area. In CDE, the part of a window wherecontrols and text appear.

work file. A file used for temporary storage of databeing processed.

working directory. Synonym for current directory.

working segment. A segment whose pages arebacked by slots in the disk paging space ratherthan by a permanent location on disk.

working set. The parts of a program’s executablecode, data areas, or both that are being usedintensively and are therefore important to keep inthe fastest possible type of storage. Thus aprogram’s instruction cache working set is the setof program cache lines that need to be kept in theinstruction cache if the program is to run atmaximum speed.

workload. A sequence of requests, such ascommands, I/O operations, and subroutine–librarycalls, that constitute the work being done by asystem. The term normally refers to a workload

1-170 Glossary

that has been captured in such a way as to berepeatable (via shell scripts, remote terminalemulators), so that it can be used to measure theperformance effect of changes to the system.

workload concurrency. The degree to which thesystem approaches the ideal of always having asmany dispatchable threads as there areprocessors.

workspace. (1.) In XDS/XOM, a space in whichOM objects of certain OM classes can be created,together with an implementation of the objectmanagement functions that supports those OMclasses. (2.) In CDE, the current screen display, theicons and windows it contains, and the unoccupiedscreen area where icons can be placed.

workspace background. In CDE, the portion ofthe display not covered by windows or icons.

workspace icon. In CDE, an icon that has beencopied from File Manager to the workspace.

workspace interface. The interface as realized,for the dispatcher’s benefit, by each workspaceindividually.

Workspace Manager. In CDE, the softwareapplication that controls the size, placement, andoperation of windows within multiple workspaces.

Workspace menu. In CDE, the menu displayed bypointing at an unoccupied area of the workspaceand clicking button 3 on the mouse.

workspace object. In CDE, an object that residesin a workspace, rather than inside a viewer in awindow. Workspace objects include windows, icons(minimized windows), and objects that have beendragged from File Manager and ApplicationManager and dropped on a workspace.

workspace switch. In CDE, a control that enablesyou to select one workspace from among severalworkspaces.

workspace switch area. In CDE, the rectangulararea in the center of the Front Panel that containsthe workspace switches, the Lock control, the Exitbutton, and the busy light.

workstation. (1.) A configuration of input/outputequipment at which an operator works. (2.) Aterminal or microcomputer, usually one that isconnected to a mainframe or to a network, at whicha user can perform applications. See also terminal.

world coordinates. In GL, the user–definedcoordinate system in which an image is described.Modeling commands are used to position primitivesin world space. Viewing and projectiontransformations define the mapping of the world

space to screen space. Synonymous with worldspace. See also modeling coordinates, eyecoordinates, primitive coordinates, screencoordinates, viewing matrxi, and transformation.

world space. Synonym for world coordinates.

wrap around. (1.) The movement of the point ofreference in a file from the end of one line to thebeginning of the next, or from one end of a file tothe other. (2.) In display–based word processingequipment, the automatic disposition of a printableline of text onto two or more display lines,necessitated by the horizontal limits of the display.(3.) The continuation of an operation from themaximum addressable location in storage to thefirst addressable location. (4.) The continuation ofregister addresses from the highest registeraddress to the lowest.

wrap test. A test that checks attachment orcontroller circuitry without testing the device itselfby returning the output of the device as input.

Wrap To Fit. In CDE, in Text Editor, this settingcontrols whether lines are automatically wrapped tofit the window width as you enter text. If set, lineswrap at the edge of the window. If not set, you mustpress Return to end the line.

write–ahead logging. A logging mechanismwherein all of the log records associated with atransaction are written to the log before thetransaction actually commits. This guarantees thatthose log records will be present in the log and cantherefore be used to restore recoverable data to acorrect state should the system fail at the exacttime of a transaction commit.

write back cache. In Enhanced X-Windows, GCscached by the library to allow merging independentchange requests into one protocol request. Seealso cache.

write queue. The message queue in a module ordriver containing messages moving downstream.Associated with output from a user process.

write verification. A mode in which the systemautomatically performs a read operation afterperforming a write operation. It then compares thedata to make sure they are the same.

writemask. A set of 8 or 12 bits (depending on theframe buffer configuration), one bit for eachbitplane of the frame buffer. During any drawingoperation, only those planes enabled by a 1 (one)in the bit mask can be altered. Planes set to 0(zero) are marked read only.

writers. See readers and writers.

1-171Glossary

XX Atom. An Enhanced X-Windows atom. See alsoatom.

X resource. In AIXwindows, synonymous withresource.

X resource file. In AIXwindows, an ASCII file thatincludes the definition of all property values thatwere specified as Public in the Widget PropertyEditor. Such files are editable by the end user.

X Server. See server.

X Toolkit. See AIXwindows Toolkit.

