SoftwareDevelopmentforEngineers

withC,Pascal,C++,AssemblyLanguage,VisualBasic,HTML,JavaScriptandJava

WilliamJ.Buchanan,BSc,CEng,PhDSeniorLecturer,DepartmentofElectricalandElectronicEngineering,NapierUniversity,Edinburgh,UK

TableofContents

Coverimage

Titlepage

Dedication

Copyright

Preface

PARTA:C/PASCAL

Chapter1:Introduction

1.1Introduction

1.2Hardware,SoftwareAndFirmware

1.3BasicComputerArchitecture

1.4Compiling,LinkingAndProducingAnExecutableProgram

1.5CCompilation

1.6PascalCompilation

1.7IntroductionToC

1.8IntroductionToPascal

1.9Exercises

Chapter2:Input/Output

2.1Introduction

2.2PascalInput/Output

2.3CInput/Output

2.4Examples

Chapter3:SelectionStatements

3.1If…ElseStatements

3.2SwitchStatement

3.3Exercises

Chapter4:RepetitiveStatements

4.1Introduction

4.2For

4.3Examples

4.4Exercises

4.5While()

4.6Repeat..Until()AndDo..While()

4.7Examples

4.8Exercises

Chapter5:Functions

5.1Introduction

5.2ArgumentsAndParameters

5.3CFunctions

5.4PascalFunctions

5.5Examples

5.6Exercises

Chapter6:ParameterPassing

6.1Introduction

6.2PascalParameterPassing

6.3CParameterPassing

6.4Examples

6.5Exercises

Chapter7:Arrays

7.1Introduction

7.2CArrays

7.3PascalArrays

7.4Examples

7.5Exercises

Chapter8:Strings

8.1Introduction

8.2PascalStrings

8.3CCharacterArrays

8.4Examples

8.5Exercises

Chapter9:FileI/O

9.1Introduction

9.2PascalFileI/O

9.3CFileI/O

9.4Examples

9.5ReadingAndWritingOneCharacterAtATime

9.6Exercises

Chapter10:StructuresandRecords

10.1Introduction

10.2RecordsInPascal

10.3StructuresInC

10.4ArrayOfStructures

10.5Exercises

PARTB:C++

Chapter11:IntroductiontoC++

11.1Introduction

11.2EnhancementsToC++

11.3I/OStream

11.4Comments

11.5FunctionOverloading

11.6Classes

11.7ComplexNumbers

11.8Exercises

Chapter12:MoreC++

12.1ConstructorsAndDestructors

12.2FunctionTemplates

12.3ClassTemplates

12.4I/OStreams

12.5Exercises

PARTC:AssemblyLanguage

Chapter13:Introduction

13.1Introduction

13.2BasicComputerArchitecture

13.3BitsAndBytes

13.4BinaryArithmetic

13.5NumbersAndRepresentations

13.6MemoryAddressingSize

13.7Exercises

Chapter14:ComputerArchitecture

14.1HistoryOfThePC

14.2IntelMicroprocessors

14.380386/80486Microprocessor

14.4Registers

14.5MemorySegmentation

14.6ViewInsideTheProcessor

14.7MachineCodeAndAssemblyLanguage

14.8Exercises

Chapter15:8086/88Instructions

15.1Introduction

15.2CharactersAndNumbers

15.3Comments

15.4Move(MOV)

15.5AddressingMemory

15.6AdditionAndSubtraction(ADDAndSUB)

15.7Compare(CMP)

15.8UnaryOperations(INC,DECAndNEG)

15.9BooleanBitwiseInstructions(AND,OR,XORAndNOT)

15.10Shift/RotateInstructions(SHL,SAL,SHR,SAR,ROL,ROR,RCLAndRCR)

15.11UnconditionalJump(JMP)

15.12ConditionalJumps

15.13SubroutineCalls(CALLAndRET)

15.14PushAndPop

15.15MovingAroundDataInMemory

15.16AssemblerDirectives

15.17DataDefinition

15.18Equates(EQU)

15.19ExercisesPart1

15.20ExercisesPart2

Chapter16:8086InterfacingandTiming

16.1Introduction

16.2InterfacingWithMemory

16.3MemoryMappedI/O

16.4IsolatedI/O

16.5DigitalI/OUsingThe8255

16.6DigitalI/OPrograms

16.7Timing

16.8Exercises

Chapter17:8086Interrupts

17.1Interrupts(INT)

17.2Interrupt21h:DOSServices

17.3Interrupt10h:BIOSVideoMode

17.4Interrupt11h:BIOSEquipmentCheck

17.5Interrupt13h:BIOSDiskAccess

17.6Interrupt14h:BIOSSerialCommunications

17.7Interrupt17h:BIOSPrinter

17.8Interrupt16h:BIOSKeyboard

17.9Interrupt19h:BIOSReboot

17.10Interrupt1Ah:BIOSSystemTime

17.11CAndPascalInterrupts

17.12Exercises

PARTD:VisualBasic

Chapter18:Introduction

18.1Introduction

18.2Event-DrivenProgramming

18.3VisualBasicFiles

18.4OtherTerms

18.5MainScreen

18.6PropertiesWindow

18.7ControlsAndEvent

18.8Exercises

Chapter19:VisualBasicLanguage

19.1Introduction

19.2ProgrammingLanguage

19.3EnteringAProgram

19.4LanguageReference

19.5Exercises

Chapter20:Forms

20.1Introduction

20.2SettingProperties

20.3FormsAndCode

20.4TemperatureConversionProgram

20.5QuadraticRootsProgram

20.6ResistanceCalculationWithSliderControlsProgram

20.7Exercises

Chapter21:MenusandDialogBoxes

21.1Introduction

21.2MenuEditor

21.3CommonDialogControl

21.4RunningAnApplicationProgram

21.5Exercises

Chapter22:Events

22.1Introduction

22.2ProgramEvents

22.3Exercises

Chapter23:Graphics

23.1Introduction

23.2LoadingGraphicsFiles

23.3Colours

23.4Drawing

23.5Exercises

PARTE:HTML/Java

Chapter24:HTML(Introduction)

24.1Introduction

24.2Links

24.3Lists

24.4Colours

24.5BackgroundImages

24.6DisplayingImages

24.7HorizontalLines

24.8Exercises

Chapter25:FurtherHTML

25.1Introduction

25.2Anchors

25.3Tables

25.4CGIScripts

25.5Forms

25.6Multimedia

25.7Exercises

Chapter26:JavaScript

26.1Introduction

26.2JavaScriptLanguage

26.3JavaScriptValues,VariablesAndLiterals

26.4ExpressionsAndOperators

26.5JavaScriptOperators

26.6JavaScriptStatements

26.7ConditionalStatements

26.8Loops

26.9Comments

26.10Functions

26.11ObjectsAndProperties

26.12DocumentObjects

26.13EventHandling

26.14WindowObjects

26.15ObjectManipulationStatementsAndOperators

26.16Exercises

Chapter27:Java(Introduction)

27.1Introduction

27.2CreatingAnApplet

27.3AppletBasics

27.4Stand-AlonePrograms

27.5JavaReservedWords

27.6AppletVariables

27.7JavaOperators

27.8MathematicalOperations

27.9Loops

27.10ConditionalStatements

27.11Exercises

Chapter28:Java(Extendedfunctions)

28.1Introduction

28.2InitializationAndExitFunctions

28.3MouseEvents

28.4MouseSelection

28.5KeyboardInput

28.6GraphicsImages

28.7Graphics

28.8Sound

28.9DialogBoxes

28.10Fonts

28.11Exercises

PARTF:DOS

Chapter29:Introduction

29.1Introduction

29.2IntroductionToDOS

29.3Disks

29.4FormattingFloppyDisks(FORMAT)

29.5FileSystemStructure

29.6DOSFilenames

29.7FileTypes

29.8ListingFiles(DIR)

Chapter30:DOSFileSystem/Editor

30.1ChangingDirectory(CDOrCHDIR)

30.2MakingADirectory(MKDIROrMD)

30.3ViewingAFile(TYPE)

30.4Wild-Cards(*Or?)

30.5CreatingATextFile

30.8DeletingFiles(DELOrERASE)

30.9CopyingFiles(COPY)

PARTG:Windows3.x

Chapter31:Introduction

31.1Introduction

31.2RunningWindows

31.3WindowsDesktop

31.4WindowItems

31.5MouseControls

31.6ProgramManagerMenus

31.7MovingAndResizingAWindow

31.8ClosingAWindowWithTheControlMenu

31.9Exercises

Chapter32:FileManagement

32.1Introduction

32.2FileManager

32.3Exercises

PARTH:Windows95/NT

Chapter33:Windows95/NT

33.1Introduction

33.2Servers,WorkstationsAndClients

33.3WorkgroupsAndDomains

33.4WindowsNTUserAndGroupAccounts

33.5FileSystems

33.6RunningWindows95AndNT

33.7BasicWindowsNT/95

33.8MouseControls

33.9QuittingWindows

33.10MovingAndResizingAWindow

33.11ClosingAWindowWithTheControlMenu

33.12Start

33.13MyComputer

33.14RunningDOS

33.15Windows95/NTNetworkDrives

33.16Exercises

Chapter34:ExtraWindows

34.1SavingImportantSet-UpFiles

34.2RunningAProgramWhenWindowsStartsUp

34.3CapturingWindowsScreen

34.4SwappingBetweenApplications

34.5TerminatingProgramsWhichHaveCrashed

34.6WindowsFileExtensions

34.7Exercises

PARTI:UNIX

Chapter35:IntroductiontoUNIX

35.1Introduction

35.2LoginIntoTheSystem

35.3DirectoryStructure

35.4On-LineManual

35.5ChangingDirectory

35.6ListingDirectories

35.7FileAttributes

35.8SpecialCharacters(*,?And[])

35.9ListingContentsOfAFile

35.10MakingAndRemovingDirectories

35.11Copying,RenamingAndRemoving

35.12StandardInputAndOutput

35.13CompilingCPrograms

35.14DisplayingTheTimeAndDate

35.15WhereToFindThings

35.16Exercises

35.17Summary

Chapter36:UNIXCommands

36.1ProcessControl

36.2Compilers

36.3FileManipulationCommands

36.4OtherCommands

36.5Exercises

Chapter37:EditingandTextProcessing

37.1Introduction

37.2VisualEditor

37.3ExampleOfTextEditing

37.4SedEditor

37.5Grep

37.6Sort

37.7Exercises

Chapter38:Csh(CShell)

38.1Introduction

38.2EnteringTheCShell

38.3LeavingTheCShell

38.4History

38.5ReexecutingEvents

38.6Alias

38.7Variables

38.8SpecialForms($#,$?And~)

38.9ShellVariables

38.10ShellScripts

38.11ControlStructures

38.12AutomaticallyExecutedCShellScripts(.Login.cshrc)

38.13Exercises

APPENDIXA:JavaClasses

APPENDIXB:ANSI-CFunctions

APPENDIXC:TurboPascalReference

APPENDIXD:AssemblyLanguageReference

APPENDIXE:ASCIICharacterSet

Index

Dedication

ThisbookisdedicatedtothememoryofmyGrandmother

Copyright

FirstpublishedinGreatBritainin1997byArnold,amemberoftheHodderHeadlineGroup,338EustonRoad,LondonNW13BHhttp://www.arnoldpublisher.comCopublishedinNorth,CentralandSouthAmericabyJohnWiley&SonsInc.,605ThirdStreet,NewYork,NY10158-0012©1997WilliamBuchananAllrightsreserved.Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronicallyormechanically,includingphotocopying,recordingoranyinformationstorageorretrievalsystem,withouteitherpriorpermissioninwritingfromthepublisheroralicencepermittingrestrictedcopying.IntheUnitedKingdomsuchlicencesareissuedbytheCopyrightLicensingAgency:90TottenhamCourtRoad,LondonW1?9HE.Whilsttheadviceandinformationinthisbookisbelievedtobetrueandaccurateatthedateofgoingtopress,neithertheauthornorthepublishercanacceptanylegalresponsibilityorliabilityforanyerrorsoromissionsthatmaybemade.BritishLibraryCataloguinginPublicationDataAcataloguerecordforthisbookisavailablefromtheBritishLibraryLibraryofCongressCataloging-in-PublicationDataAcatalogrecordforthisbookisavailablefromtheLibraryofCongressISBN0340700149ISBN0471852662(Wiley)Publisher:DavidRossProductionEditor:JamesRabsonProductionController:SarahKettCoverdesigner:TerryGriffithsPrintedandboundinGreatBritainbyJWArrowsmith,Bristol

Preface

Specialization in software development is becoming a thing of the past.PreviouslymanysoftwaredevelopersspecializedonsoftwarelanguagessuchasFORTRAN, C and Pascal. This wasmainly because these languages allowedaccesstoalltherequiredfunctionality.Inmoderntimeswiththemovetowardsgraphical user interface programming a developer must choose not only therequiredsoftwarelanguage(s)butalsotherequiredsetofdevelopmenttoolsforaspecificpurpose.Typicaldecisionmightbeto:•Minimizedevelopmenttime;•Createausableinterface(suchasDOS,orMicrosoftWindowsorX-

Windows,andsoon);•Operatewithincriticaltimings(suchastheuseoffastcode,orthatDOS

programsgenerallyoperatefasterthanMicrosoftWindowsprograms,orthatcompiledprogramsgenerallyworkfasterthaninterpretedprograms);

•Integratewithothersoftwareorsystems(suchastheintegrationwithpreviouswrittensoftware,differentoperatingsystemsorwithprecompiledlibraries);

•Maintainthelong-termdevelopmentoftheprogram(typicalquestionsmightbe:willtherebeupdatestothedevelopmenttools;willthedevelopmentcompanystillbearoundinafewyears?,andsoon).

Typical modern development languages are C/C++, Visual Basic, Ada(especially in military applications), Java and Delphi. This book introducesC/C++whichcanbeusedinC/C++andJavadevelopmentapplications.Pascalis useful in developing Delphi and Ada applications. Visual Basic is used towrite Microsoft Windows applications, and 80X86 Assembly Languageprogramming is useful in writing extremely fast sections of code and inappreciatingtheoperationofthePC.Themainobjectiveof the text is toprovideasinglesourceofreferenceand

learningmaterialformostofthemaintechnicalprogramminglanguages.Itcanbeusedbyundergraduatesthroughacourseofstudyfromfirstyeartofinaland

fromintroductorytutorialworktoadvanceduserinterfacesandprojectwork.Itcanalsobeusedbyprofessionaldeveloperswithaknowledgeofoneormoreofthesoftwaredevelopmentlanguagewhowishtolearnsome,orall,oftheothers,orhowtheselanguagescanbeusedin‘real-life’applications.Thetextsplitsintoninemainsections:PartA:Pascal/Cprogramming–givesanintroductiontostructuredsoftwaredevelopmentusingPascalandC.

PartB:C++programming–givesanintroductiontoobject-orienteddesignwithC++.

PartC:80x86AssemblyLanguageprograms–givesanintroductiontoAssemblyLanguageprogrammingandPCarchitecture.

PartD:VisualBasicprogramming–givesanintroductiontothedevelopmentofgraphicaluserinterfacesforMicrosoftWindows.

PartE:HTMLandJavaprograms–showhowtodevelopWWW-basedpagesandgivesanintroductiontoJava.

PartF:DOS.PartG:Windows3.PartH:Windows95.PartI:UNIX.The text uses C and Pascal to provide a basic grounding in software

development.Theseareusedtoshowstructuredsoftwaredevelopmentconcepts,such as repetition, decision making and modular development. The moreadvanced concepts of object-oriented design is introduced with the C++development.TheVisualBasicsectioncontainsprogramexampleswhichcanbeusedtodevelopgraphicaluserinterfaceprograms.Manysoftwaredevelopmentjobadvertisementsnowspecifytherequirement

for a mixture of software languages on possibly several different operatingsystems.Softwaredevelopmenthasthusevolvedtothepointwhereitispossibleto integrate different software tools to produce the required system. The userinterface of a program might be developed using a graphical programminglanguage such as Visual Basic and various specialized modules within theprogramcouldbedevelopedinC/C++.Insummary,inachangingemploymentmarket:

‘itisessentialtobecomemulti-skilledindifferentareasandapplications’.

PARTAC/PASCAL

1

Introduction

1.1Introduction

Softwaredevelopmenthasgrownover theyearsfromsimpleBASICprogramswritten on small hobby computers to large software systems that controlfactories.Manyapplications thatatone timeuseddedicatedhardwarearenowimplementedusingsoftwareandprogrammablehardware.Thisshiftinemphasishas meant that, as a percentage, an increasing amount of time is spent onsoftwareandlessonhardwaredevelopment.Electrical,electronicandsoftwareengineersrequireagreatdealofflexibility

in theirapproach tosystemdevelopment.Theymusthaveanunderstandingofall levels of abstraction of the system, whether it be hardware, software orfirmware. The system itself could range from a small 4-bit central heatingcontrollertoalargeindustrialcontrolsystem.Inthedevelopmentofanysystemthe engineer must understand the system specification from its interfacerequirements,itstimingrequirements,itselectricalcharacteristics,andsoon.The software that runs on a systemmust be flexible in its structure as the

developercouldrequiretointerrogatememoryaddressesfortheircontentsortomodelapartof thesystemasanalgorithm.For thispurpose theprogramminglanguages C and Pascal are excellent in that they allow a high-level ofabstraction (such as algorithm specification) and allow low-level operations(such as operations onbinarydigits).Theyhave awide rangeof applications,from commerce and business to industry and research, which is a distinctadvantage as many software languages have facilities that make them usefulonly in a particular environment. For example, in the past, business andcommercial applications used COBOL extensively, whereas engineering andscienceusedFORTRAN.

1.2Hardware,softwareandfirmware

Asystemconsistsofhardware,softwareandfirmware,allofwhichinterconnect.Hardware is ‘thebits thatcanbe touched’, that is, thecomponents, the screwsandnuts,thecase,theelectricalwires,andsoon.Softwareistheprogramsthatrun on programmable hardware and change their operation depending on theinputs to the system. These inputs could be taken from a keyboard, interfacehardware or from an external device. The program itself cannot exist withoutsome formof programmable hardware such as amicroprocessor or controller.Firmware is a hardware device that is programmed using software. Typicalfirmware devices areEEPROMs (ElectricallyErasableReadOnlyMemories),andinterfacedevicesthatareprogrammedusingregisters.In most applications, dedicated hardware is faster than hardware that is

runningsoftware,althoughsystemsrunningsoftwareprogramstendtobeeasiertomodifyandrequirelessdevelopmenttime.

1.3BasiccomputerarchitectureThemainelementsofabasiccomputersystemareacentralprocessingunit(ormicroprocessor),memory,andinput/output(I/O)interfacingcircuitry.Theseareinterconnected by threemain buses: the address bus; the control bus; and thedata bus, as illustrated in Figure 1.1. External devices such as a keyboard,display,diskdrives,andsoon,canconnectdirectlyonto thedata,addressandcontrolbuses,orconnectthroughI/Ointerfacingcircuitry.

FIGURE1.1 Blockdiagramofasimplecomputersystem

MemorynormallyconsistsofRAM(randomaccessmemory)andROM(readonlymemory).ROMstores permanent binary information,whereasRAM is anon-permanentmemory and loses its contentswhen the power is taken away.RAM memory is used to run application programs and to store information

temporarily.Themicroprocessor is themaincontrollerof thecomputer. It fetchesbinary

instructions(knownasmachinecode)frommemory,itthendecodestheseintoaseriesofsimpleactionsandcarriesouttheactionsinasequenceofsteps.Thesestepsaresynchronizedbyasystemclock.Themicroprocessoraccessesamemorylocationbyputtingitsaddressonthe

address bus. The contents at this address are placed on the data bus and themicroprocessor reads thedata from thedatabus.To storedata inmemory themicroprocessorplaces thedataon thedatabus.The addressof the location inmemory is thenputon theaddressbusand thedata is thenreadfromthedatabusintotherequiredmemoryaddresslocation.

1.4Compiling,linkingandproducinganexecutableprogramAmicroprocessoronlyunderstandsbinaryinformationandoperatesonaseriesofbinarycommandsknownasmachinecode. It is extremelydifficult towritelargeprogramsinmachinecode,sothathigh-levellanguagesareusedinstead.Alow-level language is one which is similar to machine code and normallyinvolves theusageofkeywordmacros toreplacemachinecode instructions.Ahigh-level language has a syntax that is almost like written English and thusmakes a program easy to read and to modify. In most programs the actualoperationofthehardwareisinvisibletotheprogrammer.A compiler changes the high-level language into machine code. High-level

languagesincludeC,BASIC,COBOL,FORTRANandPascal;anexampleofalow-levellanguageis80386AssemblyLanguage.Figure1.2showsthesequenceofeventsthatoccurtogenerateanexecutable

programfromaCorPascalsourcecodefile(thefilenamesusedinthisexamplerelatetoaPC-basedsystem).Aneditorcreatesandmodifiesthesourcecodefile;acompilerthenconvertsthissourcecodeintoaformwhichthemicroprocessorcan understand, that is, machine code. The file produced by the compiler isnamed an object code file code (note that Turbo Pascal does not produce anobjectcodefile).Thisfilecannotbeexecutedasitdoesnothavealltherequiredinformationtoruntheprogram.Thefinalstageoftheprocessislinking,whichinvolvesaddingextramachinecodeintotheprogramsothatitcanusedevicessuchasakeyboard,amonitor,andsoon.Alinkerlinkstheobjectcodefilewithother object code files and with libraries to produce an executable program.

Theselibrariescontainotherobjectcodemodulesthatarecompiledsourcecode.

FIGURE1.2 Edit,compileandlinkprocesses

If compilation or linking steps generate errors or warnings then the sourcecodemustbemodifiedtoeliminatethemandtheprocessofcompilation/linkingbeginsagain.Warningsinthecompile/linkprocessdonotstopthecompilerorlinkerfromproducinganoutput,buterrorswill.Allerrorsinthecompilationorlinking stage must be eliminated, whereas it is only advisable to eliminatewarnings.

1.5CcompilationBorland C++ Version 3.0 is an integrated development package available forPC-basedsystems.Itcontainsaneditor,compiler,linkeranddebugger(usedtotestprograms).Theeditorcreatesandmodifiessourcecodefilesandisinitiatedby running BC.EXE. Figure 1.3 shows a main screen with a source code filePROG1_1.C.

FIGURE1.3 BorlandC++Version3.0mainscreen

Figure 1.4 shows the compile menu options within this package. A sourcecode file is compiled by selecting Compile to OBJ. If there are no errors anobjectcodefileisproduced(inthiscasePROG_1.OBJ).ThisislinkedusingLinkEXEfile(producingthefilePROG_1.EXE).Acompileandlinkprocesscanalsobe initiated using theMake EXE file option. Programs are run from the Runmenuoption.

FIGURE1.4 BorlandC++Version3.0compilemenuoptions

1.6PascalcompilationTurbo Pascal Version 5.0 is an integrated development package available forPC-basedsystems.Itcontainsaneditor,compiler,linkeranddebugger(usedto

testprograms).TheeditorcreatesandmodifiessourcecodefilesandisinitiatedbyrunningTURBO.EXE.Figure1.5showsamainscreenwithasourcecodefilePROG1_1.PAS.

FIGURE1.5 TurboPascalVersion5.0mainscreen

Figure 1.6 shows the compile menu options within this package. A sourcecode file is compiled by selecting Compile. If there are no errors then anexecutable program is produced. If the destination is given as Memory then itdoes not save the executable file to the disk but runs it frommemory. If thedestinationistotheDiskthenanexecutablefilewillbeproduced(producingthefilePROG_1.EXE). The destination can be toggled by pressing theENTERkeywhile the linecursor ison theDestinationoption.AprogramisrunfromtheRunmenuoption.

FIGURE1.6 TurboPascalVersion5.0compilemenuoptions

1.7IntroductiontoCThissectiongivesabriefintroductiontoANSI-C.

1.7.1PreprocessorThepreprocessoractsonprogramsbefore thecompiler. Itusescommandsthathave a number-sign symbol (‘#’) as the first non-blank character on a line.Figure1.7showsitsmainuses,whichare:includingspecialfiles(headerfiles)and defining various macros (or symbolic tokens). The #include directiveincludesaheader fileand#definedefinesmacros.Byplacing thesedirectivesnearthetopofasourcecodefilethenallpartsoftheprogramhaveaccesstotheinformationcontainedinthem.

FIGURE1.7 Operationsontheprogramtoproduceanexecutablefile

Forexample,thepreprocessordirective:

includestheheaderfilemain.h.Theinvertedcommasinformthepreprocessorthatthisfilewillbefoundinthecurrentworkingdirectory,whilethedirective

includesthefilestdio.hfoundinthedefaultincludedirectory.Thisdirectoryisnormallyset-upautomaticallyby thesystem.Forexample,TurboCVersion2.0storesitsheaderfiles,bydefault,inthedirectory\TC\INCLUDEandBorlandCuses\BORLANDC\INCLUDE.Typically,headerfilesonaUnixsystemarestoredintheusrincludedirectory.To summarize, invertedcommas (” “) inform thepreprocessor to search for

thespecifiedheaderfileinthecurrentdirectory(orthedirectoryspecifiedinthepathname).Thechevroncharacters(<>)informthepreprocessortosearchinthedefaultincludedirectory.Itisnotadvisabletoincludeanyotherfileapartfromheader files. These have a ‘.h’ file extension (although this is not obligatory).Standard header files are used in conjunction with functions contained inlibraries. They do not contain program code, but have information relating tofunctions. A given set of functions, such as maths or I/O, has a header fileassociatedwithit.Table1.1givestypicalheaderfilesandtheirfunctionality.

Table1.1Typicalheaderfiles

Headerfile Comment

ctype.h characterclassificationandconversion

Math.h mathsfunctions

stddef.h definesseveralcommondatatypesandmacros

stdio.h Input/Output(I/O)routines,suchasinputfromkeyboard,outputtodisplayandfilehandling(stdioisacontractionofstandardinput/output)

stdlib.h miscellaneousroutines

string.h stringmanipulationfunctions

time.h timefunctions

Amacroreplaceseveryoccurrenceofacertain tokenwithanotherspecifiedtoken.Thefollowingexamplesshowsubstitutionsusingthe#definedirective.

Typically,asamatterofprogrammingstyle,thedefinitionsofconstants,such

asπ,aregiveninuppercasecharacters.

1.7.2StructureNormallyprogramsaresplitintoanumberofsub-tasksnamedfunctions.Theseare clearly distinctive pieces of code that perform particular operations. Themain function (main ()) is the basic routine for controlling the flow of theprogramandcallsothersub-functions.CProgram1.1isasimpleprogramwhichusestheputs()functiontodisplay

the text “Essence of Software”. The puts() function is a standard functionused to output text to the display; the header file associatedwith it is stdio.h.Thisheaderfileisincludedusingthe#includedirective.Thestatement terminator(;) isused toenda lineofcode(orstatement)and

braces({})showthebeginning({)andend(})ofablockofcode.Commentsareinserted in the program between a start comment identifier (/*) and an endidentifier(*/).

AllCprogramshaveamain()functionwhichdefinestheentrypointintotheprogramand, bymeansof calling functions, controls general program flow. Itcanbelocatedanywhereinthesourcecodeprogram,butisnormallyplacednearthe top of the file it is located in (making it easier to find).Theint keywordpreceding main() defines that the program returns a value to the operatingsystem (or calling program). In this case, the return value is 0 (return (0)).Normally,anon-zeroreturnvalueisusedwhentheprogramhasexitedduetoanerror;theactualvalueofthisgivesanindicationofwhytheprogramhasexited.The void within the parenthesis of main() defines that there is nocommunicationbetweentheprogramandtheoperatingsystem(thatis,novaluesare passed into the program). Figure 1.8 shows the basic structure of a Cprogram.

FIGURE1.8 Cprogramstructure

1.7.3DataTypesVariableswithin aprogramcanbe stored as eithernumbersor characters.Forexample, the resistance of a copperwirewould be stored as a number (a realvalue) and the name of a component (such as, “R1”) would be stored ascharacters.Table1.2givesthefourbasicdatatypeswhichdefinetheformatofvariables.

Table1.2Basicdatatypes

Type Usage

char singlecharacter‘a’,‘1’,andsoon

int signedinteger

float single-precisionfloatingpoint

double double-precisionfloatingpoint

Therearethreebasicextensionsforthefourtypes;theseare:

An integer is any value without a decimal point; its range depends on thenumberofbytesusedtostoreit.Afloatingpointvalueisanynumberandcanincludeadecimalpoint;thisvalueisalwaysinasignedformat.Again,therangedependsonthenumberofbytesused.

Integersnormallytakeup2or4bytesinmemory,dependingonthecompilerimplementation. This gives ranges of –32768 to 32767 (a 2-byte int) and –2147483648to2147483647(a4-byteint),respectively.

1.7.4DeclarationOfVariablesAprogramusesvariablestostoredata.Beforetheprogramcanuseavariable,itsnameanditsdatatypemustfirstbedeclared.Acommagroupsvariablesofthesamedatatype.Forexample,ifaprogramrequiresintegervariablesnum_stepsand bit_mask, floating point variables resistor1 and resistor2, and twocharacter variables char1 and char2, then the following declarations can bemade:

CProgram1.2 isasimpleprogramthatdetermines theequivalentresistanceof two resistors of 1000Ω and 500Ω connected in parallel. It contains threefloating point declarations for the variables resistor1, resistor2 andequ_resistance.

It is also possible to assign an initial value to a variable at the point in theprogram at which it is declared; this is known as variable initialization. CProgram1.3givesanexampleofthiswiththedeclaredvariablesresistor1andresistor2initializedto1000.0and500.0,respectively.

1.7.5KeywordsANSI-C has very few reserved keywords (only 32); these cannot be used asprogramidentifiers.Ciscase-sensitiveandthustheymustbeusedinlowercase.From these simplebuildingblocks largeprogramscanbebuilt.The followinggivesalistofthekeywords.

Functions are sections of code that perform a specified operation. Theyreceive some input and produce an output in a way dictated by theirfunctionality. These can be standardized functions which are inserted intolibraries or are written by the programmer. ANSI-C defines some standardfunctions which provide basic input/output to/from the keyboard and display,mathematical functions, character handling, and so on. They are groupedtogether into library files and are not an intrinsic part of the language. Theselibrarieslinkintoaprogramtoproduceanexecutableprogram.

1.8IntroductiontoPascalThissectiongivesabriefintroductiontoTurboPascal.

1.8.1ConstantDeclarationsPascal uses the const keyword to defined constant numeric values. Thefollowing examples show constant declarations for π and the speed of light(whichis3×108).

InPascalthecaseofthecharactersisignoredbut,asamatterofprogrammingstyle,thedefinitionofconstants,suchasπ,isgiveninuppercasecharacters.

1.8.2StructureNormally programs are split into a number of sub-tasks named procedures orfunctions. These are clearly distinctive pieces of code that perform particularoperations. The main program is the basic routine to control the flow of aprogramandcallsothersub-functions.PascalProgram1.1isasimpleprogramwhichusesthewritelnprocedureto

display the text ‘Essence of Software’. The writeln procedure is a standardprocedurewhichisusedtooutputtexttothedisplay.Thestatement terminator(;) isused toenda lineofcode(orstatement)and

thekeywordsbegin and enddefine thebeginning and endof a blockof code.Commentsareinsertedintotheprogrambetweenastartcommentidentifier(/*)andanendidentifier(*/).AllPascalprogramshaveamainprogramwhichdefinestheentrypointinto

theprogramand,bymeansofcallingfunctionsandprocedures,controlsgeneralprogramflow.Inmostcasesitisbelocatedattheendofthesourcecodefile.

Figure1.9showsthebasicstructureofaPascalprogram.Eachprogramhasaprogram header which is defined with the program keyword. After this the

programvariablesaredeclared.Inthiscasethevariablesdeclaredarevar1,var2(whichareintegers)andvar3,var4(whicharerealvalues).Themainprogramisdefined after the variable declaration and can be identified between thebeginandendkeywords.Thefinalendkeywordhasafull-stopafterit.

FIGURE1.9 Pascalprogramstructure

1.8.3DataTypesVariableswithin aprogramcanbe stored as eithernumbersor characters.Forexample, the resistance of a copperwirewould be stored as a number (a realvalue) and the name of a component (such as, ‘R1’) would be stored ascharacters.Table1.3givesthefourbasicdatatypeswhichdefinetheformatofvariables.

Table1.3BasicPascaldatatypes

Type Usage Range

char singlecharacter‘a’,‘1’,andsoon Characterrange

integer signedinteger −32768to32767

real single-precisionfloatingpoint 2.9×1939to1.7×1038

boolean booleantype trueorfalse

OtherdatatypesusedinTurboPascalinclude:

An integer is any value without a decimal point; its range depends on thenumberofbytesusedtostoreit.Afloatingpointvalueisanynumberandcanincludeadecimalpoint;thisvalueisalwaysinasignedformat.Again,therangedependsonthenumberofbytesused.The integer type uses 2 bytes in memory. This gives ranges of –32768 to

32767 (a 2-byte int) and–2147483648 to 2 147483647 (a 4-bytelongint),respectively.

1.8.4DeclarationOfVariablesAprogramusesvariablestostoredata.Beforetheprogramcanuseavariable,itsnameanditsdatatypemustfirstbedeclared.Acommagroupsvariablesofthesamedatatype.Forexample,ifaprogramrequiresintegervariablesnum_stepsand bit_mask, floating point variables resistor1 and resistor2, and twocharacter variables char1 and char2, then the following declarations can bemade:

Pascal Program 1.2 is a simple program that determines the equivalentresistanceoftworesistorsof1000Ωand500Ωconnectedinparallel.Itcontainsthree floating point declarations for the variables resistor1, resistor2 andeq_resistance.

1.8.5KeywordsTurbo Pascal has 52 reserved keywords; these cannot be used as programidentifiersandcanbeinupper-orlowercase.Largeprogramscanbebuiltfromthesesimplebuildingblocks.Thefollowinggivesalistofthekeywords.

Functions and procedures are sections of code that perform a specifiedoperation.Theyreceivesomeinputandproduceanoutputinawaydictatedbytheirfunctionality.Thesecanbestandardizedfunctionswhichare inserted intolibrariesorarewrittenbytheprogrammer.TurboPascaldefinessomestandardfunctions which provide basic input/output to/from the keyboard and display,mathematical functions, character handling, and so on. They are groupedtogether into library files and are not an intrinsic part of the language. Theselibrarieslinkintoaprogramtoproduceanexecutableprogram.

1.9Exercises1.9.1.DeterminetheerrorsintheCPrograms1.4to1.6orthePascalPrograms

1.3to1.5.Eachprogramhasasingleerror.Enterthemintothecompilerandaftertheerrorhasbeencorrected,runthem.

Worksheet1:W1.1.Whichprogramminglanguageisyourchoiceforsoftwaredevelopment

(tickone):

c []

TurboPascal []

MixtureofCandPascal []

W1.2.Ifyouarerunningthecompileroverthenetworkthenwhatisyourloginname:

W1.3.LocateandrunPascalorCcompiler:

W1.4.EntereitherCProgram1.1orPascalProgram1.1andsavethistoafileonfloppydiskasPROG1_1.PAS(forthePascalfile)orPROG1_1.C(fortheCfile).

W1.5.Compiletheprogramandnoteanymessagesthatthecompilergives.

W1.6.Ifthereareerrorsintheprogramthencomparetheenteredfilewiththeprogramlistingandtrytoidentifyhowtheydiffer.Thecompilershouldidentifythelocationoftheerror(notelookalsoatthelinebefore).Thenrecompile.

W1.7.Aftertheprogramhasbeensuccessfullycompiled,runtheprogramanddetermineitsoutput.

W1.8.EntereitherCProgram1.2orPascalProgram1.2andsavefileonfloppydiskasPROG1_2.PAS(forthePascalfile)orPROG1_2.C(fortheCfile).

W1.9.UsingCProgram1.2orPascalProgram1.2determinetheequivalentresistancefortwoparallelresistors.UsethisprogramandbychangingtheresistorvaluescompleteTableW1.1.

TableW1.1Equivalentresistance

Resistor1(Ω) Resistor2(Ω) Equivalentresistance(Ω)

1000 1000

25 100

1e6(1MΩ) 1e6

150 50

2

Input/Output

2.1Introduction

Everyprogramhassomeformofoutputandnormallyaninput.Figure2.1showssomeexamplesofinputandoutputdevices.Theinputcouldbefromakeyboard,afile,input/outputports,amouse,andsoon.Outputcanbesenttodevicessuchas displays, printers, hard-disks, and so on. Typically, engineers alsocommunicate with devices such as ADC/DACs, LEDs, interface adapters, ICprogrammers,andsoon.

FIGURE2.1 Input/outputdevices

The default input device is normal from a keyboard and the default outputfromadisplay.Mostprogramsprompttheusertoenterdatafromthekeyboard.Thisdataisthenprocessedandtheresultsdisplayedtothescreen.Theusercanthenenternewdataandsothecyclecontinues.Mostoperating systemsalsoallowsa redirectionof the inputoroutput.For

example,atextfilecanactasaninputtoaprogramandtheprinterastheoutput.

2.2Pascalinput/outputComparedwithC,Pascalhasavery limitedsetof input/outputstatements(forthis reason this chapter contains many more pages on the C input/outputstatements).Pascalusesthekeyboardasthestandardinputandthedisplayasthestandard output. The two statements which are used to control this input andoutputarereadandwrite.

2.2.1WritelnThestatementsusedtooutputdatafromaprogramtothescreenarewritelnandwrite.Thewritestatementdoesnotmovethecursortoanewlineoncethedatahasbeenprinted,whereasthewritelnwill.Thestandardformatis:

Atextstringisenclosedwithinquotes(’‘)andcanbeprintedatanyplaceinthewritestatement.Valueswillbeprintedinaformatdefinedbytheirtype.Forexample an integerwill be displayedwithout a decimal point, a very large orsmall real valuewill be displayed in exponent form.The actual format of thevaluetobeprintedcanbemodifiedusingthecolonmodifier,thestandardformatis:

2.2.2ReadInThestatementsusedtoinputdataintoaprogramfromthekeyboardarereadandreadln.Thereadstatementdoesnotmovethecursortoanewlineoncethedatahasbeenentered,whereasthereadlnwill.Thestandardformatis:

Pascal Program 2.1 shows a simple example of a program which usesinput/outputstatements

2.3Cinput/outputThestandard input/output(I/O)functions inCarenot intrinsic(built-in) to thelanguage, but are stored in libraries that are linked into the program. The#includepreprocessordirectiveincludestheheaderfilesassociatedwiththem.Input/Outputfunctionsusestdio.h.Inordertoallowallpartsofthesourcecodeaccess to the functions defined in the header file the preprocessor directive islocatednearthetopofthefileinwhichitisused.Thecompilerwilltheninitiateextra error checking whenever any of the standard I/O functions are used. CProgram2.1showsaprogramwhichincludesthefilestdio.h.

2.3.1CStandardOutput(Printf(),Puts()AndPutchar())TherearethreebasicoutputfunctionsinC,theseare:

The printf() function sends a formatted string to the standard output (thedisplay). This string can display formatted variables and special controlcharacters, such as new lines (‘\n’), backspaces (‘\b’) and tabspaces (‘\t’);thesearelistedinTable2.1.

Table2.1Specialcontrol(orescapesequence)characters

The puts() function writes a string of text to the standard output and no

formatted variables can be used. At the end of the text, a new line isautomaticallyappended.The parameters passed into printf() are known as arguments; these are

separatedcommas.CProgram2.1containsaprintf()statementwithonlyoneargument,thatis,atextstring.Thisstringisreferredtoasthemessagestringandis always the first argument of printf(). It can contain special controlcharactersand/orparameterconversioncontrolcharacters.Conversioncontrolcharactersdescribetheformatofhowthemessagestring

usestheotherarguments.Ifprintf()containsmorethanoneargumentthentheformatoftheoutputisdefinedusingapercent(%)characterfollowedbyaformatdescriptioncharacter.Asignedintegerusesthe%dconversioncontrolcharacters,an unsigned integer %u. A floating point value uses the %f conversion controlcharacters,whilescientificnotationuses%e.Table2.2liststhemainconversioncontrolcharacters.

Table2.2Conversioncontrolcharacters

Figure2.2showsanexampleoftheprintf()statementwithfourarguments.Thefirstargumentisthemessagestringfollowedbytheparameterstobeprintedinthemessagestring.Inthiscasetheparametersareval1,val2andch;val1isformattedinthemessagestringasafloatingpoint(%f),val2asaninteger(%d)andchasacharacter(%c).Finally,anewlinecharacter(‘\n’)isusedtoforceanewlineontheoutput.

FIGURE2.2 Anexampleprintf()statement

A numerical value is output to a given specification using a precisionspecifier.Thisspecifiesthenumberofcharactersusedtodisplaythevalueandthenumberofplaces after thedecimalpoint.Thegeneral formatof a floatingpointvalueis:

wheremisthewidthofthevalue(thenumberofdigitsincludingthedecimalpoint),nisthenumberofdigitsfollowingthedecimalpoint,andXistheformattype(fforfloat).Thegeneralformatofastringorintegeris:

whereXistheformattype(cforcharacter,sforstringordforinteger)andmisthewidthoftheoutput.Table2.3givesafewexamples.

Table2.3Exampleofconversioncontrolmodifiers

Format Function

%.3f formatfloatingpointvaluewith3decimalplacesandadefaultwidth

%8.3f formatfloatingpointwith8reservedspacesand3placesafterthedecimalpointsuchas32.453

%10d formatintegerfor10reservedspacessuchas23

%3o formatoctalintegernumberfor3hexadecimalcharacters

%10.6e formatexponentformatwith6decimalplaces

2.3.2CStandardInput(Scanf(),Gets()AndGetchar())Thekeyboard isnormally the standard input to aprogram.Aswith theoutputfunctions, the input functions are not part of the standard language and arecontainedinastandardClibrary.Definitions(orprototypes)ofthesefunctionsare found in the header file stdio.h. By including this header file a degree oferror checking is initiated at compilation. The compiler checks, among otherthings,thedatatypesoftheparameterspassedintothefunctions.Itisthuslesslikelythattherewillbeanyrun-timeerrors.Therearethreemaininputfunctions,theseare:

If a numeric or a character variable is used with the scanf() function anampersand(&)precedeseachparameterintheargumentlist(thereareexceptionsandthesewillbediscussedinChapters6and7).Thisprefixcausesthememoryaddressofthevariabletobeusedasaparameterandnotthevalue.Thisallowsscanf()tochangethevalueofthevariable(thiswillalsobeexplainedinmoredetailinChapter6).Fornow,itshouldbeassumedthatanampersandprecedesallsimplenumericalandcharacterdatatypeswhenusingscanf().Thegeneralformatofthescanf()functionisscanf(format,&arg1,&arg2…).The first argument format is a string that defines the format of all entered

values.Forexample,“%f%d”specifiesthatarg1isenteredasafloatandarg2asaninteger.Thisstringshouldonlycontain theconversioncontrolcharacterssuch as %d, %f, %c, %s, etc., separated by spaces. Figure 2.3 shows anexampleofthescanf()functionreadingafloat,anintegerandacharacterintothevariablesval1,val2andch.