X–Windows. A network–transparent windowingsystem developed by MIT. It is the basis forEnhanced X-Windows, which runs on the AIXOperating System. See also X11 client.

X.3. The CCITT recommendation that specifies theservice provided to an asynchronous (start/stop)device by a packet assembler/disassembler (PAD).

X11 client. An application that is compatible withversion X11 of Enhanced X-Windows. See alsoX–Windows.

X.21. In data communications, the 21st CCITTrecommendation in the X series, defining theconnection of data terminal equipment to an X.21public data network for digital leased andcircuit–switched services. In X.25 communications,X.21 is available at the physical level only.

X.21 bis. A CCITT recommendation, defining theuse on public data networks of DTEs designed forinterface to synchronous V series modems.

X.25. The 25th CCITT recommendation in the Xseries, defining the interface between data terminalequipment and packet switching data networks.

X.25 adapter. Synonym for X.25 InterfaceCo-Processor/2.

X.25 Interface Co-Processor/2. The separatelyorderable adapter card that attaches a system unitto an X.25 packet switching data network.Synonymous with X.25 adapter.

X.25 line. In X.25 communications, the physicallink between the DTE and the DCE, and theservice subscribed to. See also communicationsline.

X.25 link. The X.25 line from the X.25 adapter tothe network terminating unit. In the X.25 API, a linkis equivalent to an X.25 port. See also X.25 portand data link.

X.25 network. A service providingpacket–switched data transmission that conformsto Recommendation X.25 adopted by the CCITT.

X.25 port. A device in the /dev directory thatcorresponds to an X.25 link. See also X.25 link.

X.28. The CCITT recommendation that specifiesthe user interface between an asynchronous(start/stop) device and a packetassembler/disassembler (PAD).

X.29. The CCITT recommendation that specifiesthe user interface between a DTE and a remotepacket assembler/disassembler (PAD).

X.121. The 121st CCITT recommendation in the Xseries, defining a convention for the network useraddress (NUA).

XCOFF. See extended common object file format.

xcomms. The command that provides a menupanel for other X.25 commands (the xmanage,xroute, and xtalk commands).

XDR. See External Data Representation.

XDS. The X/Open Directory Service.

XGSL. See Graphics Support Library.

XID. See exchange identification.

XID Node ID. A field that provides the node ID ofthe physical unit. This value is the ID that isexchanged with the remote physical unit when aconnection is first established during the XIDoperation.

Xlib. In Enhanced X-Windows, a C languagesubroutine library that client programs use tointerface with the windowing system.

Xlib call. See Xlib.

xmanage. The command that enables systemmanagers to manage X.25 ports.

Xmodem protocol. A communications protocol inwhich messages are sent in blocks of 128characters, surrounded by control characters. Thisprotocol also uses the checksum program for errorchecking. The xmodem protocol can detect datatransmission errors and then retransmit the data.

xmonitor. The command that enables systemmanagers to monitor activity on X.25 ports.

xmpeek. A program that allows you to ask anyhost about the status of its xmservd daemon.

XNS. Xerox Network Systems. The networkarchitecture developed by the Xerox Corporation inthe 1970s. The XNS Internet protocol suite is

1-172 Glossary

similar to the TCP/IP suite. However, differentpacket formats and terminology are used.

XOM. X/Open Object Management.

xroute. The command that enables systemmanagers to manage the X.25 routing list.

Xt intrinsics. See intrinsics.

xtalk. The command that enables users to useX.25 to converse with other users, exchangemessages and files, and manage X.25 addresslists.

XTI. X/Open Transport Interface. A libraryimplementation, as specified by X/OPEN CAE

Specification of X/Open Transport Interface andfully conformant to X/OPEN and XPG4 CommonApplication Environment (CAE) specification, thatdefines a set of transport–level services that areindependent of any specific transport provider’sprotocol or its framework.

XTISO. XTI over SOckets.

XY format. The format of a pixmap organized as aset of bitmaps representing individual bit planesthat appear in most–significant to least–significantbit order. See also Z format.

1-173Glossary

YY/C signal. A yellow/chroma signal. Y(yellow)represents luminance and C represents chroma(color). The luminance contains both the image

detail and intensity levels, while the chroma has thecolor information for the image.

yacc source file. File containing yaccprogramming language code.

yank. To copy a word or line of text into memory.

1-174 Glossary

Zz–buffer or z–buffering. In 3D computer graphics,applies both to the device and the techniquescommonly used as an aid in removing hidden linesand hidden surfaces. If z–buffering is enabled,each pixel stores a depth value as well as a colorvalue. In simple terms, the depth can be thought ofas the distance from the viewer’s eye to the pixel.Whenever a drawing routine tries to update a pixel,it first checks the current pixel’s ”depth” or”z–value” and will only update that pixel with newvalues if the new pixel is closer than the currentpixel. The region of memory that stores thez–values is also referred to as the z–buffer. Seealso hidden surface.