FIGURE2.3 Anexampleofthescanf()statement

Thegets(str)functionreadsanumberofcharactersintoavariable(inthiscase str); these characters are read until the ENTER key is pressed. Thegetchar() function reads a single character from the input. This character isreturnedviathefunctionheaderandnotthroughtheargumentlist.

2.4ExamplesThis section contains some practical electronics-related examples of C andPascalprograms.EachofthetestrunsrelatetoarunoftheCprogram(althoughmostofthePascaltestrunsarealmostidentical).

2.4.1FahrenheitToCentigradeConversionTemperature is typically measured in either centigrade or Fahrenheit. TheconversionfromFahrenheittocentigradeis:Program 2.2 converts from an entered value of Fahrenheit (faren) into

centigrade(cent),andTestrun2.1showsasamplerunforanenteredvalueof80°F.Theresultantvalueisdisplayedwith8placesreservedfortheanswerand2decimalplaces.ThisisspecifiedinCas%8.2fandinPascalwith:8:2afterthevariable.

2.4.2GradientOfAStraightLineTheequationofastraightlineis:

wheremisthegradientofthelineandcisthepointatwhichthelinecutsthey-axis. If two points on the line are known, (x1,y1) and (x2,y2) thenm can becalculatedby:andthecvaluecanbecalculatedfrom:

Program 2.3 determines the gradient of a straight line for entered value ofx1,y1 and x2,y2 (Note that the solution of the value for c will be left as anexercise).Testrun2.2isasampletestrun.

2.4.3ForceOfAttractionThegravitationalforcebetweentwoobjectsofmassm1andm2ofadistancedapartisgivenby:where G is a gravitation constant and is equal to 6.67×10−11 m3.kg_1sec−2.

Program2.4determinesthegravitationforceandTestrun2.3showsatestrunfor the gravitation force between an apple and the earth.The parameters used

are:

The resultant gravitation force is 0.99N,which is similar to the calculationusing:

The gravitation force constant (G) has been defined, inC,with the#definestatementand,inPascal,withaconst.

2.4.4CapacitiveReactanceThe reactance of a capacitor depends upon the applied frequency. At lowfrequenciesthereactanceisextremelyhighandathighfrequenciesitislow.Thereactance(Xc)ofacapacitor,ofcapacitanceC(Farads),atanappliedfrequencyf(Hertz)isbegivenby:Figure 2.4 shows a schematic of this arrangement. There is one output

variable(Xc),twoinputvariables(fandC)andasingleconstant(π).Program2.5shows a sample program and test run 2.4 is a sample run. In C a constant isdeclared with the #define preprocessor option and Pascal uses the constkeyword.

FIGURE2.4 Capacitorconnectedtosinusoidalvoltagesource

2.4.5ImpedanceOfAnRLSeriesCircuitThemagnitudeoftheimpedanceofanRLseriescircuit(modulus|Z|)isgivenbytheequation:andtheangleoftheimpedance(argument Z )isgivenby:

Figure2.5showsaschematicofanRLseriescircuit.Program2.3determinesthemagnitudeandtheangleoftheimpedanceusingenteredvaluesofresistance(R), inductance (L) and frequency (freq). In C the inverse tangent (tan−1)function is defined (or prototyped) in math.h and is named atan(), whereas,Pascal uses the arctan() function. Both these functions return the inversetangent in radians. The program converts the returned value into degrees byscalingitbyπ/180.

FIGURE2.5 RLseriescircuit

The program uses the square root function; in C this function is (sqrt())whichisprototypedinthemath.hheaderfile.Thisinclusionhelpsthecompilerchecktheformatofthevaluessenttothefunctionasitchecksthegeneralsyntaxof the function call. It also informs the compiler that the value returned is afloatingpoint(thiswillbediscussedingreaterdetailinalaterchapter).InPascalitisalsonamedsqrt().Testrun2.5isasampleoutputusingenteredvaluesR=100Ω,L=100mH

and frequency= 1 kHz.The impedance has amagnitude of 118.10Ω and anangleof32.14°.

2.4.6ResistorsInParallel

Program2.7determinestheequivalentresistanceofthreeresistorsconnectedinparallel. Figure 2.6 gives a schematic diagram of this set-up. The resistorsconnectedareR1,R2andR3andtheequivalentinputresistanceisRequ.Testrun2.6showsarunwithvaluesof250,500and1000Ω.

FIGURE2.6 Threeresistorsconnectedinparallel

2.4.7BitOperationsProgram 2.8 relates to digital electronics and illustrates the power of C andPascalwhendealingwithlow-levelbitoperators.TheCprogramuses&,|,⁁and~bitwise operators to create AND, OR, EX-OR, NAND and NOR Booleanfunctions.Pascalusestheoperators:and,or,xorandnot.TheNANDandNORfunctionsaregeneratedbyinvertingtheANDandORoperations.TheCprogramallowstheentryofhexadecimalvaluesusingthe%xformat

descriptorinscanf()statement.Testrun2.7showsarunwithtestvalues.

Thebitpatternsused in the test runare1110001000010101 (E215h)and1100 0100 0011 0001 (C431h). To verify the program the hexadecimalequivalents of these values are operated on by the Boolean operators and theresultscheckedagainstthetestrunresults.TheANDoperationgivesthefollowing:

TheORoperationgivesthefollowing:

TheEX-ORfunctiongivesthefollowing:

The inverse of AND (NAND) will be 0011 1111 1110 1110(3FEEh); theinverseoftheOR(NOR)is0001100111001010(19CAh).Theseresultsareidenticaltotheseintestrun2.16.Thusthetesthasbeensuccessful.ThePascalProgram2.8allowstheinputofthevaluesasaninteger.Testrun

2.8showsasampletestrun.

Worksheet2W2.1.Entertwoprogramsfromthechapterandverifythattheiroutputconforms

withthesampletestruns.

W2.2.Modifyprogram2.3sothatitalsocalculatesthevalueofc.UsethisprogramtocompleteTableW2.1.

TableW2.1Straightlinescalculations

W2.3.Writeaprogramwhichcalculatesthemagnitudeofacomplexnumberofx+jy(orinanotherformx+iy)andcompleteTableW2.2(notethatthefirstrowhasbeencompleted).Themagnitudeisgivenby:

TableW2.2Magnitude

W2.4.Writeaprogramwhichcalculatestheangleofacomplexnumberofx+jy(orinanotherformx+iy)andcompleteTableW2.3.Theangleisgivenby:

TableW2.3Angle

Worksheet3W3.1.ModifytheprogramwritteninW2.4sothatitconvertstheangleto

degreeandcompleteTableW3.1.Anangleconvertedfromradianstodegreeusing:

TableW3.1Angle

W3.2.Writeaprogramwhichdeterminestheequivalentresistanceofthreeparallelresistors.UsethisprogramtocompleteTableW3.2.

TableW3.2Equivalentparallelresistance

W3.3.ModifytheprograminQuestionW3.2sothattheuserenterstheappliedvoltagetotheparallelresistorsandtheprogramdeterminesthecurrentineachoftheresistorandtheinputcurrent.UsethisprogramtocompleteTableW3.3.Notethatthecurrentineachoftheresistorsissimplytheappliedvoltagedividedbyeachoftheresistors.AsampletestisgiveninTestrun2.9.

TableW3.3Currentflow

W3.4.ModifytheprograminQuestionW3.3sothatisdisplaysthecurrentinmilliAmps(mA).NotetoconverttomAthenmultiplythevalueby1000.AsampletestisgiveninTestrun2.10.

3

SelectionStatements

3.1if…elsestatements

A decision is made with the i f statement. It logically determines whether aconditionalexpressionisTRUEorFALSE.ForaTRUE,theprogramexecutesone block of code; a FALSE causes the execution of another (if any). Thekeywordelse identifiestheFALSEblock.InC,braces({})areusedtodefinethestartandendoftheblock.InPascal,thebeginandendkeywordsareused.Relationshipoperators,include:•Greaterthan(>).•Lessthan(<).•Greaterthanorequalto(>=).•Lessthanorequalto(<=).•Equalto(inC,itis==and,inPascal,itis=).•Notequalto(inC,itis!=and,inPascalitis<>).These operations yield a TRUE or FALSE from their operation. Logical

statements (&&, | |, !) can then group these together to give the requiredfunctionality.Theseare:•AND(inC,itis&&,and,inPascalitisand);•OR(inC,itis||,and,in

Pascalitisor);•NOT(inC,itis!,and,inPascalitisnot).If the operation is not a relationship, such as bitwise or an arithmetic

operation,thenanynon-zerovalueisTRUEandazeroisFALSE.Thefollowingis an example syntax of the if statement.If the statement block has only onestatement then, inC, thebraces ({})canbeexcluded(inPascal thebeginandendcanbeexcluded).

Thefollowingisanexampleformatwithanelseextension.

It ispossibletonestif..elsestatementstogivearequiredfunctionality.Inthenextexample,statementblock1isexecutedifexpression1isTRUE.IfitisFALSE then the program checks the next expression. If this is TRUE theprogramexecutesstatementblock2,elseitchecksthenextexpression,andsoon.IfallexpressionsareFALSEthentheprogramexecutesthefinalelsestatementblock,inthiscase,statementblock4:

Figure3.1showsadiagrammaticrepresentionofthisexamplestatement.

FIGURE3.1 Structureofthecompoundifstatement

3.1.1ExamplesThissectioncontainssomeCandPascalexampleprograms.

QuadraticequationsSome electrical examples require the solution of a quadratic equation. Thestandardformis:

Thesolutionofxinthisequationisgivenby:

Thiscanyieldthreepossibletypesofresults:1.ifb2=4ac,therewillbeasinglerealroot(x=–b/2a)2.else,ifb2>4ac,

therewillbetworealroots:

3.else,therootswillbecomplex:

Program3.1determinestherootsofaquadraticequation.Inthisprogramtheif..else statement is used to determine if the roots are real, complex orsingular.Thevaluepassedtothesquare-rootfunction(sqrt())shouldbetestedtodetermineifitisnegative.Ifitis,itmaycausetheprogramtoterminateasthesquarerootofanegativenumbercannotbecalculated(itisnumericallyinvalid).Theprogrammayalsoterminateifaiszeroasthiscausesadividebyzeroerror(thetrapforthiserrorisleftasatutorialquestion).Notethat,inC,thesqrt()function isprototyped in themath.h, thus themath.h header is included in theprogram.

Threetestruns3.1,3.2and3.3testeachofthethreetypesofrootsthatoccur.InTest run3.1 the rootsof theequationare real. InTest run3.2 the rootsarecomplex,i.e.intheformx+jy.InTestrun3.3theresultisasingularroot.

Electromagnetic(EM)wavesProgram3.2usestheifstatementtodeterminetheclassificationofanEMwavegivenitswavelength.Figure3.2illustratestheEMspectrumspanningdifferentwavelengths. The classification of the wave is determined either by thefrequency or the wavelength (normally radio and microwaves are defined bytheirfrequency,whereasothertypesbytheirwavelength).Forexample,anEMwavewithawavelengthof10misclassifiedasaradiowave,awavelengthof

500nmasvisiblelightandawavelengthof50cmisinthemicrowaveregion.Testrun3.4showsasamplerun.

FIGURE3.2 EMspectrum

EMwavescanalsobe specifiedby their frequency.Program3.3allows theuser to enter the frequency of thewave, and the program then determines thewavelengthusingtheformula:wherecisthespeedoflightandfthefrequencyofthewave.

Testrun3.5showsasamplerun.

Series/parallelresistancesProgram 3.4 determines the equivalent resistance of two resistors connectedeitherinseriesorparallel.TheCprogramusesscanf()togetthetworesistancevalues and getchar() to select the circuit configuration. Problems can occurwhenusinggetchar()afterscanf()duetonew-linecharactersbeingstoredinthe keyboard buffer. The statement fflush(stdin) has been inserted into theprograminordertoclearthebufferbeforegetchar()iscalled(stdinrepresentsthe standard input device, that is, the keyboard). TheC program also uses tolower() to convert the entered circuit selection character to lowercase (this isprotoyped in thectype.h). InTurboPascal there isno lowercaseconversionsotheuppercaseequivalentisused(upcase).

3.2switchstatementThecasestatement(andswitchinC)isusedwhentherearemultipledecisiontobemade.Itisnormallyusedtoreplacetheifstatementwhentherearemanyroutesofexecutiontheprogramexecutioncantake.Thesyntaxofcase/switchisasfollows.

In Pascal, the case statement simply selects which one of the constants(const1, const2, and so on) matches the constant value. In C, the switchstatementcheckstheexpressionagainsteachoftheconstantsinsequence(theconstantmustbeanintegerorcharacterdatatype).Whenamatchisfoundthestatement(s)associatedwiththeconstantis(are)executed.Theexecutioncarriesontoallotherstatementsuntilabreak isencounteredortotheendofswitch,whichever is sooner. If thebreak is omitted, the execution continues until theendofswitch.If none of the constantsmatches the switch expression a set of statements

associatedwiththedefaultcondition(default:)isexecuted.

3.2.1ExamplesResistorcolourcodeResistorsarenormallyidentifiedbymeansofacolourcodesystem,asoutlinedinTable3.1.Program3.5usesacase/switchstatementtodeterminethecolourofaresistorbandforanenteredvalue.

Table3.1Resistorcolourcodingsystem

Testrun3.6showsasamplerun.

Program 3.6 uses #define directives to define each of the resistor colourbands.Theremaybeaclashwiththesedefinesifotherheaderfilescontainthesedefinitions.IfthisoccurschangethedefinestoRES_BLACK,RES_BROWN,etc.Adefault:hasbeenaddedtocatchanyinvalidinput(suchaslessthan0or

greaterthan9).

ResistanceofaconductorThe resistance of a cylindrical conductor is a function of its resistivity, cross-sectional area and length. These parameters are illustrated in Figure 3.3. Theresistanceisgivenby:

FIGURE3.3 Cylindricalconductor

whereρ=resistivityoftheconductor(Ω.m);l=lengthoftheconductor(m);A=cross-sectionalareaoftheconductor(m2).Program3.7determines the resistanceofacylindricalconductormade from

either silver, manganese, aluminium or copper. The resistivities of thesematerialshavebeendefinedusing#definemacros(inC)orconst(inPascal).The user enters the conductor type as a character (‘c’, ‘a’, ‘s’ or ‘m’)

which can either be in upper or lowercase format as the tolower() functionconverts theenteredcharacter to lowercase (this isprotyped inctype.h).Whenan invalid character is entered the default condition of the case statement isexecuted,andthetextInvalidoptionisdisplayed.Theprogramthencallstheexit()function;theargumentpassedtothisfunctionistheterminationstatus.Avalueof0describesanormaltermination;anyothervaluesignalsanabnormalprogramtermination.InC,theprintf()statementdisplaystheresistanceinscientificformat(%e)

asvaluesaretypicallymuchlessthan1Ω(suchasmΩorμΩ).

Testrun3.7usesanaluminiumconductorwitharadiusof1mmandlength1000m.Theresistanceisfoundtobe8.08Ω.

ThePascalProgram3.7showsthatseveralconstantsforasinglecaseoptioncan be used (for example, ‘a’, ‘A’). In C, it is possible to have several case

optionsintheswitchstatement.Forexample,ifthetolower()functionisnotusedinprogram3.7thenthecaseoptioncanbemodifiedsothatitincludestheupperandlowercaseoptions,asshowninthefollowingcode:

3.3Exercises3.3.1.ModifyProgram3.1sothatitcannotgenerateadividebyzeroerror,that

is,whenais0(zero).Notethatifais0thentherootwillbe–c/b.3.3.2.ModifyProgram3.2sothattheusercanentertheEMwaveasafrequency

orawavelength.Asamplerunisshownintestrun3.8.

3.3.3.ModifyProgram3.2soitusesthe#definestatementtodefinelimitsforthewavelength,forexample:

3.3.4.Capacitanceisnormallydefinedasavalueandaspecifiedunit,suchaspF,nF,μF,mForF.WriteaprograminwhichacapacitancevalueandtheunitareenteredandtheprogramdisplaystheactualnumericalvalueinFarads.Thecapacitanceunitshouldbeenteredasacharacter.AsampletestrunisgiveninTestrun3.9.NotethatpFis10−12F,pFis10−9F,μFis10−6FandmFis10−6F.

3.3.5.RepeatQ3.10forthevalueoftheresistance.TheunitsenteredareeithermΩ(‘m’),Ω(‘1’),kΩ(‘k’)orMΩ(‘M’).Testrun3.11showsasamplerun.NotethatmΩis10−3Ω,kΩis103Ωand?Ωis106Ω.

Worksheet4:W4.1.EnterProgram3.1anduseittocompleteTableW4.1

TableW4.1Rootsofaquadraticequation

Equation Root(s)

x2+21x–72=0

5×2+2x+1=0

25×2–30x+9=0

6×2+9x–20=0

W4.2.ModifyProgram3.1sothatitcannotgenerateadividebyzeroerror,thatis,whenais0(zero).Notethatifais0thentherootwillbe-c/b.

TableW4.2Rootofaquadraticequation

Equation Root

0×2+4x–2=0

0×2+6x+6=0

W4.3.Writeaprograminwhichtheuserentersavalueofresistanceandtheprogramdisplaystheresistancevalueinthebestpossibleunits.A

possibleimplementationcouldbe:Iftheresistanceislessthan1000Ω(1e3)thenitisprintedasthevalueinohms;else,ifitisbetween1000(le3)and1000000Ω(1e6)thenthevalueisprintedaskΩ;else,ifitisgreaterthan1000000(1e6)thenitisprintedinMΩ.

TestrunW4.1showssomesampleruns.

Worksheet5:W5.1.OPTIONAL.EnterProgram3.5andtesttheresults.W5.2.Writeaprogramusingthecase(orswitch)statementthatallowstheuser

toselectfromamenuofoptions.Theseoptionsallowtheusertoselecteitherthecalculationoftheequivalentresistanceoftwoseriesortwoparallelresistors.Theusershouldentera1iftheseriesequivalentisrequiredora2ifparallelrequired.SamplerunW5.1showsasampletestrun.

W5.3.ThetextbackgroundfunctionallowsthecolourofthebackgroundtobechangedtoBLACK,BROWN,RED,…andclrscrclearsthescreen.Sampleprogram3.8showsanexampleprogramoftheiruse.Writeaprogramwhichallowstheusertoenteracolourandthethenprogramchangesthebackgroundcolour.TableW5.1showsthecolourdefinitions.

TableW5.1

OPTIONALEXERCISE:W5.4.ModifytheprogramwritteninW5.2sothattheuserentersan‘s’for

seriesresistanceanda‘p’forparallel.SamplerunW5.2showsasample

testrun.Notethattheprogramshouldaccepttheinputcharactersinuppercaseorlowercase.

4

RepetitiveStatements

4.1Introduction

Iterative,orrepetition,allowstheloopingofasetofstatements.Therearethreeformsofiteration:

4.2forManytaskswithinaprogramarerepetitive,suchaspromptingfordata,countingvalues, and soon.Thefor loopallows theexecutionofablockofcode foragivencontrolfunctionoragivennumberoftimes.InPascaltheformatis:

Inthiscase,valuestartsatstartvalandendsatendval.Eachtimeroundtheloop,valuewillbeincrementedby1.Ifthereisonlyonestatementintheblockthenthebeginandendreservedwordscanbeomitted.InCtheformatis:

where:

4.3Examples4.3.1ASCIICharactersProgram4.1DisplaysASCIICharactersForEnteredStartAndEndDecimalValues.TestRun4.1DisplaysTheASCIICharactersFromDecimal40(‘(‘)To50(‘2’).

4.3.2TransientResponseOfAnRCCircuitFigure4.1 illustratesanRCcircuitwithavoltage stepappliedat t=0.Whenavoltage step, amplitude E volts, is applied to this circuit it produces anexponentialcurrent.

FIGURE4.1 RCcircuitwithstepinputappliedatt=0

Thefollowingdefinesthetransientcurrentinthecircuit.

andthevoltageacrosstheresistorwillbe:

Program4.3determinesthevoltageacrosstheresistoratgiventimeintervals.Theuserenterstheendtimeandthenumberoftimestepsrequired;theprogramdeterminesthevoltageateachofthetimesteps.

Testrun4.2showsthatthevoltageacrosstheresistorstartsatamaximumatt=0. This is because the voltage across the capacitor is initially zero. As thecapacitor charges, the voltage across itwill increase until it almost equals theappliedvoltage.Thecurrentinthecircuitwillalsobeatamaximumwhenthestepisapplied.Itwillthendecaytoalmostzeroataratedeterminedbythetimeconstant(whichisaproductofRandC).

4.3.3BooleanLogicProgram4.3isanexampleofhowaBooleanlogicfunctioncanbeanalyzedanda truth table generated. The for loop generates all the required binarypermutationsforatruthtable.TheBooleanfunctionusedis:A schematic of this equation is given in Figure 4.2. Test run 4.3 shows a

samplerun.

FIGURE4.2 Digitalcircuit

4.4Exercises4.4.1.Writeaprogramwhichprintsallthecharactersfrom‘0’(zero)to‘z’in

sequenceusingaforloop.4.4.2.Writeaprogramwhichdisplaysthesquares,cubesandfourthpowersof

thefirst15integers.Asampleoutputisgivennext.

4.4.3.Writeaprogramwhichdisplaystheyvaluesintheformulasgivenbelowandwiththegivenxsteps.

Asamplerunofthefirstequationisgivennext.

4.4.4.Writeaprogramwhichdisplaysthesineofanumberfrom0°degreesto90°instepsof10°.

4.4.5.ModifyProgram4.3sothatitdeterminesthetruthtableforthefollowingBooleanequation:

Table4.1

Truthtable

4.4.6.WriteaprogramwhichwilldeterminetheimpedanceofanRLseriescircuit.Theprogrammustcalculatethemagnitudeoftheimpedance.

Worksheet6:W6.1.EnterProgram4.1anduseittocompleteTableW6.1.

TableW6.1ASCIIcharacters

Value Character

34

35

36

37

38

64

65

66

67

68

69

70

W6.2.Writeaprogramwhichliststhesquareofthevaluesfrom1to10.AsampleruninshowninTestrunW6.1.

W6.3.CompleteeitherExercise4.4.3(i),Exercise4.4.4orExercise4.4.5.

4.5while()The while statement allows a block of code to be executedwhile a specifiedcondition is TRUE. It checks the condition at the start of the block; if this isTRUEtheblockisexecuted,elseitwillexittheloop.Thesyntaxis

If the statement block contains a single statement then the braces may beomitted(althoughitdoesnoharmtokeepthem).Afewexamplesare:

4.6repeat..until()anddo..while()InCthedo..while()statementissimilarinitsoperationtowhile()exceptthatit tests the condition at the bottomof the loop.The repeat..until() inPascal isalsosimilar tothewhile()statementbutunlikewhile() theloopquitswhentheassociated condition is true. These loops thus allow statement block to beexecutedatleastonce.Thesyntaxis:

Aswithfor andwhile loops thebracesareoptional.Thedo..while() andrepeat..until()loopsrequireasemicolonattheendoftheloop,whereasthewhile()doesnot.

4.7Examples4.7.1RepeatingProgramOftenAUserIsAskedToRepeatTheProgramOnceItHasFinishedCalculatingValues.ThisIsSometimesDoneByAskingTheUserIfTheyWantToRepeat(OrContinue)TheProgram.IfTheUserEntersA‘Y’CharacterThenTheProgramIsRepeated,ElseA‘N’CharacterWillExitTheProgram.Program4.4ImplementsThisWithARepeat..Until()/Do..While()Loop.

4.7.2LimitingRangesOfInputsMost of the values that are entered into a program have a certain range. Forexampleifauserisaskedentertheiragethenthevaluewillalwaysbe:•Aninteger.•Apositivevalue.•Lessthan130.Ifauserentersaninvalidvaluethentheprogramcouldeither:•Crash,whichtypicallyhappenswhenaprogramtriestodividebyzeroor

determinesthesquarerootofanegativenumber.•Givesinvalidresults.Thus it is important that theuser is stopped fromenteringvalueswhichare

invalid. Program 4.5 allows the user to determine the equivalent parallelresistance for two resistors in parallel. The range of value values of enteredresistanceisbetween0Ωand1MΩ.Therepeat..until()/dowhile()loopisplacedaroundtheuserentryofeachofthevalues.Theseloopscontinueuntilauserentersavalidvalue.Testrun4.4showsasamplerun.

Program4.6givesanexampleofthedeterminationofaccelerationgivingtheinitialandendvelocity,andthetimedifference.Therangeofvelocityvaluesisbetween0and1000m/s,and the rangeof timedifferencevalues isbetween0and60s.Testrun4.5showsasamplerun.

4.8Exercises4.8.1.Correcttheerrorsinthefollowingprograms:

(a)

(b)

4.8.2.Whatwillthefollowingsectionsofcodeoutputtothescreen.(i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

4.8.3.Determinetheerrorsinthefollowingprograms(i)

(ii)

(iii)

(iv)

(v)

4.8.4.Determinetheoutputfromthefollowingsectionsofcode(bewareofinfiniteloops).(i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

(viii)

(ix)

4.8.5.WriteaProgramtoconvertadecimalnumbertooctal(base8).AsamplerunisgiveninTestrun4.6.

4.8.6.Replacethefollowingforloopwitharepeat..untilandwithawhile..dointheexamplesbelow.(i)

(ii)

(iii)

4.8.7.Writeaprogramtoconverthexadecimaltodecimal.AsamplerunisshowninTestrun4.7.

4.8.8.Thedraincurrent,inmilliamps,ofasampledepletion-typeFETisgiven

by:

Writeaprogramwhichdeterminesthedraincurrent(inmA)forgate-sourcevoltages(VGS)from–5to5Vinstepsof0.5V.AsamplerunisgiveninTestrun4.8.

Worksheet7:W7.1.Modifyaprogramfromapreviousworksheetsothatitpromptstheuser

toiftheywanttorepeattheprogram.W7.2.Writeaprogramwhichwillcalculatetheequivalentresistanceofthree

resistorsinparallel.Iftheuserentersaninvalidvalue(suchasanegativevalue)theprogramwillprompttheusertoenteravalidinput.AsamplerunisshowninTestrunW7.1.

W7.3.Writeaprogramwhichwillconvertdecimalvaluetohexadecimal(base16).AsamplerunisshowninTestrunW7.2.

W7.4.WriteaPrograminwhichyouenterthenumberofbitsinabinarynumber,enterthesebitsandthencalculatethedecimalequivalent.AsamplerunisgivenintestrunW7.3.Notethatthevalidinputforthebitsshouldbeonlya0ora1.

5

Functions

5.1Introduction

Functions are identifiable pieces of code with a defined interface. They arecalledfromanypartofaprogramandallowlargeprogramstobesplitintomoremanageabletasks,eachofwhichcanbeindependentlytested.Functionsarealsousefulinbuildinglibrariesofroutinesthatotherprogramsuse.Severalstandardlibrariesexist,suchasamathsandinput/outputlibraries.Afunctioncanbethoughtofasa‘blackbox’withasetofinputsandoutputs.

It processes the inputs in a way dictated by its function and provides someoutput. Inmostcases theactualoperationof the ‘blackbox’ is invisible to therest of the program.Amodular program consists of a number of ‘black box’working independently of all others, of which each uses variables declaredwithin it (localvariables)andanyparameterssent to it.Figure5.1 illustratesafunctionrepresentedbyanideal‘black-box’withinputsandoutputs,andFigure5.2showsamainfunctioncallingseveralsub-functions(ormodules).

FIGURE5.1 Anideal‘black-box’representationofafunction

FIGURE5.2 Hierarchicaldecompositionofaprogram

5.2ArgumentsandparametersThedata typesandnamesofparameterspassed intoa functionaredeclared inthe function header (its interface) and the actual values sent are referred to asarguments.Theycanbepassedeitherasvalues(knownas‘passingbyvalue’)oraspointers(knownas‘passingbyreference’).Passingbyvalueinvolvessendingacopyofitintothefunction.Itisnotpossibletochangethevalueofavariableusing this method. Variables can only be modified if they are passed byreference (thiswill be covered in thenext chapter).This chapter looksathowparameterspassintoafunctionandhowasinglevalueisreturned.Anargumentandaparameteraredefinedasfollows:

An‘argument’istheactualvaluepassedtoafunction.

A‘parameter’isthevariabledefinedinthefunctionheader.

5.3CfunctionsFigure 5.3 shows a program with two functions, main() and functionl().Functionmain()callsfunctionl()andpassesthreeparameterstoit; thesearepassedasvalues.Acopyofthecontentsofdgoesintog,eintohandfintoi.

FIGURE5.3 Localandglobalvariables

Variablesdeclaredwithina functionaredescribedas localvariables.Figure5.3showsthatd,eandfarelocalvariableswithinmain();g,h,i,jandkarelocal within function1(). These will have no links to variables of the samenamedeclaredinotherfunctions.Localvariablesonlyexistwithinafunctioninwhichtheyaredeclaredanddonotexistoncetheprogramleavesthefunction.Variablesdeclaredat the topof the source file (andnotwithin a function) aredefined as global variables. These allow functions, within the source file, toaccessthem.Caremustbetakenwhenusingglobalvariablesformanyreasons,one of which is that they tend to lead to programs that are unstructured and

difficulttomaintain.InFigure5.3thefunctionfunction1()makesuseofthevariableaasthisis

declaredasaglobalvariable.Thisfunctioncannotbemodelledasa‘blackbox’as it can modify a variable which is not passed to it. In a relatively smallprogramthismaynotcreateaproblembutasthesizeoftheprogramincreasesthecontrolofvariablescanbecomedifficult.Figure 5.4 shows an example of how things can go wrong with global

variables.Inthisexample,aglobalvariableiisusedbytwofunctions.Initially,thevalueofiwithintheloopinmain()willbe0.Thefunction1()functioniscalledwithinthisloop,whichusesthevariableiwithinanotherloop.Eachtimeit is incremented theglobalvariable takeson the incrementedvalue.Whentheprogramleavesthisfunctionthevalueofiwillhavechanged(thatis,itwillbe10). This causes the for() loop in main() to end. If the variable i had beendeclared locallywithin bothmain() andfunction1() this problemwould nothaveoccurred.Asarule,calledmodulesshouldbeself-containedanduseonlytheparameterssenttothem.

FIGURE5.4 Anexampleoftheuseofglobalvariables

Program5.1containsafunctionnamedprint_values().Thisiscalledfrommain() and variables a and b are passed into the parameters c and d,respectively;canddarelocalparametersandonlyexistwithinprint_values().Thevaluesofcanddcanbechangedwithnoeffectonthevaluesofaandb.

5.3.1ReturnValueThe return statement returns a single value from a function to the callingroutine.Programsinpreviouschaptershaveusedfunctionsthatreturnvalues.Iftherearenoreturnstatementsinafunctiontheexecutionreturnsautomaticallytothe calling routine upon execution of the closing brace (i.e. after the finalstatementwithin the function). Program5.2 contains functionswhichwill addandmultiplytwonumbers.Thefunctionaddition()usesreturn tosendbacktheadditionofthetwovaluestothemain().

Figure 5.5 shows a simple structure chart of this program. The functionaddition()iscalledfirst;thevariablessentareaandbandthereturnvalueisput into the variablesummation.Next, themultiply() is called; the variablessentarealsoaandbandthevaluereturnedgoesintomulti.Finally,thefunctionprint_values()iscalled;thevaluessentarea,b,multiandsummation.

FIGURE5.5 Basicstructurechartforprogram5.2

A function can have several return points, although it is normally better tohaveonlyonereturnpoint.Thisisnormallyachievedbyrestructuringthecode.An example of a function with two returns is shown next. In this example adecisionismadeastowhetherthevaluepassedintothefunctionispositiveornegative. If it isgreater thanor equal to zero it returns the samevalue, else itreturnsanegativevalue(return(-value)).

5.3.2FunctionTypeProgram 5.2 contains functions that return integer data types. It is possible toreturn any other of C’s data types, including float, double and char, byinsertingthedatatypebeforethefunctionname.Ifnodatatypeisgiventhenthedefaultreturntypeisint.Thefollowinggivesthegeneralsyntaxofafunction.

Cisaflexiblelanguageinitsstructure.Itallowsthearrangementoffunctionsinanyorderandevenwithindifferentfiles.Ifthecompilerfindsafunctionthathasnotbeendefined(orprototyped)thenitassumesthereturntypewillbeint.It also assumes that at the linking stage the linker will be able to find therequired functioneither in thecurrent compiledprogram, the librariesorotherobject codes. It is thus important that the function return data type is definedwhen thecompiler is compiling the function;otherwise itwill assume that thereturntypeisint.Functiondeclarations(orprototypes)arenormallyinsertedeitheratthetopof

each file, locally within a function, or in a header file (the .h files). Thesedeclarationsallowthecompilertodeterminethereturntypeandthedatatypesofall parameters passed to the function. It thus allows the compiler to test forillegal data types passed to a function in error. For example the following areinvalid uses of the function printf (), sqrt() and scanf(). The printf() has anincorrectsyntaxasthefirstargumentshouldbeaformatstatement(i.e.astring),the sqrt() function should be passed a floating point value and the scanf()functionrequiresaformatstringasthefirstargument.

Ifthestdio.hheaderisnotincludedthecompilerdoesnotgenerateanyerrorsfortheincorrectusageofprintf()andscanf().Thesameappliestothemath.hheaderfileandthefunctionsqrt().When a function prototype is inserted at the top of the file it is a global

declaration of that function within the source code file. Otherwise, thedeclarationcanbe inserted into thevariabledeclaration listswithina function;thiswillmakethedefinitionlocalonlytothefunctioninwhichitisdefined.Ifafunctiondoesnotreturnavaluethenthedatatypedefinitionforthereturn

value should bevoid.Also, if no parameters are sent to the function then theargumentlistcontainsavoid.Thecompilerwouldthusflaganerrororwarning

if any parameters are passed to a function with a void argument list or if areturnedvalueisusedfromavoidreturndatatype.Figure5.6showstheoperationofafunctionprototype.Atthetopofthefile

theprototypedeclarestheparametertypesoftheargumentspassed(inthiscase,twofloats)andthereturndatatype(inthiscasefloat).Thecompilerchecksallarguments sent to this function to see if they match up with these types. Awarning or error is generated if there is a mismatch. The return type is alsochecked.

FIGURE5.6 Checkingconductedbythecompileronfunctionprototypes

Program5.3containsafunctionpower()whichisprototypedatthetopoftheprogram.Thereturnvalueisdouble;thefirstargumentisdoubleandthesecondis int. This function uses logarithms to determine the value of x raised to thepowerofn.Theformulausedisderivednext;thelog()functionisthenatural

logarithm and the exp() the exponential function. Both of these require theparametersentasdoubleandthereturntypeisalsodouble.

Somecompilersgiveawarningifthereturnvaluedatatypeisdifferentfromthedatatypeofthevariabletowhichitisassigned.Forexample,ifthedatatypeofthevariablexinProgram5.3ischangedtoafloatthenitisgoodpracticetorecastthereturnvaluetoafloat,asshownnext.

5.4PascalfunctionsInPascalafunctionreturnsasinglevalue.Itisidentifiedbythefunctionheader,whichisintheform:

wheretheparametersarepassedthroughtheformal_parameter_listandtheresulttypeisdefinedbyresult_type.Program5.1containstwofunctionsnamedadditionandmultiply.Incalling

theadditionfunctionandvariablesaandbarepassedintotheparameterscandd,respectively;canddarelocalparametersandonlyexistwithinaddition().Thevaluesofcanddcanbechangedwithnoeffectonthevaluesofaandb.Thisfunctionreturnsavaluebacktothemainprogrambysettingavaluewhichisthesamenameasthefunction.Program5.1alsousesaprocedurewhich,inthiscase,issimilartoafunction

butdoesnotreturnanyvaluesbacktothecallingprogram.

Figure 5.5 shows a simple structure chart of this program, The functionaddition()iscalledfirst;thevariablessentareaandbandthereturnvalueisput into the variablesummation.Next, themultiply() is called; the variablessentarealsoaandbandthevaluereturnedgoesintomulti.Finally,thefunctionprint_values()iscalled;thevaluessentarea,b,multiandsummation.Program5.2containsfunctionsthatreturnintegerdatatypes.Itispossibleto

return anyother ofC’s data types, includingreal,double andcharacter, byinsertingthedatatypeafterthefunctionname.A function can have several return points, although it is normally better to

haveonlyonereturnpoint.Thisisnormallyachievedbyrestructuringthecode.An example of a function with two returns is shown next. In this example adecisionismadeastowhetherthevaluepassedintothefunctionispositiveornegative. If it isgreater thanor equal to zero it returns the samevalue, else itreturnsanegativevalue(mag=-val).

Program 5.2 contains a function power() which has a return data type ofdouble; the first argument is double and the second isinteger.This functionuseslogarithmstodeterminethevalueofxraisedtothepowerofn.Theformulausedisderivednext;theIn()functionisthenaturallogarithmandtheexp()theexponentialfunction.

5.5ExamplesThissectioncontainsafewsampleCandPascalprogramswhichusefunctions.

5.5.1TanFunctionThere is no tan function in Pascal; thus to overcome this Pascal Program 5.3containsatanfunctionandTestrun5.1showsasamplerun.

C,unlikePascal,hasatanfunction,thustoavoidredeclaringitCProgram5.4hasafunctioncalledtangent().Toimproveaccuracytheprogramusesdoubledatatypes.Forthisreasonthescanf()andprintf()functionsusethedatatype%Ifconversioncharacters.

5.5.2CentigradeToFahrenheitConversionPascalProgram5.4usestwofunctionstoconvertfromFahrenheittocentigrade,andviceversa.Testrun5.2showsasampletestrun.

PascalProgram5.5andCProgram5.6usesthetwofunctiondevelopedintheprevious programs to display a table of values from0°C to 100°C in steps of10°C.Testrun5.3showsasamplerun.

5.5.3CombinationalLogicIn this example, the followingBoolean equation is processed to determine itstruthtable.

Figure5.7givesaschematicrepresentationofthisBooleanfunction.

FIGURE5.7 Schematicrepresentationofthefunction

Thefournodesnumberedonthisschematicare:1.

2.A.C3.

4.

Table 5.1 gives a truth table showing the logical level at each point in theschematic.Thistableisnecessarytochecktheprogramresultsagainstexpectedresults.Table5.2givestheresultingtruthtable.

Table5.1Truthtable

Table5.2Truthtable

Thepermutationsofthetruthtableinputvariables(i.e.000,001,010,011,…,111)aregeneratedusing3nestedforloops.TheinnerlooptogglesCfroma0 to a 1, the next loop toggles B and the outer loop toggles A. The Booleanfunctionsusethelogicaloperators&&and||.Recallthattheseoperatorstreatavalueof0(zero)asFALSEandanyothervalueasTRUE.

Test run5.4 showsa sample runof theprogram.Notice that the results areidenticaltothetruthtablegeneratedbyanalyzingtheschematic.

Pascal Program 5.6 shows the equivalent Pascal program. As Pascal hasreserved keywords for AND, OR and NOT the function names have beenchangedtoreflectthenumberofinputstheyhave,suchasOR3fora3-inputORgateandAND2fora2-inputANDgate.

5.5.4ImpedanceOfASeriesRLCircuitThemagnitudeoftheimpedanceofanRLcircuitisgivenbytheequation:

andthephaseangleofthisimpedanceisgivenby:

Figure5.8givesaschematicofanRLseriescircuit.

FIGURE5.8 RLseriescircuit

Figure 5.9 gives a structure chart which outlines a basic design for thisproblem. Inputs are resistance (R), inductance (L) and frequency (f). Theprogramdeterminesthemagnitudeandphaseangleoftheimpedance.Inordertodetermine thesevalues the reactanceof the inductormustbedeterminedusingXL=2πfL.

FIGURE5.9 StructurechartforaseriesRLcircuitprogram

Testrun5.5givesasamplerunofthisprogram.Theinputparametersusedareresistance1kΩ,inductance1mHandappliedfrequency1MHz.

PascalProgram5.7givestheequivalentPascalprogram.

5.6Exercises5.6.1.Writeaprogramwhichdeterminesthemagnitudeofanenteredvalue.The

programshoulduseafunctiontodeterminethis.5.6.2.Writeaprogramwhichdeterminesthemagnitudeandangleofacomplex

number(intheformx+iy,orx+jy).Theprogramshouldusefunctionstodetermineeachofthevalues.CompleteTable5.3usingtheprogram(thefirstrowhasalreadybeencompleted).

Table5.3Complexnumbercalculation

5.6.3.Writeamathematicalfunctionforafactorialcalcuation,where:

5.6.4.Writemathematicalfunctionsforthefollowing

Thesineandcosinefunctionsshouldcalculatedfromfirstprincipleswith:

Theerrorinthefunctionsshouldbelessthan1×10−6.5.6.5.UsingthefunctionsdevelopedinExercise5.6.2andthestandardsineand

cosinelibraryfunctions,writeaprogramwhichdeterminestheerrorbetweenthestandardlibraryfunctionsandthedevelopedfunctions.From

this,completeTable5.3.

Table5.3Sineandcosineresults

5.6.6.Writeamathematicalfunctionwhichdeterminestheexponentialofavalueusingthefirstprinciplesformula:

Comparetheresultwiththestandardexp()libraryfunction.5.6.7.WriteBooleanlogicfunctionsforthefollowingfourdigitalgates:

Worksheet8:W8.1.Writeaprogramwithseparatefunctionswhichdeterminethegradientof

astraightline(m)andthepointatwhichastraightlinecutthey-axis(c).Theenteredparametersaretwopointsontheline,thatis,(x1,y1)and(x2,y2).FromthisprogramcompleteTableW8.1(thefirstrowhasalreadybeencompleted).

TableW8.1Straightlinecalculations

W8.2.Writeaprogramwhichhasafunctionwhichwillonlyreturnarealvalue

whentheenteredvalueiswithinaspecifiedrange.Examplesofcallstothisfunction(which,inthiscase,isnamedget_real)aregivennext.

whichwillonlyreturnavaluefromthefunctionwhentheenteredvalueisbetween0and100.Asamplerunisgivennext.

W8.3.Modifytheprogramdevelopedanduseittoprompttheusetoenteravalueofcurrent(between0Aand10A)andvoltage(between0Vand100V).Theprogramwillthendeterminetheresistancebydividingtheenteredvoltagebytheenteredcurrent.Theprogramshouldcontaintwofunctions:get_real()andcale_current().

6

ParameterPassing

6.1Introduction

Parameterpassing involvespassing inputparameters intoamodule (a functioninC and a function and procedure in Pascal) and receiving output parametersbackfromthemodule.Forexampleaquadraticequationmodulerequiresthreeparameterstobepassedtoit,thesewouldbea,bandc.Thesearedefinedastheinputparameters.Theoutputparameterswouldbethetworootsoftheequation,such as root1 and root2. Another parameter could also be passed back toindicate the typeof root (suchas singular, realorcomplex).This indication isnormallyknownasa flag.Figure6.1 illustrates thepassingofparameters intoandoutofamodule.

FIGURE6.1 Parameterpassing

InPascalthemodulewouldbedefinedas:

InCaflagistypicallypassedbackthroughthefunctionheader,thus:

6.2PascalparameterpassingProcedures are used inPascalwhen parameters need to be passed back to thecallingroutine.Functionsarenormallyusedwhenthereisonlyonevaluepassedback,whereasaprocedurecanreturnanynumber(orevennone).Thefirstpartof defining a procedure is to define the input parameters and the outputparameters.The inputparameters aredeclared in theparameter list andoutputparametersaredefinedwithaprecedingvarkeyword.Forexample,iftheinputparametersarexandy,andtheoutputparametersarewandzthenthefollowingprocedurewouldbedefined:

Inthiscaseonlyvalueswillbepassedintothevariablesxandy,whereasthevalues of w and z will be passed back to the calling module. If a procedurerequires localvariables then thesearedeclaredafter theprocedureheader.Forexample, if the procedure in the last example has two local variables namedtemp1andtemp2thenitwillhavetheform:

Local variables only exist within the procedure and their contents are lostwhentheprocedurequits.Program6.1 shows an example programwith a procedurewhich swaps the

valuesoftwovariables.Inthiscaseatemporarylocalvalue(temp)holdsoneofthevalues(temp:=x)so that thecontentsof theothervaluecanbeplaced in it(x:=y).The temporaryvalue is thenput into theothervariable(y:=temp).Thisoperationperformsaswap.

Program6.2 calculates the gradient of a straight line given two coordinates(x1,y1)and(x2,y2).

6.3Cparameterpassing

One of the most confusion areas of C programming is the usage of pointers.TheybasicallyrefertoaddressesinmemorybuttothenovicetheyareoneoftheleastlikedelementsofCprogramming.Inmanycasestheyareextremelyusefulandallowtheprogrammertodirectlyaccessareasofmemory.

6.3.1IntroductionIfacompanyweretosendaformtoapersonandtheyneglectedtoinformtheperson of the correct return address then it would not be possible for therecipient tosendback themodified form(unless thepersonalreadyknows theaddress).Variablessenttofunctionsoperateinasimilarmanner.Ifthefunctiondoesnotknowwhereavariablelives(itsaddressinmemory)thenthefunctioncannotchangeitscontents.A program uses data which is stored by variables. These are assigned to a

unique space inmemory, the number of bytes they use depends on their datatype.Forexample,acharuses1byte,anintwill typicallytake2or4bytes,andafloat,typically,4or8bytes.Eachmemorylocationcontainsonebyteandhasauniqueaddressassociatedwithit(thatis,itsbinaryaddress).Thisaddressisnormallyspecifiedasahexadecimalvalueas thiscanbeeasilyconvertedtothe actual binary address. The memory map in Figure 6.2 shows how threevariablesvaluel,value2 and ch could be allocated inmemory. This diagramassumesthatafloatuses4bytes,andanint2bytes.Thecompiler,inthiscase,hasallocatedvaluelfromaddresses100hto103h,value2at104hand105h,andch is allocated to 106h. The start of the variable’s address inmemory can bedescribedasamemorypointertothevariable.Apointervariableisusedtostoreamemoryaddress.

FIGURE6.2 Examplememorymap

Variables sent to a function can have their contents changed by passing apointer in the argument list. Thismethod involves sending amemoryaddressratherthanacopyofthevariable’svalue.Aprecedingampersand(&)specifiesapointer.Thiscanbethoughtofasrepresentingtheaddressof:

A pointer to a variable will store the address to the first byte of the areaallocatedtothevariable.Anasterisk(*)precedingapointerisusedtoaccessthecontentsofthelocationpointedto.Thenumberofbytesaccessedwilldependonthe data type of the pointer. The * operator can be thought of representingataddress:

Figure6.3showsanexamplememorymap.Avariableresistance_1hasthevalueof310.0 and is storedatamemory locationstartingat107h. If thedatatype is a short integer then it will take up 2 bytes in memory (i.e. 107h and108h),ifitisafloatitmaytakeup4bytesinmemory(i.e.107hto110h).Thememorymapalsoshowsthatapointerptrpointstomemorylocation102h.The

valuestoredatthislocationis15;*ptraccessesitscontents.Thedeclarationofthepointerdefinesthedatatypeofthepointerandthusthenumberofbytesusedtostorethevalueattheaddresspointedtobythepointer.

FIGURE6.3 Examplememorymap

6.3.2PointersWithFunctionsIn the previous chapter it was shown that a single value is passed out of afunction through the function header. In order to pass values out through theargumentlisttheaddressofthevariableispassed;thatisreferredtoas‘callbyreference’.Todeclareapointerthedatatypeisspecifiedandthepointernameisprecededbyanasterisk.Thefollowingisthegeneralformat:

Inthiscaseptr_nameisthenameofthepointer.Thecontentsofthevariableatthisaddresscanbeaccessedusing*ptr_name.Whenafunctionistomodifyavariable thenapointer to itsaddress issent.Forexample, if thevariable tobemodifiedisvaluethentheargumentpassedis&value.Program6.1showsanexampleofa function thatswaps thecontentsof two

variables (a andb).Figure6.4 showshow thecompiler checks theparameterspassedtothefunctionandthereturntype.Thefunctionprototype,inthiscase,specifies that the parameters sent are pointers to integer values and the return

type isvoid.The compiler checks that theparameters sent to the function areinteger pointers and that nothing is assigned to the return value from thefunction.

FIGURE6.4 CompilercheckingforProgram6.1

Program6.2 calculates the gradient of a straight line given two coordinates(x1,y1)and(x2,y2).Withintheget_coord()functionthescanf()donotrequireaprecedingampersand;thevariableargumentsarealreadypointers.

An example of a standardC function that uses call by reference is scanf()whereapointer ispassedforeachvariable.Thisallowsthefunctiontochangeitscontents.

6.4Examples6.4.1QuadraticEquationsC Program 6.2 determines the roots of a quadratic equation. The functionget_values()getsvariablesa,bandc;thesevariablesarepassedaspointers.The function to determine the root(s) of a quadratic equation is

quadratic_equ().Thisreturnstheroottype(suchas,singular,realorcomplex)through the function header and passes the equation root(s) through theargumentlistusingpointers.Theroottypereturnedcanbereferredtoasareturnflag;thisflagissetupusinganenumdeclaration.Therearethreepossiblestatesforthis:SINGULAR(avalueof0),REAL_ROOTS(avalueof1)andCOMPLEX_ROOTS(avalueof2).Theprogramthenusestheflagtodeterminehowtheroot(s)aretobedisplayed.Iftherootissingularthenprint_results()printsasinglevalueofroot1;else,iftherootsarereal,thentwovaluesroot1androot2areprinted;andiftherootsarecomplexthefunctionwillprinttherootsintheformroot1

+/-jroot2.Figure6.5givesabasicstructurechartofthisprogram.Thereturnflagfrom

thequadratic_equ() function is represented by an arrowwith a circle on theend.

FIGURE6.5 StructurechartforProgram6.3

PascalProgram6.3issimilartotheCProgram6.3forthefollowing:•Theflagforthequadraticequationispassedasoneofthevariablesinthe

parameterofquadratic_equ(rtype).•Thequadraticequationroottypesaredefinedasconstantsusingconst.

Testrun6.1showstestsforeachoftheroottypes.

6.4.2EquivalentParallelResistanceCProgram6.3 uses pointers to determine the equivalent parallel resistance oftwo resistors. A basic structure chart, given in Figure 6.6, shows thatget_values() returns the variablesR1 andR2; in order to change their valuesthey are sent as pointers. It also shows that the variables sent tocalc_parallel_res() are R1, R2 and R_equ is returned. Variables R1, R2 andR_equarethenpassedintoprint_results().

FIGURE6.6 Structurechartforprogram6.3

PascalProgram6.4givesthePascalequivalentofthisprogram.

Testrun6.2showsasamplerun.

6.5Exercises6.5.1.Writeaprogramwithasinglemodulethatreturnsboththevalueofmand

cforastraightline,givenpassedvaluesof(x1,y1)and(x2,y2).Theequationofthestraightlineisgivenby:

ExamplecallsforCandPascalare:

wherex1,y1,x2,y2arethecoordinates,misthereturngradientandcisthereturnedvalueforthepointatwhichthelinecutsthey-axis.

6.5.2.Writeaprogramwhichcontainsamodulewhichispassedtwoparameters.Themoduleshouldarrangethevaluesoftheparameterssothatthefirstparameteristhelargest.

6.5.3.Resistorsarenormallyidentifiedbymeansofacolourcodingsystem,whichisgiveninTable6.1.Figure6.7showsa4-bandresistor,wherethefirsttwobandsgiveadigit,thethirdamultiplierandthefourththetolerance.Writeaprogram,withparameterpassing,inwhichtheuserentersthefirstthreevaluesofthecodeandtheprogramdeterminestheresistorvalue.Thevaluerangeofinputsisbetween0and9andAsamplerunisshowninTestrun6.3.

Table6.1Resistorcolourcoding

FIGURE6.7 4-bandresistorcolourcode

6.5.4.Writeamodule,withparameterpassing,inwhichaminimumandmaximumvaluearepassedtoitandthemodulereturnsbackanenteredvaluewhichisbetweentheminimumandmaximumvalue.

ExamplecallsforCandPascalare:

whereministheminimumvalue,maxisthemaximumvalueandvalisthereturnvalued.

Usethisprogramwiththepreviousexercisesothattheenteredvaluesarebetween0and9.

Worksheet9:W9.1.Writeaprogramwhichhasamodulewhichconvertsacomplexnumber

inrectangularformintopolarform(magnitudeandangle).Themoduleshouldhavetwovaluespassedtoit(xandy)andreturntwovaluesforthemagnitudeandangleofthecomplexnumber(magandangle).Thesevaluesaredeterminedusing:

then

ExamplecallsforCandPascalare:

W9.2.Writeaprogramwhichhasamodulewhichconvertsacomplexnumberinpolarformintorectangularform(realandimaginary).Themoduleshouldhavetwovaluespassedtoit(magandangle)andreturntwovaluesfortherealandimaginarypartsofthecomplexnumber(xandy).Thesevaluesaredeterminedusing:

then

ExamplecallsforCandPascalare:

7

Arrays

7.1Introduction

Anarraystoresmorethanonevalue,ofacommondatatype,underacollectivename. Each value has a unique slot and is referenced using an indexingtechnique.Figure7.1showsacircuitwith5resistors,whichcouldbedeclaredwithaprogramwith5simplefloat(inC)orreal(inPascal)declarations.Iftheseresistorvariableswererequiredtobepassedintoafunctionall5wouldhavetobepassedthroughtheparameterlist.Aneatermethodusesarraystostoreallofthevaluesunderacommonname(inthiscaseR).Thusasinglearrayvariablecanthenbepassedintoanyfunctionthatusesit.

FIGURE7.1 Simplevariablesagainstarrayindexing

7.2CarraysThe declaration of an array specifies the data type, the array name and thenumber of elements in the array in brackets ([]). The following gives thestandardformatforanarraydeclaration.

Figure7.2showsthat thefirstelementof thearrayis indexed0andthe lastelement as size–1. The compiler allocates memory for the first elementarray_name[0]tothelastarrayelementarray_name[size–1].Thenumberofbytesallocatedinmemorywillbethenumberofelementsinthearraymultipliedbythenumberofbytesusedtostorethedatatypeofthearray.

FIGURE7.2 Arrayelements

Thefollowinggivessomeexamplearraydeclarations:

7.2.1PointersAndArraysIn C, there is a strong relationship between pointers and arrays. A pointervariablestoresamemoryaddresswhichcanbemodified,whereasanarraynamestoresafixedaddress,settothefirstelementinthearray.Theaddressofthefirstelement of an array named arrname is thus &arrname [0]. Table 7.1 showsexamplesofhowarraysandpointersusedifferentindexingnotationsandhowitispossibletointerchangethem.

Table7.1Relationshipbetweenarraysandpointers

Figure7.3showstwoarraydeclarationsforarrname.Eachhasfiveelements;the first is arrname [0] and the last arrname [4]. The number of bytesallocatedtoeachelementdependsonthedatatypedeclaration.Achararrayusesonebyteforeachelement,whereasanintarraywilltypicallytake2or4bytes.Thearraynamearrname is set to theaddressof the first elementof thearray.Eachelementwithinthearrayisreferencedwithrespecttothisaddress.

FIGURE7.3 Arrayelements

Table7.2givessomeexamplesofarrayandpointerstatements.

Table7.2Examplesofarrayandpointerstatements

Statements Description

inttmp[100]; declareanarraynamedtmpwith100elements

tmp[1]=5; assign5tothesecondelementofarraytmp*(tmp+1)=5/ equivalenttopreviousstatement

ptr=&tmp[2]; getaddressofthirdelement

7.2.2PassingArraysToCFunctionsAtcompilationthecompilerreservesenoughspaceforallelementsinanarray

andinitializesthearraynametothestartofit.Inorderforafunctiontomodifythe array the base address is passed through the parameter list. The functionitself does not know themaximum number of elements in the array; unless aparameter relating to the maximum number of elements in the array is alsopassed.Itisthuspossibletorunofftheendofanarrayandaccessmemorynotallocatedtothearray.The notation used to signify that an array is being passed in a function is

square brackets (this signifies that it is a fixed address and not a pointervariable).Thefollowinggivesanexampleofarraypassing.

7.3PascalarraysInPascal,thedeclarationofanarrayspecifiesthedatatype,thearraynameandthe number of elements in the array in brackets ([]). The following gives thestandardformatforanarraydeclaration.

Thisdeclaresanarrayoftypedatatypewiththefirstelementofarray_name[startval] to the last array element array_name [endval]. The following givessomeexamplearraydeclarationsandassignments.

7.3.1PassingArraysToFunctionsIn order to pass an array into aPascal function or a procedure the arraytypemust first be defined. This is achieved with the type keyword and an arraydefinition is normally done before any of the procedures or functions. Forexampletodefineanarraytypewith100elementsofrealvalues:

andanexamplearrayisdeclaredwith:

When an array is passed into a function or a procedure, the type definitionmustbeused todefine the array type.The following sectionof codegives anexampleof arraybeingpassing intoa function. In this case thearray typehasbeendefinedasarrtypeandthenameofthearrayinthemainprogramisarr1.Inthefunctionthearraynameisarrayin.

If an array is passed to a procedure, the only way that the procedure canmodifythecontentsofanarraysothatwhenitscontentsarechangedwhentheprocedurehascompletedistoputthevarkeywordinfrontofitsdeclarationin

the parameter list. The following shows an example of two procedureswhichcanmodifythecontentsofanarray.Inthefirst,fill_arr,thefunctionmodifiesthearraypassedtoitasthereisavarinfrontofitintheparameterlist.Iftherewasnovarinfrontofthearraynamethenthecontentsofthepassedarraycouldbemodifiedwithin this functionbutwhen the functionwas complete then thearraywhich ispassed to thefill_arr function (array1)wouldnothavebeenmodified.Inthecopy_arrprocedure,thefirstarraypassed(arr1)doesnothaveitscontentschangedasthereisnovarkeywordinfrontofitintheparameterlist,whereasthesecondarraypassed(arr2)hasthevarkeywordinfrontofit.Thesectionofthecodeshouldfillanarraywithenteredvalues(arr1)andthencopythisarrayintoanother(arr2).

7.4Examples7.4.1RunningAverageProgramProgram7.1IsA3-PointRunningAverageProgram.This

TypeOfProgramHasALow-PassFilterResponseAndCanFilterDataSamples.Figure7.4IllustratesHowTheOutputIsAFunctionOfTheAverageOfThreeElementsInTheInputArray;ThisIsAchievedByGeneratingARunningAverage.

FIGURE7.4 Arrayelements

Thefirstandlastvaluesoftheprocessedarraywilltakeonthesamevaluesastheinputarrayastherearenotthreevaluesoverwhichtotakeanaverage.Testrun7.1showsasamplerunwith10enteredvalues.

7.4.2SortingProgramProgram7.2isanexampleofasortingprogramwhereanarrayispassedtothesort function, which then orders the values from smallest to largest. Thealgorithminitiallychecksthefirstvalueinanarraywithalltheothervalues.Ifthevalueinthefirstpositionisgreaterthanthesampledarrayvaluethenthetwovaluesareswapped.Figure 7.5 shows an example of how a 6-element array can be sorted to

determine the smallestvalue. In the first iteration thevalueof20 is comparedwith22.Since20issmallerthan22thevaluesarenotswapped.Next,thevalueof20 iscomparedwith12(the thirdelement),as this issmaller thevaluesareswapped. This now makes 12 the first element. This continues until the lastvalue(15)istested.Attheendoftheseiterationsthesmallestvalue(3)willbethe first element in the array. As the first element now contains the smallestvalue the operation can now continue onto the second element. This is testedagainst the third, fourth, fifth and sixth elements and so on. The number ofiterationsrequiredtocompletethisprocesswillthereforebe15(5+4+3+2+1).

FIGURE7.5 Arrayelements

Testrun7.2showsasamplerunwith10enteredvalues.

7.4.3PreferredValuesInC,theinitializationofanarraywithvalues(orcharacters)isdefinedbetweenasetofbraces({}).Thefollowinggivesthestandardformatfor initializinganarray:

Program7.3determinesthenearestpreferredresistorvalueintherange10to100Ω.Aninitializedarraypref_values[]containsnormalizedpreferredvaluesof10,12,15,18,22,27,33,39,47,56,68,82and100Ω.In Pascal, it is not possible to initialize an array with values. Thus the

set_prefprocedureisusedtofillupthepref_valuesarray.Thefind_nearest_pref functiondetermines thenearestpreferredvalue. Its

operationusesthedifferencebetweentheenteredvalueandanindexvalueinthepreferred value array. If the difference is less than the difference between thepreviousnearestvalueandtheenteredvaluethenthecurrentpreferredvaluewilltakeonthecurrentindexedarrayvalue.Figure7.6showsabasicstructurechartfor thisprogram(note, theset_pref functionhasbeen includedfor thePascalequivalentprogram).Testrun7.3showsasamplerun.

FIGURE7.6 StructurechartforProgram7.3

7.5Exercises7.5.1.Writeafunctionthatwillarrangeanarrayindescendingvalues.Referto

Program7.2.

7.5.2.ModifyProgram7.3sothatitdeterminesthenearestpreferredresistorvaluebetween10and100ΩforthesetofpreferredvaluesgiveninTable7.3.

Table7.3Preferredresistorvalues

7.5.3.Writeafunctionwhichscalesanenteredrealvaluesothatitscalesitbetween10and100anddisplaysthenumberofzeros.AsamplerunisgiveninTestrun7.4.

Possiblealgorithmis:

where,afterthesecodesarecomplete,thevalueofvalwillbebetween10and100andthenum_zeroswillhavethenumberofscalingzeros.

7.5.4.Modifytheprogramin7.2sotheusercanenteranyvalueofresistanceandtheprogramwilldeterminethenearestpreferredresistorvalue.Testrun7.5givesasamplerun.Hint:writeafunctionwhichscalestheenteredvaluebetween10and100Ω(aswritteninExercise7.5.3)thenpassthescaledvaluetothepreferredvalue’sfunction.

7.5.5.Modifytheprogramin7.2sotheusercanenteranyvalueofresistanceandtheprogramwilldeterminethenearestpreferredresistorvalue.Testrun7.5givesasamplerun.Hint:writeafunctionwhichscalestheenteredvaluebetween10and100Ω(aswritteninExercise7.5.3)thenpassthescaledvaluetothepreferredvalue’sfunction.

7.5.6.Figure7.7showsanalternativerepresentationoftheprogramdevelopedinSection7.4.1withthearrayvaluesrepresentedastimesampledvalues,wheretheDrepresentsasingletimestepdelay.Inthiscasetheinputvaluevalueisdelayedbyasingletimestep(Input[i–1])andtwotimesteps(Input[i–2]).Therepresentationoftheoutputcanbewrittenas:

FIGURE7.7 Averagingsystemfortimesampling

Fortheinputdataof:

Determinetheoutputforthefollowingfunctions:(i)

(ii)

(iii)

Assumethattheprevioussamplestoi=0arezero.Testrun7.6givesasamplerunof (i) andProgram7.4 shows a sampleprogramwhichdoesnot have anyfunctionsorprocedures.

Worksheet10:W10.1.Writeaprogram,usingarrays,withafunctionthatwillreturnthelargest

valueenteredbytheuser.W10.2.RepeatW10.1withaminimumfunction.W10.3.Writeaprogramwhichwillfillanarraywithvaluesforthefunction:

for;x=1to10(thatis,1,2,3,4,5,…10).W10.4.ModifytheprograminW10.3forarangeof–1to1,withastepof0.1

in-between(thatis,–1,–0.9,–0.8,…0.8,0.9,1).

8

Strings

8.1Introduction

Strings are one-dimensional arrays containing characters. In most cases thenumberofcharactersastringhaswillvary,dependingon the input.Thus theymustbedeclaredwiththemaximumnumberofcharactersthatislikelytooccur.InPascal, stringsare relativelyeasy touse;whereas strings inCare relativelycomplex, but C has the advantage of having powerful string manipulationroutines.

8.2PascalstringsPascalhasaspecialdatatypereservedforcharacterarrays,whichisstring.Thestringsizecanbesetasthestandardformofanarraydeclaration.Forexample:

Ifthestringsizeparameterisexcluded,suchas:

thenthestringisassumedtohaveasizeof255characters.Table 8.1 lists the routines (functions and procedures) which are used to

manipulatestringsandTable8.2shows theroutineswhichareused toconvertfromnumericvalueintostrings,andvice-versa.

Table8.1Pascalarrayroutines

Table8.2Pascalstringconversionroutines

Program8.1showsanexampleprogramwhichusesstrings.Theassignmentoperator(:=)isusedtoassignonestringtoanother(inthiscase,str1tostr2).Thelength function isalsoused todetermine thenumberofcharacters in theenteredstring.Amajorproblem in softwaredevelopment is toguardagainst incorrectuser

input. Typically a user may enter a string of characters instead of a numericvalue, or a real value instead of an integer. Program 8.2 contains a function(get_int) which overcomes this problem. In this function the user enters aninputintoastring(inp).Thisstringisthenconvertedintoanumericvalueusingthevalfunction.Oneoftheparametersofthevalfunctioniscode.If,afteritis

called,it isazerothenthestringhasbeensuccessfullyconverted,elseeitherastringorarealvaluewasentered.Theuserwillbetoldthattheinputisinvalidandwillbe repromptedforanothervalue (as therepeat…untilcondition isfalse).Theequivalentfunctiontogetarealvalueis:

8.3CcharacterarraysInCanarrayissetupwithanarrayofcharacters,suchas:

The end of a string in C is identified with the ASCII Null or terminationcharacter(‘\0’).Ifdoublequotesareusedtodefineastring,suchas“Cap1”,thenaNullcharacterisautomaticallyappendedontoit.Ifthestringisloaded,asanarray,with single characters then theNull charactermust be inserted after thelast character.For example, if the string tobe loaded is“Cap1” then the arrayelements would be ‘C, ‘a’, ‘p’, ‘1’, ‘\0’. In Figure 8.1 the string “Res–1” is

terminatedinaNullcharacter(thatis,00000000b).

FIGURE8.1 Exampleofstringallocation

Strings are character arrays with maximum size. The string name is thememoryaddressforthefirstcharacterinthestring.Foradeclaredstringofcharname[SIZE],thearraynamenameisafixedaddressatthestartofthestringandSIZE the number of characters reserved inmemory for the string. Figure 8.1shows a sample string allocation in memory; the declared string contains amaximumof11characters.Themaximumnumberofdisplayablecharacters inthestoredstringwillonlybe10astheNullcharacterterminatesthestring.Aswitharrays,thefirstcharacterofastringdeclaredascharstr1[SIZE]is

indexed as str1 [0] and the last as str1 [SIZE–1]. As with arrays, it ispossibletooverruntheendofastring(especiallyiftheterminationcharacterisnotpresent).Thiscancausedatatobereadfromorwrittentoareasofmemorynotassignedforthispurpose.Thedimensionedstringshouldalwayscontainatleastthemaximumnumberofenteredcharacters+1.Ifastringisreadfromthekeyboardthenthemaximumnumberofcharactersthatcanbeenteredislimitedby the keyboard buffer. A macro BUFSIZ, defined in stdio.h, can be used todetermineitssize.

8.3.1StandardStringFunctionsThere are several string handling functions in the standard library; most areprototyped in string.h. Table 8.3 lists these. All the string functions return avalue;forexample,Strlen()returnsanintegervaluerelatingtothelengthofastringandthefunctionsstrcat(),strupr(),strlwr()andstrcpy()returnpointers to the resultant string. This pointer can be used, if required, but theresultantstringisalsopassedbackasthefirstargumentofthesefunctions.Thestrcmp()functionreturnsa0(zero)onlyifbothstringsareidentical.

Table8.3Themainstringhandlingfunctions

CProgram8.1showshowsscanf()scansastringwithdifferentdatatypes.Inthiscase,theuserentersastringoftext.Thefirstwordofthestringisread

asastring(res_name)and thesecondasa float (res_values).Thesscanf()returns the number of fields successfully scanned; if the number of fieldsscanned is equal to2 thevariableokay is set toTRUE and thedo{}while()loopwillthusend.Ifitisnotequalto2theokayvariableissettoFALSEandanerrormessageisdisplayed,theuserwillthenbepromptedtore-enterthevalues.

Testrun8.2showsasamplerun.

C Program 8.2 uses the string function strcmp(). The do{} while() loopcontinuesuntiltheuserenterstheword“exit”.Testrun8.3showsasamplerun.

8.4Examples8.4.1CountingTheNumberOfCharactersProgram8.3ContainsAFunction(Nochars())WhichScansAStringAndDeterminesTheNumberOfOccurrencesOfAGivenCharacter.ItUsesGets()ToReadTheStringAsItAcceptsSpacesBetweenWords.Thefunctionnochars()usespointerarithmetictoreadeachofthecharacters

inthepassedstringuntilaNullcharacter.Thegetchar()functionisusedtogetthesearchcharacter.Testrun8.4showsasamplerun.

8.4.2SettingUpAnArrayOfStringsInC,thesimplestwayofsettingupanarrayofstringsistodefineanewstringdatatype.InCprogram8.4anewdatatypenamedstringisdefinedusingthestatementtypedefcharstring[BUFSIZ].An arrayof strings is then set upusing thedeclarationstringdatabase[MAX_COMP_NAMES].Each string in thearraycancontainamaximumofBUFSIZcharacters(notethiscanbechangedtoanysizeifrequired)andcanbeaccessedusingnormalarrayindexing.

Asample run isgiven inTest run8.5.Note that the string“exit”quits theprogram.

TheequivalentPascalprogramisgiveninPascalProgram8.4.Inthiscaseanewdatatypeofdeclared(str_arr)whichisanarrayofstrings.

InC,anarrayofstringscanalsobeinitializedusingbraces.Program8.5andTestrun8.6showhowthisissetup.

8.4.3ImpedanceOfAParallelRCCircuitTheprogramin thissectiondetermines the impedanceofaparallelRCcircuit.Figure8.2givesaschematicofthiscircuit.Theimpedanceofthiscircuitcanbefoundusingtheproductoftheimpedancesoverthesum.Thus:

FIGURE8.2 ParallelRCcircuit

Themagnitudeoftheimpedanceisthus:

Astructurechart foraprogramwhichdetermines thismagnitudeisgiveninFigure8.3(notethatforclaritytheparameterspassedtothetwoofthecallstothe get_float() function have not been included). The get_parameters()function gets three variables (Res, Cap and freq); parallel_impedance()determinestheinputimpedanceandreturnsitbackintothevariableZin.Finally,print_impedance()displaystheinputparametersandcalculatedimpedance.

FIGURE8.3 StructurechartforProgram8.7

The get_float() (or get_real() in Pascal) function gets a value by firstputtingtheenteredinformationintoastringandthenconvertingitintoafloatingpointvalue.Iftheconversionfailsthentheuserisaskedtore-enterthevalue.Italsocontainsacheckfortheminimumandmaximumvalueoftheenteredvalue.

Testrun8.7showsthattheusercanenteravalueintheincorrectformatandthe program will reprompt for another. Notice that the user has entered thestrings“none”and“fred”;theprogramcopeswiththeseandrepromptsforaninput.

8.5Exercises8.5.1.Explainwhyitisbettertoinputnumericvaluesasastringandthen

convertingittoanumericvalueratherthanenteringitwithscanf()(inC)orreadln()(inPascal).

8.5.2.Writeaprogramthatdeclaresthefollowingsevenstrings.

Storethesestringsasasinglearrayofstringsnamedmenubydeclaringanarrayofstrings.Theprogramshoulddisplaythesestringsasmenuoptionsusingaforloop.Testrun8.8showsasamplerun.

8.5.3.ModifytheprograminExercise8.5.2sothattheusercanenterthemenuoption.Theprogramwilldisplayamessageontheoptionselected.Testrun8.9showsasamplerun.

8.5.4.Modifysomeprogramsinpreviouschapterssothatprogramparametersareenteredusingtheget_float()(orget_real())function.

8.5.5.Writeafunctionthatwillcapitalizeallthecharactersinastring.8.5.6.RepeatExercise8.5.5butmakethecharacterslowercase.8.5.7.Writeafunctionthatwilldeterminethenumberofwordsinastring.Worksheet11:W11.1.Writeaprograminwhichtheuserentersastringoftextandthenpresses

theRETURNkey.Theprogramwillthendisplaythenumberofcharactersintheenteredtext.AsamplerunisshowninTestrun8.10.

W11.2.Writeaprograminwhichtheuserentersastringofeither“sin”,“cos”or“tan”andthenavalue.Theprogramwillthendeterminethecorrespondingsine,cosineortanofthevalue.AsamplerunisshowninTestrun8.11.

W11.3.ModifytheprograminW11.2sothattheprogramreadsintheenteredvalueasastringandconvertsittoarealvalue.Theprogramshouldrepromptifthevalueisinvalid.

W11.4.Writeaprograminwhichtheuserentersanumberofnames,eachfollowedbytheRETURNkey.Theendofthenamesissignifiedbyenteringnocharacters.Theprogramshouldstoretheseinanarrayofstringsandthendisplaythemtotheuser.AsamplerunisshowninTestrun8.12.

9

FileI/O

9.1Introduction

Informationoncomputersisorganizedintodirectoriesandfiles.Typicallyfileshavea filename followedbya filenameextensionwhich identifies the typeoffile. This file extension is important in some operating systems, such asWindows95andWindowsNT,asitidentifiestheapplicationprogramwhichisassociatedwiththefile.Table9.1showssometypicalfiletypes.

Table9.1Typicalfiletypes

FileseithercontaintextintheformofASCII(atextfile)orabinaryfile.AtextfileusesASCIIcharactersandabinaryfileusesthebinarydigitswhichthecomputeruses tostorevalues. It isnotnormallypossible toviewabinary filewithoutaspecialprogram,butatextfilecanbeviewedwithatexteditor.Figure9.1showsanexampleof twofileswhichcontainfour integervalues.

Thebinaryfilestoresintegersusingtwobytesin2scomplementsignednotation,whereasthetextfileusesASCIIcharacterstorepresentthevalues.Forexample,

the value of –1 is represented as1111111111111111 in 2s complement. Thisbinarypatternisstoredtothebinaryfile.ThetextfileusesASCIIcharacterstorepresent–1(thesewillbe‘-’and‘1’),andthebitpatternstoredforthetextfilewillthusbe00101101(ASCII‘-’)and00110001(ASCII‘1’).Ifanewlineisrequired after eachnumber then anew-line character is inserted after it.Note,thereisnonew-linecharacterinASCIIanditistypicaltorepresentanew-linewithtwocharacters,acarriagereturn(CR)andalinefeed(LF).InC,thenew-linecharacterisdenotedby‘\n’.

FIGURE9.1 Filepointer

Thefilepointermovesaseachelementisread/written.Figure9.2showsafilepointerpointingtothecurrentpositionwithinthefile.

FIGURE9.2 Binaryandtextfiles

Thenumber of bytes used to store eachof the elementswill dependon thedatatypeofthevariable.Forexample,alongintegerwillbestoredasfourbytes,whereas a floatingpoint value canbe stored as four bytes (on some systems).The floating point format differs from an integer format; the standard floatingpointformatusesasign-bit,asignificandandanexponent.TheendofthefileissignifiedbyanEOFcharacter.

9.2PascalfileI/OPascalhasaverybasicsetoffileinput/output.ThefunctionsusedaredefinedinTable9.2.

Table9.2PascalfileI/Ofunctions

Function Description

assign(fptr,fname) Assignsafilepoint(fbtr)toafile(fname).

rewrite(fptr) Createsandopensafilewhichhasbeenassignedwithfbtr.

reset(fptr) Opensanexistingfilewhichhasbeenassignedwithfbtr.

write(fptr,val) Writesavalue(val)toafilewhichhasbeenassignedwithfbtr.

read(fptr,val) Readsafilewhichhasbeenassignedwithfbtrandputsthevalueintoval.

InPascal,afilepointerisdefinedeitherwiththetextkeyword(foratextfile)orwith:

Thusafilepointerforanintegerfilewouldusethefollowing:

PascalProgram9.1readsinanumberofintegervaluesandwriteseachoneinturntoafile(‘out.dat’).Theprograminitiallyassignsthefilenametothefilepointer (fout) using the assign function. Next the file is created with therewritefunction.Eachvaluethatisenteredisthenwrittentothefileusingthewritefunction.Theprogramkeepspromptingforvaluesuntiltheuserentersa–

1value.Whenthishappenstheprogramwillexittherepeat…untilloop.Thefilepointeristhenresettothestartofthefilewiththeresetfunction.Nextthevaluesarereadbackusingthereadfunction.Finally,afterthe–1valueisread-in,thefileisclosedwiththecloseroutine.

9.3CfileI/OThere are 11 main functions used in file input/output (I/O), which are listedbelow. The fprint() and fscanf() functions are similar to printf() andscanf(),buttheiroutputgoestoafile.

Afilepointerstores thecurrentpositionofa readorwritewithina file.Alloperationswithinthefilearemadewithreferencetothepointer.Thedatatypeofthispointerisdefinedinstdio.handisnamedFILE.

9.3.1OpeningAFile(Fopen())Afilepointerisassignedusingfopen().Thefirstargumentisthefilenameandthe second a stringwhich defines the attributes of the file; these are listed inTable9.3.

Table9.3Fileattributes

Attribute Function

“r” openforreadingonly

“w” createforwriting

“a” append;openforwritingattheend-of-fileorcreateforwritingifthefiledoesnotexist

“r” openanexistingfileforupdate(readandwrite)

“w+” createanewfileforupdate

“a+” openforappend:open(orcreateifthefiledoesnotexist)forup-dateattheendofthefile)

Thedefaultmodeforopeningfilesis text,butatattributecanbeappendedonto the attribute string to specify a text file. For example, the attribute “wt”

opensatextfileforwriting.Abinaryfileisspecifiedbyappendingabontotheattributestring.Forexample,“rb”willopenabinaryfileforreading.Theformatofthefopen()functionis:

Iffopen()iscompletedsuccessfullyafilepointerwillbereturned,andthisisinitializedtothestartofthefile.IfwasnotabletoopenthefilethenaNULLwillbereturned.Therecanbemanyreasonswhyafilecannotbeopened,suchas:•Thefiledoesnotexist.•Thefileisprotectedfromreadingfromand/orwritingto.•Thefileisadirectory.Itisimportantthataprogramdoesnotreadfromafilethatcannotbeopened

as it may cause the program to act unpredictably. A test for this condition isgivennext.

9.3.2ClosingAFile(Fclose())Onceafilehasbeenuseditmustbeclosedbeforetheprogramisterminated.Afile which is not closed properly can cause problems in the file system. Thestandard format is given next; the return value (rtn) returns a 0 (a zero) onsuccess,otherwiseEOFifanyerrorsoccur.ThemacroEOFisdefinedinstdio.h.

The feof() function detects the end-of-file character. It returns a non-zerovalue (that is, a TRUE) if the file pointer is at the end of a file, else a 0 isreturned.Thefunctionshownnextusesthefeof()functiontodetecttheendof

the file and also tests the return from the fscanf() so that an unsuccessfulreadingfromthefileisdisregarded.

9.3.3ReadingFromFilesTable9.4liststhemainfunctionsandexamplesusedinreadingfromfiles.

Table9.4Readingfromfiles

9.3.4WritingToFilesTable9.5liststhemainfunctionsusedinwritingtofiles.

Table9.5Writingtofiles

9.4Examples9.4.1AveragesProgramCProgram9.1 andPascalProgram9.2use text files todetermine the averagevalueofanumberoffloatingpointvaluescontainedinafile.Theget_values()functionisusedtoreadthevaluesfromafile,inthiscase,IN.DAT.Thisfilecanbecreatedusingatexteditor.

AnexampleofthecontentsoftheIN.DATfilearegivennext.

AsamplerunusingthisfileisgiveninTestrun9.1.

9.4.2BinaryRead/WriteCProgram9.2andPascalProgram9.3isanexampleofhowanarrayoffloatingpointvaluesiswrittentoabinaryfile.IntheCprogramthefloatingpointvaluesare writen using fwrite() and then read back using fread(). Note that theNOFILE flags returned from dump_data() and read_data() are ignored bymain().InthePascalprogramthevaluesarewrittentothefileusingwriteandreadusingthereadroutine.

AsampletestrunisgiveninTestrun9.2.

9.5ReadingandwritingonecharacteratatimeInCasinglecharacterisreadfromafilewithfgetc()andreadbackwiththefputc().CProgram9.3showsanexampleofreadingacharacter,oneatatime,

fromafileandwritingittoanotherfile.PascalProgram9.4givestheequivalentprogram.Itusesthereadandwriteroutines.

9.6Exercises9.6.1.Writeaprograminwhichtheuserentersanycharacterandtheprogram

willdeterminethenumberofoccurrencesofthatcharacterinthespecifiedfile.Forexample:

9.6.2.Writeaprogramwhichwilldeterminethenumberofwordsinafile.(Hint:countthenumberofspacesinthefile.)9.6.3.Writeaprogramwhichwilldeterminethenumberoflinesinafile.Apossiblemethodistocountthenew-linecharacters.

9.6.4.Writeaprogramwhichwillgetridofblanklinesinaninputfileandwritestheprocessedfiletoanoutputfile.Exampleinputandoutputfilesaregivennext.

Worksheet12:W12.1.Writeaprogramwhichwilldeterminetheaverage,thelargestandthe

smallestvaluesofatextfilecontainingfloatingpointvaluesinatextform.

W12.2.Writeaprogramwhichwillcountthenumberofcharactersinafile.Hint:readthefileonecharacteratatime.

W12.3.Writeaprogramwhichwillcounttheoccurrencesoftheletter‘a’inafile.Hint:readthefileonecharacteratatime.

W12.4.ModifyProgram9.1sothattheoutputiswrittentoafile.

10

StructuresandRecords

10.1Introduction

Astructure(or, inPascal,arecord)isanidentifiableobjectthatcontainsitemswhichdefineit.Theseitemsarelinkedunderacommongrouping.Forexample,anelectricalcircuithascertainpropertiesthatdefineit.Thesecouldbe:•Acircuittitle.•Circuitcomponentswithidentifiablenames.•Circuitcomponentswithknownvalues.Forexample,acircuitmayhavea titleof“RCFilterCircuit”, thecircuit

componentsarenamed“R1”,“R2”and“C1”andthevaluesoftheseare4320Ω,1200Ωand1μF,respectively.Thetitleandthecomponentnamesarecharacterstrings,whereasthecomponentvaluesarefloatingpoints.Astructure(orrecord)groups theseproperties into a single entity.Thesegroupings are referred to asfieldsandeachfieldismadeupofmembers.

10.2RecordsinPascalA structure is a type that is a composite of elements that are distinctive andperhapsofdifferentdatatypes.Thefollowingisanexampleofastructurewhichwill store a single electrical component. The record variable declared, in thiscase,isComponent.Ithasthreefieldsofdifferingdatatypes;cost(afloat),code(aninteger)andname(acharacterstring).

The dot notation (.) accesses each of the members within the record. Forexample:

Pascal Program 10.1 is a simple database program. The database stores arecord of a single electrical component which includes its name(Component.name), its cost (Component.cost) and its code number(Component.code).Thenameisastring,thecodeasignedintegerandthecostafloatingpointvalue.

Testrun10.1showsasamplerun.

Pascal Program 10.2 contains a procedure to print the record(print_component ()). To pass a structure into a function the data type ofparameterpassedmustbedefined.Forthepurposethetypekeywordisusedtodefineanewdatatype,inthiscase,itisnamedcomp.

Testrun10.2showsasamplerun.

Pascal Program 10.3 uses a function to get data into the record(get_component()).Theparameterpassedintothisfunctionhasavarinfrontoftheparametersothatitcanbepassedbacktothecallingroutine.

Testrun10.3showsthattheresultsareidenticaltothepreviousrun.

10.3StructuresinCA structure is a type that is a composite of elements that are distinctive andperhapsofdifferentdata types.The followinggives an exampleof a structuredeclaration(inthiscasethestringshavebeendeclaredwithamaximumof100characters).

Thefollowingisanexampleofastructurewhichwillstoreasingleelectrical

component. The structure variable declared, in this case, is Component. It hasthreefieldsofdifferingdatatypes;cost(afloat),code(aninteger)andname(acharacterstring).

The dot notation (.) accesses each of thememberswithin the structure. Forexample:

CProgram10.1isasimpledatabaseprogram.Thedatabasestoresarecordofa single electrical component which includes its name (Component.name), itscost (Component.cost) and its codenumber (Component.code).Thename is astring,thecodeasignedintegerandthecostafloatingpointvalue.

Testrun10.4showsasamplerun.

Note that the structure could have been set up at initialization using thefollowing:

CProgram10.2containsa function toprint the structure (print_component()).Topassastructureintoafunctionthedatatypeofparameterpassedmustbedefined.Forthepurposethetypedefkeywordisusedtodefineanewdatatype;inthiscase,itisnamedCompType.Theprogramalsousesbracestoinitializethefieldswithinthestructure.

Testrun10.5showsasamplerun.