Z format. The format of a pixmap organized as aset of pixel values in scanline order. See also XYformat.

zero bit insertion and deletion. Inserting a zeroafter every four 1–bits and then removing the zerosto return the data to normal.

zero suppression. The removal or substitution ofblanks for leading zeros in a number. For example,00057 becomes 57 when using zero suppression.

zombie process. An ended process whose entryremains in the process table, but to which a user orkernel space is not allocated. A process becomes azombie process when it issues the exit subroutineand the following circumstances occur: Its parentprocess is not running a wait subroutine and hasnot set its SIGCLD signal action to the SIG_IGNvalue indicating that it does not intend to wait for itschildren to finish.

zone of authority. The set of names managed bya single name server.

zoom factor. A multiplier to determine the amountof enlargement of a specified screen rectangle.The x zoom factor determines the enlargement inthe x direction; the y zoom factor determines theenlargement in the y direction.

zooming. In computer graphics, the progressivescaling of a display image to give the visualimpression of going from a faraway view of animage to a close–up view, or a close–up view to afaraway view.

Vos remarques sur ce document / Technical publication remark form

Titre / Title : Bull AIX Glossary

Nº Reférence / Reference Nº : 86 A2 79JX 01 Daté / Dated : December 1998

ERREURS DETECTEES / ERRORS IN PUBLICATION

AMELIORATIONS SUGGEREES / SUGGESTIONS FOR IMPROVEMENT TO PUBLICATION

Vos remarques et suggestions seront examinées attentivement.

Si vous désirez une réponse écrite, veuillez indiquer ci-après votre adresse postale complète.

Your comments will be promptly investigated by qualified technical personnel and action will be taken as required.

If you require a written reply, please furnish your complete mailing address below.

NOM / NAME : Date :

SOCIETE / COMPANY :

ADRESSE / ADDRESS :

Remettez cet imprimé à un responsable BULL ou envoyez-le directement à :

Please give this technical publication remark form to your BULL representative or mail to:

BULL ELECTRONICS ANGERS

CEDOC

34 Rue du Nid de Pie – BP 428

49004 ANGERS CEDEX 01

FRANCE

Technical Publications Ordering Form

Bon de Commande de Documents Techniques

To order additional publications, please fill up a copy of this form and send it via mail to:

Pour commander des documents techniques, remplissez une copie de ce formulaire et envoyez-la à :

BULL ELECTRONICS ANGERSCEDOCATTN / MME DUMOULIN34 Rue du Nid de Pie – BP 42849004 ANGERS CEDEX 01FRANCE

Managers / Gestionnaires :Mrs. / Mme : C. DUMOULIN +33 (0) 2 41 73 76 65Mr. / M : L. CHERUBIN +33 (0) 2 41 73 63 96

FAX : +33 (0) 2 41 73 60 19E–Mail / Courrier Electronique : srv.Cedoc@franp.bull.fr

Or visit our web site at: / Ou visitez notre site web à:

http://www–frec.bull.com (PUBLICATIONS, Technical Literature, Ordering Form)

CEDOC Reference #No Référence CEDOC

QtyQté

CEDOC Reference #No Référence CEDOC

QtyQté

CEDOC Reference #No Référence CEDOC

QtyQté

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

_ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ] _ _ _ _ _ _ _ _ _ [ _ _ ]

[ _ _ ] : no revision number means latest revision / pas de numéro de révision signifie révision la plus récente

NOM / NAME : Date :

SOCIETE / COMPANY :

ADRESSE / ADDRESS :

PHONE / TELEPHONE : FAX :

E–MAIL :

For Bull Subsidiaries / Pour les Filiales Bull :

Identification:

For Bull Affiliated Customers / Pour les Clients Affiliés Bull :

Customer Code / Code Client :

For Bull Internal Customers / Pour les Clients Internes Bull :

Budgetary Section / Section Budgétaire :

For Others / Pour les Autres :

Please ask your Bull representative. / Merci de demander à votre contact Bull.

BULL ELECTRONICS ANGERS

CEDOC

34 Rue du Nid de Pie – BP 428

49004 ANGERS CEDEX 01

FRANCE

86 A2 79JX 01

ORDER REFERENCE

PLA

CE

BA

R C

OD

E I

N L

OW

ER

LE

FT

CO

RN

ER

Utiliser les marques de découpe pour obtenir les étiquettes.

Use the cut marks to get the labels.

AIX

86 A2 79JX 01

AIX Glossary

AIX

86 A2 79JX 01

AIX Glossary

AIX

86 A2 79JX 01

AIX Glossary