CProgram10.3usesafunctiontogetdataintothestructure(get_component()).Theparameterpassedintothisfunctionwillbeapointertothebaseaddressofthestructure.Forthispurpose,anampersandis insertedbeforethestructurename. The structure pointer operator (->) is usedwith the structure pointer toaccessamemberofafield.

Testrun10.6showsthattheresultsareidenticaltothepreviousrun.

10.4ArrayofstructuresAnarrayofstructurescanbesetupinawaysimilartonormalarrayindexing.Whenanarray isdeclared thecompilerassignsenoughmemory toholdall itselements. Program 10.4 is similar to Program 10.3, but uses an array ofstructurestostoreupto5electricalcomponents.Figure10.1showsastructurechartof thisprogram. Itusesget_float() andget_int() to filterany invalidinputsforthecostandcodeofacomponent.ThesefunctionsweredevelopedinChapter 9 and have been reused as they have beenwell tested and are easilyported intoanyprogram.Thecostof theelectrical components isnow limitedbetween0and1,000andthecomponentcodefrom0to32,767.Aget_string()functionhasalsobeenadded toget thenameof thecomponent.Test run10.7showsasamplerun.

FIGURE10.1 StructurechartforProgram10.4

10.4.1ComplexArithmeticProgram 10.5 uses a structure (or record) tomultiply to complex numbers. Ifthesecomplexnumbersarea+jbandc+jdandtheresultiszthen:

Thisoperationisimplementedinthefunction(procedure)multi_complex().Testrun10.8givesatestrunfortheresultof3+j4and6+j2.

10.5Exercises10.5.1.Writeadatabaseprogram,basedonProgram10.4,whichgivesamenu

choiceastowhethertheuserwishestoenterinputanewelectriccomponent,tolistallthecomponentsalreadyinthedatabase,ortoexittheprogram.AsamplerunisgiveninTestrun10.9.

10.5.2.Writeaprogramwhichconvertsfromrectangularnotationtopolarform.Inrectangularnotation:

inpolarformthisis:

10.5.3.Writeaprogramusingstructures(orrecords)withcompleximpedancevaluesthatwilldeterminetheparallelimpedanceoftwoimpedancesZ1andZ2.Theformulafortheimpedancesinparallelisgivenbelow:

10.5.4.Writeaprogramwhichcontainsthefollowingcomplexnumbermanipulationroutines:(i)complexnumberadd.

(ii)complexnumbersubtract.(iii)complexnumbermultiply.(iv)complexnumberdivide.

10.5.5.Modifythedatabaseprograminthetextsothattheusercanselectanoptionwhichwillorderthecomponentnamesinalphabeticorder.

PARTBC++

11

IntroductiontoC++

11.1Introduction

C is an excellent software development language for many general purposeapplications.Itsapproachisthatdataandassociatedfunctionsaredistinct,datais declared and the functions are then implemented. Object-orientedprogramming languages allow the encapsulation of a set of data types andassociatedfunctionsintoobjects.Theseobjectsareintegratedentities.C++isbyfarthemostpopularobject-orientedlanguage.Itwasdevelopedby

Bjane Stoustrup at AT&T Bell Laboratories. A new programming language,basedonC++,calledJava,hassincebeendevelopedbySunMicrosystems.C++iswellsupportedandtherearemanydifferentdevelopmentsystems.Figure11.1shows Microsoft Visual C++ Version 4.0. Microsoft Visual Version 5.0 issimilar but has enhanced support for WWW applications. The default fileextensionforaC++programisCPP.

FIGURE11.1 MicrosoftVisualC++

11.2EnhancementstoC++C++hasmanyenhancementsoverC.Theseinclude:I/Ostreamsupport.Thisfacilityallowsdatatobedirectedtoaninputand/or

anoutputstream.Section11.3outlinesthis.Objects. An object incorporates data definitions and the declaration and

definitionsoffunctionswhichoperateonthatdata.Classes. These are used to implement objects and can be initialized and

discardedwith constructors anddestructors, respectively.Section11.6outlinesthis.Complex numbers. C++ supports the usage of complex numbers and their

mathematicaloperations.Section11.7outlinesthese.Datahiding.Thisallowscertaindata tobehidden frompartsofaprogram

whicharenotallowedaccesstoit.Section11.6outlinesthis.Overloading.Thisallowsmore thanonedefinitionandimplementationofa

function.Section11.5outlinesthis.Virtual functions. This allows any one of a number of multiple defined

functionstobecalledatrun-time.Templateclasses.Thisallowsthesameclasstobeusedbydifferentdata.

11.3I/OstreamInC,outputissenttothestandardoutputusingtheprintf()function.InC++,standardinputandoutputaretakenfromstreams.Thestandardoutputstreamiscout(normallytothemonitor)andthestandardinputstreamistakenfromcin(normallyfromthekeyboard).Tobeabletousethesestreams,theiostream.hheader filemust be included in the program. The redirection operator (<<) isused todirect thedata to the inputoroutput.Program11.1showsanexampleprogramandTestrun11.1showsasamplerun.

Program11.2showsanotherexampleandTestrun11.2showasamplerun.

11.4CommentsC++supportssinglelinecommentwithadoubleslash(//)ormultilinecommentwhich are defined between a (* and a *). The single line comment makeseverythingonthelineafterthedoubleslashacomment.Afewexamplesare:

11.5FunctionoverloadingOften theprogrammerrequires tocalla function inanumberofwaysbutstillwants the same name for the different implementations. C++ allows thiswithfunction overloading.With this the programmerwrites a number of functionswith the same number but which are called with a different argument list orreturn type. The compiler then automatically decides which one should becalled. For example, in C++ Program 11.3 the programmer has defined threesquare functions named sqr(). The data type of the argument passed is of adifferent type for each of the functions, that is, either an int, a float or adouble. The return type is also different. In this program, three variables, ofdifferent types, have been declared in the main() function. The compilerwillthencallthecorrectformatfunctionforeachofthecalls.Testrun11.3showsasamplerun.Itcanbeseenthattheimplementationofthesquarefunctionwithafloatdatatypeproducessomeroundingerrors.

Theargumentlistoftheoverloadedfunctiondoesnothavetohavethesamenumberof arguments for eachof theoverloaded functions.C++Program11.4shows an example of an overloaded functionwhich has a different number ofarguments for each of the function calls. In this case, the show_results()function can either be calledwith amessage, followedby three values, or thethreevalues,orwithasinglevalue.

11.6ClassesClassesareageneralformofstructures(struct).InC,astructgatherstogetherdatamembersandinC++thestructmayalsohavefunctionmembers.Themaindifferencebetweenaclassandastructisthatinastructallmembersofthe

structure are public, while in a class the members are, by default private(restricted).Inaclass,membersaremadepublicwiththepublickeyword,andprivatewiththeprivatekeyword.C++Program11.3showsanexampleofaclass.Itcanbeseenthatitissimilar

toastructure,butthatsomepartsoftheclassareprivatewhileothersarepublic.Thesearedefinedasfollows:•Apublicmemberofaclasscanbeaccessedbyexternalcodethatisnotpart

oftheclass.Oftenthepublicmemberisafunction.•Aprivateclassmembercanonlybeusedbycodedefinedinamember

functionofthesameclass.It is obvious that all classesmust have a public content so that they canbe

accessed by external functions. In C++ Program 11.5 the circuit class has aprivatepart, in thiscase, thevariablertemp.Thepublicpartsare thefunctionsparallel()andserial(),whichdeterminetheparallelandseriesresistanceoftwo resistors. In the main function the class is declared to c1. The seriescalculationiscalledwithc1.series(r1,r2)andtheparallelcalculationiscalledwithc1.parallel(r1,r2).

Theclasswouldgetcumbersomeifthefunctionswithinitwheretobedefinedinit.C++Program11.6showshowthefunctionscanbedefinedinanotherpartoftheprogram.Inthiscasetheclassnameisdefinedfollowedbyadoublecolon(::)andthenthefunctionname.

Theprivatepartofaclassistypicallyusedtostorevariableswhicharelocal

onlytotheclass.AnexampleisshowninC++Program11.7wherethevariableslocaltothecircuitclassarer1andr2.Theget_res()functionisthenusedtosetthesevaluesandtheothertwofunctionsthenusethem.

Inmanycasestheuseofpassingparametersbypointerscanbeeliminatedbyusingclasses.ThisisshowninC++Program11.8wheretheget_res()functionis private to the circuit class. Then within the series() and parallel()functionstheget_res()functioniscalled.Notethatnootherfunctioncancallthisfunctionasitisprivatetocircuit.

11.7ComplexnumbersC++containsa rangeof functionswhich supportcomplexnumbers.Theseareprototypedincomplex.handareoutlinedinTable11.1.

Table11.1Complexfunctionsprototypedincomplex.h

Thedatatypecomplexisusedtodeclareacomplexvariable.InC++Program11.9 the variable z has been declared a complex variable. The complex()function is used to convert thex andy variables into a complex number.Thefunctionsreal(),imag(),conj(),abs()andpow()areusedandTestrun11.6displaysasamplerun.

11.8Exercises11.8.1.Writeanoverloadedfunctionwhichdeterminesthegradientofastraight

line.Theparameterspassedareeithertwo(x,y)coordinates(x1,y1x2,y2)orifthechangeinxandthechangeiny(dx,dy).Thegradientwillbecalculatedasfollows:

11.8.2.Writeanoverloadedfunctionwhichdeterminestheangleofastraightline.Theparameterspassedareeithertwocoordinates(x1,y1,x2,y2)orifthechangeinxandthechangeiny(dx,dy).Thegradientwillbe

calculatedasfollows:

11.8.3.ThefollowingC++classdefinitioncontainsdatefunctions.Theget_date()functionshouldfillthevariablesday,monthandyear.Thevalid_data()functionshouldthentestiftheentereddateisvalid.

WriteaC++programwhichcontainsthisclassdefinition.11.8.4.C++Program11.10hasamathfunctionclasswhichcontainsmultiply

anddividefunctions.Writeaprogramwhichaddsseveralothermathematicalfunctions,togivethefollowing:

11.8.5.ModifyExercise11.8.4sothatthevaluesareenteredfromthekeyboard.11.8.6.ThefollowingC++classdefinitioncontainsaninitialization,increment,

decrementanddisplayingfunctions.Theinitializationfunctionshouldinitializethesamplesvariableto0;theincrementfunctionshouldaddoneontothesamplesvariable;thedecrementshouldtakeoneawayfromsamplesandtheshow_samplesdisplaythesamplesvalue.CompletetheclassdeclarationandwriteaC++whichcallsit.Theincrementfunctionshouldbecalledwhenthe‘j’keyispressed(followedbytheRETURNkey)andthedecrementfunctionshouldbecalledwhenthe‘1’key(followedbytheRETURNkey)ispressed.ThevalueofsamplesshouldbedisplayedwhentheRETURNkeyispressedwithouteitherthe‘j’or‘1’keys.

11.8.7.Usingthecomplexnumberfunctionsdeterminethefollowing,forthecomplexnumbera=4+i5andb=6+i10:(a)a+b(b)axb(c)a-b(d)a÷b(e)a2(f)b3(g)|a|(h)ea(i)√a

Notethatinelectricalengineeringacomplexnumberistypicallyrepresentedasa+jb.

12

MoreC++

12.1Constructorsanddestructors

Aconstructorallowsfortheinitializationofaclassandadestructorallowstheclassfunctiontoberemovedfrommemory.Theyaredefinedasfollows:•Aconstructorisaspecialinitializationfunctionthatisautomaticallycalled

wheneveraclassisdeclared.Theconstructoralwayshasthesamenameastheclassname,andnodatatypesaredefinedfortheargumentlistorthereturntype.Normallyaconstructorisusedtoinitializeaclass.

•Adestructorisamemberofafunctionwhichisautomaticallycalledwhentheclassisdestroyed.Ithasthesamenameastheclassnamebutisprecededbyatilde(~).Normallyadestructorisusedtoclean-upwhentheclassisdestroyed.

C++Program12.1hasaclasswhichisnamedclass_ex.Theconstructorforthisclassisclass_ex()andthedestructoris~class_ex().Testrun12.1showsasamplerun.ItcanbeseenthatinitiallywhentheprogramisrunthemessageConstructing is displayed. This is because the class is initially declared toc1.Then when the function test() is called the Constructing message is againdisplayedasanewclassisdefined(c2).Whentheprogramleavesthisfunctionthe destructor is called and thus themessageDestructor is displayed. Finally,whentheprogramquitsthedestructorisagaincalled.

12.2FunctiontemplatesFunctiontemplatesallowfunctions tobecapableofoperatingonargumentsofanydatatype.Todefineafunctiontemplatethefollowingisdone:•Prefixthefunctionwiththetemplatekeyword.•Defineoneormoreidentifiersthatdefineparameterizedtypeswithinangled

brackets.InC++Program12.2 the template is created for amaximum() function.The

templatedefinition:

definesthatnumbercanbeofanydatatype.Thus:

couldbematchedtoanyoneofthefollowing:

Thedefinitionofthefunctionisgivenas:

12.3ClasstemplatesThe class template is a generalization of the function template. These allowcollectionsofobjectsofany typeusing thesameclass template.Program12.3showsanexampleofaclasscalc_current.Inthiscasethetemplateisdefinedas:

whichdefines thatnumbercanbeofanydata type.Whendefining theclassvariablethedatatypeisdefined.Forexample,todefinethedatatypeofnumberasanint,then:

orasafloat:

In the case ofC++Program12.3 the classwhich uses anintwill performintegeroperationsandthefloatdeclarationwillperformfloatoperations.

12.4I/OstreamsThe standard C++ library provides an expanded set of functions, templates,string-handling classes and many other enhancements to C. One of the mainenhancementsisthestreamI/Olibrary.ThestreamI/OlibrarygetsridsofaparticularprobleminCwherefunctions

such as printf() and scanf(), gives run-time errors when the data they arehandlingisintheincorrectdataform.Forexample:

wouldcreateanerror if iwasdeclaredasafloating-pointvalue.ThestreamI/Ofunctionforinputfromthestandardinputis:

Thisallowsforautomaticdatatypeconversion.TosupportthestreamI/Othestdio.h header file has been replaced by the header files iostream.h,fstream.handiomanip.h,andclasseswhichareautomaticallydefinedare:

cout forstandardoutput.

cin forstandardinput.

cerr forstandarderror

The stream I/O class hierarchy is given in Figure 12.1. The ios (I/O state)classisdeclarediniostream.h,anditcontainsinformationaboutthestateofthestream. It includes functionswhich are used to open and close streams, and italsohasstreamformatflags.

FIGURE12.1 Blockdiagramofasimplecomputersystem

The file I/O classes ifstream and ofstream are declared in the header filefstream.h. and the classiostream inherits bothistream andostream, and isdeclared in iostream.h.ifstream inherits all the standard input streamoperationsdefinedbyistream and adds a fewmore, such as constructors andfunctionsforopeningfiles.ofstreamsimilarlyrelatedtoostream.Finally,fstream,declared in theheader file fstream.h, inherits iostreamand

containsfunctionsandconstructorsthatallowfilestobeopenedininput/outputmode.Theclassescanbesummarizedby:

AbstractStreamBaseClass

ios Streambaseclass.

InputStreamClasses

istream General-purposeinputstreamclassandbaseclassforotherinputstreams.

ifstream Inputfilestreamclass.

OutputStreamClasses

ostream General-purposeoutputstreamclassandbaseclassforotheroutputstreams.

ofstream Outputfilestreamclass.

Input/OutputStreamClasses

iostream General-purposeinput/outputstreamclassandbaseclassforotherinput/outputstreams.

fstream Input/outputfilestreamclass.

12.4.1OpeningAndClosingAFileThe functions used to open and close a stream are open() and close (),respectively.

open()Foraprogram tousea file stream(fstream) itmust firstbeassociatedwithaspecificdiskfilewiththeopenfunction.Thisfunctionisusedwithanassociatedopen_mode flag, which can be combined together with the bitwise OR (|)operator.Table12.1definestheseflags.

Table12.1Fileopenflags

Flag Function

ios::app Opensanoutputfileforappending.

ios::ate Opensanexistingfileandsetsthefilepointertotheendofthefile.

ios::binary Opensfileinbinarymode(Notethatthedefaultmodeistextmode).

ios::in Opensaninputfile.Useios::inasanopen_modeforanofstreamfiletopreventtruncatinganexistingfile.

ios::nocreate Openthefileonlyifitalreadyexists.Otherwisetheoperationfails.

ios::noreplace Opensthefileonlyifitdoesnotexist.Otherwisetheoperationfails.

ios::out Opensanoutputfile.Whenyouuseios::outforanofstreamobjectwithoutios::app,ios::ate,orios::in,ios::truncisimplied.

ios::trunc Opensafileanddeletestheoldfile(ifitalreadyexists).

Todeclareafilepointertheclassofstreamisused.Forexample,todeclareastreamofmyfilewhichhasthefilenameofout.datandisanoutputfile:

This typeofdeclarationcanbeusedwhen the streamhasa fixednameandfile_openflag.It isalsopossibletousetheopenfunctiontoopenthefile.Thefollowingachievesthesameastheprevioussampleprogram.

Thefollowinggivesanexampleofabinaryfilewhichisonlyforinput:

whilethefollowinggivesanexampleofabinaryfilewhichisonlyforinputandoutput:

close()Theclosemember function isused toclose the fileassociatedwithanoutputfilestream.Thefstreamdestructorautomaticallyclosesthefilewhentheclassis destroyed. It is typically usedwhen the stream needs to be associatedwithanotherfile.C++Program12.4opensafileforoutputandwritesthecharacter‘H’toitand

thenclosesthefile.

12.4.2TextI/OThetwomainfunctionsusedfortextI/Oareput()andget().

put()Theputmember functionwrites a single character to the output stream.C++Program12.4showsanexampleoftheput()function.

get()The unformatted get member function works like the >> operator with twoexceptions:•Thegetfunctionincludeswhite-spacecharacters,whereastheextractor

excludeswhitespace.•Thegetfunctionislesslikelytocauseatiedoutputstream(cout,for

example)tobeflushed.Toextractastring:

Ortoextractasinglecharacter:

where nCount is the maximum number of characters to store the line anddelimisthedelimitercharacter(whichbydefaultisanew-line).

getline()Thegetlinemember function is similar to theget function,but theydifferasthegetfunctionleavestheterminatingcharacterinthestream;whereasgetlineremovestheterminatingcharacter.C++Program12.5givesanexampleofthegetline()function.

12.4.3ErrorProcessingFunctionsTheI/Ostreamlibrariesalsocontainanumberofmemberfunctionswhichcanbeusedtotestforerrorswhilereadingandwritingtoastream.Table12.2liststheseflags.

Table12.2Errorprocessingfunctions

Function Returnvalue

bad ReturnsTRUEifthereisanunrecoverableerror.

fail ReturnsTRUEifthereisanunrecoverableerrororan“expected”condition,suchasaconversionerror,orifthefileisnotfound.

error,orifthefileisnotfound.

good ReturnsTRUEifthereisnoerrorcondition(unrecoverableorother-wise)andtheend-of-fileflagisnotset.

eof ReturnsTRUEontheend-of-filecondition.

clear Setstheinternalerrorstate.Ifcalledwiththedefaultarguments,itclearsallerrorbits.

rdstate Returnsthecurrenterrorstate.

C++ Program 12.6 shows an example programwhich uses the fail() andgood()functions.Thefail()functionallowstheprogramtotestifthefilehasbeenopenedandthegood()functionallowstheprogramtotestiftheend-of-filehasbeenreached(orifanerrorhasoccurred).

Notethat:

canbereplacedby:

as the ! operator is overloaded to perform the same function as the fail()function.

12.4.4FilePointersTheseekg()andtellg()areusestoset(seekg)orget(tellg)thecurrentfilepoint for an input stream.On the output stream theseekp() andtellp() areused.Theseekgformatis:

where pos specifies the new position value, off is the new offset value,(streamoff and streamposare a typedef equivalent to a long int) anddir is theseekdirectionwhichmustbeoneofthefollowing:

C++ Program 12.7 gives an example of a file pointer being set to thebeginningofafilewithmyfile.seekp(01,ios::beg)),where01representsazerooffsetandios::begtheflagforthebeginningofthefile.Thetellg()formatis:

wherethestreampostypeisalongint.

12.4.5BinaryI/OreadThe read member function is similar to the read function in C. It reads aspecified number of bytes from a file into specified areas of memory. C++Program12.7givesanexampleasinglefloatingpointvaluebeginningwrittentoafileandthenreadback.

writeThewritememberfunctionissimilartothewrite()functioninC.Itwritesaspecifiednumberofbytesfrommemoryintoafile.C++Program12.8givesanexampleofwritinga10elementarraytoafileandthenreadingitback.

12.5Exercises12.5.1.ModifyC++Program12.2sothatitimplementsaminimumfunction.12.5.2.Usingafunctiontemplatewriteaprogramwhichwillcalculatethe

currentinacircuitwherethevoltageandresistancecaneitherbeints,floatsordoubles.Thecurrentisgivenby:

12.5.3.Writeaprogramwhichwillreadthetextfromafilein.datandcopyit,onecharacteratatime,tothefileout.dat.

12.5.4.Writeaprograminwhichtheuserenters10floating-pointvaluesfromthekeyboard.Theprogramshouldthenstorethesetoabinaryfile(file1.dat).Finallythefileshouldberead-backtocheckitscontents.

PARTCAssemblyLanguage

13

Introduction

13.1Introduction

High-level languages such as C, Pascal, Basic and FORTRAN are useful inrepresentingoperationsinanalgorithm-likemanner.Thesehigh-levellanguagestendtohidemuchofthesystemoperationsawayfromtheprogrammer.Inmostcases, the operation of the program within the computer is invisible and thelocationofthedataortheprogramcodeinmemoryisalsounimportant.Thisisimportantinmostapplicationsastheprogrammercanforgetaboutmuchofthelow-leveloperationsandgetonwithhigh-leveloperationssuchasmathematicalcalculations,graphics,andsoon.TherearethreemainreasonsforlearningAssemblyLanguage,theseare:•Itincreasestheunderstandingoftheoperationofthecomputer.•AssemblyLanguagecodesgenerallycanbeusedtofinelytunetheoperation

ofthecode.Thisfinetuningoftenspeeds-uptheoperationoftheprogram.Thisisbecausehigh-levelcompilersdonotalwaysoptimizethegeneratedcodeforspeed.

•Togainaccesstocertainhardwareoperations.Many programs use a mixture of a high-level language and Assembly

Languageformachineortimecriticaloperations.

13.2BasiccomputerarchitectureThemainelementsofabasiccomputersystemareacentralprocessingunit(ormicroprocessor),memory,andinput/output(I/O)interfacingcircuitry.Theseareconnectedbymeansof threemainbuses: theaddressbus; thecontrolbus;andthedatabus,asillustratedinFigure13.1.Externaldevicessuchasakeyboard,display,diskdrives,andsoon,canconnectdirectlyonto thedata,addressandcontrol bus or can be connected via the I/O interfacing circuit. A bus is acollectionofcommonelectricalconnectionsgroupedbyasinglename.

FIGURE13.1 Blockdiagramofasimplecomputersystem

MemorynormallyconsistsofRAM(randomaccessmemory)andROM(readonlymemory).ROMstores permanent binary information,whereasRAM is anon-permanentmemoryandwillloseitscontentswhenthepoweristakenaway.Applicationsof this typeofmemory includerunningapplicationprogramsandstoringtemporaryinformation.Themaincontrollerforthecomputeristhemicroprocessor.Itfetchesbinary

instructions from memory, decodes these instructions into a series of simpleactionsandcarriesouttheactionsinasequenceofstepswhicharesynchronizedbyasystemclock.Toaccessalocationinmemorythemicroprocessormustputtheaddressof the locationon theaddressbus.Thecontentsat thisaddressarethenplacedon thedatabus and themicroprocessor reads thedataon thedatabus.Tostoredatainmemorythemicroprocessorplacesthedataonthedatabus.Theaddressofthelocationinmemoryisputontheaddressbusandthedataisthenreadfromthedatabusintotherequiredmemoryaddresslocation.Theclassificationofamicroprocessorrelatestothemaximumnumberofbits

itcanprocessatatime,thatistheirwordlength.Theevolutionhasgonefrom4-bit,8-bit,16-bit,32-bitandto64-bitarchitectures.

13.3BitsandbytesAcomputeroperatesonbinarydigitsnamedbits.Thesecaneitherstorea‘1’ora‘0’(ON/OFF).Agroupof4bitsisanibbleandagroupof8bitsabyte.These8-bits provide 256 different combinations of ON/OFF, from 00000000 to11111111.A16-bitfieldisknownasawordanda32-bitfieldasalongword.Binarydataisstoredinmemorieswhichareeitherpermanentornon-permanent.Thisdataisarrangedasbytesandeachbytehasadifferentmemoryaddress,as

illustratedinFigure13.2.

FIGURE13.2 Memorystorage(eachaddressholdseightbits).

13.3.1BinaryNumbersAcomputeroperatesonbinarydigitswhichuseabase-2numberingsystem.Todeterminethedecimalequivalentofabinarynumbereachcolumnisrepresentedby 2 raised to the power of 0, 1, 2, and so on. For example, the decimalequivalentsof10000001and01010011are:

Thus01001111gives:

Thenumberofdecimalvalues that abinarynumbercan represent relates tothenumberofbits.Forexample:•8bitsgives0to28–1(255)differentrepresentations;•16bitsgives0to216–1

(65535)differentrepresentations;•32bitsgives0to232–1(4294967295)differentrepresentations.

Themost significant bit (msb) is at the left-hand side of the binary numberandtheleastsignificantbit(lsb)ontheright-handside.Toconvertfromdecimal(base-10)tobinarythedecimalvalueisdividedby2recursivelyandremaindernoted.Thefirstremaindergivestheleastsignificantdigit(LSD)andthelastthe

mostsignificantdigit(MSD).Forexample:

Thus110110inbinaryis54decimal.

13.4BinaryarithmeticThebasicbinaryadditionoperationisgivennext.

Thisisusedwhenaddingtwobinarynumberstogether.Forexample:

13.5NumbersandrepresentationsNumbersarestoredinseveraldifferentways.Thesecanbe:•integersorfloatingpointvalues.•singleprecisionordoubleprecisionnumbers.•signedorunsignedintegers.

13.5.1NegativeNumbersSigned integers use a notation called 2s complement to represent negativevalues.Inthisrepresentationthebinarydigitshavea‘1’inthemostsignificant

bitcolumnifthenumberisnegative,elseitisa‘0’.Toconvertadecimalvalueinto 2s complement notation, the magnitude of the negative number isrepresentedinbinaryform.Next,allthebitsareinvertedanda‘1’isadded.Forexample,todeterminethe16-bit2scomplementofthevalue–65,thefollowingstepsaretaken:

Thus,–65is111111111011111in16-bit2scomplementnotation.Table13.1shows that with 16 bits the range of values that can be represented in 2scomplementisfrom–32767to32768(thatis,65536values).

Table13.116-bit2scomplementnotation

Whensubtractingonevaluefromanother thevaluetobe takenawayisfirstconvertedinto2scomplementformat.Thisisthenaddedtotheothervalueandtheresult is in2scomplement.Forexample, tosubtract42from65,first42isconvertedinto2scomplement(that is,–42)andaddedtothebinaryequivalentof65.Theresultgivesacarryintothesignbitandacarry-out.

Fora16-bitsignedintegercanvaryfrom–32768(1000000000000000)to

32767 (0111111111111111).AsimpleCprogram toconvert froma16-bitsignedintegerto2scomplementbinaryisgiveninProgram13.1.

AsamplerunisgiveninTestrun13.1.

13.5.2HexadecimalAndOctalNumbersInassembly languagebinarynumbersare representedwithaproceedingb, forexample010101111010band101111101010barebinarynumbers.Binarydigitsare often commonly represented in hexadecimal (base 16) or octal (base 8)representation.Table13.2showsthebasicconversionbetweendecimal,binary,octal and hexadecimal numbers. In assembly language hexadecimal numbershave a proceeding h and octal number an O. For example, 4 3 F1h is ahexadecimalvaluewhereas4310oisoctal.

Table13.2Decimal,binary,octalandhexadecimalconversions

Torepresentabinarydigitasahexadecimalvalue thebinarydigitsaresplitintogroupsof fourbits (starting from the least significantbit).Ahexadecimalequivalent value then replaces each of the binary groups. For example, torepresent0111010111000000bthebitsaresplitintosectionsof4togive:

Thus, 75C0h represents the binary number 0111010111000000b. To convertfromdecimaltohexadecimalthedecimalvalueisdividedby16recursivelyandeachremaindernoted.Thefirstremaindergivestheleastsignificantdigitandthefinalremainderthemostsignificantdigit.Forexample,thefollowingshowsthehexadecimalequivalentofthedecimalnumber1103:

Thusthedecimalvalue1103isequivalentto044Fh.InC,hexadecimalvaluesareprecededbya0(zero)andthecharacter‘x’(0x)

andanoctalnumberaprecedingzero0(zero).InPascal,adollarsignisusedtosignifyahexadecimalvalue, forexample$C4.Table13.3gives someexample

formats.

Table13.3Decimal,binary,octalandhexadecimalconversions

13.6MemoryaddressingsizeThesizeoftheaddressbusindicatesthemaximumaddressablenumberofbytes.Table13.4showsthesizeofaddressablememoryforagivenaddressbussize.Forexample:

Table13.4Addressablememory(inbytes)relatedtoaddressbussize

Addressbussize Addressablememory(bytes)

1 2

2 4

3 8

4 16

5 32

6 64

7 128

8 256

9 512

10 1K*

11 2K

12 4K

13 8K

14 16K

15 32K

16 64K

17 128K

17 128K

18 256K

19 512K

20 1M†

21 2M

22 4M

23 8M

24 16M

25 32M

26 64M

32 4G‡

64 16GG

*1Krepresents1024†1Mrepresents1048576(1024K)‡1Grepresents1073741824(1024M)•A1-bitaddressbuscanaddressuptotwolocations(thatis0and1).•A2-bitaddressbuscanaddress22or4locations(thatis00,01,10and11).•A20-bitaddressbuscanaddressupto220addresses(1MB).•A24-bitaddressbuscanaddressupto16MB.•A32-bitaddressbuscanaddressupto4GB.

13.7Exercises13.7.1.Completethetablebelow(assume8-bitunsignedbinaryvalues):

Decimal Binary(8-bit)

12

235

128

255

10110110

01101001

13.7.2.Determinethebinaryordecimalequivalentsforthefollowingvalues(assume16-bitvaluesand2scomplementnotation):

13.7.3.Completethetablebelow(assume16-bitsignedintegersand2scomplement):

13.7.4.Determinethefollowingsubtractionsusing2scomplementnotation(assume8-bitvaluesandtheanswershouldbein2scomplement):(i)43–21

(ii)12–46(iii)127–126(iv)0–72(v)32+75

14

ComputerArchitecture

14.1HistoryofthePC

In1959,IBMbuiltthefirstcommercialtransistorizedcomputernamedtheIBM7090/7094series.Itwassosuccessfulthatitdominatedthecomputermarketformanyyears.Later, in1965, theyproduced the famous IBMsystem360whichwasbuiltwithintegratedcircuits.Thenin1970IBMintroducedthe370system,which includedsemiconductormemories.Unfortunately, thesecomputerswereextremelyexpensivetopurchaseandmaintain.Around the same time the electronics industrywas producing cheap pocket

calculators. The development of affordable computers happened when theJapanesecompany,Busicon,commissionedasmall,atthetime,companynamedInteltoproduceasetofeighttotwelveICsforacalculator.InsteadofdesigningacompletesetofICs,IntelproducedasetofICswhichcouldbeprogrammedtoperform different tasks. Thesewere the first evermicroprocessors. Soon Intel(short for Integrated Electronics) produced a general-purpose 4-bitmicroprocessor,namedthe4004,andamorepowerful8-bitversion,namedthe8080.Other companies, such asMotorola,MOSTechnologies andZilogweresoonalsomakingmicroprocessors.IBM’s virtualmonopoly on computer systems soon started to slip asmany

companies developed computers based around the newly available 8-bitmicroprocessors, namely MOS Technologies 6502 and Zilog’s Z–80. IBM’smain contenders were Apple and Commodore who introduced a new type ofcomputer– thepersonalcomputer(PC).TheleadingsystemsweretheAppleIand theCommodore PET.These spawnedmany others, including the SinclairZX80/ZX81, the Sinclair Spectrum, the Commodore Vic-20 and the classicAppleII(allofwhichwherebasedonoraroundthe6502orZ–80).IBMrealizedthepotentialofthemicroprocessorandusedIntel’s16-bit8086

microprocessor in their version of thePC. Itwas named the IBMPC and hassincebecometheparentofall thePCseverproduced.IBM’smainaimwas to

make a computer which could run business applications, such as wordprocessors, spreadsheets and databases. To increase the production of thissoftwaretheymadeinformationonthehardwarefreelyavailable.Thisresultedinmanysoftwarepackagesbeingdevelopedandhelpedclonemanufacturerstocopytheoriginaldesign.Sotheterm‘IBM-compatible’wasbornanditquicklybecameanindustrystandardbysheermarketdominance.

14.2IntelmicroprocessorsIntel marketed the first microprocessor, named the 4004, and it caused arevolutionintheelectronicsindustrybecausepreviouselectronicsystemshadafixed functionality.With thisprocessor the functionalitycouldbeprogrammedbysoftware.Itcouldhandlejustfourbitsofdataatatime(anibble),contained2,000 transistors, operated with 46 instructions and allowed 4KB of programcodeand1KBofdata.ThesecondgenerationofIntelmicroprocessorsbeganin1974withthe8-bit

processors; these were named the 8008, 8080 and the 8085. As they couldhandlemorebitsatatimetheyweremuchmorepowerfulthantheprevious4-bitdevices.Theyweretypicallyusedinearlymicrocomputersandapplicationssuchas electronic instruments and printers. The 8008 had a 14-bit address bus andcouldthusaddressupto16KBofmemoryandthe8080hada16-bitaddressbusthusgivingita64KBlimit.The thirdgenerationofmicroprocessorsbeganwith the launchof the16-bit

processors. Intel released the 8086 microprocessor, which was mainly anextensiontotheoriginal8080processor,andthusretainedadegreeofsoftwarecompatibility.IBM’sdesignersrealizedthepowerofthe8086anduseditintheoriginalIBMPCandIBMXT(eXtendedTechnology).Ithada16-bitdatabusanda20-bit addressbus,givingamaximumaddressable capacityof1MB. Itcouldalsohandleeither8or16bitsofdataatatime(althoughinamessyway).ThePChasevolvedsinceusingIntelprocessors.A stripped-down 8-bit external data bus version called the 8088 was also

available. This stripped down processor allowed designers to produce lesscomplex(andcheaper)computersystems.Animprovedarchitectureversionofthe8088/88,calledthe80286,waslaunchedin1982,andwasusedintheIBMAT(AdvancedTechnology).In 1985, Intel introduced its first 32-bitmicroprocessor, the 80386DX.This

devicewas compatiblewith theprevious8088/8086/80286 (80×86)processors

andgaveexcellentperformance. Itcouldhandle8,16or32bitsata timeandhad a full 32-bit data and address buses. This gave it a physical addressingcapabilityof4GB.Astripped-down16-bitexternaldatabusand24-bitaddressbus version called the 80386SX was released in 1988. Thus, because of itslimitedaddressbussize,itcouldonlyaccessupto16MBofphysicalmemory.In 1989, Intel introduced the 80486DX which was basically an improved

80386DXwithamemorycacheandmathco-processorintegratedontothechip.It had an improved internal structure making it around 50% faster than acomparable 80386. The 80486SX was also introduced, which was merely a80486DXwiththelinktothemathco-processorbroken.Amajorlimitingfactoron the speed of the processor became the speed of the system clock. For thisreasonclockdoublersandtreblerswherereleasedallowedtheprocessortouseahigher clock speed than the system clock. Thus internal operationswithin theprocessorsweremuchfasterbut theprocessorhadtoslowdownto thesystemclock to communicate with external devices. Typically, systems with clockdoublerprocessorsoperatedaround75%fasterthanthecomparablenon-doubledprocessors(becausemuchoftheoperationwithinthecomputerisdonewiththeprocessor). Typical clock doubler processors areDX2–66 andDX2–50whichrunfrom33MHzand25MHzclocks,respectively.IntelalsoproducedarangeofmicroprocessorsthatrunatthreeorfourtimesthesystemclockspeedandarereferredtoasDX4processors.TheseincludetheIntelDX4–100(25MHzclock)andIntelDX4–75(25MHzclock).ThePentium(orP–5)isa64-bit‘superscalar’processor.Itcanexecutemore

thanoneinstructionatatimeandhasafull64-bit(8-byte)databusanda32-bitaddressbus,andcanoperateatspeedsfrom75MHztoover200MHz(whichrunsfromthe66MHzsystemclock).Intermsofperformance,itoperatesalmosttwice as fast as the equivalent 80486. It also has improved floating-pointoperations (roughly three times faster) and is fully compatible with previous80x86processors.Figure14.1showshowIntelprocessors interfacetoexternalequipment.

FIGURE14.1 Intelmicroprocessorsandtheirexternalinterfacing

14.380386/80486microprocessorFigure 14.2 shows themain 80386/80486processor connections.ThePentiumprocessor connections are similar but it has a 64-bit data bus. There are threemain interface connections: the memory/IO interface, interrupt interface andDMA(directmemoryaccess)interface.

FIGURE14.2 Someofthe80386/80486signalconnections.

Thewrite/read (w / ) linedetermineswhether data iswritten to (w)or readfrom ( )memory. PCs can interface directlywithmemory or can interface toisolatedmemory.Signal lineM / differentiatesbetween the two types. If it ishigh then the direct memory is addressed, else if it is low then the isolated

memoryisaccessed.The80386DXand80486haveanexternal32-bitdatabus(D0-D31)anda32-

bitaddressbusrangingfromA2toA31.Thetwoloweraddresslines,A0andA1,aredecodedtoproducethebyteenablesignals , , and .The lineactivates when A1A0 is 00, activates when A1A0 is 01, activates whenA1A0and activateswhenA1A0is11.Figure14.3illustratesthisaddressing.

FIGURE14.3 Memoryaddressing

Thebyteenablelinesarealsousedtoaccesseither8,16,24or32bitsofdataatatime.Whenaddressingasinglebyte,onlythe linewillbeactive(D0-D7);if16bitsofdataaretobeaccessedthen and willbeactive(D0-D15);if32bitsaretobeaccessedthen , , and areactive(D0-D31).The D/ linedifferentiatesbetweendata and control signals.When it is high

then data is read from or written to memory, else if it is low then a controloperationisindicated,suchasashutdowncommand.Theinterruptlinesareinterruptrequest(INTR),non-maskableinterruptrequest

(NMI)andsystemreset(RESET),allofwhichareactivehighsignals.TheINTRlineisactivatedwhenanexternaldevice,suchasaharddiskoraserialport,wishestocommunicatewith the processor. This interrupt ismaskable and the processorcan ignore the interrupt if itwants.The NMI is a non-maskable interrupt and isalwaysacted-on.When itbecomesactive theprocessorcalls thenon-maskableinterruptserviceroutine.TheRESETsignalcausesahardwareresetandisnormallymadeactivewhentheprocessorispowered-up.

14.4RegistersAll the PC-based Intelmicroprocessors are compatiblewith the original 8086processandarenormallybackwardlycompatible.Thus,forexample,aPentiumcan run 8086 and 80386 code.Microprocessors use registers to perform theiroperations.These registers are basically specialmemory locations in that theyare given names. The 8086 has 14 registers which are grouped into fourcategories,asillustratedinFigure14.4.

FIGURE14.4 8086/88registers

14.4.1GeneralPurposeRegistersTherearefourgeneralpurposeregisterswhichareAX,BX,CXandDX.Eachcanbeusedtomanipulateawhole16-bitwordorwithtwoseparate8-bitbytes.Thesebytesarecalledthelowerandupperorderbytes.Eachof theseregisterscanbeusedas two8-bitregisters;forexample,ALrepresentsan8-bitregisterwhichisthelowerhalfofAXandAHrepresentstheupperhalfofAX.The AX register is the most general purpose of the four registers and is

usuallyused for all typesofoperations.Eachof theother registershasoneormoreimpliedextrafunctions.Theseare:•AX,whichisnamedtheaccumulator.Itisusedforallinput/outputoperations

andsomearithmeticoperations.Forexample,multiply,divideandtranslateinstructionsassumetheuseofAX.

•BX,whichisnamedthebaseregister.Itcanbeusedasanaddressregister.•CX,whichisthecountregister.Itisusedbyinstructionswhichrequireto

count.Typicallyitisusedforcontrollingthenumberoftimesaloopisrepeatedandinbitshiftoperations.

•DX,whichisthedataregister.Itisusedforsomeinput/outputandalsowhenmultiplyinganddividing.

14.4.2AddressingRegistersThe addressing registers are used in memory addressing operations, such asholding the source address of thememory and the destination address. TheseaddressregistersarenamedBP,SP,SIandDI,whichare:•SI,whichisthesourceindex.Thisisusedwithextendedaddressing

commands.•DI,whichisthedestinationindex.Thedestinationisusedinsomeaddressing

modes.•BP,whichisthebasepointer.•SS,whichisthestackpointer.

14.4.3StatusRegistersStatusregistersareusedtotestforvariousconditionsinanoperation,suchas‘istheresultnegative’,‘istheresultzero’,andsoon.Thetwostatusregistershave16bitsandarecalledtheinstructionpointer(IP)andtheflagregister(F):•IP,whichistheinstructionpointer.TheIPregistercontainstheaddressofthe

nextinstructionoftheprogram.•Flagregister.Theflagregisterholdsacollectionof16differentconditions.

Table14.1outlinesthemostusedflags.

Table14.1Processorflags

14.4.4SegmentsRegistersTherearefourareasofmemorycalledsegments,eachofwhichhave16bitsandcanthusaddressupto64KB(from0000htoFFFFh).Thesesegmentsare:•Codesegment(csregister).Thisdefinesthememorylocationwherethe

programcode(orinstructions)isstored.•Datasegment(dsregister).Thisdefineswheredatafromtheprogramwillbe

stored(dsstandsfordatasegmentregister).•Stacksegment(ssregister).Thisdefineswherethestackisstored.•Extrasegment(es).Alladdressesarewithreferencetothesegmentregisters.The 8086 has a segmentedmemory, these registers are used to manipulate

thesesegments.Eachsegmentprovides64KBofmemory,thisareaofmemoryisknownasthecurrentsegment.Segmentedmemorywillbediscussedinmoredetailinthenextsection.

14.4.5MemoryAddressingThereareseveralmethodsofaccessingmemorylocations,theseare:•Impliedaddressingwhichusesaninstructioninwhichitisknownwhich

registersareused.•Immediate(orliteral)addressingusesasimpleconstantnumbertodefinethe

addresslocation.•Registeraddressingwhichusestheaddressregistersfortheaddressing(such

asAX,BX,andsoon).•Memoryaddressingwhichisusedtoreadorwritetoaspecifiedmemory

location.

14.5MemorysegmentationThe 80386, 80486 and Pentium processors run in one of two modes, eithervirtual or real.When using the virtualmode they act as a pseudo-8086 16-bitprocessor,knownastheprotectedmode.Inthereal-modetheycanusethefullcapabilities of their address and data bus. The mode and their addressingcapabilities depend on the software and thus allDOS-based programs use thevirtualmode.The 8086 has a 20-bit address bus so that when the PC is running 8086-

compatible code it can only address up to 1 MB of memory. It also has asegmentedmemoryarchitectureandcanonlydirectlyaddress64KBofdataatatime. A chunk of memory is known as a segment and hence the phrase‘segmentedmemoryarchitecture’.Memoryaddressesarenormallydefinedbytheirhexadecimaladdress.A4-bit

address bus can address 16 locations from 0000b to 1111b. This can berepresented in hexadecimal as 0h to Fh. An 8-bit bus can address up to 256locationsfrom00htoFFh.Two importantaddressingcapabilities for thePCrelate toa16-anda20-bit

addressbus.A16-bitaddressbusaddressesupto64KBofmemoryfrom0000hto FFFFh and a 20-bit address bus addresses a total of 1MB from 00000h toFFFFFh.The80386/80486/Pentiumprocessorshavea32-bitaddressbusandcanaddressfrom00000000htoFFFFFFFFh.Amemorylocationisidentifiedwithasegmentandanoffsetaddressandthe

standard notation is segment:offset. A segment address is a 4-digithexadecimal addresswhich points to the start of a 64 kB chunk of data. The

offset isalsoa4-digithexadecimaladdresswhichdefines theaddressoffsetfromthesegmentbasepointer.ThisisillustratedinFigure14.5.

FIGURE14.5 Memoryaddressing

The segment:offset address is defined as the logical address, the actualphysicaladdress iscalculatedbyshifting thesegmentaddress4bits to the leftandaddingtheoffset.Theexamplegivennextshowsthattheactualaddressof2F84:0532is2FD72h.

14.5.1AccessingMemoryUsingCAndPascalInCtheaddress1234:9876hisspecifiedas0×12349876.TurboPascalaccessesamemorylocationusingthepredefinedarraymem[](toaccessabyte),memw[](aword)ormemw[](alonginteger).Thegeneralformatismem[segment:offset].

14.5.2NearAndFarPointersAnearpointerisa16-bitpointerwhichcanonlybeusedtoaddressupto64KBofdatawhereasafarpointerisa20-bitpointerwhichcanaddressupto1MBofdata.A farpointer canbedeclaredusing the fardata typemodifier, as shown

next.

In the program shown in Figure 14.6 a near pointer ptr1 and a far pointerptr2havebeendeclared. In thebottompartof the screen theactualaddressesstoredinthesepointersaredisplayed.Inthiscaseptr1isDS:1234handptr2is0000:12 34h. Notice that the address notation of ptr1 is limited to a 4-digithexadecimaladdress,whereasptr2hasasegment:offsetaddress.Theaddressofptr1isintheformDS:XXXXwhereDS(thedatasegment)isafixedaddressinmemoryandXXXXistheoffset.

FIGURE14.6 Nearandfarpointers

Thereareseveralmodes inwhich thecompileroperates. In thesmallmodelthe compiler declares all memory addresses as near pointers and in the largemodel they are declared as far pointers. Figure 14.7 shows how the largememorymodelisselectedinBorlandC(Options→Compiler→Model→Large).The large model allows a program to store up to 1 MB of data and code.Normallythesmallmodelisthedefaultandonlyallowsamaximumof64KBfordataand64KBforcode.

FIGURE14.7 Compilingaprograminthelargemodel

14.6ViewinsidetheprocessorTobeabletoviewtheprocessortheusermustuseadebuggingprogram.Figure 14.8 shows an example of Turbo Debugger which is available with

mostoftheBorlandsoftwaredevelopmentproductsandcanbeusedtoviewtheoperation of a program. It can be seen that the machine code and equivalentassembly languagemacroappears in the top lefthandwindow.Asamplecodelineis:

FIGURE14.8 ExamplescreenfromTurboDebugger

which specifies that the memory location is 01FA in the code segment(cs:01FA).Machinecodeat this location is55 (01010101)and theequivalentAssemblyLanguageinstructionispushbp.Notethatthecssegmentaddressinthiscaseis5757h,thustheactualphysicaladdresswillbewithreferencetotheaddress57570h(seeSection14.5forafullerexplanation).Thecontentsoftheflagregisterareshownontheright-handside.Inthiscase

theflagsare:

Theregistersareshowntotheleftoftheflagregister.Inthiscasethecontentsare:

Thedata(inthedatasegment)isshownatthebottomlefthandcornerofthescreen.Thefirstline:

showsthefirst8bytesinmemory(fromDS:0000toDS:0007).Thefirstbyteinmemory is00h (0000 0000) and the next is also00h.After the 8 bytes aredefinedthe8equivalentASCIIcharactersareshown.Inthiscase,theseare:

TheASCIIequivalentcharacter for5A(10011010) is ‘T’andfor75(01110101)itis‘u’.Notethat,inthiscase,thedatasegmentregisterhas58A0h.Thusthelocationofthedatawillbereferencedtotheaddress58A00h.Thebottomright-handwindowshowsthecontentsofthestack.

14.7Machinecodeandassemblylanguage

An important differentiation is betweenmachine code and assembly language.Theactualcodewhichrunson theprocessor ismachinecode.Thesearemadeuptouniquebitsequenceswhichidentifiesthecommandandothervalueswhichthesecommandsoperateon.Forexample,forthedebuggerscreenfromFigure14.8,theassemblylanguagelinetomoveavalueintotheAXregisteris:

theequivalentmachinecodeis:

where the codeB8h(10111000b) identifies the instruction tomove a 16-bitvalueintotheAXregisterandthevaluetobeloadedis0194h(0000000110010100b).Notethatthereasonthe94hvalueisstoredbeforethe01hvalueisthatonthePCtheleastsignificantbyteisstoredinthefirstmemorylocationandthemost significant byte in the highest memory location. Figure 14.9 gives anexampleofstoragewithinthecodesegment.Inthiscasethetwoinstructionsaremovandpush.InmachinecodetheseareB8hand50h,respectively.

FIGURE14.9 Examplememorystorageforcodesegment

14.8Exercises14.8.1.ForthedebugscreengiveninFigure14.10determinethefollowing:

FIGURE14.10 ExamplescreenfromTurboDebugger

(i)ContentsofAX,BX,CX,DX,SI,DI.(ii)ContentsofAH,AL,BHandBL.(iii)Thefirstassemblylanguagecommand.(iv)Thememoryaddressofthefirstlineofcode(Hint:thecs:02C2and

thevalueinthecsregisterneedtobeused).(v)Thememoryaddressofthedata(Hint:theds:0000andthevaluein

thedsregisterneedtobeused).

15

8086/88Instructions

15.1Introduction

Thischapterdiscusses8086/88assemblylanguage.Aspreviouslymentionedallofthe80X86andPentiumprocessorscanrun8086code.The80386,80486andPentiumprocessorsruninoneoftwomodes,eithervirtualorreal.Whenusingthe virtual mode they act as a pseudo-8086 16-bit processor, known as theprotectedmode.AllDOS-basedprogramsusethevirtualmode.

15.2CharactersandnumbersIntegerscanberepresentedasbinary,octal,decimal,orhexadecimalnumbers;8086 Assembly Language represents these with a preceding B, O, D or H,respectively. A decimal integer is assumed if there is no letter. Examples ofnumericconstantsare:

Character constants are enclosedwith single quoteswhen theyhave a fixednumberofcharacters(suchas‘b’,‘fired’,andsoon),oriftheyhaveavariablenumberofcharacterstheyareenclosedwithdoublequotes(suchas“a”,“fred”,andsoon).Forexample:

15.3Comments

Assembly Language programs probably need more comments than high-levellanguageassomeoftheoperationsgivelittleinformationontheirpurpose.Thecharacter used to signify a comment is the semi-colon (;) and all commentswithinaprogramareignoredbytheassembler.Forexample,thefollowinglineshavecomments:

15.4Move(MOV)Themoveinstruction(mov)moveseitherabyte(8bits)oraword(16bits)fromoneplacetoanother.Therearethreepossiblemethods:•Movingdatafromaregistertoamemorylocation.•Movingdatafromamemorylocationtoaregister.•Movingdatafromoneregistertoanother.Notethatin8086/88itisnotpossibletomovedatadirectlyfromonememory

location toanotherusingasingle instruction.Tomovedata fromonememorylocationtoanotherthenfirst thedataismovefromthememorylocationintoaregister,nextitismovedfromtheregistertothedestinationaddress.Examplesofmovingaconstantvalueintoregistersare:

An address location is identified within square bracket ([]). Then tomovedataintoaspecifiedaddresstheaddresslocationmustbeloadedintoaregister.Forexample,toloadthevalueof50h(01010000)intoaddresslocation200hthefollowinglinesareused:

Thegeneralformatofthemovinstructionis:

Wherer/mstandsforregister(suchasAH,AL,BH,BL,CH,CL,DH,DL,AX,BX,CX,DX,BP,SI,DI) ormemory location.Andr/m/d stands for aregister, memory or a constant value. The register sr stands for any of thesegment registers (CS,DS,ES,SS)andr16/m16 stand forany16-bit register(AX,BX,CX,SP,BP,SI,DI)and16-bitmemoryaddress.

15.5AddressingmemoryAnaddresslocationcanbespecifiedwitheithertheBX,BP,SIorDIregister.Examplesare:

Program 15.1 gives an Assembly Language; it loads 1234h into addressDS:0000h,5678hintoaddressDS:0002hand22hintoaddressDS:0005h.

Figure15.1showsasamplerunofProgram15.1.Itcanbeseenthatthemov[bx],1234 operation loads the value34h into address locationDS:0000h and12h into address DS:0001h. This is because the processor loads the leastsignificantbyteintotheloweraddresslocation.

FIGURE15.1 SamplerunofProgram15.1

It can be seen from Figure 15.1 that the associated machine code for theinstructionsis:

ThusBBhisthemachinecodetoloadavalueintotheBXregister,C707hloadsasvalue into the addresspointed to andC747h loads anoffsetedvalue into anaddresslocation.

15.6Additionandsubtraction(ADDandSUB)Astheyimply,theADDandSUBperformadditionandsubtractionoftwowordsorbytes.TheADDandSUBinstructionoperateontwooperandsandputtheresultinto the first operand. The source or destination can be a register or address.Examplesare:

Thestandardformatoftheaddinstructionis

whererisanyregister,mismemorylocationanddisanyconstantvalue.

15.7Compare(CMP)TheCMP instruction acts like theSUB instruction, but the result is discarded. Itthus leaves both operands intact but sets the status flags, such as the O(overflow),C(carry),Z(zero)andS(signflag).Itistypicallyusedtodetermineif two numbers are the same, or if one value is greater, or less than, anothervalue.Examplesare:

15.8Unaryoperations(INC,DECandNEG)Theunaryoperationsoperateonasingleoperand.AnINCinstructionincrementstheoperandby1, theDEC instructiondecrements theoperandby1andtheNEGinstructionmakestheoperandnegative.Examplesare:

15.9Booleanbitwiseinstructions(AND,OR,XORandNOT)TheBooleanbitwiseinstructionsoperatelogicallyonindividualbits.TheXOR

functionyieldsa1whenthebitsinagivenbitpositiondiffer;theANDfunctionyieldsa1onlywhenthegivenbitpositionsareboth1s.TheORoperationgivesa 1 when any one of the given bit positions are a 1. These operations aresummarisedinTable15.1.Forexample:

Table15.1Bitwiseoperations

Examples of Assembly Language instructions which use bitwise operationsare:

15.10Shift/rotateinstructions(SHL,SAL,SHR,SAR,ROL,ROR,RCLandRCR)Theshift/rotateinstructionsare:

SHL–shiftbitsleft SHR–shiftbitsright

SAL–shiftarithmeticleft SAR–shiftarithmeticright

RCL–rotatethroughcarryleft RCR–rotatethroughcarryright

ROL–rotatebitsleft ROR–rotatebitsright

The shift instructionsmove thebits,withorwithout the carry flag, andcan

eitherbeanarithmeticshiftor logical shift,whereas the rotate instructionsarecyclicandmayinvolvethecarryflag.TheSHLandSHRshiftbitstotheleftandright,respectively.Theyshiftthebitstotheleftorrightwherethebitshiftedoutisputintothecarryflagandthebitshiftedinisa0.Therotateoperations(ROL,ROR,RCL,RCR)arecyclic.Rotatewithcarry instructions (RCLandRCR) rotatethebitsusingthecarryflag.Thusthebitshiftedoutisputintothecarryflagandthebitshiftinistakenfromthecarryflag.Therotatebits(ROLandROR)rotatethebitswithoutthecarryflag.TheSALinstructionisidenticaltoSHL,buttheSARinstructiondiffersfromSHRinthatthemostsignificantbitisshiftedtotheright for each shift operation. This operation, and the others, are illustrated inFigure15.2.

FIGURE15.2 Rotateoperations

Thenumberofshiftsonthevalueisspecifiedeitherasaunitaryvalue(1)orthenumberofshiftisstoredinthecounterregister(CL).Thestandardformatis

wherer/m is for registerormemoryand1stands foroneshift. Ifanymore

than one shift is required the CL register is used. These operations take adestinationandacountervaluestoredinCL.Forexample,withbitpattern:Initialconditions:01101011andcarryflag1Resultafter:

ThefollowingisanexampleoftheSARinstruction:

Aftersarax,1stores005Bh(0000000001011011b)thenthesarax,c1instructionmovesthecontentsofAXby3bitpositionstotheright.ThecontentsofAXafterthisoperationwillbe0005h(0000000000000101b).ThefollowingshowsanexampleoftheSHRinstruction:

AndanexampleoftheRORinstruction:

15.11Unconditionaljump(JMP)TheJMPinstructiontransfersprogramexecutiontoanotherpartoftheprogram.Itusesalabeltoidentifythejumplocation;thisisdefinedasanamefollowedby

acolon.TheJMPinstructionisnotconditional–theprogramwillalwaysjump.Anexampleisgivennext:

15.12ConditionaljumpsWiththeJMPtheprogramalwaysgoestothelabel,buttheunconditionaljumpswillonlybranchifacertainconditionismet,suchasiftheresultsisnegative,ortheresultiszero,andsoon.Table15.2outlinestheconditionjumpinstructions.

Table15.2Conditionaljumpinstructions

Afewexampleare:

15.13Subroutinecalls(CALLandRET)Subroutinesallowasectionofcode tobecalledand for theprogram to returnback towhere itwascalled.The instructionsareCALLandRET.Anexample isgivennext:

15.14PushandpopThe PUSH and POP instructions are typically used with subroutines. A PUSHinstructionputstheoperandontoatemporarystoragecalledastack(thiswillbecovered inmoredetail later).Thestack isaLIFO(last in, firstout)where thelast element to be loaded is the first to be taken off, and so on. The POPinstructionisusedtoextractthelastvaluewhichwasputonthestack.Typically they are used to preserve the contents of various registers so that

their contents are recovered after a subroutine is called. For example, if asubroutinemodifiestheAX,BXandCXregisters,thentheregistersareputonthestackwith:

Nextthesubroutinecanusetheseregistersforitsownuse.Finally,withinthesubroutine,theoriginalregistersarerestoredwith:

TheorderofthePOPinstructionsmustbethereverseofthePUSHinstructionssothatthecontentsareproperlyrestored.Forexample:

15.15MovingarounddatainmemoryProgram 15.2 loads the memory locations from DS:0000h to DS:00FFh withvalues starting at 00h and ending atFFh.After theALandBX registers havebeen initialized to 00h then the code runs round a loop until all the memorylocationshavebeenloaded.TheBXregistercontainstheaddressthevaluewillbeloadedto.Thisincrementseachtimeroundtheloop.TheALregisterstoresthevaluetobeloadedintothecurrentlyspecifiedmemorylocation.Figure15.3showsasamplerun.

FIGURE15.3 Sampledebugscreen

15.16AssemblerdirectivesThere are various structure directives that allow the user to structure theprogram.ThesearedefinedinTable15.3.

Table15.3Assemblerdirectives

15.17DatadefinitionVariablesaredeclaredinthedatasegment.TodefineavariabletheDB(definebyte) and DW (define word) macros are used. For example, to define (andinitialize)avariabletemp,whichhasthevalue15assignedtoit, isdeclaredasfollows:

anuninitializedvariablehasavaluewhichisaquestionmark,forexample:

Thereareotherdefinitiontypesused,theseare:

•dd(definedoubleword–2times16bitswhichis4bytes).•dq(definequadword,whichis8bytes).•dt(define10bytes).Thedata definition is definedwithin the data segment. InTurboAssembler

(TASM) the data segment is defined after the .DATA directive (as shown inTASMProgram15.4).MicrosoftAssembler(MASM)definesthedatasegmentbetweenthedatasegmentanddataends,asshowninMASMProgram15.3.Program15.3declarestwovariablesnamedval1andval2.Thevalueval1is

loadedwiththevalue1234handval2isloadedwith5678h.Figure15.4showsanexamplescreenafterthethreemovinstructionshavebeenexecuted.Itcanbeseenval1hasbeenstoredatDS:0000andval2atDS:0002.

FIGURE15.4 Sampledebugscreen

15.18Equates(EQU)Todefinea tokentoacertainvalue theEQU (equates)statementcanbeused.Forexample:

Thegeneralformatis:

Theassemblersimply replaceseveryoccurrenceof the tokenwith thevaluegiven.

15.19ExercisesPart1Inthistutorialthesamplecodeshouldbeinserted,byreplacingthehighlightedcode,intoProgram15.5.

15.19.1.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivennext.

15.19.2.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.3.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.4.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.5.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.6.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.7.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.8.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.9.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.10.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.11.Enterthefollowingcodeandrunthedebuggertodeterminethevalues

givenbelow.

15.19.12.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.13.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.14.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.19.15.Enterthefollowingcodeandrunthedebuggertodeterminethevaluesgivenbelow.

15.20ExercisesPart215.20.1.WriteanAssemblyLanguageprogramwhichcontainsafunctionwhich

addsthecontentsoftheAXandBXregistersandputstheresultintotheCXregister.

15.20.2.Writeaprogramwhichloadsthevalues00h,01h,02h,…FEh,FFhintothememorylocationsstartingfromaddressDS:0008h.Abasiclayoutisshownbelow.

15.20.3.WriteaprogramwhichwillloadthevaluesFFh,FEh,FDh,…01h,00hintothememorylocationsstartingfromaddressDS:0000h.

15.20.4.WriteaprogramwhichmovesablockofmemoryfromDS:0020hto0100htoaddresseswhichstartataddress0200h.

15.20.5.Writeaprogramwhichdeterminesthelargestbyteinthememorylocations0000hto0050h.

16

8086InterfacingandTiming

16.1Introduction

Therearetwomainmethodsofcommunicatingexternalequipment,eithertheyaremapped into thephysicalmemory andgiven a real addresson the addressbus(memorymappedI/O)ortheyaremappedintoaspecialareaofinput/outputmemory (isolated I/O). Figure 16.1 shows the twomethods. Devices mappedintomemoryareaccessedbyreadingorwritingtothephysicaladdress.IsolatedI/O provides ports which are gateways between the interface device and theprocessor.Theyare isolated from the systemusingabufferingsystemandareaccessedbyfourmachinecodeinstructions.TheINinstructioninputsabyte,oraword,andtheOUTinstructionoutputsabyte,oraword.CandPascalcompilersinterpret the equivalent high-level functions and producemachine codewhichusestheseinstructions.

FIGURE16.1 Memorymappingorisolatedinterfacing

16.2InterfacingwithmemoryThe80×86processorinterfaceswithmemorythroughabuscontroller,asshowninFigure16.2.Thisdevice interprets themicroprocessor signalsandgeneratestherequiredmemorysignals.Twomainoutputlinesdifferentiatebetweenareadorawriteoperation(R/ )andbetweendirectandisolatedmemoryaccess(M/ ).TheR/ lineislowwhendataisbeingwrittentomemoryandhighwhendataisbeingread.WhenM/ ishigh,directmemoryaccessisselectedandwhenlow,theisolatedmemoryisselected.

FIGURE16.2 AccessmemorymappedandisolatedI/O

16.3MemorymappedI/OInterface devices canmap directly onto the system address and data bus. In aPC-compatiblesystemtheaddressbus is20bitswide, fromaddress00000h toFFFFFh (1MB). If the PC is being used in an enhanced mode (such as withMicrosoftWindows)itcanaccesstheareaofmemoryabovethe1MB.Ifituses16-bit software (such asMicrosoftWindows3.1) then it can address up to 16MB of physicalmemory, from 000000h to FFFFFFh. If it uses 32-bit software

(suchasMicrosoftWindows95) then the softwarecanaddressup to4GBofphysical memory, from 00000000h to FFFFFFFFh. Table 16.1 and Figure 16.3givesatypicalmemoryallocation.

Table16.1MemoryallocationforaPC

Address Device

00000h–00FFFh Interruptvectors

00400h–0047Fh ROMBIOSRAM

00600h–9FFFFh Programmemory

A0000h–AFFFFh EGA/VGAgraphics

B0000h–BFFFFh EGA/VGAgraphics

C0000h-C7FFFh EGA/VGAgraphics

FIGURE16.3 TypicalPCmemorymap

16.4IsolatedI/O

Devicesarenotnormallyconnecteddirectlyontotheaddressanddatabusofthecomputerbecausetheymayusepartofthememorythataprogramusesortheycould cause a hardware fault. On modern PCs only the graphics adaptor ismappeddirectlyintomemory,therestcommunicatethroughaspeciallyreservedareaofmemory,knownasisolatedI/Omemory.IsolatedI/Ouses16-bitaddressingfrom0000htoFFFFh,thusupto64KBof

memory can be mapped.MicrosoftWindows 95 can display the isolated I/OmemorymapbyselectingControlPanel→System→DeviceManager, thenselecting Properties. From the computer properties window the Input/output(I/O) option is selected.Figure16.4 showsan example for a computer in therangefrom0000hto0064handFigure16.5showsfrom0378hto03FFh.

FIGURE16.4 ExampleI/Omemorymapfrom0000hto0064h

FIGURE16.5 ExampleI/Omemorymapfrom0378hto03FFh

ItcanbeseenfromFigure16.5thatthekeyboardmapsintoaddress0060hand0064h, thespeakermapstoaddress0061handthesystemtimerbetween0040hand0043h.Table16.2showsthetypicalusesoftheisolatedmemoryarea.

Table16.2TypicalisolatedI/Omemorymap

Address Device

000h–01Fh DMAcontroller

020h–021h Programmableinterruptcontroller

040h–05Fh Counter/Timer

060h–07Fh DigitalI/O

080h–09Fh DMAcontroller

0A0h–0BFh NMIreset

0C0h–0DFh DMAcontroller

0E0h–0FFh Mathcoprocessor

170h–178h Hard-disk(SecondaryIDEdriveorCD-ROMdrive)

lF0h-lF8h Hard-disk(PrimaryIDEdrive)

200h–20Fh GameI/Oadapter

210h–217h Expansionunit

278h–27Fh Secondparallelport(LPT2:)

Secondserialport(COM2:)

2F8h–2FFh Secondserialport(COM2:)

300h–31Fh Prototypecard

378h–37Fh Primaryparallelport(LPT1:)

380h–38Ch SDLCinterface

3A0h–3AFh Primarybinarysynchronousport

3B0h–3BFh Graphicsadapter

3C0h–3DFh Graphicsadapter

3F0h–3F7h Floppydiskcontroller

3F8h–3FFh Primaryserialport(COM1:)

16.4.1InputtingAByteFromAnI/OPortTheassemblylanguagecommandtoinputabyteis:

whereDX is theDataRegisterwhich contains the address of the input port.The8-bitvalueloadedfromthisaddressisputintotheregisterAL.ForTurbo/BorlandCtheequivalentfunctionisinportb().Itsgeneralsyntax

isasfollows:

wherePORTADDRESSistheaddressoftheinputportandvalueisloadedwiththe8-bitvaluefromthisaddress.Thisfunction isprototypedin theheaderfiledos.h.ForTurboPascaltheequivalentisaccessedviatheport[]array.Itsgeneral

svntaxisasfollows:

wherePORTADDRESSistheaddressoftheinputportandvaluethe8-bitvalueatthisaddress.Togainaccesstothisfunctionthestatementusesdosrequirestobeplacednearthetopoftheprogram.Microsoft C++ uses the equivalent inp() function (which is prototyped in

conio.h).

16.4.2InputtingAWordFromAPortTheassemblylanguagecommandtoinputawordis:

whereDX is theDataRegisterwhich contains the address of the input port.The16-valueloadedfromthisaddressisputintotheregisterAX.ForTurbo/BorlandCtheequivalentfunctionisinport().Itsgeneralsyntaxis

asfollows:

wherePORTADDRESSistheaddressoftheinputportandvalueisloadedwiththe 16-bit value at this address. This function is prototyped in the header filedos.h.ForTurboPascaltheequivalentisaccessedviatheportw[]array.Itsgeneral

syntaxisasfollows:

wherePORTADDRESS is the address of the input port andvalue is the 16-bitvalue at this address. To gain access to this function the statement uses dosrequirestobeplacednearthetopoftheprogram.MicrosoftC++ uses the equivalentinpw() function (which is prototyped in

conio.h).

16.4.3OutputtingAByteToAnI/OPortTheassemblylanguagecommandtooutputabyteis:

whereDX is theDataRegisterwhichcontains theaddressof theoutputport.The8-bitvaluesenttothisaddressisstoredinregisterAL.ForTurbo/BorlandCtheequivalentfunctionisoutportb().Itsgeneralsyntax

isasfollows:

wherePORTADDRESS is the address of the output port andvalue is the 8-bitvalue to be sent to this address. This function is prototyped in the header filedos.h.ForTurboPascaltheequivalentisaccessedviatheport[]array.Itsgeneral

syntaxisasfollows:

wherePORTADDRESS is the address of the output port andvalue is the 8-bitvalue to be sent to that address. To gain access to this function the statementusesdosrequirestobeplacednearthetopoftheprogram.MicrosoftC++ uses the equivalentoutp() function (which is prototyped in

conio.h).

16.4.4OutputtingAWordTheassemblylanguagecommandtoinputabyteis:

whereDX is theDataRegisterwhichcontains theaddressof theoutputport.The16-bitvaluesenttothisaddressisstoredinregisterAX.ForTurbo/BorlandCtheequivalentfunctionisoutport().Itsgeneralsyntax

isasfollows:

wherePORTADDRESS is theaddressof theoutputportandvalue is the16-bitvalue to be sent to that address.This function is prototyped in the header filedos.h.ForTurboPascaltheequivalentisaccessedviatheport[]array.Itsgeneral

syntaxisasfollows:

wherePORTADDRESS is theaddressof theoutputportandvalue is the16-bitvalue to be sent to that address. To gain access to this function the statementusesdosrequirestobeplacednearthetopoftheprogram.MicrosoftC++ uses the equivalentoutp() function (which is prototyped in

conio.h).

16.5DigitalI/Ousingthe8255Each 8255 IC has 24 digital input/output lines. These are grouped into threegroupsof8bitsandarenamedPortA,Port?andPortC.Asingle8-bitregister,knownasthecontrolregister,programsthefunctionalityof theseports.PortCcanbesplitintotwohalvestogivePortC(upper)andPortC(lower).Theportsandthecontrolregistermapintotheinput/outputmemorywithanassignedbaseaddress.ThearrangementoftheportaddresseswithrespecttothebaseaddressisgiveninTable16.3.

Table16.3PPIaddresses

Portaddress Function

BASE_ADDRESS PortA

BASE_ADDRESS+1 PortB

BASE_ADDRESS+2 PortC

BASE_ADDRESS+3 Controlregister

Figure 16.6 shows the functional layout of the 8255. The control registerprogramseachof theports tobean inputor anoutput andalso theirmodeofoperation.Therearefourmainpartswhichareprogrammed:PortA,PortB,PortC(lower)andPortC(upper).

FIGURE16.6 LayoutofPPI

Figure16.7showsthedefinitionoftheControlRegisterbits.Themsb(mostsignificantbit)D7eithermakesthedeviceactiveorinactive.Ifitissettoa0itisinactive,elseitwillbeactive.Theinput/outputstatusofPortAissetbyD4.Ifitisa0thenPortAisanoutput,elseitwillbeaninput.ThestatusofPort?issetbyD1,PortC(lower)byDOandPortC(upper)byD3.

FIGURE16.7 PPIControlRegisterBitDefinitions

PortAcanoperateinoneofthreemodes–0,1and2.ThesearesetbybitsD5andD6. If theyare set to00 thenMode0 is selected,01 toMode1and10 toMode2.PortBcanbeusedintwomodes(Mode0and1)andissetbybitD2.ExamplesofbitdefinitionsandthemodeofoperationaregiveninTable16.4.

Table16.4

Table16.4Examplebitpatternsforcontrolregister

Bitpattern Modeofoperation

01101000 DeviceisinactiveasD7setto0

10011000 Mode0PortAinput,PortC(upper)input,Mode0PortBoutput,PortC(lower)output

10101000 Mode1PortAoutput,PortC(upper)input,Mode0PortBoutput,PortC(lower)output

16.5.1Mode0Mode0isthesimplestmodewithnohandshaking.InthismodethebitsonPortCcanbeprogrammedasinputsoroutputs.

16.5.2Mode1Thismode gives handshaking for the synchronization of data.Handshaking isnormally required when one device is faster than another. In a typicalhandshakingoperationtheoriginatorofthedataaskstherecipientifitisreadytoreceive data. If it is not then the recipient sends back a ‘not ready for data’signal.Whenitisreadyitsendsa‘readyfordata’signalandtheoriginatorthensendsthedata.IfPortsAandBareinputsthenthebitsonPortChavethedefinitionsgiven

inTable16.5.

Table16.5Mode1handshakinglinesforinputtingdata

Wheninputtingdata,the goinglow(active)writesdataintotheport.Afterthis data is written into the port, the IBF line automatically goes high. Thisautomaticallyremainshighuntilthedataisreadfromtheport.Ifanyoftheportsareoutputs,thenthebitdefinitionsofPortCaregivenin

Table16.6.

Table16.6

Table16.6Mode1handshakinglinesforoutputtingdata

In thismode,when data iswritten to the port the line goes low,whichindicatesthatdataisreadytobereadfromtheport.The linewillnotgohighuntilthe ispulledlow.

16.5.3Mode2Thismodeallowsbi-directionalI/O.ThesignallinesaregiveninTable16.7.

Table16.7Mode2operationforbi-directionalI/O

16.6DigitalI/OprogramsProgram16.1outputsthebinarycodefor0to255toPortBwithaone-seconddelaybetweenchanges.Theprogramexitswhentheoutputreaches255.Adelayroutinehasbeenaddedwhichuses thesystem timer.Thiswillbediscussed inmore detail in Section 17.10. Figure 16.8 shows a typical set-up to test theprogramwherePort?hasbeenconnectedtoeightlight-emittingdiodes(LEDs).

FIGURE16.8 Possiblesystemset-up

In 8086 Assembly Language a macro is defined using the equ statement.Program 16.1 uses these to define each of the port addresses. This helps todocumenttheprogramandmakesiteasiertomakeglobalchanges.Forexample,a different base address is relatively easy to set up, as a single change toBASE_ADDRESSautomaticallyupdatesallportdefinesintheprogram.Inthiscasethebase address is1F0h.This address shouldbe changed to the requiredbaseaddressoftheDIOcard.Thestatements:

output the value90h(10010000b) to the control register (CNTRLREG). Thestatements:

initiallysettheALregisterto00h.Thenexttwostatements(movdx,PORTBandoutdx,a1)output thevalueofAL toPORTB.Next thedelay routine iscalled (withcalldelay).This routinedelays foraperiodof1second.Next the

AL register is incremented (inc a1). After this the AL register value iscomparedwith100h(000100000000b).Iftheresultofthecomparestatementisnotequaltozerothentheprogramloopsbacktotheloop1:label.

Program16.2readsthebinaryinputfromPortAandsendsittoPortB.Itwill

stoponlywhenall theinputbitsonportAare1s.Itshowshowabytecanberead from a port and then outputted to another port. Port A is used, in thisexample,as the inputandPort?as theoutput.Figure16.9showshowPortAcould be connected to input switches and Port ? to the light-emitting diodes(LEDs). Loading the bit pattern 90h into the control register initializes thecorrectset-upforPortsAandB.

FIGURE16.9 Typicalsystemset-up

16.7TimingEach instruction takes a finite time to complete. The speed of operation isdetermined by the processor clock speed. To find out how long a certaininstruction will take determine the number of clock cycles to execute it andmultiply thisby the clockperiod.For example, if the clock rate is8MHz theclock period is 0.125 μs. The following gives the number of clock cycles forvarious instructions. Note that different processors take differing numbers ofclock cycles to execute a command. Notice also that the 80386 processor isaround twice as fast as the 8086 for many of the commands. This is due toimprovedarchitecture.

Table16.8Instructiontimingsfordifferentprocessors

where(b)–bytedivide,(w)–worddivide,(nj)–nojump.For example, the mov ax, 1234 statement takes 0.5 μs assuming a 8MHz

clock.Thefollowingprogramwilloutputanincrementvalueeverytwoseconds.Note the great improvement in the 80286/386 over the 8086 on dealing withmathematicsoperations.Inthe8086ittakes144clockcyclestoperformaworddividewhilethe80386onlytakes22clockcycles(nearlyseventimesfaster).

Withinthesecond(inner)loop:

willbeexecuted64777times.Thenumberofcyclestodoadecandajnzis3+16 cycles. Thus it takes 19 cycles to complete this loop. The total time tocompletethisinnerloopisthus:Numberofcycles×clockperiod=19×0.125μs=2.375μs.Totaltimetocompletethisloopis64777×2.375μs=0.1538s.Thisinnerloopisexecuted7times,thusthetotaldelaytimeis13×0.1538=

2s.Ingeneral,forageneralpurposeloopwithAandBasthevariablesinAXand

BX,then:

Firsttheinnerloop:

ThenthenumberofcyclesforinnerloopwillbeB×19:

Numberofcycles=A×((B×19)+16+3)If 19×B ismuchgreater than19 then the following approximation canbe

made:

Thus:

Forexample,inthelastexample(assuminga4MHzclock)thevalueofAis13andBis64777,thus:Typicalprocessorclocksare:

8086 4.77MHz,8MHz.

386 16MHz,25MHz,33MHz.

486 33MHz,50MHz,66MHz,100MHz.

Pentium 60MHz,90MHz,120MHz,200MHz.

16.8Exercises16.8.1.WriteaprogramtoinputabytefromPortA.16.8.2.WriteaprogramwhichwillsendtoPortBall1’s.16.8.3.WriteaprogramwhichwillreadabytefromPortA.Thisbyteisthen

senttoPortB.16.8.4.Writeaprogramthatsendsa‘walking-ones’codetoPortB.Thedelay

betweenchangesshouldbeonesecond.A‘walking-ones’codeisasfollows:

Hint:Usetheshiftleftoperator,thatis<<orsh1.16.8.5.Writeseparateprogramswhichoutputthepatternsin(a)and(b).The

sequencesareasfollows:

16.8.6.Writeseparateprogramswhichoutputthefollowingsequences:

(e)Theinverseof(d)above.16.8.7.WriteaprogramthatreadsabytefromPortAandsendsthe1s

complementrepresentationtoPortB.Notethat1scomplementisallbitsinverted.

16.8.8.ChangetheprograminExercise16.8.9sothatitgivesthe2scomplementvalueonPortB.Hint:Eithercomplementallthebitsofthevalueandadd1orsendthenegatedvalue.

16.8.9.Writeaprogramwhichwillcountfrom00htoffhwith1sdelaybetweeneachcount.TheoutputshouldgotoPortB.

16.8.10.WriteaprogramwhichwillsamplePortAevery1sthensendsittoPortB.

16.8.11.Writeaprogramwhichwillsimulatethefollowinglogicfunctions.

wherePA0isbit0ofPortA,PA1isbit1ofPortAandPB0isbit0ofPortB.16.8.12.Writeaprogramwhichwillsimulateatrafficlightsequence.Thedelay

betweenchangesshouldbeapproximately1second.

andthesequenceis:

16.8.13.Modifytheprogramin16.8.12sothatthesequenceis:

16.8.14.WriteaprogramwhichwillinputavaluefromPortA.ThisvalueissenttoPortBandthebitsarerotatedwithadelayof1second.

16.8.15.WriteaprogramwhichwillsampleportAwhenbit0ofPortCischangedfroma0toa1.ValuesarethenenteredviaPortAbyswitchingPC0froma0toa1.Thesevaluesareputintomemorystartingfromaddress100h.TheendoftheinputsessionisgivenbyPC1beingset(iePC1isequaltoa1).WhenthisissetalltheinputvaluesaresenttoPortBwitha2sinterval.

17

8086Interrupts

17.1Interrupts(INT)

The interrupt function (INT) interrupts the processor. It can be used to gainaccess to eitherDOSorBIOS functions.BIOS functions are typicallyused togain access to the hardware, whereas DOS functions are used to quit fromprograms,readacharacterfromthekeyboardandwriteacharactertothescreen.

FIGURE17.2 Bitdefinitionsforserialportinitialization

17.2Interrupt21h:DOSservicesPrograms access DOS functions using interrupt 21h. The functionality of thecall is set by the contents of theAH register.Other registers are used either topassextrainformationtothefunctionortoreturnvaluesback.Forexample,todetermine the system time the AH is loaded with the value 2AH. Next, theprocessor is interruptedwith interrupt21H. Finally,when the program returnsfromthisinterrupttheCXregisterwillcontaintheyear,DHthemonth,DLthedayandALthedayoftheweek.

Table 17.1 is only a small section of all the DOS related interrupts. Forexample,function2Fhcontainsmanyfunctionsthatcontroltheprinter.Notethatfor the Get free disk space function the total free space on a drive isAX×BX×CXandtotalspaceondisk,inbytes,isAX×CX×DX.

Table17.1DOSinterrupts

InProgram17.1,function02h(writecharactertotheoutput)isusedtodisplaythecharacter‘A’.Inthiscase,thefunctionnumber02hisloadedintoAHandthecharactertobedisplayedisloadedintoDL.

Program17.2usesthefunction01htogetacharacterfromthekeyboardandthenthefunction02htodisplayit.

Program17.3displays thedefaultbootdrive. Inmostcases thedefaultbootdrivewillbeC.

17.3Interrupt10h:BIOSvideomodeInterrupt 10h allows access to the video display. Table 17.2 outlines typicalinterruptcalls.Program17.4uses theBIOSvideo interrupt todisplayaborderaround the screenwhichchanges colour each second fromblack to lightblue.

Thesecoloursareset-upwithanenumdatatypedefinition.Inthiscase,BLACKisdefinedas0,BLUEas1,andsoon.

Table17.2BIOSvideointerrupt

Todisplay aborder theAH register is loadedwith0Bh,BHwith00h andBLwith thebordercolour.Next, the interrupt10h iscalledwith theseparameters.Figure17.1showsthebitdefinitionforthecolours.

FIGURE17.1 Characterattribute

17.4Interrupt11h:BIOSequipmentcheckInterrupt 11h returns a word which gives a basic indication of the types ofequipmentconnected. It isuseful indetermining if there isamathcoprocessorpresentandthenumberofparallelandserialportsconnected.Table17.3showstheformatofthecall.

Table17.3BIOSequipmentcheckinterrupt

Description Inputregisters Outputregisters

Getequipmentlist AX=BIOSequipmentlistword

17.5Interrupt13h:BIOSdiskaccessInterrupt13hallowsaccesstomanydiskoperations.Table17.4liststwotypicalinterruptcalls.

Table17.4BIOSdiskaccessinterrupt

17.6Interrupt14h:BIOSserialcommunicationsBIOSinterrupt14hcanbeusedtotransmitandreceivecharactersusingRS-232and also to determine the status of the serial port. Table 17.5 lists the maininterruptcalls.Program17.5initializesCOM2:with4800baud,evenparity,1stopbitand7databits.

Table17.5

Table17.5BIOSserialcommunicationsinterrupts

17.7Interrupt17h:BIOSprinterTheBIOSprinterinterruptallowsaprogrameithertogetthestatusoftheprinterortowriteacharactertoit.Table17.7outlinestheinterruptcalls.

Table17.7BIOSprinterinterrupt

17.8Interrupt16h:BIOSkeyboardInterrupt 16h allows access to the keyboard. Program 17.6 uses the BIOSkeyboard interrupt to display characters, entered from the keyboard, to thescreen.Initially,thecode:

teststoseeifakeyhasbeenpressed.Itrepeatsuntilthezeroflagisunset(thishappenswhenakeyhasbeenpressed.Thecheckforkeystrokeinterruptcallsetsthezeroflag(ZF)iftherearenocharactersinthebuffer,otherwiseitwillbea0.

Nextthecode:

gets the key that has been pressed and puts the result into theDL register.Finally,theDOSinterruptisusedtodisplaythecharactertothescreen.

Table17.6BlOSkeyboardinterrupt

17.9Interrupt19h:BIOSrebootInterrupt19hrebootsthesystemwithoutclearingmemoryorrestoringinterruptvectors. For a warm boot, equivalent to Ctrl-Alt-Del, then 1234h should bestored at 0040h:0072h. For a cold boot, equivalent to a reset, then 0000h isstoredat0040h:0072h.CareshouldbetakenwiththisinterruptasitmaycausethePCto‘hang’.

17.10Interrupt1Ah:BIOSsystemtimeTheBIOS system time interrupt allows a program to get access to the systemtimer.Table17.8outlinestheinterruptcalls.

Table17.8BIOSsystemtimeinterrupt

17.11CandPascalinterrupts

SeeSectionD.3.

17.12Exercises17.11.1.UsingBIOSvideointerrupt10hwriteprogramswhichperformthe

following:(a)fillacompletescreenwiththecharacter‘A’ofatextcolourofred

withabackgroundofblue;(b)repeat(a),butthecharacterdisplayedshouldcyclefrom‘A’to‘Z’withaone-seconddelaybetweenoutputs;(c)repeat(a),buttheforegroundcolourshouldcyclethroughallavailablecolourswithaone-seconddelaybetweenoutputs;(d)repeat(a)sothatthebackgroundcolourcyclesthroughallavailablecolourswithaone-seconddelaybetweenoutputs.

17.11.2.UsingBIOSkeyboardinterrupt16hwriteaprogram,inCorPascal,thatdisplaysthestatusoftheShift,Capslock,Cntrl,ScrollandNumkeys.

PARTDVisualBasic

18

Introduction

18.1Introduction

MicrosoftWindowshasbecomethede-factoPCoperatingsystem.Allversionsup to, and including,Windows 3.11 used DOS as the core operating system.NewversionsofWindows, suchasWindowsNTandWindows95donotuseDOSandcanthususethefullcapabilitiesofmemoryandoftheprocessor.ThemostpopularprogramminglanguagesforWindowsprogrammingare:•MicrosoftVisualBasic.•MicrosoftVisualC++andBorlandC++.•Delphi(whichisavailablefromBorland).VisualBasichastheadvantageovertheotherlanguageinthatitisrelatively

easytouseandtoprogramwith,althoughthedevelopmentpackageswhichareusedwithC++andDelphimakeconstructingtheuserinterfacerelativelyeasy.VisualBasicVersion4isshowninFigure18.1andVersion5isshowninFigure18.2.

FIGURE18.1 VisualBasic4userinterface

FIGURE18.2 VisualBasic5userinterface

18.2Event-drivenprogrammingTraditional methods of programming involve writing a program which flowsfromoneparttothenextinalinearmanner.Mostprogramsaredesignedusingatop-downstructureddesign,wherethetaskissplitintoanumberofsubmodules,these are then called when they are required. This means that it is relativelydifficult to interrupt theoperationofacertainpartofaprogram todoanotheractivity,suchasupdatingthegraphicsdisplay.VisualBasicingeneralis:•Object-oriented.Wheretheprogramisdesignedaroundanumberofready-

madeobjects.•Event-driven.Wheretheexecutionofaprogramisnotpredefinedandits

executionistriggeredbyevents,suchasamouseclick,akeyboardpress,andsoon.

•Designedfromtheuserinterfaceoutwards.Theprogramistypicallydesignedbyfirstdevelopingtheuserinterfaceandthencodedtorespondtoeventswithintheinterface.

18.3VisualBasicfilesAlistingofasampledirectorywhichcontainsVisualBasicfilesis:

Thefilesare:•Projectfiles.ProjectsbindtogethertheindividualelementsofaVisualBasic

program.Initiallytheusercreatesaprojectfilefortheprogramandthisisloadedwhenevertheprogramisbeingdeveloped.Thedefaultextensionforaprojectiseither.MAKor.VBPextension.Projectsgenerallymakeiteasiertocontrolthevariouselementsofaprogram.

•Modules.Codethatisattachedtoaformisaccessiblefromanywhereonthatform,butaprogrammayhavemorethanoneform.Itwillsometimesbenecessarytohaveprogramcodethatcanbereachedfromanyform,andinthiscasethecodewouldbewrittenonamodule.Modulesdisappearfromviewwhentheprogramruns–onlyformshaveanon-screen

existence.Theremaybeseveralmodulesinoneprogram,andeachissavedasaseparatefile.Thesearemarkedbya.BASextension.

•Forms.AformformstheanchorforallpartsofaVisualBasicprogram.Initiallyitisablankwindowandtheuserpastescontrolsontoittocreatetherequireduserinterface.Codeisthenassociatedwitheventsontheform,suchasrespondingtoabuttonpressoraslidercontrol,althoughsomecontrolelementsdonothaveassociatedcode.Aprogramcanhaveoneormoreforms,eachofwhichdisplaysandhandlesdataindifferentways.Tomakeformsshareablewithotherprogramstheneachissavedseparatelywitha.FRMextension.

•Icons.Theseare,normally,smallgraphicsimagesandhavea.ICOextension.•Graphicsimages.ThesearenormallyeitherBMP(bitmapped)filesorWMF

(windowsmetafile)fileswiththe.BMPand.WMFextensions,respectively.•Others.Otherfilesalsoexist,suchasVBXwhichisVisualBasiceXtension.

18.4OthertermsVisualBasicusesanumberofother terms todescribedesignprocedure, theseare:•Controls.TheVBinterfacecontainsawindowwithcontrolobjectswhichare

pastedontoaform.Thesecontrolscanbesimpletext,menus,spreadsheetgrids,radiobuttons,andsoon.Eachcontrolhasasetofpropertiesthatdefinestheiroperation,suchastheircolour,thefontsize,whetheritcanberesized,andsoon.Somecontrols,suchascommandbuttons,menus,andsoon,normallyhavecodeattachedtothem,butsimplecontrols,suchastextandagraphicsimagecansimplyexistonaformwithnoassociatedcode.

•Procedures.AswithCandPascal,VisualBasicusesprocedures,orsubroutines,tostructurecode.Mostoftheseareassociatedwithaneventthatoccursfromacontrolandsomewillbefree-alonewithnoassociatedevent.

18.5MainscreenFigure18.3showstheVisualBasic4desktop(VisualBasic5issimilar,butthewindowsdonot float on thedisplay). It contains amenu form, controls,mainform,projectwindowsandpropertieswindow.

FIGURE18.3 VisualBasic4desktop

18.5.1MenuBarAndToolbarThemenu bar and tool bar appear in a single, floating window, as shown inFigure18.4.Themenubarcontainsoptionsforfilemanipulation(File),editing(Edit), viewing (View), running (Run), testing the program (Debug),manipulatingwindows (Window) andgettinghelp (Help).These can eitherbeselected with the mouse, using the function key F10 and then selecting theoptionwiththearrowkeysandpressingreturnorusethehot-key.ThehotkeyisAltandtheunderlinedcharacter,thusAlt-FselectstheFilemenu,Alt-EselectstheEditmenu,andsoon.

FIGURE18.4 VisualBasic4menubarandtoolbar

Thetoolbarcontainsshortcutbuttonsforcommonlyusedmenuitems.Tothe

rightofthetoolbartherearetwoindicators;thesedisplaythepositionandsizeofa selected form or control. This area of the window is also used in thecompilationphasetodisplaythestatusofthecompilation.Thetoolbarbuttonsare:Createsanewform.Createsanewstandardmodule.Opensanexistingproject.Savesthecurrentlyactiveproject.Locks/unlocksthecontrolsontheactiveform.DisplaystheMenuEditor.DisplaysthePropertieswindow.DisplaystheObjectBrowser.DisplaystheProjectwindow.Runstheapplication.Pausesprogramexecution.Stopsexecution.

Togglesabreakpoint(breakpointonoroff).DisplaysthevalueofthecurrentselectionintheCodewindow.Displaysthestructureofactivecalls.Tracesthrougheachlineofcodeandstepsintoprocedures.ExecutescodeoneprocedureorstatementatatimeintheCodewindow.

18.5.2ProjectWindowThe Projectwindow displays all the forms andmodules used in the currentlyactiveproject;anexampleisshowninFigure18.5.AnewprojectisopenedbyselectingNewProject fromtheFilemenu,whereas toopenanexistingprojecttheOpenProjectoption is selected from theFilemenu, else theopenexistingprojectoptionisselectedfromthetoolbar.

FIGURE18.5 VisualBasicProjectwindow

Only one project can be opened at a time, but that project can have anynumberofforms.IntheProjectwindowtheusercandothefollowing:•OpenaFormwindowforanexistingformbyselectingtheformnameand

clickingtheViewFormbutton.•OpentheCodewindowforanexistingformbyselectingthemodulename

andclickingtheViewCodebutton.•RemoveafilefromaprojectbyselectingthefileintheProjectwindow,and

thenfromtheFilemenuchooseRemoveFile.

18.5.3FormWindowTheFormwindow, as shown inFigure 18.6, creates applicationwindows anddialogboxes.AnewformiscreatedbyselectingtheFormfromtheInsertmenu(orusethetoolbarshortcut)andanexistingformisopenedbyselectingtheformnameand thenclicking theViewFormbutton.Anexisting form isadded toaprojectbyselectingtheAddFilecommandfromtheFilemenu.AnyassociatedcodeonaformcanbeviewedbyclickingontheViewCodebutton.

FIGURE18.6 VisualBasicFormwindow

Each formhasaControl-menubox,MinimizeandMaximizebuttons,andatitlebar,andcanbemovedandresized.Table18.1showsthekeycombinationsintheFormwindow.

Table18.1KeycombinationinFormwindow

Keycombination Operation

alpha EnteravalueinthePropertieswindowfortheselectedproperty.

CLICK–Drag Selectmultiplecontrols.

CTRL+CLICK+DRAG Addorremovecontrolsfromthecurrentselection.

CTRL–C CopytheselectedcontrolstotheClipboard.

CTRL-CLICK Addorremoveacontrolfromtheselection.

CTRL–E DisplaytheMenuEditor.

CTRL–J Bringcontroltofront(ifcontrolsareoverlapping).

CTRL–K Sendcontroltoback(ifcontrolsareoverlapping).

CTRL–V PastefromClipboardontotheform.

CTRL–X CuttheselectedcontrolstotheClipboard.

CTRL–Z Undoadeletedcontrol.

DEL Deletetheselectedcontrols.

F4 DisplaythePropertieswindow

F7 OpentheCodewindowfortheselectedobject.

SHIFT–CTRL–alpha SelectapropertyinthePropertylistofthePropertieswindow.

SHIFT-TAB Cyclebackwardthroughcontrolsintaborder.

TAB Cycleforwardthroughcontrolsintaborder.

18.5.4ToolboxThe Toolbox contains the icons for controls. These are standardVisual Basiccontrolsandanycustomcontrolsandinsertableobjects,asshowninFigure18.7.TheToolbox is displayed, if it is not already in view,withToolbox from theViewmenuanditisclosedbydouble-clickingtheControl-menubox.

FIGURE18.7 Toolboxcontrols

Figure18.6showssometypicalcontrols,theseinclude:

• Pointer.Thepointerdoesnotdrawanycontrolobjectsandisusedtoresizeormoveacontrolonceithasbeendrawnonaform.Whenacontrolisaddedtoaformthenthepointerisautomaticallyselected.

• PictureBox.Displaysgraphicalimages(BMP,WMF,ICOorDIB).

• Label.Usedtodisplaytextthatcannotbechangedbytheuser.

• TextBox.Allowstheusertoeitherenterorchangetext.

• Frame.Usedtocreateagraphicalorfunctionalgroupingforcontrols.ThesearegroupedbyfirstdrawingaFramearoundthemandthendrawingcontrolsinsidetheframe.

• CommandButton.Usedtocarryoutacommand.

• CheckBox.Usedtocreateacheckbox,wheretheusercanindicateifsomethingisonoroff(trueorfalse),or,whenthereismorethanoneoption,amultipleofchoices.

• OptionButton.Usedtodisplayanumberofoptionsbutonlyonecanbechosen(thisdiffersfromthecheckboxwhichonlyallowsoneoptiontobechosen).

• ComboBox.Usedtogiveacombinationofalistboxandtestbox,wheretheusercaneitherenteravalueinatextboxorchooseanitemfromthelist.

• ListBox.Usedtodisplayalistofitemsandtheuserisallowedtochooseoneofthem.Thislisthasascrollbuttontoallowthelisttobescrolled.

• HScrollBar(horizontalscrollbar).Usedtoscrollupanddownthroughalistoftextorgraphicalinformation.Itcanalsobeusedtoindicatethecurrentpositiononascaleorbytheusertoindicateagivenstrengthofvalue.

• VScrollBar(verticalscrollbar).Usedtoscrollacrossalistoftextorgraphicalinformation.Itcanalsobeusedtoindicatethecurrentpositiononascaleorbytheusertoindicateagivenstrengthofvalue.

• Timer.Usedtogeneratetimedeventsatgivenintervals.

• DriveListBox.Usedtodisplaycurrentlyconnecteddiskdrives.

• DirListBox(directorylistbox).Usedtodisplaydirectoriesandpaths.

• FileListBox.Usedtodisplayalistoffiles.

• Shape.Usedtodrawshapes,suchasrectangles,roundedrectangles,squares,roundedsquares,ovalsorcircles.

• Line.Usedtodrawavarietyoflinestylesonyourformatdesigntime(transparent,solid,dash,dot,dash-dotanddash-dot-dot).

• Image.Usedtodisplayagraphicalimage,suchasabitmap(BMP),icon(ICO),ormetafile(WMF).TheseimagescanonlybeusedtodisplayandimageanddonothavethesamecontrolfunctionsasPictureBox.

• Data.Usedtoprovideaccesstodataindatabases.

• OLEController.Usedtolinkandembedobjectsfromotherapplications(suchasWordDocuments,ExcellSpreadsheets,andsoon).OLEstandsforObjectLinkingandEmbedding.

• CommonDialog.Usedtocreatecustomizeddialogboxesforoperationssuchasprintingfiles,openingandsavingfiles,settingfontsandhelpfunctions.

• DBList(data-boundlistbox).UsedasanenhancedListBoxwhichcanbecustomizedtodisplayalistofitemsfromwhichtheusercanchooseone.Thelistcanbescrolledifithasmoreitemsthancanbedisplayedatonetime.

• DBCombo(data-boundcombobox).UsedasanenhancedCombowhichcanbecustomizedtodisplayalistofitemsfromwhichtheusercanchooseone.Usetodrawacombinationlistboxandtextbox.Theusercaneitherchooseanitemfromthelistorenteravalueinthetextbox.

• DBGrid(data-boundgrid).Usetodisplayaseriesofrowsandcolumnsandtomanipulatethedatainitscells.DBGridisacustomcontrolandhasincreaseddataaccesscapabilitiesthatthestandardGriddoesnothave.

18.6PropertieswindowThe Properties window displays the properties of the currently selected form,controlormenu.Theyallowpropertiessuchasthecolour,fonttypeandsizeoftext,backgroundcolourofaform,typeofgraphicimage,andsoon.First, the item to be changed is selected and then the Properties option is

chosenfromtheViewmenu,elsethefunctionkeyF4.ThePropertywindowisclosedwithadouble-clickontheControl-menubox.ThePropertieswindowcontainstwomainparts,theseare:•TheObjectbox.Thisisfoundbelowthetitlebarandidentifiesthecurrently

selectedformorcontrolontheform.InFigure18.8thecommandbuttonhasanassociatedPropertieswindow.TheObjectboxinthiscaseis:

FIGURE18.8 Propertieswindow

WhereCommandButtonisthecontrolitemandisnamedCommand1,othercontrolitemsarePictureBox,Label,TextBox,Frame,CheckBox,OptionButton,ComboBox,ListBox,HScrollBar,VScrollBar,Timer,DriveListBox,FileListBox,Shape,Line,Image,Data,andsoon.ClickthearrowattherightsideoftheObjectbox( )togetalistofthecontrolsonthecurrentform.Fromthelist,choosethecurrentformoracontrolontheformwhosepropertiesyouwanttochange.AnexampleisgiveninFigure18.9.Inthiscasetherearethreecommandbuttons(namedCommand1,Command2andCommand3)ontheform,adrivelistbox(namedDrive1),andsoon.Thelistalsocontainsthecurrentlyactiveform(inthiscaseitisnamedForm1).Namesofcontrolsareassignedconsecutively,sothatthefirstcommandbuttonisCommand1,thesecondisCommand2,andsoon.

FIGURE18.9 Examplelistofcontrols

•ThePropertieslist.Thisisatwo-columnlistthatshowsallpropertiesassociatedwithaformorcontrolandtheircurrentsettings.Tochangeapropertiessettingthenthepropertiesnameisselectedandthenewsettingiseithertypedorselectedfromamenu.Propertiesthathavepredefinedsettings(suchasarangeofcoloursortrue/false)displaythelistofsettingsbyclickingthedownarrowattherightofthesettingsbox( ),ortheycanbecycledthroughbydouble-clickingthepropertynameintheleftcolumn.InFigure18.8theDefaultpropertyhaseitheraTrueorFalsesetting.A inthesecondcolumnindicateseithertheselectionofcoloursfromapaletteortheselectionofpicturefilesthroughadialogbox.

Figure 18.10 shows an example of colour settings. Note that the colourappearsasa24-bithexadecimalequivalent(with8otherattributebits),butwhentheuserselectsthecolouritappearsasacolourinthepalette.This24-bitcolourismadeuptored,greenandblue(RGB).Thestandardformatis:

FIGURE18.10 Settingcolour

TheRRhexadecimaldigitsgivethestrengthoftheredfrom00htoFFh(0to255), theGG hexadecimal digits give the strength of green andBB gives thestrength of blue. Thus for the colour strength parts:white is&HaaFFFFFF&,black is&?aa000000&, red is&Haa0000FF&, yellow is&Haa00FFFF& andcyanis&HaaFFFF00&.

18.7ControlsandEventControlshaveassociatedpropertiesandalsoanumberofevents.TheseeventscanbeviewedbydoubleclickingonacontrolorbyselectingViewCodefromProjectwindow.Figure18.11showsanexampleoftheCodewindows.Itcanbethat theobjectcanbeselectedbypullingdown themenuof the left-handsideandtheassociatedeventsintheright-handmenu.Theassociatedcodewiththatobjectandeventisshowninthewindowbelowthesemenuoptions.

FIGURE18.11 Selectingobjects

Figure18.12showsanexampleoftheeventsthatoccurwhenthecontrolisacommandbutton(inthiscasetheobjectisCommand1).Itcanbeseenthattheassociated events are: Click, DragDrop, DragOver, GotFocus, KeyDown,KeyPress and KeyUp. Each of these can have associated sections of code toreacttotheevent.Forexample,theClickeventisinitiatedwhentheuserclicksthemousebuttononthecommandbuttonandKeyDownisinitiatedwhenakeyhasbeenpresseddown.

FIGURE18.12 Eventswhenthecontrolisacommandbutton

18.8Exercises18.8.1.PlaceaCommandButtononaformanddisplayitsproperties.Noteallof

thepropertiesand,withthehelpofthehelpmanual,identifyofthefunctionofeachoftheproperties.Notethathelponapropertycanbe

foundbyhighlightingthepropertyandpressingF1.18.8.2.WithaCommandButtonidentifytheeventsthatareassociatedwithit.18.8.3.DeterminetheactualcoloursofthefollowingRGBcolourvalues:

(i)&H0080FF80&(ii)&H00FF8080&(ii)&H00C000C0&(iv)&H00E0E0E0&

18.8.4.Conductthefollowing:(i)Addacommandbuttontoaform.

(ii)ChangethetextontheCommandButtonto‘EXIT’.(iii)ChangethefontontheCommandButtonto‘TimesRoman’andthe

fontsizeto16.(iv)ResizetheCommandButtonsothatthetextfitscomfortablyintothe

button.(iv)Changethebackgroundcolouroftheformtoyellow.(v)ChangetheCaptionnameoftheformto‘MyApplication’.

18.8.5.DeveloptheformgiveninFigure18.13.

FIGURE18.13 Exercise

18.8.6.Explainwhy,inthepreviousexercise,thataradiobuttonisusedfortheageoptionandacheckboxisusedtoselectthechoicesofShowGraphicsandPlaySounds.Whichofthefollowingwouldberadiobuttonsorcheckboxes:(i)Itemsonashoppinglist.

(ii)Selectionofahorsetowinarace.

(iii)Selectionofpaintcolouronanewcar.(iv)Selectionofseveralmodulesonacourse.

19

VisualBasicLanguage

19.1Introduction

This chapter discusses the Visual Basic language and how a program isdeveloped.

FIGURE19.4 ButtonsforMsgBox

FIGURE19.5 IconsforMsgBox

19.2ProgramminglanguageVisualBasichasanexcellenton-linemanualinwhichtheusercaneithersearchfortheoccurrenceofkeywords(withHelp→SearchForHelpOn)orviewthecontents of themanual (Help→Contents). The left-hand side of Figure 19.1showsanexamplemanualpageaftertheuserhasselectedHelp→Contents→Visual Basic Help, and then leads to other parts of the manual, such as theProgrammingLanguageandContentsTopic.The left-handsideofFigure19.1showsanexampleoftheContentslist.

FIGURE19.1 VisualBasic4on-linehelpmanual

19.3EnteringaprogramTostartthedevelopmentofaprogramwithnocontrolsonaformthentheuserselects theViewCode from the Projectwindow. Figure 19.2 shows the basicsteps.AftertheViewCodeisselectedthentheuserselectstheFormobjectfromwithin the form codewindow.Next the code is entered between the PrivateSubLoad_From()andEndSub.Thiscodeisautomaticallyrunwhentheformisrun,astheprocedureisLoad.ThecodeinFigure19.2simplydisplaysthetext“Hellotoyou”toawindow.

FIGURE19.2 Stepstakentoentercode

19.4LanguagereferenceThissectioncontainsacondensedreferencetoVisualBasic.

19.4.1DataTypesAndDeclaringVariablesAvariableisdeclaredwiththeDimkeyword.Thesevariablesmustconformto

thefollowing:•Beginwithanalphabetcharacter.•Cannotcontainadot,‘$’,T,‘@’,‘#’or‘%’.•Mustbelessthan256characterslong.Examplesare:

whichdeclaresaBooleanvariablecalledval1,twosingleprecisionfloating-pointvariables:xandy,anintegernamedi,adatenamednewdateandastringof30charactersnamedname.Variablesareassignedvalueswiththeassignmentoperation(=),suchas:

whichsets theBooleanvariableval1toaTrue, thevalueofxto2.134,yto10.1, thedatenewdate isassigned thecurrentdate fromthe functionNowandthestringnameisassignedthestring“Fred”.Notethatstringsofcharactersaredefinedbetweeninvertedcommas(“”).

19.4.2OperatorsThebasicoperatorsinVisualBasicaresimilartotheonesusedinPascal.Table19.1showsthemainoperators.Theoperatorprecedenceis:

Table19.1Operatorprecedence

Arithmetic Comparison Logical

Exponentiation(^) Equality(=) Not

Negation(−) Inequality(<>)

Negation(−) Inequality(<>)And

Multiplicationanddivision(*,/) Lessthan(<) Or

Integerdivision(\) Greaterthan(>) Xor

Moduloarithmetic(Mod) LessthanorEqualto(<=)

Additionandsubtraction(+,–) GreaterthanorEqualto(>=)

Stringconcatenation(&)

•Arithmeticoperatorshavethehighestprecedence,followedbycomparisonoperatorsandfinallylogicaloperators.

•ArithmeticandlogicaloperatorsareevaluatedintheordergiveninTable19.1.

•Comparisonoperatorsallhaveequalprecedence.•Multiplicationanddivisionhavethesameprecedence,thentheoperationis

executedfromlefttoright.Thesameoccurswithadditionandsubtraction.

19.4.3DataTypesAswithCandPascal,VisualBasichasawholerangeofdatatypes.Theirrangedependsontheirformat(suchascharacters, integersandfloatingpointvalues)and the number of bytes used to store them. Table 19.2 outlines the mainpredefined(intrinsic)datatypes.AuserdefinedtypecanalsobedefinedusingtheTypestatement.

Table19.2Datatypes

Datatype Storagesize Range

Byte 1byte 0to255

Boolean 2bytes TrueorFalse

Integer 2bytes −32,768to32,767

Long(longinteger) 4bytes −2,147,483,648to2,147,483,647

Single(single-precisionfloating-point)

4bytes ±3.402823×1038to±1.401298×10−45

Double(double-precisionfloating-point)

8bytes ±4.94065645841247×10−324to±1.79769313486232×10308

Currency(scaledinteger) 8bytes ±922,337,203,685,477.5808

Date 8bytes January1,100toDecember31,9999.

String(variable-length) 10bytes+stringlength

0toapproximately2billion

length

String(fixed-length) Lengthofstring 1toapproximately65,400

Themaindatatypesare:

19.4.4ConvertBetweenDataTypesVisual Basic has strong data type checking where the compiler generates anerrorwhenonedatatypeisassigneddirectlytoavariablewithanotherdatatype.Thusdifferentdatatypesmayneedtobeconvertedintoanothertypesothattheycanbeused.Thebasicconversionfunctionsare:

Cbool(expr) WhichconvertsanexpressionintoBoolean.Theexpressionargumentisanyvalidnumericorstringexpression.IfexpressioniszerothenaFalseisreturned,elseaTrueisreturned.

Cbyte(expr) WhichconvertsanexpressionintoByte.Theexpressionargumentisanyvalidnumericorstringexpression.IfexpressionliesoutsidetheacceptablerangefortheBytedatatypethenanerroroccurs.

Ccur(expr) WhichconvertsanexpressionintoCurrency.Theexpressionargumentisanyvalidnumericorstringexpression.IfexpressionliesoutsidetheacceptablerangefortheCurrencydatatypethenanerroroccurs.

Cdate(expr) WhichconvertsanexpressionintoDate.Thedateargumentisanyvaliddateexpression.

Cdbl(expr) WhichconvertsanexpressionintoDouble.Theexpressionargumentisanyvalidnumericorstringexpression.

Cint(expr) ConvertsanexpressiontoanInteger.Theexpressionargumentisanyvalidnumericorstringexpression.CintdiffersfromtheFixandIntfunctions,whichtruncate,ratherthanround,thefractionalpartofanumber.Whenthefractionalpartisexactly0.5,theCintfunctionalwaysroundsittothenearestevennumber.Forexample,0.5roundsto0,and1.5roundsto2.

Clng(expr) WhichconvertsanexpressionintoLong.Theexpressionargumentisanyvalidnumericorstringexpression.AswithCintthevalueisroundedtothenearestwholenumber.

Csng(expr) WhichconvertsanexpressionintoSingle.Theexpressionargumentisanyvalidnumericorstringexpression.IfexpressionliesoutsidetheacceptablerangefortheSingledatatype,anerroroccurs.

Cstr(expr) Whichconvertsanexpressionintostring.Theexpressionargumentisanyvalidnumericorstringexpression.IftheexpressionisBooleanthenastringisreturnedwitheitherTrueorFalse,elseanumericvaluereturnsastringcontainingthenumber.

lnt(expr)

Fix(expr) Returnstheintegerportionofanumber.IntdiffersfromFixinthatIntwhenthenumberisnegativethenitreturnsthefirstnegativeintegerwhichislessthanorequaltonumber,whereasFixreturnsthefirstnegativeintegergreaterthanorequaltonumber.Forexample,ifthevalueis–12.3thenIntconvertsthisto–13whileFixconvertsitto–12.

Atypicalconversionisfromanumericordatevariable intoastringformat.Program19.1showsanexampleofaVisualBasicprogramwhichcontainstheCStrfunctionwhichisusedtoconvertfromtwofloatingpointvalues(xandy),an integer (i) and date (newdate) into a string format. This is then used todisplay thevalues to awindowusing theMsgBox function.Theprogramalsouses theFix function to round-up thevalueofx.Figure19.3 showsa samplerun.

FIGURE19.3 SamplerunforProgram19.1

19.4.5Input/OutputThefunctionsthatcanbeusedtoinputandoutputinformationareInputBoxandMsgBox,respectively.Boththesefunctionsinputandoutputinformationintheformofastringofcharacters.Thuswhenoutputingnon-stringvariables,suchasintegersandfloating-pointvalues,theymustfirstbeconvertedtoastringusingoneofthestringconversionfunctions.Thesamemustbedoneforinput,wherethe input stringmustbe converted into the requireddata type, againusing thedatatypeconversionfunctions.

Output

TheMsgBoxfunctiondisplaysamessageinadialogboxwithspecifiedbuttonsand thenwaits for theuser to selectabutton.Thevalue returned indicates thechosenbutton.Thebasicformatis:

wheretheparametersinbracketsareoptional.Theparametersare:

prompt stringofbedisplayedinthedialogbox.

buttons Numericvaluethatisthesumofvaluesthatspecifiesthenumber,thetypeofbuttonstodisplay,theiconstyleandthedefaultbutton.Table19.3outlinesthesevaluesandifitisomittedthenthedefaultvalueforbuttonsis0.

title stringwhichcontainsthetitlebarofthedialogbox.Ifitisomittedthentheapplicationnameisplacedinthetitlebar.

helpfile stringthatidentifiestheHelpfiletousetoprovidecontext-sensitiveHelpforthedialogbox.Ifhelpfileisprovidedthencontextmustalsobeprovided.

context NumericvaluethatistheHelpcontextnumbertheHelpauthorassignedtotheappropriateHelptopic.Ifcontextisprovided,helpfilemustalsobeprovided.Whenbothhelpfileandcontextareprovided,theusercanpressF1toviewtheHelptopiccorrespondingtothecontext.

Table19.1definesthebuttonsettings.Thevaluesfrom0to5definethetypeofthebuttontobedisplayed.Forexample,avalueof5willhavetwobuttons,whichareRetryandCancel.Thevalues16,32,48and64identifytheicontobedisplayed.Forexample,avalueof32willdisplayaquestionbubble.The0,256and512definewhichbutton is thedefault.Eachof thesevaluescanbeaddedtogether to create the requires set of buttons, icon and default button. Forexample,tocreateadialogboxwiththeOKandCancelbuttons,aCriticaliconandtheCancelbuttontobethedefault,thenthesettingwouldbe:

Table19.3Buttonsettings

Constant Value Description

vbOKOnly 0 DisplayOKbuttononly

vbOKCancel 1 DisplayOKandCancelbuttons.Seeexample1inFigure19.4.

vbAbortRetryIgnore 2 DisplayAbort,Retry,andIgnorebuttons.Seeexample2inFigure19.4.

vbYesNoCancel 3 DisplayYes,No,andCancelbuttons.Seeexample3inFigure19.4.

vbYesNo 4 DisplayYesandNobuttons.Seeexample4inFigure19.4.

vbRetryCancel 5 DisplayRetryandCancelbuttons.Seeexample5inFigure19.4.

16

vbCritical16

DisplayCriticalMessageicon.Seeexample1inFigure19.5.

vbQuestion 32 DisplayWarningQueryicon.Seeexample2inFigure19.5.

vbExclamation 48 DisplayWarningMessageicon.Seeexample3inFigure19.5.

vbInformation 64 DisplayInformationMessageicon.Seeexample4inFigure19.5.

vbDefaultButton1 0 Firstbuttonisdefault

vbDefaultButton2 256 Secondbuttonisdefault

vbDefaultButton3 512 Thirdbuttonisdefault

which is 273. Note that to aid documentation in the program then thepredefinedconstantvaluescanbeused,soforthepreviousexample:

TheMsgBoxfunctionreturnsavaluedependingonthebuttonpressed;thesereturnvaluesareoutlinedinTable19.4.Forexample,iftheuserpressestheOKbuttonthenthereturnvaluewillbe1.IfthedialogboxhasaCancelbuttonthentheuserpressingESChasthesameeffectaschoosingCancel.Ifthedialogboxcontains aHelp button, context-sensitiveHelp is provided for the dialog box.However,novalueisreturneduntiloneoftheotherbuttonsischosen.

Table19.4MsgBoxreturnvalues

Constant Value Buttonchosen

vbOK 1 OK

vbCancel 2 Cancel

vbAbort 3 Abort

vbRetry 4 Retry

vblgnore 5 Ignore

vbYes 6 Yes

vbNo 7 No

Program19.2givesanexampleofaprogramwhichdisplaysadialogboxwithYesandNobuttons,andaquestionmarkicon.Theresponsewillthuseitherbea6(iftheYesbuttonisselected)ora7(iftheNobuttonisselected).Figure19.6

showsasamplerun.

FIGURE19.6 Examplerun

InputTheInputBoxfunctionpromptstheusertoinputtext,orchooseabutton.Itthenreturnsthecontentsofthetextbox.Thebasicformatis:

wheretheparametersinbracketsareoptional.Theparametersare:

prompt stringofbedisplayedinthedialogbox.

title stringwhichcontainsthetitlebarofthedialogbox.Ifitisomittedthentheapplicationnameisplacedinthetitlebar.

inthetitlebar.

default stringwhichisdisplayedinthetextboxandisthedefaultresponseifnootherinputisprovided.Ifthisfieldisomittedthenthetextboxisinitiallyempty.

xpos Numericvaluethatspecifies(intwips)thehorizontaldistanceoftheleftedgeofthedialogboxfromtheleftedgeofthescreen.Ifxposisomittedthenthedialogboxishorizontallycentred.

ypos Numericvaluethatspecifies(intwips)theverticaldistanceoftheupperedgeofthedialogboxfromthetopofthescreen.Ifyposisomittedthenthedialogboxisverticallypositionedapproximatelyone-thirdofthewaydownthescreen.

helpfile stringthatidentifiestheHelpfiletousetoprovidecontext-sensitiveHelpforthedialogbox.Ifhelpfileisprovidedthencontextmustalsobeprovided.

context NumericvaluethatistheHelpcontextnumbertheHelpauthorassignedtotheappropriateHelptopic.Ifcontextisprovided,helpfilemustalsobeprovided.Whenbothhelpfileandcontextareprovided,theusercanpressF1toviewtheHelptopiccorrespondingtothecontext.

Program19.3showsanexampleusageoftheInputBoxfunction.Inthiscasethemessage for the title is ‘Inputdemonstration’, thedefaultvalue is ‘10’andthevalueisreturnintotheinvalvariable.

FIGURE19.7 Examplerun

19.4.6DecisionsAndLoopsThedecisionsand loops inVisualBasicare similar to theonesused inCandPascal.

IfstatementThebasicifstatementformatis:

or,ingeneral:

Where the conditioncanbeanumericor stringexpression that evaluates toTrueorFalse.Thestatementblockcontainsoneormorestatementsseparatedbycolons.AswithC and Pascal, if the first condition is True then the first statement

blockisexecuted,elseifthesecondconditionisTruethenthesecondstatementblock is executed, and soon. Ifnoneof the conditions areTrue then the finalelsestatementblockisexecuted(ifitexists).Note thatElse andElseIf arebothoptional and there canbeanynumberof

Elself clauses but none of them can occur after the Else clause Program 19.4givesanexampleofaprograminwhichtheuserentersavaluefrom0to2andtheprogramdisplaystheequivalentresistorcolourcodecolour.

CaseTheCasestatement issimilar to thecaseandswitchstatementsused inPascalandC.Itsgeneralformis:

The expression can be any numeric or string expression. A match of theexpressiontotheexpressionvaluecausesthecorrespondingstatementblocktobeexecuted. Ifnoneof theblockmatch then theCaseElse statementblock isexecuted. If testexpression matches any expressionlist expression associatedwithaCaseclause,thestatementsfollowingthatCaseclauseareexecuteduptothenextCaseclause,or, for the lastclause,up to theEndSelect.Control thenpasses to the statement following End Select. If testexpression matches anexpressionlist expression in more than one Case clause, only the statementsfollowingthefirstmatchareexecuted.MultipleexpressionsorrangescanbeaddedtotheCasecause,suchas:

It isalsopossible tospecifyrangesandmultipleexpressionsforstrings.Forexample the following matches the string to ‘apple’ and everything,alphabeticallybetween,‘banana’and‘carrot’:

Program 19.5 shows an example of a programwhich is similar to Program19.4butusesacasestatementtoselecttheresistorcolourcodecolour.

ForloopTheForloopissimilartotheforloopinPascal.Itrepeatsagroupofstatementsanumberoftimes.Itsgeneralformis:

or

Wherecounterisanumericvariablewhichasusedaloopcounter,startistheInitialvalueofcounter,endisthefinalvalueofcounterandstepistheamountbywhichthecountischangedforeachloop.Thisvaluecaneitherbepositiveornegative.Thedefaultstepsize,ifnotspecifiedis1.Program 19.6 uses a for loop to calculate the factorial value of an entered

value.

FIGURE19.8 Examplerun

Do..whileloopTheDo..whileloopissimilartothewhile()statementsusedinPascalandC.Itsgeneralformis:

or

or

or

Program19.7usesado..whilelooptotesttoseeiftheuserinputiswithinavalidrange.Inthiscasethevalidinputisbetween0and10forthevoltageinputandgreater than0andupto10for thecurrent input.If theuserentersavaluewhich isoutside this range thenaMsgBox isdisplayedwithanerrormessage(INVALID:re-enter).

19.5Exercises19.5.1.CompleteProgram19.5sothatitimplementsthecompleteresistor

colourcode(seeTable6.1onpage117).19.5.2.Changetheprogramin19.5.1sothatitloopsuntiltheuserentersavalid

value(between0and9).19.5.3.Changetheprogramin19.5.2sothataftertheresulthasbeendisplayed

theuserispromptedastowhethertorepeattheprogram(OK)orexittheprogram(Cancel).

19.5.4.Writeaprogramwhichwillcontinuallydisplaythecurrentdateandtime.Thesamplecodegivenbelowdisplaysasingledateandtime.

19.5.5.ModifytheprograminExercise19.5.4sothattheOKandCancelbuttonsareshown.IftheuserselectstheCancelbuttonthentheprogramshouldexit,elsetheprogramshoulddisplaythenewdate.Thesample

codegivenbelowdisplaysasingledateandtimewiththeOKandCancelbuttons.

19.5.6.CompleteWorksheet2onpage37usingVisualBasic.NotethatforW2.2thesquarerootfunctioninVisualBasicissqr,andinW2.3theinversetangentfunctionisatn.

20

Forms

20.1Introduction

This chapter discusses how forms are constructed and how code is associatedwiththeform.

20.2SettingpropertiesEachcontrolobjecthasasetofpropertiesassociatedwith it.Forexample, theTextBoxcontrolinFigure20.1hasanobjectnameofText1.Thisobjecthasanumber of associated properties, such as Alignment, Appearance, BackColor,andsoon.Thesepropertiescanbechangedwithintheprogrambyusingthedotnotation.Forexample,tochangethefontto‘CourierNew’,thetextdisplayedintheobjectto‘Hello’andtheheightofthewindowto1000thefollowingcanbeused:

FIGURE20.1 Objectproperties

20.3FormsandcodeVisualBasicprogramsarenormallydesignedbyfirstdefiningtheuserinterface(the form) andwriting the codewhich is associatedwith events and controls.Thebestwaytoillustratetheprocessiswithanexample.

20.3.1MultipleChoiceExampleIn this example the user is to design a formwith a simple question and threeoptionalexamples. It shoulddisplay if theanswer iscorrect (TRUE)orwrong(FALSE).Theprogramshouldcontinueaftereachselectionuntiltheuserselectsanexitbutton.

Step1:Thelabelcontrolisselected Thenthetext‘WhatisthecapitalofFrance’isenteredthecaptionfield,asshowninFigure20.2.

FIGURE20.2 Step1

Step2:

Nexttheuseraddacommandbuttonbyselectingthecommandcontrol .The button is then added to the form and the Caption property is set to

‘Edinburgh’,asshowninFigure20.3.

FIGURE20.3 Step2

Step3:Next the user adds another command button by selecting the command

control.ThebuttonisthenaddedtotheformandtheCaptionpropertyissetto‘Paris’,asshowninFigure20.4.

FIGURE20.4 Step3

Step4:Next the user adds another command button by selecting the command

control.ThebuttonisthenaddedtotheformandtheCaptionpropertyissetto‘Munich’,asshowninFigure20.5.

FIGURE20.5 Step4

Step5:

NexttheuseraddsaTextBox .Thisisthenaddedtotheright-handsideoftheform,asshowninFigure20.6.TheTextpropertyisthenchangedtohaveanemptyfield.TheTextBoxwillbeusedtodisplaytextfromtheprogram.

FIGURE20.6 Step5

Step6:Next the user adds another command button by selecting the command

control.ThebuttonisthenaddedtotheformandtheCaptionpropertyissetto‘Exit’,asshown inFigure20.7.Acharacter in thenamecanbeunderlinedbyputtingan&beforeit.Thus‘&Exit’willbedisplayedas‘Exit’.

FIGURE20.7 Step6

Step7:Nextthecodecanbeattachedtoeachofthecommandbuttons.Thisisdone

byeitherdoubleclickingonthecommandbuttonorbyselectingthebuttonandpressing theF7key.Todisplay to theTextBox (theobjectnamedText1) thenthetextpropertyissetwith:

whichdisplaythestring“FALSE”tothetextwindow.TheassociatedcodeisshowninFigure20.8.

FIGURE20.8 VisualBasic4on-linehelpmanual

Step8:Nextthecodeassociatedwiththesecondcommandbuttonisset,with:

asshowninFigure20.9.

FIGURE20.9 VisualBasic4on-linehelpmanual

Step9:Nextthecodeassociatedwiththethirdcommandbuttonisset,with:

asshowninFigure20.10.

FIGURE20.10 VisualBasic4on-linehelpmanual

Step10:Finallythecodeassociatedwiththeexitcommandbuttonissetbyaddingthe

code:

whichcausestheprogramtoendandthecodeisshowninFigure20.11.

FIGURE20.11 VisualBasic4on-linehelpmanual

The program can then be executed with Run→Start. Figure 20.12 shows asamplerun.

FIGURE20.12 Sampletestrun

NexttheformandtheprojectaresavedusingtheFile→Saveoption.Ifthefilehasnotbeensavedbeforethentheuserwillbepromptedtogivetheprojectandthe form a new file name. In this case save the project and the form asVB03_01.VBPandVB03_01.FRM.ThesearelistedinProgram20.1.Itcanbeseenthat theformfile(VB03_01.FRM)containstheVisualBasiccodealongwiththepropertiesanddefinitionsofthecontrols,whereastheprojectfile(VB03_01.VBP)definestheuser’senvironment,suchas:•Thenamesofanyforms.•Thecontroltypes.

20.4TemperatureconversionprogramIn this example the user will enter either a temperature in Centigrade orFahrenheit and the program will convert to an equivalent Fahrenheit orCentigradetemperature.Thestepstaken,withreferencetoFigure20.13,are:

FIGURE20.13 Temperatureconversionform

1.AddaLabelcontrolandchangeitsCaptionpropertyto‘Centigrade’.2.AddaLabelcontrolandchangeitsCaptionpropertyto‘Fahrenheit’.3.AddaTextBoxcontrolandputitbesidetheCentigradeLabel.Next

changeitsTextpropertyto‘0’.4.AddaTextBoxcontrolandputitbesidetheFahrenheitLabel.Next

changeitsTextpropertyto‘32’.5.AddaCommandButtoncontrolandputitbelowthetextboxes.Next

changeitsCaptionpropertyto‘CtoF’.ThiscommandbuttonwillconvertthevalueintheCentigradetoFahrenheitandputtheresultintheFahrenheittextbox.

6.AddaCommandButtoncontrolandputitbesidetheothercommandbutton.NextchangeitsCaptionpropertyto‘FtoC’.ThiscommandbuttonwillconvertthevalueintheFahrenheittoCentigradeandputtheresultintheCentigradetextbox.

7.SelecttheformandchangetheCaptionpropertyto‘TemperatureConversion’.

Nextthecodeassociatedwitheachcontrolcanbeadded,asfollows:1.Firstaddcodetothefirstcommandbutton(CtoF)whichwillbeusedto

convertthetextfromtheCentigradetextbox(Text1)anddisplayittotheFahrenheittextbox(Text2).Thisisachievedwith:

2.Nextaddcodetothesecondcommandbutton(FtoC)whichwillbeusedtoconvertthetextfromtheFahrenheittextbox(Text2)anddisplayittotheCentigradetextbox(Text1).Thisisachievedwith:

AtestrunoftheprogramisgiveninFigure20.14.

FIGURE20.14 Samplerun

Thetemperatureconversionprogramuptothispointhasseveralweaknesses.One of these is that it does not have an exit option (this will be left as anexercise) and the other is that the user can enter a valuewhich is not a validtemperaturevalueandtheprogramwillacceptit.Forexample,iftheuserentersastringofcharactersthentheprogramstopsanddisplaysthemessageshowninFigure20.15.

FIGURE20.15 Samplerunwithinvalidinput

Toovercome thisproblem thevalue that is entered is tested to see if it is avalidnumericvalue,usingtheIsNumeric()function.ThisreturnsaTRUEifthevaluecanbeconvertedtoanumericvalue,elseaFALSE.Themodifiedcodeforthe two command buttons is given next and a sample run is shown in Figure20.16.

FIGURE20.16 Samplerunwithinvalidinput

20.5QuadraticrootsprogramInthisexampletheprogramcalculates therootsofaquadraticequationwithauserenteredvaluesofa,bandc.Thegeneralformofaquadraticequationis:

thegeneralsolutionis:

Thisleadstothreetypesofroots,theseare:if(b2>4ac)thentherearetworealroots;elseif(b2=4ac)thenthereisasinglerootof–b/4a;elseif(b2<4ac)thenthesearetwocomplexrootswhichare:

Thestepstaken,withreferencetoFigure20.17,are:

FIGURE20.17 Quadraticequationform

1.AddaLabelcontrolandchangeitsCaptionpropertyto‘a’.2.AddaLabelcontrolandchangeitsCaptionpropertyto‘b’.3.AddaLabelcontrolandchangeitsCaptionpropertyto‘c’.4.AddaLabelcontrolandchangeitsCaptionpropertyto‘x1’.5.AddaLabelcontrolandchangeitsCaptionpropertyto‘x2’.6.AddaTextBoxcontrolandputitbesidetheaLabel.NextchangeitsText

propertyto‘0’(thisistheText1object).7.AddaTextBoxcontrolandputitbesidethebLabel.NextchangeitsText

propertyto‘0’(thisistheText2object).8.AddaTextBoxcontrolandputitbesidethecLabel.NextchangeitsText

propertyto‘0’(thisistheText3object).9.AddaTextBoxcontrolandputitbesidethex1Label.Nextchangeits

Textpropertyto‘0’(thisistheText4object).10.AddaTextBoxcontrolandputitbesidethex2Label.Nextchangeits

Textpropertyto‘0’(thisistheText5object).11.AddaCommandButtoncontrolandputitbelowthetextboxes.Next

changeitsCaptionpropertyto‘Calculate’.Thiscommandbuttonwillbeusedtodeterminetherootsoftheequation.

12.AddaCommandButtoncontrolandputitbesidetheothercommandbutton.NextchangeitsCaptionpropertyto‘Exit’.Thiscommandbuttonwillbeusedtoexittheprogram.

13.SelecttheformandchangetheCaptionpropertyto‘QuadraticEquation’.Nextthecodeassociatedwitheachcontrolcanbeadded,asfollows:1.Firstaddcodetothefirstcommandbutton(Calculate)whichwillbeused

tocalculatetherootsanddisplaytotherootstextbox(Text4andText5).Thisisachievedwith:

Noticethatthecodeincludesthe_characterwhichallowstheprogrammertocontinueastatementontoanotherline.

2.Nextaddcodetothesecondcommandbutton(Exit):

Figure20.18showstwosampleruns.

FIGURE20.18 Sampleruns

20.6ResistancecalculationwithslidercontrolsprogramAnexcellentmethodofallowingtheusertoinputavaluewithinafixedrangeistouseaslidercontrol.Theseslidercontrolscaneitherbevertical (VScroll)orhorizontal(HScroll).Themainproperties,asshowninFigure20.19,ofascrollbarare:

FIGURE20.19 Scrollbarproperties

•Max.Whichdefinesthemaximumvalueofthescrollbar.•Min.Whichdefinestheminimumvalueofthescrollbar.•Value.Whichgivesthecurrentslidervalue.

Asanexample,ahorizontalsliderwillbesetupwithavoltagerangeof0to100.Thevalueof the sliderwill be shown.The steps taken,with reference toFigure20.20,are:

FIGURE20.20 Voltageform

1.AddaLabelcontrolandchangeitsCaptionpropertyto‘Voltage’.2.AddaLabelcontrolandchangeitsCaptionpropertyto‘0’.3.AddaHScrollBarcontrolbelowthelabels.NextchangeitsMaxproperty

to‘100’anditsMinpropertyto‘0’.Nextthecodeassociatedwitheachcontrolcanbeadded,asfollows:1.Addcodetothehorizontalscrollbarwhichwillbeusedtodisplayits

valuetothevoltagevaluelabel(Label2).Thisisachievedwith:

Thiswill take thevalue from the scroll bar (HScroll1.Value) anddisplay tothesecondlabelbox(Label2).Whentheprogramisrunthentheusercanmovethescrollbarbackandforwardwhichcausesachangeinthedisplayedvoltagevalue(from0to100).AsamplerunisshowninFigure20.21.

FIGURE20.21 Samplerun

This project can now be enhanced by adding another slider for current anddisplaying theequivalent resistance (which isvoltagedividedbycurrent).Thestepstaken,withreferencetoFigure20.22,are:

FIGURE20.22 Newform

1.AddaLabelcontrolandchangeitsCaptionpropertyto‘Voltage’.2.AddaLabelcontrolandchangeitsCaptionpropertyto‘0’.3.AddaHScrollBarcontrolbelowthelabels(HScrolll).Nextchangeits

Maxpropertyto‘100’anditsMinpropertyto‘0’.4.AddaLabelcontrolandchangeitsCaptionpropertyto‘Current’.5.AddaLabelcontrolandchangeitsCaptionpropertyto‘0’.6.AddaHScrollBarcontrolbelowthelabels(HScroll2).Nextchangeits

Maxpropertyto‘100’anditsMinpropertyto‘0’.7.AddaLabelcontrolandchangeitsCaptionpropertyto‘Resistance’.8.AddaLabelcontrolandchangeitsCaptionpropertyto‘0’.

Nextthecodeassociatedwitheachcontrolcanbeadded,asfollows:1.Addcodetothefirsthorizontalscrollbar(HScrolll)whichwillbeusedto

displayitsvaluetothevoltagevaluelabel(Label2).Theresistancelabel(Label6)isalsoupdatedwiththeresultofthevoltagedividedbythecurrent.Thisisachievedwith:

2.Addcodetothesecondhorizontalscrollbar(HScroll2)whichwillbeusedtodisplayitsvaluetothecurrentvaluelabel(Label4)withthevalueofthescrollbardividedby100.Theresistancelabel(Label6)isalsoupdatedwiththeresultofthevoltagedividedbythecurrent.Thisisachievedwith:

Figure20.23showsasamplerun.

FIGURE20.23 Samplerun

Oneof theproblemsof thedesign is that thecontrolsandformhavenameswhichdonotdocument their function.VisualBasicusesanamingconventionwhichusesthetypeofcontrolandconsecutivelyaddsanumber,asshowninthedesigninFigure20.24.

FIGURE20.24 Objectnames

Inthiscaseanimprovednamingconventionmightbe:

These are set by selecting the properties of each of the objects and thenchangingtheNamepropertytotherequiredname.AnexampleofchangingthenameoftheformtoResistance_CalcisgiveninFigure20.25.

FIGURE20.25 Changingthenameoftheform

Figure 20.26 shows the list of objects after each of their names has beenchanged.Noticethatitisnoweasiertolocatetherequiredobject.

FIGURE20.26 Changingthenameoftheform

Nextthecodemustbemodifiedsothatthereferencesaretothenewlynamedobjects.Thecodeforthevoltagescrollbar(Voltage_Value)isnow:

andthecodeforthecurrentscrollbar(Current_Value)isnow:

20.7Exercises20.7.1.WriteaVisualBasicprograminwhichtheuserenterseitheravaluein

eitherradiansordegreesandtheprogramconvertstoeitherdegreesorradians,respectively.Figure20.27showsasamplerun.

FIGURE20.27 Radianstodegreesconversion

20.7.2.ModifytheprograminExercise20.7.1sothatinvalidentriesarenotaccepted.

20.7.3.ModifytheprograminExercise20.7.2sothattheconversionvalueisautomaticallyconvertedwhentheuserentersavalue(thatis,thereisnoneedforthecommandbuttons).

20.7.4.WriteseparateVisualBasicprogramswithslidercontrolsforthefollowingformula:(i)F=marange:m=0.01to1000g,a=0.01to100m.s−2

(ii)V=IRrange:1=0.1to100A,V=0.1to100V20.7.5.WriteaVisualBasicprogramthatcalculatesthevaluesofmandcfora

straightline.Thevaluesof(x1,y1)and(x2,y2)shouldbegeneratedwithslidercontrols(witharangeof–100to+100foreachofthevalues).Figure20.28showsasampledesign.

FIGURE20.28 Straightlineprogramdesign

20.7.6.ModifytheprograminExercise20.7.5sothatadividebyzerodoesnotoccurwhenthedifferenceinthexvaluesiszero.Ifthisissothentheprogramshoulddisplay‘INFINITY’forthegradient.Ifthetwocoordinatesarethesamethentheprogramshoulddisplaythemessage‘INVALID’forthegradient.

20.7.7.WriteaVisualBasicprogramwhichhasamultiplechoiceoptionquestionwhichisrepeated.Theprogramshouldkeeparunningtallyofthenumberofcorrectanswersandthenumberofincorrectanswers.

20.7.8.CompleteWorksheet3onpage39usingVisualBasic.

21

MenusandDialogBoxes

21.1Introduction

Thischapterdiscusseshowmenusanddialogboxesareused.

21.2MenueditorMostWindowsprogramshavemenusinwhichtheuserselectsfromarangeofdefinedpull-downmenuswithdefinedoptions.VisualBasichasaneasy-to-usefunction called the Menu Editor which is used to create custom menus. The

MenuEditorisstartedfromtheToolsMenuorfromthetoolbarshortcut .AnexamplescreenfromtheMenuEditorisshowninFigure21.1.Itincludes:

FIGURE21.1 Menueditor

•Caption.Whichisatextboxinwhichthenameofthemenubarormenuoptionisentered.Ahyphen(-)isenteredasacaptionifamenuseparatorbarisrequired.Thisbarhelpstoseparatemenuoptions.OfteninmenustheusercanselectamenuoptionbypressingtheALTkeyandanassignedkey(hotkey).TospecifytheALT-hotkeythenan&isinsertedbeforetheletterofthemenuoption.Whentheprogramisrunthenthisletterisunderlined.ForexampleFi&lewouldbedisplayedasFileandtheassignedkeyswouldbeALT-L.Adoubleampersandspecifiestheampersandcharacter.

•Name.Whichisatextboxinwhichthecontrolnameforthemenuoptionisspecified.Thisisusedbytheprogramcodeandisnotdisplayedtotheuserwhentheprogramisrun.

•Index.Whichisanumericvaluethatcanbeusedtospecifythemenuoption.Typicallyitisusedwhencallingasinglefunctionwhichservicesseveralmenuitems.Forexample,aFilemenumayhavetheoptions:New,OpenandSave,thenasinglefunctioncouldbecreatedtoservicetheserequestsandtheindexvaluewouldbeusedwhichoptionhasbeenselected.

•Shortcut.Whichisapull-downmenuthatcanbeusedtospecifyashortcutkey(Cntrl-AtoCntrl-Z,F1toF12,Cntrl-F1toCntrl-F12,Shift-F1toShift-F12,Shift-Cntrl-F1toShift-Cntrl-F12,Cntrl-Ins,Shift-Ins,Del,Shift-Del,Alt-Bkspace).

•HelpContextlD.WhichisatextboxinwhichauniquenumericvalueisspecifiedforthecontextID.ThisvaluecanbeusedtofindtheappropriateHelptopicintheHelpfileidentifiedbytheHelpFileproperty.

•NegotiatePosition.Whichisapull-downlistboxwhichallowstheusertospecifythemenu’sNegotiatePositionpropertyanddeterminehowthemenuappearsinaform.Valueoptionsare0(None),1(Left)and2(Middle)and3(Right).

•Checked.Whichisacheckboxwhichspecifiesifacheckmarkistoappearinitiallyattheleftofamenuitem.Itisgenerallyusedtospecifyifatoggledmenuoptionisinitiallyonoroff.

•Enabled.Whichisacheckboxwhichspecifiesifthemenuitemistorespondtoevents.Ifitisnotenabledthenthemenuitemappearsdimmed.

•Visible.Whichisacheckboxwhichspecifiesifthemenuitemistoappearinthemenu.

21.2.1CreatingAMenuSystemThe user enters the caption and name and then uses the outlining buttons toeitherpromoteordemote the itemtoahigheror lower level (with the leftandrightarrowbuttons)orupanddown(withtheupanddownarrowbuttons).Withthisupto4levelsofsubmenuscanbecreated.Thelistboxdisplaysahierarchicallistofmenuitemswithindentedsubmenu

itemswhichindicatetheirhierarchicalposition.AmenuoptionisinsertedusingtheInsertbuttonanddeletedwith theDeletebutton.TheOKbuttoncloses theMenuEditorandsavesthemostrecentchanges.Thecodeassociatedwithamenuitemisdefinedbythemenuitemname.For

exampleifamenuitemhasthecaptionofFileandanameofFileOptionthentheassociatedcodefunctionwillbeFileOption_Click.Forexample,tocreateamenuwith:

1.Createacaption&FileandaddthenameofMenuFile.NextpresstheNextbutton.

2.Createacaption&OpenandaddthenameofMenuFileItem.Addanindexvalueof0.Thenselecttherightarrowbuttontomovetheoptiontothenextlevel,asshowninFigure21.2.NextpresstheNextbutton.

FIGURE21.2 Addingamenuitem

3.Createacaption&SaveandaddthenameofMenuFileItem.Addanindexvalueof1,asshowninFigure21.3.NextpresstheNextbutton.

FIGURE21.3 Addingamenuoption

4.Createacaption&CloseandaddthenameofMenuFileItem.Addanindexvalueof2,asshowninFigure21.4.NextpresstheNextbutton.

FIGURE21.4 Addingamenuoption

5.Createacaption&ExitandaddthenameofExit.Thenselecttheleftarrowbuttontomovetheoptiontothenextlevel,asshowninFigure21.5.NextpresstheOKbuttonandtheformshowninFigure21.6shouldbedisplayed.

FIGURE21.5 Addingamenuoption

FIGURE21.6 Menueditor

The associated code modules which are related to these menus items areMenuFile_Click(), MenuFileItem_Click() and Exit_Click(). TheMenuFileItemClick()modulehastheIndexparameterpassedtoit.Thishasavalueof0whenOpenisselect,a1whenSaveisselectedanda2whenCloseisselected.TheMenuFileItemisspecifiedwith:

thusthevalueofIndexwilleitherbe0,1or2.Next a textbox is added to the form (Text1), as shown inFigure21.7.The

resultingobjectsareshowninFigure21.8.

FIGURE21.7 Addingtextbox

FIGURE21.8 Programobjects

Next the code can be added. The MenuFileItem object services the Open,SaveandCloseoptionsandtheIndexparameterpassedintoit.InthecodebelowtheCasestatementisusedtotesttheIndexparameterand,inthiscase,displaysometexttothetextbox.

This code appends either ‘Open’, ‘Save’ or ‘Close’ to the text box (Text1).The&characterconcatenatestwostringstogether, thusthecodeText1.Text&“Open”simplyaddsthetext‘Open’tothetextalreadyinthetextwindow.Theexitcodeisaddedasfollows:

Figure 21.9 shows a sample run of the developed program. The Exitmenuoption is used toquit theprogramand theFile options (File,Save andClose)simplydisplaytherequiredtexttothetextbox.

FIGURE21.9 Examplerun

21.3CommondialogcontrolTheCommonDialogcontrolallowsforfileoperationssuchasopening,savingorprinting files. It is basically a control betweenVisualBasic and theMicrosoftWindows dynamic-link library COMMDLG. DLL. Thus this file must be in theMicrosoftWindowsSYSTEMdirectoryforthecommondialogcontroltowork.Adialog box is added to an application by first adding theCommonDialog

control to a form and setting its properties.Whendeveloping the program thecommon dialog box is displayed as an icon on the form.A program calls thedialog with one of the following (assuming that the dialog box is namedCommonDialog1): CommonDialog1.Filter A string which displays thefilenamefilter.The|characterisusedtodifferentiatedifferentForexamplethefollowingfilterenables theuser toselect text filesorgraphicfiles that includebitmapsandicons:

CommonDialog1.FilenameWhichreturnsorsetsthepathandfilenameofaselectedfile.CommonDialog1.FilterlndexWhichdefinesthedefaultfilter(withreference

totheFilter).CommonDialog1.ShowSaveWhichreturnsorsetsthepathandfilenameofa

selected file. Displays the CommonDialog control’s Save As dialog box. TheobjectplaceholderrepresentsanobjectexpressionthatevaluatestoanobjectintheAppliesTolist.CommonDialog1.ShowOpen Which displays the CommonDialog control’s

Opendialogbox.CommonDialog1.ShowPrinterWhichdisplaystheCommonDialogcontrol’s

Printerdialogbox.CommonDialog1.ShowFont Which displays the CommonDialog control’s

Fontdialogbox.CommonDialog1.ShowHelp Which runsWINHELP.EXE and displays the

specifiedhelpfile.Adialogbox is added to a form in anyposition, as shown inFigure21.10.

Thisboxcanbeplacedanywhere as itwill notbe seenon the formwhen theprogramisrun.

FIGURE21.10 Examplerun

Thecommondialogboxcanbeusedtodeterminethefilenameofafiletobeopenedorsaved.ItisusedinProgram21.3(whichisamodificationofProgram21.1)intheOpenandSavefilemenuoptions.Thefilterissetto:

This displays, in the Type of File field, the three options “All Files

(*.*),*.*,Text Files (*.txt),*.txt and Temp Files (*.tmp) |*.tmp”.Thedefaultfiletypeissettothesecondoptionwiththefilterindexsettingof:

Figure21.11showsasamplerunandthedialogbox.Itcanbeseen that thedefaultTypeofFileissetto“TextFiles(*.txt)”andFigure21.12showsanexamplemessagebox.

FIGURE21.11 Examplerun

FIGURE21.12 Examplerun

21.3.1FileOpen/SaveDialogBoxFlagsVariousflagscanbesetbeforethefileopen/savedialogbox.ThesearedefinedinTable21.1aresetwith:

Table21.1CommonDialogcontrolconstants

Constant Value Description

cdlOFNReadOnly &H1(1) ChecksReadOnlycheckboxforOpenandSaveAsdialogboxes,seeFigure21.13.

cdlOFNOverwritePrompt &H2(2) CausestheSaveAsdialogboxtogenerateamessageboxiftheselectedfilealreadyexists.

cdlOFNHideReadOnly &H4(4) HidestheReadOnlycheckbox,seeFigure21.14.

cdlOFNNoChangeDir &H8(8) Setsthecurrentdirectorytowhatitwaswhenthedialogboxwasinvoked.

cdlOFNHelpButton &H10(16) CausesthedialogboxtodisplaytheHelpbutton.

cdlOFNNoValidate &H100(256)

Allowsinvalidcharactersinthereturnedfilename.

cdlOFNAllowMultiselect &H200(512)

AllowstheFileNamelistboxtohavemultipleselections,seeFigure21.15.

cdlOFNExtensionDifferent &H400(1024)

TheextensionofthereturnedfilenameisdifferentfromtheextensionsetbytheDefaultExtproperty.

cdlOFNPathMustExist &H800(2096)

Usercanenteronlyvalidpathnames.

cdlOFNFileMustExist &H1000(4096)

Usercanenteronlynamesofexistingfiles.

The flags can either be defined with their constant name (such ascdlOFNReadonly)orby thevalue (0x01).Thesevaluesornamescanbeaddedtogether to achieve the required functionality. For example, modifying the

previous example to checks the read-only check box for Open dialog box. AsampledialogboxisshowninFigure21.13.

FIGURE21.13 Examplerun

For example, modifying the previous example to hide the read-only checkbox.AsampledialogboxisshowninFigure21.14.

FIGURE21.14 Examplerun

For example,modifying the previous example toAllows theFileName listboxtohavemultipleselections.AsampledialogboxisshowninFigure21.15.

FIGURE21.15 Examplerun

Theflagsettingsforadialogboxwiththeread-onlyboxcheckingandthattheuserisnotallowedtochangethedirectorycaneitherbesetwith:

which is1 (cdlOFNReadonly)added to8 (cdlOFNNochangeDir).Themethodofusinglableconstantsispreferableasithelpstodocumenttheprogram.

21.3.2ShowingHelpManualsThecommondialogboxcanalsobeusedtorunthehelpprogramWINHELP.EXE.Thisisachievedby:

andthenameofthehelpmanualisspecifiedby:

Variousoptionsflagscanalsobesetwiththehelpoption,thesearespecifiedinTable21.2.

Table21.2CommonDialogcontrolconstants

Constant Value Description

cdlHelpCommand &H102 Executesahelpmacro.

cdlHelpContents &H3 Displaysthehelpcontentstopic.

cdlHelpContext &H1 Displayshelpforaparticularcontext.

cdlHelpContextPopup &H8 Displaysinapop-upwindowaparticularHelptopic.

cdlHelpForceFile &H9 EnsuresthatWinHelpdisplaysthecorrectHelpfile.IfthecorrectHelpfileiscurrentlydisplayed,noactionoccurs.IftheincorrectHelpfileisdisplayed,WinHelpopensthecorrectfile.

cdlHelpHelpOnHelp &H4 DisplaysHelpforusingthehelpapplicationitself.

cdlHelpIndex &H3 DisplaystheindexofthespecifiedHelpfile.

cdlHelpKey &H101 DisplaysHelpforaparticularkeyword.

Typicallyahelpmenuoptionisaddedtoaprogram.Anexamplehelpeventisgiven in Program 21.4. The help command used is cdlHelpConents whichshowstheindexpageofthehelpmanual.Figure21.16showsanexampleofarun and Figure 21.17 shows an example for the An example of Vbcbt helpmanual.

FIGURE21.16 Selectinghelpfile

FIGURE21.17 Examplehelpmanual

21.4RunninganapplicationprogramVisualBasicallowsfortheexecutionofapplicationswiththeShellcommand.Itsformatis:

wherethewindowstyleisasdefinedinTable21.3.Ifthisargumentismissingthenthewindowstyleisthattheprogramisstartedwithaminimizedfocus.

Table21.3

Windowstylenamedargument

Constant Val Description

vbHide 0 Windowishiddenandfocusispassedtothehiddenwindow.

vbNormalFocus 1 Windowhasfocusandisrestoredtoitsoriginalsizeandposition.

vbMinimizedFocus 2 Windowisdisplayedasaniconwithfocus.

vbMaximizedFocus 3 Windowismaximizedwithfocus.

vbNormalNoFocus 4 Windowisrestoredtoitsmostrecentsizeandposition.Thecurrentlyactivewindowremainsactive.

vbMinimizedNoFocus 6 Windowisdisplayedasanicon.Thecurrentlyactivewindowremainsactive.

ThefollowingshowsanexampleofexecutingtheCalc.exeandNotepad.exeprograms:

21.5Exercises21.4.1.WriteaVisualBasicprogramwiththefollowingmenusystem:

21.4.2.ModifythemenusysteminExercise21.4.1sothattheprogramdisplaysthefunctionofthemenuoption.

21.4.3.ExpandProgram21.5anditsmenusystemsothatitrunsotherWindowsprograms.Anexamplecouldbe:

21.4.4.Integratesomeoftheprogramsfrompreviouschaptersintoasingleprogramwithmenuoptions.Forexample,themenusystemcouldbe:

Onepossiblemethodofimplementingthisprogramistocompilethetemperatureconversion,quadraticequationandstraightlineprogramstoanEXE(File→MakeEXEfile…).ThenruntheShellfunctionfromtheobjectcall.

22

Events

22.1Introduction

VisualBasicdiffersfrommanyotherprogramminglanguagesinthatitisevent-drivenwhere theexecutionofaprogram isdefinedby theevents thathappen.This is a different approach to many programming languages which follow adefinedsequenceofexecutionandtheprogrammermustdeveloproutineswhichreacttoevents.ThischapterdiscussestheeventsthathappeninVisualBasic.

22.2ProgrameventsEachobjectinVisualBasichasvariouseventsassociatedwithit.Forexample,the single click on an object may cause one event but a double click causesanother.Theeventsaredisplayedattheright-handsideofthecodewindow.AnexampleisshowninFigure22.1whichinthiscaseshowstheevents:KeyPress,KeyUp,LinkClose,LinkError,LinkExecute,LinkOpenandLoad.Thenameoftheroutinewhichcontainsthecodefortheeventandobjectisintheform:

FIGURE22.1 Formevents

ThemaineventsthatoccurinVisualBasicinclude:•Click.Whichoccurswhenauserperformsasingleclickofthemousebutton

ontheobject.•DblClick.Whichoccurswhenauserperformsadoubleclickofthemouse

buttonontheobject.•MouseUp.Whichoccurswhentheuserreleasesthemousebutton.•MouseDown.Whichoccurswhentheuserpressesthemousebuttondown.•MouseMove.Whichoccurswhentheusermovesthemouse.•KeyUp.Whichoccurswhentheuserreleasesakey.•KeyDown.Whichoccurswhentheuserpressesakey.•KeyPress.Whichoccurswhentheuserpressesandreleasesakey(the

KeyDownandKeyUpevents).•Load.Whichoccurswhenaformisloaded.•DragDrop.Whichoccursatthebeginandendofadragoperationofany

control.•LostFocus.Whichoccurswhenanobjectlosesthefocus,eitherbyuser

action,suchastabbingtoorclickinganotherobject.•Resize.Whichoccurswhenaformisfirstdisplayedoriftheobjectsizeis

changed.•Unload.Whichoccurswhenaformisabouttoberemovedfromthescreen.Notallcontrolsandforms(objects)havealltheeventsassociatedwiththem.

Forexampleaformmayhavethefollowing:

whereasacommandbuttonhasareducedsetofroutines:

Theparameterspassedintotheroutinedependontheactionsassociatedwiththe events. For example, theKeypress event on a commandbutton causes theroutine:

to be called. The value of KeyAscii will contain the ASCII value of thecharacterpress.The mouse down event for a command button has the following routine

associatedwithit:

wherethevalueofButtonisthevalueofthebuttonpress(0fornone,1fortheleft button and2 for the rightbutton).Shift specifies if the shift keyhasbeenpressed,andX,Yspecifythex,ycoordinatesofthemousepoint.Thefollowingsectionsdiscusssomeeventswhichoccur.

22.2.1ClickTheClickeventoccurswhentheuserpressesandthenreleasesamousebuttonoveranobject.Whentheobjectisaformtheeventoccurswhentheuserclicksonablankareaor adisabledcontrol. If theobject is a control, then theeventoccurswhentheuser:•Clicksonacontrolwithanyofthemousebuttons.Whenthecontrolisa

CheckBox,CommandButton,orOptionButtoncontrolthentheClickeventoccursonlywhentheuserclickstheleftmousebutton.

•PressestheALT-hotkeyforacontrol,suchaspressingAlt-XfortheE&xitcontrolpropertyname.

•PressestheEnterkeywhentheformhasacommandbutton.•PressestheSpacekeywhencommandbutton,optionbuttonorcheckbox

controlhasthefocus.

22.2.2DblClickTheDblClickeventoccurswhentheuserpressesandreleasesthemousebuttontwiceoveranobject.Inaformitoccurswhentheuserdoubleclickseitheronadisabledcontrolorablankareaofaform.Onacontroltheeventhappenswhentheuser:•Double-clicksonacontrolwiththeleftmousebutton.•Double-clicksanitemwithinaComboBoxcontrolwhoseStylepropertyisset

to1(Simple).AnexampleformisshowninFigure22.2.Inthiscaseatextboxisaddedto

theform.Thenthefollowingcodeisaddedtotheform:

FIGURE22.2 Formevents

whichwilldisplaythetext‘MISS’whentheuserclickonanyblankareaontheform.Thefollowingcodeisaddedtothetextbox:

whichdisplaysthetext‘HIT’whentheuserdoubleclicksonthetextbox.

22.2.3MouseUp,MouseDownTheMouseUp event occurs when the user releases themouse button and theMouseDowneventwhentheuserpressesamousebutton.Thestandardformatfortheassociatedroutinesare:

where•buttonidentifieswhichbuttonwaspressed(MouseDown)orreleased

(MouseUp).Thefirstbitofthevalueidentifiestheleftbutton,thesecondidentifiestherightbuttonandthethirdbitidentifiesthemiddlebutton.Thusavalueof1identifiestheleftbutton,avalueof2identifiestherightandavalueof4identifiesthemiddlebutton(ifthemousehasone).Acombinationofthesevaluescanbeusedtoidentifybuttonpresscombinations,suchasavalueof6identifiesthatthemiddleandrightbuttonshavebeenpressed.Table22.1showstheconstantnamesforthebuttons.

Table22.1Buttonconstants

Constant(Button) Value Description

vbLeftButton 1 Leftbuttonispressed

vbRightButton 2 Rightbuttonispressed

vbMiddleButton 4 Middlebuttonispressed

•shiftidentifiesthestateoftheShift,Cntrl,andAltkeyswhenthebuttonwaspressed(orreleased).ThefirstbitofthevalueidentifiestheShiftkey,thesecondbitidentifiestheCntrlkeyandthethirdbitidentifiestheAltkey.Thusavalueof1identifiestheShiftkey,avalueof2identifiestheCntrlkeyandavalueof4identifiestheAltkey.Acombinationofthesevaluescanbeusedtoidentifykeycombinations,suchasavalueof6identifiesthattheCntrlandAltkeysarepressed.Table22.1showstheconstantnamesforthekeys.

•x,yidentifiesthecurrentlocationofthemousepointer.ThexandyvaluesarerelativelytotheScaleHeight,ScaleWidth,ScaleLeft,andScaleToppropertiesoftheobject.

AnexampleofcodeforthemousedowneventisgivennextandasamplerunisshowninFigure22.3.

FIGURE22.3 Formevents

Table22.2Buttonconstants

Constant Value Description

vbShiftMask 1 SHIFTkeyispressed

vbCtrlMask 2 CTRLkeyispressed

vbAltMask 4 ALTkeyispressed

22.2.4MouseMoveThe MouseMove event occurs when the user moves the mouse. Thus it iscontinuallybeingcalledasitmovesacrossanobject.Thestandardformatfortheassociatedroutinesare:

wherebutton,shift,xandyhavethesamesettingsastheonesdefinedintheprevioussection.An example of code for theMouseMove event is given next and a sample

codeisshowninFigure22.4.Figure22.5showsasamplerun.Inthiscase,thexandycoordinateisthemousepointerandthebuttonpressedaredisplayedtothetextbox.

FIGURE22.4 Samplecode

FIGURE22.5 Samplerun

22.2.5DragAndDropThe DragDrop event occurs at the end of a drag and drop operation of anycontrol.Thestandardformatfortheassociatedroutinesare:

where:•sourceisthecontrolbeingdragged.•x,yspecifiesthecurrentxandycoordinateofthemousepointerwithinthe

targetformorcontrol.ThexandyvaluesarerelativetotheScaleHeight,ScaleWidth,ScaleLeft,andScaleToppropertiesoftheobject.

22.2.6KeypressThe KeyPress event occurs when the user presses and releases a key (theKeyDownandKeyUpevents).Thestandard format for theassociated routinesare:

whereKeyasciispecifiesastandardANSIkeycode,thiscanbeconvertedintoanASCIIcharacterwiththeconversionfunction:

AnexampleofcodefortheKeyPresseventisgivennextandasamplerunisshowninFigure22.6.Forthisprogramtheusercantypeintheblankareaontheform(thegreyarea)andthetextwillbedisplayedinthetextbox.

FIGURE22.6 Samplerun

22.2.7LostFocusTheLostfocusoccurswhenanobjectlosesthefocus,eitherbyuseraction,suchastabbingtoorclickinganotherobject.Thestandardformatfortheassociatedroutinesare:

22.2.8ResizeTheResize eventoccurswhena form is first displayedor if theobject size ischanged.Thestandardformatfortheassociatedroutinesare:

where:•heightisavaluespecifyingthenewheightofthecontrol.•widthisavaluespecifyingthenewwidthofthecontrol.

22.2.9UnloadTheUnloadeventoccurswhenaformisabouttoberemovedfromthescreen.Theniftheformisreloadedthecontentsofallitscontrolsarereinitialized.Thestandardformatfortheassociatedroutinesare:

wherecanceldetermineswhethertheformisremovedfromthescreen.Ifitis0thentheformisremovedelseitwillnotberemoved.

22.3Exercises22.3.1.WriteaVisualBasicprogramwhichhasasingleformandatextbox.

Thetextboxshouldshowalloftheeventsthatoccurwiththeform,thatis:

Investigatewhentheseeventsoccur.NoticethatwhenaneventhascodeattachedthentheprocedurenameintheViewCodepull-downmenubecomeshighlighted.

22.3.2.WriteaVisualBasicprogramwhichhasasinglecommandbuttonandatextbox.Thetextboxshouldshowalloftheeventsthatoccurwiththecommandbutton,thatis:

Investigatewhentheseeventsoccur.22.3.3.WriteaVisualBasicprograminwhichtheprogramdisplaysthemessage

‘INTEXTAREA’whenthemouseiswithinthetextboxareaand‘OUTOFTEXTAREA’whenitisoutofthetextboxarea.

22.3.4.WriteaVisualBasicprogramwhichhasacommandbutton.Iftheuserpressesanylowercaseletterthentheprogramends,elseitshouldcontinue.Asampleeventwhichquitswhentheletter‘x’ispressedisgivennext:

22.3.5.ModifytheprograminExercise22.3.4sothatiftheuserclicksontheform(andnotonthecommandbutton)theprogramautomaticallypromptstheuserforhis/hername.Thisnameshouldthenappearinthecommandbuttoncaptionproperty(Command1.caption).Anoutlineoftheeventisgivennext:

22.3.6.WriteaVisualBasicprogramwhichdisplaysthemessage‘Solongandthanksforthefish’whenthemainformisUnloaded.Theformshouldberemovedfromthescreen.

22.3.7.WriteaVisualBasicprogramwithatextboxwhichdisplaysthecurrentkeypress,includingAlt-,Ctrl-andShift-keystrokes.

22.3.8.ModifytheprograminExercise22.3.7sothatitalsodisplaysthemousebuttonpressandthecoordinatesofthemouse.

23

Graphics

23.1Introduction

Thischapterdiscusseshowgraphicsfilesareloadedintotheprogramandhowgraphicobjectscanbedrawn.

23.2LoadinggraphicsfilesVisualBasicallowsagraphicfile tobe loaded intoaform,apictureboxoranimagecontrol.Thestandardfunctionis:

Wheregraphfile specifies thenameof thegraphics file, ifnoname isgiventhen the graphic in the form, picture box or image control is cleared. ThestandardgraphicsfilessupportedbyVisualBasicare:•BMP.Windowsbitmapfile.•ICO.Iconfile(maximumsizeof32×32pixels).•RLE.Run-lengthencodedfiles.•WMF.Windowsmetafilefiles.

NormallygraphicsfilesaredisplayedinaPictureBox Thustodisplaythegraphicfile“CLOUD.BMP”toPicture1then:

Apicturecanbeloadedputintotheclipboardusing:

The following example loads a graphics file into a PictureBox. Figure 23.1shows a sample formwhich contains a PictureBox, a CommandButton and aDialogBox.

FIGURE23.1 Form

Thecodeaddedtothecommandbuttonisasfollows:

Thiswilldisplayadialogboxwiththedefaultfilesettingof*.BMP.AftertheuserhasselectedagraphicthentheLoadPicturefunctionisusedtodisplaythegraphicfiletothepicturebox(Picture1).Figure23.2showsasampledialogboxandFigure23.3showsasamplegraphic.

FIGURE23.2 Dialogbox

FIGURE23.3 Samplegraphic

Oneproblemwiththepreviousexamplecodeisthatanon-graphicfilecouldbeloadedandtheprogramwouldnotgiveanerrormessage.Thefollowingcodeovercomes this by testing for an error. This is achieved by testing the Errparameter after thepicturehasbeen loaded. If it is set toTRUE thenan errormessage isdisplayedand,after theuserhasaccepted theerror then thepicturewillbeclearedfromthepicturebox.

23.3ColoursThe background and foreground colour of an object can bemodifiedwith theBackColororForeColorproperty,respectively.Thestandardformis:

AcolourisdefinedasitsRGB(red/green/blue)strength,withahexadecimalstrength from&H00 to&H77 for each colour.The valid ranges of colour arethusfrom0to&HFFFFFF.

23.3.1RGBFunctionThe RGBColor function returns the hexadecimal colour value given the threestrengthsofred,greenandblue.Itsstandardformis:

wherered,greenandblueareavaluefrom0to255.Table23.1givessomeexamplecolourswiththeirRGBcolour.Forexample:

Table23.1Colourstrengths

23.3.2QBColorFunctionTheQBColorfunctionhasalimitedrangeof15,typicallycoloursasspecifiedinTable23.1.Forexample,thefollowingsetsthe

Table23.2Colourvalues

23.4DrawingVisualBasic has awide rangeof drawing functions (graphicsmethods); theseinclude:•Line.Drawslinesandrectanglesonanobject.

•Circle.Drawsacircle,ellipse,orarconanobject.•Cls.ClearsgraphicsandtextfromaFormorPictureBox.•Fillcolour.Returnsorsetsthecolourusedtofillinshapes(drawnbyLine

andCirclegraphicsmethods).•Fillstyle.ReturnsorsetsthepatternusedtofillShapes(ascreatedbyLineor

Circlegraphicsmethods).

23.4.1LineTheLinegraphicmethoddraws linesand rectanglesonanobject. Its standardformis:

where:•Step.Keywordspecifyingthestartingpointco-ordinates.(Optional)•(x1,y1)

Definethestartingpointco-ordinatesofalineorrectangle.Iftheyareomittedthenthelinestartsatthecurrentx,yposition(CurrentXandCurrentY).Optional•Step.Keywordspecifyingtheendpointco-ordinates.(Optional)•(x2,y2)Definetheendpointco-ordinatesofalineorrectangle.(Required)•color.DefinestheRGBcolourusedtodrawtheline.IfitisomittedthentheForeColorpropertysettingisused.(Optional)•B.IftheBoptionisaddedthenaboxisdrawnusingtheco-ordinatesforoppositecorners.(Optional)•F.IftheFoptionisaddedthentheboxisfilledwiththesamecolourasthelinecolour.(Optional)

TheCurrentXandCurrentYvaluesareset to theendof the lineaftera linehas been drawn. The DrawWidth property sets the width of the line andDrawMode and DrawStyle properties define the way that the line or box isdrawn.ThefollowingcodeisaddedtoaformandwiththeClickevent.Itdisplays15

solidrectanglesofarandomsizeandrandomcolour.TheQBColorfunctionisused to display one of the 16 predefined colours. Note that the Rnd functionreturnsarandomnumberfrom0to1.

FIGURE23.4 Samplegraphic

23.4.2CircleThe Circle graphic method draws a circle, ellipse or an arc on an object. Itsstandardformis:

where:•Step.Keywordspecifyingthatthecentreofthecircle,ellipse,orarcis

relativetothecurrentco-ordinatesgivenbytheCurrentXandCurrentYpropertiesofobject.(Optional)•(x,y).Valuewhichgivestheco-ordinatesofthecentreofthecircle,ellipseorarc.(Required)•radius.

Valuewhichspecifiestheradiusofthecircle,ellipseorarc.(Required)•color.Valuewhichspecifiesthecolourofthecircle’soutline.Ifomitted,thevalueoftheForeColorpropertyisused.(Optional)•start,end.Valuesspecifyingthestartandendangle(inradians)foranarcorapartialcircleorellipseisdrawn,startandendspecify(inradians)thebeginningandendpositionsofthearc.(Optional)•aspect.Valuespecifyingtheaspectratioofthecircle.Thedefaultvalueis1.0,whichyieldsaperfectcircle.(Optional)

TheQBColororRGBfunctionaretypicallyusedtosetthecolour.AcircleisfillwithadefinedcolourwiththeFillColorpropertyandthefillstyleissetbytheFillStyleproperties.TheDrawWidthpropertydefines thewidthof the lineusedtodrawthecircle,ellipse,orarc.Thefollowingexamplecodedraws10circlesofincreasingsizeofarandom

colour.Figure23.5showsasamplerun.

FIGURE23.5 Samplegraphic

23.4.3DrawWidthTheDrawWidthpropertyreturnsorsetsthelinewidthofagraphicmethod.Tosetthewidthoflinethefollowingisused:

where the size is a value from1 (the default) to 32,767 and ismeasured inpixels.

23.4.4DrawStyleTheDrawWidthpropertyreturnsorsetsthelinestyleofagraphicmethod.Tosetthelinestylethefollowingisused:

wherevalue is anumber from0 (thedefault) to6whichcorresponds to thefollowinglinestyles:

ForexampletosetalinestyleonaFormtodashed:

DrawWidth=l

23.4.5FillColorTheFillColor property returns or sets the colour used to fill in shapes, circlesandboxes.Tosetthefillcolourthefollowingisused:

wherethesizeisahexadecimalcolourandbydefaultitisBlack.

23.4.6FillStyleTheFillStylepropertyreturnsorsetsthefillstyleofagraphicmethod.Tosetthelinestylethefollowingisused:

wherevalue is anumber from0 (thedefault) to6whichcorresponds to thefollowinglinestyles:

The following example displays 15 randomly filled circleswith a radius of200pixels.It is initiatedwiththeuserclicksontheform.Figure23.6showsasamplerun.

FIGURE23.6 Samplegraphic

23.4.7CurrentX,CurrentYTheCurrentXandCurrentYproperty returnor sets the horizontal andvertical(CurrentY)co-ordinates,respectively.Thestandardformatis:

The(0,0)co-ordinateisattheupper-lefthandcornerofanobject.

23.4.8CIs

TheClsmethodclearsgraphicsand textgeneratedat run timefromaFormorPictureBox.Itsstandardformis:

23.5Exercises23.5.1.Writeaprogramwhichdisplaysacolouredrectangleinthemiddleofa

form.Eachtimetheuserclicksontheformtherectangleshouldchangecolour.

23.5.2.WriteaVisualBasicprogramwhichautomaticallymovesarectanglefromthetopleft-handsideofthescreentothebottomright-handside.Theprogramshouldquitonceitreachesthebottomcorner.

23.5.3.WriteaVisualBasicprogramwhichrandomlymovesasmallrectanglearoundthescreen.Iftherectangletouchesanyoftheedgesitshouldreboundofftheedge.

23.5.4.WriteaVisualBasicprograminwhichtheusercontrolsthemovementofasmallrectanglebythearrowkeys.

23.5.5.WriteaVisualBasicprogramwhichdisplaysacircleontheformwhichfollowstheusersmousecursor(noteusetheclsfunctiontogetridoftheexistingcircle).

23.5.6.WriteseparateVisualBasicprogramswhichdrawthefollowingobjects:(i)Acar.

(ii)Aship.(iii)Ahouse.

23.5.7.WriteaVisualBasicprogramwhichdisplaysthefollowingimages.Usethesleepandclsfunctionstocreateatimingdelayof1secondbetweeneachimagedisplay(theanimationshouldlookasifitiswinking).

PARTEHTML/Java

24

HTML(Introduction)

24.1Introduction

HTMLisastandardhypertextlanguagefortheWWWandhasseveraldifferentversions.MostWWWbrowserssupportHTML2andmostofthenewversionsof the browsers supportHTML3.WWWpages are created and editedwith atext editor, a word processor or, as is becoming more common, within theWWWbrowser.HTMLtagscontainspecialformattingcommandsandarecontainedwithina

less than (<) and a greater than (>) symbol (which are also known as angledbrackets). Most tags have an opening and closing version; for example, tohighlight bold text the bold opening tag is <B>and the closing tag is</B> .Table24.1outlinesafewexamples.

Table24.1ExampleHTMLtags

Opentag Closingtag Description

<HTML> </HTML> StartandendofHTML

<HEAD> </HEAD> DefinestheHTMLheader

<BODY> </BODY> DefinesthemainbodyoftheHTML

<TITLE> </TITLE> DefinesthetitleoftheWWWpage

<I> </I> Italictext

<B> </B> Boldtext

<U> </U> Underlinedtext

<BLINK> </BLINK> Maketextblink

<EM> </EM> Emphasizetext

<FONTSIZE=+1> </FONT> Increasefontsizebyoneincrement

<FONTSIZE=–1> </FONT> Reducefontsizebyoneincrement

Centertext

<CENTER> </CENTER>Centertext

<H1> </H1> Sectionheader,level1

<H2> </H2> Sectionheader,level2

<H3> </H3> Sectionheader,level3

<P> Createanewparagraph

<BR> Createalinebreak

<excl––> ––> Comments

<SUPER> </SUPER> Superscript

<SUB> </SUB> Subscript

HTMLscript1givesanexamplescriptandFigure24.1showstheoutputfromtheWWWbrowser.Thefirstlineisalways<HTML>andthelastlineis</HTML>.After this line theHTMLheader isdefinedbetween<HEAD>and</HEAD>.ThetitleofthewindowinthiscaseisMyfirstHTMLpage.ThemainHTMLtextisthendefinedbetween<BODY>and</BODY>.

FIGURE24.1 ExamplewindowfromexampleHTMLscript

TheWWWbrowserfitstextintothewindowsizeanddoesnotinterpretlinebreaksintheHTMLsource.Toforceanewlinethe<BR>(linebreak)oranewparagraph (<p>) is used. The example also shows bold, italic and underlinedtext.

24.2LinksThe topology of the WWW is set-up using links where pages link to otherrelatedpages.Areferencetakestheform:

whereurl defines theURL for the file,ReferenceName is the name of thereference and </A> defines the end of the reference name. HTML script 24.2shows an example of the uses of references and Figure 24.2 shows a samplebrowser page. The background colour is set using the <BODY BGCOLOR= “#

FFFFFF”>whichsetthebackgroundcolourtowhite.Inthiscasethedefaulttextcolourisblackandthelinkiscolouredblue.

FIGURE24.2 ExamplewindowfromexampleHTMLscript24.2

24.2.1OtherLinksLinkscanbeset-uptosende-mailandnewsgroups.Forexample:

tolinktoatennisnewsgroupand

tosendamailmessagetothee-mailaddress:f.bloggs@fredco.co.uk.

24.3ListsHTMLallowsorderedandunorderedlists.ListscanbedeclaredanywhereinthebodyoftheHTML.

24.3.1OrderedListsThestartofanorderedlistisdefinedwith<OL>andtheendofthelistby</OL>.Eachpart of the list is defined after the<LI> tag.Unordered lists are definedbetween the <UL> and </UL> tags. HTML script 24.3 gives examples of anorderedandanunorderedlist.Figure24.3showstheoutputfromthebrowser.

FIGURE24.3 WWWbrowserwithanorderedandunorderedlists

Some browsers allow the type of numbered list to be definedwith the <OLTYPE=x>,wherexcaneitherbe:•Aforcapitalletters(suchasa,b,c,andsoon).•aforsmallletters(suchasa,b,c,andsoon).•Iforcapitalromanletters(suchasI,II,III,andsoon).•iforsmallromanletters(suchasi,ii,iii,andsoon).•Ifornumbers(whichisthedefault).

wouldbedisplayedas:IList1

IIList2IIIList3

AList1BList2CList3

Thestartingnumberofthelistcanbedefinedusingthe<LIVALUE=n>wherendefinestheinitialvalueofthedefineditemlist.

24.3.2UnorderedListsUnorderedlistsareusedtolistaseriesofitemsinnoparticularorder.Theyaredefined between the <UL> and </UL> tags. Some browsers allow the type ofbulletpointtobedefinedwiththe<LITYPE=shape>,whereshapecaneitherbe:•discforroundsolidbullets(whichisthedefaultforfirstlevellists).•roundforroundhollowbullets(whichisthedefaultforsecondlevellists).•squareforsquarebullets(whichisthedefaultforthird).HTMLscript 24.4gives an exampleof anunnumbered list andFigure24.4

shows theWWWpageoutput for this script. It canbe seen from this that thedefaultbulletsforlevel1listsarediscs,forlevel2theyareroundandforlevel3theyaresquare.

FIGURE24.4 WWWpagewithanunnumberedlist

24.3.3DefinitionListsHTMLusesthe<DL>and</DL>tagsfordefinitionlists.Thesearenormallyusedwhenbuildingglossaries.Eachentryinthedefinitionisdefinedbythe<DT>tagandthetextassociatedwiththeitemisdefinedafterthe<DD>tag.Theendofthelist isdefinedby</DL>.HTMLscript24.5showsanexamplewithadefinitionlist andFigure 24.5 gives a sample output.Note that it uses the<EM> tag toemphasizethedefinitionsubject.

FIGURE24.5 WWWpagewithdefinitionlist

24.4ColoursColoursinHTMLaredefinedintheRGB(red/green/blue)strength.Theformatis#rrggbb,whererr is thehexadecimal equivalent for the redcomponent,ggthe hexadecimal equivalent for the green component and bb the hexadecimalequivalentforthebluecomponent.Table24.2listssomeofthecodesforcertaincolours.

Table24.2Hexadecimalcolours

Individual hexadecimal numbers use base 16 and range from 0 to F (indecimalthisrangesfrom0to15).Atwo-digithexadecimalnumberrangesfrom00toFF(indecimalthisrangesfrom0to255).Table24.3outlineshexadecimalequivalents.

Table24.3Hexadecimaltodecimalconversions

HTMLusespercentagestrengthsfor thecolours.Forexample,FF representsfull strength (100%) and 00 represent no strength (0%). Thus, white is madefromFF (red),FF (green) andFF (blue) andblack ismade from00 (red),00(green)and00(blue).Greyismadefromequalweightingofeachofthecolours,suchas43,43,43fordarkgrey(#434343)andD4,D4andD4forlightgrey(#D4D4D4).Thus,pureredwithbe#FF0000,puregreenwillbe#00FF00andpurebluewithbe#0000FF.Eachcolourisrepresentedby8bits,thusthecolourisdefinedby24bits.This

givesa totalof16777216colours (224differentcolours).Note thatsomevideodisplayswillnothaveenoughmemorytodisplay16.777millioncoloursinthecertainmode so that coloursmaydifferdependingon theWWWbrowser andthegraphicsadapter.The colours of the background, text and the link can be defined with the

BODY tag. An example with a background colour of white, a text colour oforangeandalinkcolourofdarkredis:

andforabackgroundcolourofred,atextcolourofgreenandalinkcolourofblue:

When a link has been visited its colour changes. This colour itself can bechangedwiththeVLINK.Forexample,toset-upavisitedlinkcolourofyellow:

Notethatthedefaultlinkcoloursare:

24.5BackgroundimagesImage(suchasGIFandJPEG)canbeusedasabackgroundtoaWWWpage.For this purpose the option BACKGROUND=‘src.gif’ is added to the <BODY>tag.AnHTML scriptwith a background ofCLOUDS.GIF is given inHTMLscript24.6.AsampleoutputfromabrowserisshowninFigure24.6.

FIGURE24.6 WWWpagewithCLOUD.GIFasabackground

24.6DisplayingimagesWWW pages can support graphics images within a page. The most commonsources of images are either JPEG or GIF files, as these types of imagesnormally have a high degree of compression. GIF images, as was previouslymentioned, support only 256 colours from a pallet of 16.7 million colours,whereasJPEGsupportsmorethan256colours.

24.6.1InsertingAnImageImages can be displayed within a page with the <‘IMG SRC=‘src.gif’> whichinserts thegraphicsrc.gif.HTMLscript24.7contains three images:myson.gif,me.gifandmyson2.gif.ThesearealignedeithertotheleftortherightusingtheALIGNoptionwithinthe<IMGSRC>tag.Thefirstimage(myson.gif)isalignedtotheright,whilethesecondimage(me.gif)isalignedtotheleft.Figure24.7shows a sample output from this script. Note that images are left aligned bydefault.

FIGURE24.7 WWWpagewiththreeimages

24.6.2AlternativeTextOften users choose not to view images in a page and select an option on theviewerwhichstopstheviewerfromdisplayinganygraphicimages.IfthisisthecasethentheHTMLpagecancontainsubstitutetextwhichisshowninsteadoftheimage.Forexample:

24.6.3OtherOptionsOtherimageoptionscanbeadded,suchas:•HSPACE=xVSPACE=ydefinestheamountofspacethatshouldbeleftaround

images.Thexvaluedefinesthenumberofpixelsinthex-directionandtheyvaluedefinesthenumberofpixelsinthey-direction.

•WIDTH=xHEIGHT=ydefinesthescalinginthex-andy-direction,wherexandyarethedesiredpixelwidthandheight,respectively,oftheimage.

•ALIGN=directiondefinesthealignmentoftheimage.Thiscanbeusedtoalignanimagewithtext.Validoptionsforaligningwithtextaretexttop,top,middle,absmiddle,bottom,baselineorabsbottom.HTMLscript24.8showsanexampleofimagealignmentwiththeimagea.gif(whichisjust

theletter‘A’asagraphic)andFigure24.8showsasampleoutput.Itcanbeseenthattexttopalignstheimagewithhighestpartofthetextontheline,topalightstheimagewiththehighestelementintheline,middlealignswiththemiddleoftheimagewiththebaseline,absmiddlealightsthemiddleoftheimagewiththemiddleofthelargestitem,bottomalignsthebottomoftheimagewiththebottomofthetextandabsbottomalignsthebottomoftheimagewiththebottomofthelargestitem.

FIGURE24.8 WWWpageshowingimagealignment

24.7HorizontallinesAhorizontal line can be addedwith the <HR> tag.Most browsers allow extraparameters,suchas:SIZE=n–whichdefinesthattheheightoftheruleisnpixels.WIDTH=w–whichdefinesthatthewidthoftheruleiswpixelsorasapercentage.

ALIGN=direction–wheredirectionreferstothealignmentoftheruleValidoptionsfordirectionareleft,rightorcenter.

NOSHADE–whichdefinesthatthelineshouldbesolidwithnoshading.HTMLscript24.9givessomeexamplehorizontallinesandFigure24.9shows

anexampleoutput.

FIGURE24.9 WWWpageshowinghorizontallines

24.8Exercises24.8.1.ThehomepageforthisbookcanbefoundattheURL:

Accessthispageandfollowanylinksitcontains.24.8.2.Ifpossible,createaWWWpagewiththefollowingblinkingtext:

24.8.3.Thelastpartoftheservernamenormallygivesanindicationofthecountrywheretheserverislocated(forexamplewww.fredco.co.ukislocatedintheUK).Determinewhichcountriesusethefollowingcountrynames:(a)de(b)nl(c)it(d)se(e)dk(f)sg(g)ca(h)ch(i)tr(j)jp(k)au

Determinesomeothercountryidentifiernames.24.8.4.DeterminetheHTMLcolourrepresentforthefollowing:

(a)red(b)green(c)blue(d)white(e)black

24.8.5.DeterminetheHTMLforthebackground,textandlinkcolour:

24.8.6.DeterminetheerrorinthefollowingHTMLscript:

25

FurtherHTML

25.1Introduction

Chapter 24 introduced HTML; this chapter discusses some of HTML’s moreadvanced features. HTML differs from compiled languages, such as C andPascal,inthattheHTMLtextfileisinterpretedbyaninterpreter(thebrowser)while languagessuchasCandPascalmustbeprecompiledbefore theycanberun.HTMLthushas theadvantage that itdoesnotmatter if it is theoperatingsystem,thebrowsertypeorthecomputertypethatreadstheHTMLfile,asthefile does not contain any computer specific code. The main disadvantage ofinterpretedfilesisthattheinterpreterdoeslesserrorcheckingasitmustproducefastresults.ThebasicpagesontheWWWarelikelytoevolvearoundHTMLandwhile

HTML can be produced manually with a text editor, it is likely that, in thecomingyears,therewillbeanincreaseintheamountofgraphically-basedtoolsthatwillautomaticallyproduceHTMLfiles.Althoughthesetoolsaregraphics-basedtheystillproducestandardHTMLtextfiles.ThusaknowledgeofHTMLis important as itdefines thebasic specification for thepresentationofWWWpages.

25.2AnchorsAnanchor allowsusers to jump froma reference in aWWWpage to anotheranchorpointwithinthepage.Thestandardformatis:

whereanchornameisthenameofthesectionwhichisreferenced.The</A>tagdefinestheendofananchorname.Alinkisspecifiedby:

followedbythe</A>tag.HTMLscript25.1showsasamplescriptwithfouranchorsandFigure25.1showsasampleoutput.Whentheuserselectsoneofthereferences, thebrowser automatically jumps to that anchor.Figure25.2 showsthe output screen when the user selects the #Token reference. Anchors aretypicallyusedwhenanHTMLpage is longorwhenabackwardsor forwardsreferenceoccurs(suchasareferencewithinapublishedpaper).

FIGURE25.1 Examplewindowwithreferences

FIGURE25.2 Examplewindowwithreferences

25.3TablesTablesareoneof thebestmethodstodisplaycomplexinformationinasimpleway.Unfortunately,inHTMLtheyarerelativelycomplicatedtosetup.Thestartofatableisdefinedwiththe<TABLE>tagandtheendofatableby</TABLE>.Arow is defined between the <TR> and </TR>, while a table header is definedbetween <TH> and </TH>. A regular table entry is defined between <TD> and</TD>.HTMLscript25.2showsanexampleofatablewithlinkstootherHTMLpages.TheBORDER=noptionhasbeenaddedtothe<TABLE>tagtodefinethethickness of the table border (in pixels). In this case the border size has athicknessof10pixels.

FIGURE25.3 ExamplewindowfromexampleJavascript

Otheroptionsinthe<TABLE>tagare:•WIDTH=x,HEIGHT=y–definesthesizeofthetablewithrespecttothefull

windowsize.Theparametersxandyareeitherabsolutevaluesinpixelsfortheheightandwidthofthetableorarepercentagesofthefullwindowsize.

•CELLSPACING=n–definesthenumberofpixelsdesiredbetweeneachcellwherenisthenumberofpixels(notethatthedefaultcellspacingis2

pixels).Anindividualcellcanbemodifiedbyaddingoptionstothe<TH>or<TD>tag.

Theseinclude:•WIDTH=x,HEIGHT=y–definesthesizeofthetablewithrespecttothetable

size.Theparametersxandyareeitherabsolutevaluesinpixelsfortheheightandwidthofthetableorarepercentagesofthetablesize.

•COLSPAN=n–definesthenumberofcolumnsthecellshouldspan.•ROWSPAN=n–definesthenumberofrowsthecellshouldspan.•ALIGN=direction–defineshowthecell’scontentsarealignedhorizontally.

Validoptionsareleft,centerorright.•VALIGN=direction–defineshowthecell’scontentsarealignedvertically.

Validoptionsaretop,middleorbaseline.•NOWRAP–informsthebrowsertokeepthetextonasingleline(thatis,withno

linebreaks).HTML script 25.3 shows an example use of some of the options in the

<TABLE> and <TD> options. In this case the text within each row is centrealigned. On the second row the second and third cells are merged using theCOLSPAN=2 option. The first cell of the second and third rows have also beenmergedusingtheROWSPAN=2option.Figure25.4showsanexampleoutput.Thetablewidthhasbeenincreasedto90%ofthefullwindow,withawidthof50%.

FIGURE25.4 Examplewindowfromexamplescript

25.4CGIscriptsCGI (CommonGateway Interface) scripts are normallywritten in either C orPerl andare compiled toproduce an executableprogram.Theycanalso comeprecompiledorintheformofabatchfile.Perlhastheadvantageinthatitisascript thatcanbeeasily runonanycomputer,whileaprecompiledCprogramrequirestobeprecompiledfortheservercomputer.CGI scripts allow the user to interactwith the server and store and request

data. They are often used in conjunction with forms and allow an HTMLdocumenttoanalyze,parseandstoreinformationreceivedfromaform.OnmostUNIX-typesystemsthedefaultdirectoryforCGIscriptsiscgi-bin.

25.5FormsFormsareexcellentmethodsofgatheringdataandcanbeused inconjunctionwithCGIscriptstocollectdataforfutureuse.Aformisidentifiedbetweenthe<FORM>and</FORM>tags.Themethodused

to get the data from the form is defined with the METHOD= “POST”. The

ACTIONoptiondefines theURLscript tobe runwhen the form issubmitted.Datainputisspecifiedbythe<INPUTTYPE>tag.HTMLscript25.4formhasthefollowingparts:•<formaction="cgi-binAnyForm2”method="POST">–whichdefinesthe

startofaformandwhenthe“submit”optionisselectedthecgiscriptcgi-binAnyForm2willbeautomaticallyrun.

•<inputtype="submit”value="SendFeedback">-whichcausestheprogramdefinedintheactionoptioninthe<form>tagtoberun.Thebuttonontheformwillcontainthetext“SendFeedback”,seeFigure25.5forasampleoutputscreen.

FIGURE25.5 Examplewindowshowinganexampleform

•<inputtype=“reset”value=“ResetForm”>–whichresetsthedataintheform.Thebuttonontheformwillcontainthetext“ResetForm”,seeFigure25.5forasampleoutputscreen.

•<inputtype="hidden”name="AnyFormTo”value=“f.bloggs@toytown.ac.uk">–whichpassesavalueoff.bloggs@toytown.ac.ukwhichhastheparameternameof“AnyFormTo”.TheprogramAnyForm2takesthisparameterandautomaticallysendsittotheemailaddressdefinedinthevalue(thatis,f.bloggs@toytown.ac.uk).

•<inputtype="hidden”name="AnyFormSubject”value="Feedbackform">–

whichpassesavalueofFeedbackformwhichhastheparameternameof“AnyFormSubject”.TheprogramAnyForm2takesthisparameterandaddsthetext“Feedbackform”inthetextsenttotheemailrecipient(inthiscase,f.bloggs@toytown.ac.uk).

•Surname<inputname="Surname">–whichdefinesatextinputandassignsthisinputtotheparameternameSurname.

•<textareaname="Address”rows=2cols=40></textarea>–whichdefinesatextinputareawhichhastworowsandhasawidthof40characters.Thethumbbarsappearattheright-handsideoftheformifthetextareaexceedsmorethan2rows,seeFigure25.5.

Inthiscasetherecipient(f.bloggs@toytown.ac.uk)willreceiveanemailwiththecontents:

Theextraoptionstothe<input>tagaresize=”n“,wherenisthewidthoftheinputboxincharacters,andmaxlength=”m“,wheremisthemaximumnumberofcharactersthatcanbeentered,incharacters.Forexample:

definesthattheinputtypeistext,thewidthoftheboxis15charactersandthemaximumlengthofinputis10characters.

25.5.1InputTypesThe type options to the <input> tag are defined in Table 25.1.HTML script25.5givesafewexamplesofinputtypesandFigure25.6showsasampleoutput.

Table25.1Inputtypeoptions

FIGURE25.6 Examplewindowwithdifferentinputoptions

25.5.2MenusMenus are a convenient method of selecting from multiple options. The<SELECT> tag is used to define start of a list of menu options and the</SELECT> tag defines the end. Menu elements are then defined with the<OPTION>tag.Theoptionsdefinedwithinthe<SELECT>are:•NAME=”name“–whichdefinesthatnameisthevariablenameofthemenu.

Thisisusedwhenthedataiscollectedbytheserver.•SIZE=“n”–whichdefinesthenumberofoptionswhicharedisplayedinthe

menu.HTMLscript25.6showsanexampleofamenu.Theadditionaloptionstothe

<OPTION>tagare:•SELECTED–whichdefinesthedefaultselectedoption.•VALUE=”val“–wherevaldefinesthenameofthedatawhenitiscollectedby

theserver.

FIGURE25.7 Examplewindowshowinganexampleform

25.6MultimediaIf thebrowser cannothandle all the file types itmaycall onother applicationhelperstoprocessthefile.Thisallowsother‘third-party’programstointegrateinto the browser. Figure 25.8 shows an example of the configuration of thehelperprograms.Theoptionsinthiscaseare:

FIGURE25.8 Examplewindowshowinganexampleform

•Viewinbrowser.•Savetodisk.•Unknown:promptuser.•Launchanapplication(suchasanaudioplaybackprogramorMPEGviewer).For certain applications the user can select as to whether the browser

processesthefileoranotherapplicationprogramprocessesit.Helperprogramsmakeupgrades inhelperapplications relativelysimpleandalsoallownewfiletypes to be added with an application helper. Typically when a program isinstalled which can be used with a browser it will prompt the user toautomatically update the helper application list so that it can handle the givenfiletype(s).Eachfiletypeisdefinedbythefileextension,suchas.psforpostscriptfiles,

.exe for a binary executable file, and so on. These file extensions have beenstandardized in MIME (Multipurpose Internet Mail Extensions) specification.Table25.2showssometypicalfileextensions.

Table25.2Inputtypeoptions

Mimetype Extension Typicalaction

application/octet-stream exe,bin Save

application/postscript ps,ai,eps Askuser

application/x-compress Z Compressprogram

application/x-gzip gz GZIPcompressprogram

application/x-javascript js,mocha Askuser

application/x-msvideo avi Audioplayer

application/x-perl P1 Save

application/x-tar tar Save

application/x-zip-compressed zip ZIPprogram

audio/basic au,snd Audioplayer

image/gif gif Browser

image/jpeg jpeg,jpg,jpe Browser

image/tiff tif,tiff Graphicsviewer

image/x-MS-bmp bmp Graphicsviewer

text/html htm,html Browser

text/plain text,txt Browser

video/mpeg mpeg,mpg,mpe,mpv,vbs,mpegv Videoplayer

video/quicktime qt,mov,moov Videoplayer

25.7Exercises25.7.1.ConstructaWWWpagewithanchorpointsforthefollowing:Selectthenetworkyouwishtofindoutabout:EthernetTokenringFDDI

EthernetEthernet is themost widely used networking technology used in LAN (LocalAreaNetwork).Initselfitcannotmakeanetworkandneedssomeotherprotocolsuch as TCP/IP or SPX/IPX to allow nodes to communicate. Unfortunately,Ethernetinitsstandardformdoesnotcopewellwithheavytraffic.Itshasmanyadvantages,though,including:•Networksareeasytoplanandcheaptoinstall.•Networkcomponentsarecheapandwellsupported.•Itiswell-proventechnologywhichisfairlyrobustandreliable.•Simpletoaddanddeletecomputersonthenetwork.•Supportedbymostsoftwareandhardwaresystems.

TokenringToken ring networks were developed by several manufacturers, the mostprevalentbeingtheIBMTokenRing.Tokenringnetworkscopewellwithhighnetwork traffic loadings. They were at one time extremely popular but theirpopularityhassincebeenovertakenbyEthernet.Tokenringnetworkshave, inthepast, suffered fromnetworkmanagementproblemsandpoornetwork faulttolerance.Tokenringnetworksarewellsuitedtosituationswhichhavelargeamountsof

trafficandalsoworkwellwithmosttrafficloadings.Theyarenotsuitedtolargenetworksornetworkswithphysicallyremotestations.Theirmainadvantage isthattheycopebetterwithhightrafficratesthanEthernet,butrequireagreatdealofmaintenanceespeciallywhenfaultsoccurorwhennewequipmentisaddedtoorremovedfromthenetwork.ManyoftheseproblemshavenowbeenovercomebyMAUs (multi-station access units), which are similar to the hubs using inEthernet.

FDDIA token-passing mechanism allows orderly access to a network. Apart fromtoken ring the most commonly used token-passing network is the FiberDistributedDataInterchange(FDDI)standard.Thisoperatesat100Mbpsand,toovercometheproblemsof linebreaks,hastwoconcentric tokenrings.Fibreoptic cables have a much high specification over copper cables and allowextremelylonginterconnectionlengths.Themaximumcircumferenceoftheringis100km(62miles),withamaximum2kmbetweenstations(inFDDIstationsare also known as stations). It is thus an excellentmechanism for connectinginterconnectingnetworksoveracityoracampus.Upto500stationscanconnecttoeachringwithamaximumof1,000stationsforthecompletenetwork.EachstationconnectedtotheFDDIhighwaycanbeanormalstationorabridgetoaconventionallocalareanetwork,suchasEthernetortokenring.25.7.2.ConstructaWWWglossarypagewiththefollowingterms:

Address Auniquelabelforthelocationofdataortheidentityofacommunicationsdevice.

AddressResolutionProtocol(ARP)

ATCP/IPprocesswhichmapsanIPaddresstoanEthernetaddress.

AmericanNationalStandardsInstitute(ANSI)

ANSIisanon-profitorganizationwhichismadeupofexpertcommitteesthatpublishstandardsfornationalindustries.

AmericanStandard AnANSI-definedcharacteralphabetwhichhassincebeenadoptedasastandardinternationalalphabetfortheinterchangeofcharacters.

CodeforInformationInterchange(ASCII)

internationalalphabetfortheinterchangeofcharacters.

Amplitudemodulation(AM)

Informationiscontainedintheamplitudeofacarrier.

Amplitude-ShiftKeying(ASK)

Usestwo,ormore,amplitudestorepresentbinarydigits.Typicallyusedtotransmitbinarydataoverspeech-limitedchannels.

Applicationlayer ThehighestlayeroftheOSImodel.

Asynchronoustrans-mission

Transmissionwhereindividualcharactersaresentone-by-one.Normallyeachcharacterisdelimitedbyastartandstopbit.Withasynchronouscommunicationthetransmitterandreceiveronlyhavetoberoughlysynchronized.

25.7.3.ConstructaWWWpagewhichcanbeusedtoenteraperson’sCV(note,useaform).Thebasicfieldsshouldbe:

Name:Address:Emailaddress:Telephonenumber:Experience:Interests:Anyotherinformation:

25.7.4.WriteanHTMLscriptwhichdisplaysthefollowingtimetable.

25.7.5.Designyourownhomepagewithabasicuserhomepage(index.html)whichcontainslinkstoabasicCVpage(forexample,itcouldbenamedcv.html)andapagewhichlistsyourmaininterests(myinter.html).Designoneofthehomepageswithalistoflinksandanotherwithatableoflinks.Ifpossibleincorporategraphicsfilesintothepages.

26

JavaScript

26.1Introduction

Computersystemscontainamicroprocessorwhichcontrolstheoperationofthecomputer.Themicroprocessoronlyunderstandsbinaryinformationandoperatesonaseriesofbinarycommandsknownasmachinecode.Itisextremelydifficulttowrite largeprogramsinmachinecode,so thathigh-level languagesareusedinstead. A low-level language is one which is similar to machine code andnormally involves the usage of keyword macros to replace machine codeinstructions. High-level languages have a syntax that is almost like writtenEnglishandthusmakeprogramseasytoreadandtomodify.Inmostprogramstheactualoperationofthehardwareisinvisibletotheprogrammer.Acompilerchanges the high-level language into machine code. Typical high-levellanguagesincludeC/C++,BASIC,COBOL,FORTRANandPascal;anexampleofalow-levellanguageis80486AssemblyLanguage.Java is a high-level language that has been developed specifically for the

WWWandiswellsuitedtonetworkedapplications.ItwasoriginallydevelopedbySunMicrosystemsand isbasedonC++ (butwith lessof thedifficultiesofC++).MostnewversionsofWebbrowsersnowsupport itsusage.Java’smainattributesare:•Itrunseitherasastand-aloneprogramoritcanrunwithintheWebbrowser.

WhenrunwithinthebrowsertheJavaprogramisknownasanapplet.•Javaisaportablelanguageandappletscanrunonanytypeofmicroprocessor

type(suchasaPCbasedonIntel80486orPentium,oraMotorola-basedcomputer).

•Javaappletsarehardwareandoperatingsystemindependent.Forexample,theprogramitselfdoesnothavetointerfacedirectlytothehardwaresuchasavideoadapterormouse.Typicalhigh-levellanguages,suchasC/C++andPascal,producemachine-dependentmachinecode,andcanthusonlybeexecutedonaspecificcomputeroroperatingsystems.

•Javaallowsforaclient/serverapproachwheretheappletcanrunontheremotecomputerwhichthusreducestheloadingonthelocalcomputer(typicallytheremotecomputerwillbeapowerfulmultitaskingcomputerwithenhancedcomputerarchitecture).

•AJavacompilercreatesstand-aloneprogramsorapplets.ManynewversionsofbrowsershaveanintegratedJavacompiler.

Figure 26.1 shows the main functional differences between a high-levellanguage, a Java applet and JavaScript. JavaScript is interpret by the browser,whereasaJavaappletiscompiledtoavirtualmachinecodewhichcanberunonanycomputersystem.Thehigh-levellanguageproducesmachine-specificcode.

FIGURE26.1 DifferencesbetweenC++/JavaandJavaScript

AnormalC++ program allows access to hard-disk drives. Thiswould be aproblemontheWebasunsolicitedusers(‘hackers’)ornoviceuserscouldcausedamageontheWebserver.ToovercomethisJavadoesnothaveanymechanismforfileinput/output(I/O).Itcanreadstandardfiletypes(suchasGIFandJPG)butcannotstorechangestotheWebserver.AJavadeveloperskit isavailable,freeofcharge,fromhttp://java.sun.com.ThefollowingisanexampleHTMLscriptandhighlightedJavaScript.Figure

26.2givesthebrowseroutput.

FIGURE26.2 ExamplewindowfromexampleJavaScript

26.2JavaScriptlanguageProgramming languages can either be compiled to produce an executableprogramor they can be interpretedwhile the user runs the program. Java is aprogramlanguagewhichneedstobecompiledbeforeitisused.Itthuscannotbeused unless the user has the required Java compiler. JavaScript, on the otherhand, is a languagewhich is interpreted by the browser. It is similar inmanywaystoJavabutallowstheusertoembedJava-likecodeintoanHTMLpage.JavaScriptsupportsasmallnumberofdatatypesrepresentingnumeric,Boolean,and string values and is supported bymostmodernWWWbrowsers, such asMicrosoftInternetExplorerandNetscape.HTMLisusefulwhenpagesareshortanddonotcontainexpressions,loopsor

decisions. JavaScript allowsmost of the functionalityof ahigh-level languagefordevelopingclientandserverInternetapplications.Itcanbeusedtorespondtousereventssuchasmouseclicks,forminput,andpagenavigation.AmajoradvantagethatJavaScripthasoverHTMListhatitsupportstheuse

of functionswithout any special declarative requirements. It is also simpler tousethanJavabecauseithaseasiersyntax,specializedbuilt-infunctionality,andminimalrequirementsforobjectcreation.Important concepts in Java and JavaScript are objects.Objects are basically

containersforvalues.ThemaindifferencesbetweenJavaScriptandJavaare:•JavaScriptisinterpretedbytheclient,whileJavaiscompiledontheserver

beforeitisexecuted.•JavaScriptisembeddedintoHTMLpages,whileJavaappletsaredistinct

fromHTMLandaccessedfromHTMLpages.•JavaScripthasloosetypingforvariables(thatis,avariablesdatatypedoes

nothavetobedeclared),whileJavahasstrongtyping(thatis,avariablesdatatypemustalwaysbedeclaredbeforeitisused).

•JavaScripthasdynamicbindingwhereobjectreferencesarecheckedatrun-time.Javahasstaticbindingwhereobjectreferencesmustexistatcompile-time.

26.3JavaScriptvalues,variablesandliteralsJavaScript values, variables and literals are similar to the C programminglanguage.Theirsyntaxisdiscussedinthissection.

26.3.1ValuesThefourdifferenttypesofvaluesinJavaScriptare:•Numericvalue,suchas12or91.5432.•BooleanvalueswhichareeitherTRUEorFALSE.•Stringtypes,suchas‘FredBloggs’.•AspecialkeywordforaNULLvalueNumeric values differ from those in most programming languages in that

there is no explicit distinction between a real value (such as 91.5432) and aninteger(suchas12).

26.3.2DataTypeConversion

JavaScriptdiffersfromJavainthatvariablesdonotneedtohavetheirdatatypesdefined when they are declared (loosely typed). Data types are thenautomatically converted during the execution of the program. Thus a variablecouldbedeclaredwithanumericvalueas:

andtheninthesamescriptitcouldbeassignedastringvalue,suchas:

Theconversionbetweennumericvaluesandstrings inJavaScript iseasy,asnumericvaluesareautomaticallyconvertedtoanequivalentstring.Forexample:

Samplerun26.1givestheoutputfromthisscript.Itcanbeseenthatxandyhavebeenconvertedtoastringvalue(inthiscase,“13”and“10”)andthatx+yin the string conversion statement has been converted to “1310”. If amathematical operation is carried out (z=x+y) then z will contain 23 after thestatementisexecuted.

JavaScript provides several special functions for manipulating string andnumericvalues:•Theeval(string)functionwhichconvertsastringtoanumericalvalue.•TheparseInt(string[,radix])functionwhichconvertsastringintoan

integerofthespecifiedradix(numberbase).Thedefaultradixisbase–10.•TheparseFloat(string)functionwhichconvertsastringintoafloating-point

value.

26.3.3VariablesVariables are symbolic names for values within the script. A JavaScriptidentifier must either start with a letter or an underscore (‘_’), followed byletters,anunderscoreoranydigit(0–9).LikeC,JavaScriptiscasesensitivesothatvariableswiththesamecharactersequencebutwithdifferentcasesforoneormorecharactersaredifferent.Thefollowingaredifferentvariablenames:

26.3.4VariableScopeAvariablecanbedeclaredbyeithersimplyassigningitavalueorbyusingthevar keyword. For example, the following declares to variables Valuel andValue2:

Avariabledeclaredwithinafunctionistakenasalocalvariableandcanonlybeusedwithin that function.Avariabledeclaredoutsideafunction isaglobalvariable and canbeused anywhere in the script.Avariablewhich is declaredlocallywhichisalreadydeclaredasglobalvariableneedstobedeclaredwiththevarkeyword,otherwisetheuseofthekeywordisoptional.

26.3.5LiteralsLiteralvalueshavefixedvalueswithinthescript.Variousreservedformscanbe

usedtoidentifyspecialtypes,suchashexadecimalvalues,exponentformat,andsoon.Withanintegerthefollowingareused:•Ifthevalueisprecededbya0xthenthevalueisahexadecimalvalue(thatis,

base16).Examplesofhexadecimalvaluesare0×1FFF,0xCB.•Ifthevalueisprecededbya0thenthevalueisanoctalvalue(thatis,base8).

Examplesofoctalvaluesare0777,010.•Ifitisnotprecededbyeithera0xora0thenitisadecimalinteger.

Floating-pointvaluesFloating-pointvaluesaretypicallyrepresentedasarealvalue(suchas1.342)orinexponentformat.Someexponentformatvaluesare:

Value Exponentformat

0.000001 le-6

1342000000 1.342e9

BooleanThetrueandfalseliteralsareusedwithBooleanoperations.

StringsIn C a string is represented with double quotes (“str”) whereas JavaScriptaccepts a string within double (“) or single (‘) quotationmarks. Examples ofstringsare:

26.4ExpressionsandoperatorsTheexpressionsandoperatorsused inJavaandJavaScriptarebasedonCandC++. This section outlines the main expressions and operators used inJavaScript.

26.4.1ExpressionsAs with C, expressions are any valid set of literals, variables, operators and

expressions that evaluate to a single value. There are basically two types ofexpression,onewhichassignsavaluetoavariableandtheotherwhichsimplygivesasinglevalue.Asimpleassignmentis:

whichassignsthevalueof21tovalue(notethattheresultoftheexpressionis21).TheresultfromaJavaScriptexpressioncaneitherbe:•Anumericvalue.•Astring.•Alogicalvalue(trueorfalse).

26.5JavaScriptoperatorsBoth Java and JavaScript have a rich set of operators, ofwhich there are fourmaintypes:•Arithmetic.•Logical.•Bitwise.•Relational.

26.5.1ArithmeticArithmetic operators operate on numerical values. The basic arithmeticoperationsareadd(+),subtract(–),multiply(*),divide(/)andmodulusdivision(%).Modulusdivisiongivestheremainderofanintegerdivision.Thefollowinggivesthebasicsyntaxoftwooperandswithanarithmeticoperator.

Theassignmentoperator(=)isusedwhenavariable‘takesonthevalue’ofanoperation.Other short-handed operators are usedwith it, including add equals(+=),minusequals(–=),multipliedequals(*=),divideequals(/=)andmodulusequals(%=).Thefollowingexamplesillustratetheiruses.

Statement Equivalent

x+=3.0 x=x+3.0

voltage/=sqrt(2) voltage=voltage/sqrt(2)

bitmask*=2 bitmask=bitmask*2

Inmanyapplicationsitisnecessarytoincrementordecrementavariableby1.For this purpose Java has two special operators; ++ for increment and –– fordecrement.Thesecaneitherprecedeorfollowthevariable.Iftheyprecede,thena pre-increment/decrement is conducted, whereas if they follow it, a post-increment/decrementisconducted.Thefollowingexamplesshowtheirusage.

Statement Equivalent

no_values++ novalues=novalues+1

i–– i=i-l

Table26.1summarizesthearithmeticoperators.

Table26.1Arithmeticoperators

Operator Operation Example

- subtractionorminus 5–4→1

+ addition 4+2→6

* multiplication 4*3→12

/ division 4/2→2

% modulus 13%3→1

+= addequals χ+=2isequivalenttox=x+2

-= minusequals x-=2isequivalenttox=x–2

/= divideequals x/=yisequivalenttox=x/y

*= multipliedequals x*=32isequivalenttox=x*32

= assignment x=1

++ increment Count++isequivalenttoCount=Count+1

decrement Sec–-isequivalenttoSec=Sec-l

26.5.2RelationshipThe relationship operators determine whether the result of a comparison isTRUEorFALSE.Theseoperatorsaregreaterthan(>),greaterthanorequalto

(<=),lessthan(<),lessthanorequalto(>=),equalto(==)andnotequalto(!=).Table26.2liststherelationshipoperators.

Table26.2Relationshipoperators

26.5.3Logical(TRUEOrFALSE)A logical operation is one in which a decision is made as to whether theoperation performed is TRUE or FALSE. If required, several relationshipoperationscanbegroupedtogethertogivetherequiredfunctionality.Cassumesthatanumericalvalueof0(zero)isFALSEandthatanyothervalueisTRUE.Table26.3liststhelogicaloperators.

Table26.3Logicaloperators

The logicalAND operationwill yield a TRUE only if all the operands areTRUE.Table26.4gives the resultof theAND(&&)operator for theoperationA&&B.ThelogicalORoperationyieldsaTRUEifanyoneoftheoperandsisTRUE.Table26.4givesthelogicalresultsoftheOR(||)operatorforthestatementA||B

andalsogivesthelogicalresultoftheNOT(!)operatorforthestatement!A.

Table26.4Logicaloperations

26.5.4BitwiseThebitwiselogicaloperatorsworkconceptuallyasfollows:•Theoperandsareconvertedto32-bitintegers,andexpressedaseriesofbits

(zerosandones).•Eachbitinthefirstoperandispairedwiththecorrespondingbitinthesecond

operand:firstbittofirstbit,secondbittosecondbit,andsoon.•Theoperatorisappliedtoeachpairofbits,andtheresultisconstructed

bitwise.Thebitwiseoperatorsaresimilartothelogicaloperatorsbuttheyshouldnot

beconfusedastheiroperationdiffers.Bitwiseoperatorsoperatedirectlyontheindividualbitsofanoperand(s),whereaslogicaloperatorsdeterminewhetheraconditionisTRUEorFALSE.Numerical values are stored as bit patterns in either an unsigned integer

format,signedinteger(2’scomplement)orfloating-pointnotation(anexponentandmantissa).CharactersarenormallystoredasASCIIcharacters.ThebasicbitwiseoperationsareAND(&),OR(|),1scomplementorbitwise

inversion(~),XOR(⁁),shift left(<<)andshiftright(>>).Table26.5givestheresultsoftheANDbitwiseoperationontwobitsBit1andBit2.

Table26.5Bitwiseoperations

The Boolean bitwise instructions operate logically on individual bits. TheXORfunctionyieldsa1when thebits inagivenbitpositiondiffer, theANDfunction yields a 1 only when the given bit positions are both 1’s. The ORoperationgivesa1whenanyoneofthegivenbitpositionsarea1.Forexample:

Toperformbitshifts,the<<,>>and>>>operatorsareused.Theseoperatorsshiftthebitsintheoperandbyagivennumberdefinedbyavaluegivenontheright-handsideoftheoperation.Theleftshiftoperator(<<)shiftsthebitsoftheoperand to the left and zeros fill the result on the right. The sign-propagatingrightshiftoperator(>>)shiftsthebitsoftheoperandtotherightandzerosfilltheresultiftheintegerispositive;otherwiseitwillfillwith1s.Thezero-filledrightshiftoperator(>>>)shiftsthebitsoftheoperandtotherightandfillstheresultwithzeros.Thestandardformatis:

26.5.5PrecedenceThereareseveralrulesfordealingwithoperators:•Twooperators,apartfromtheassignment,shouldneverbeplacedsideby

side.Forexample,x*%3isinvalid.•Groupingsareformedwithparentheses;anythingwithinparentheseswillbe

evaluatedfirst.Nestedparenthesescanalsobeusedtosetpriorities.•Aprioritylevelorprecedenceexistsforoperators.Operatorswithahigher

precedenceareevaluatedfirst;iftwooperatorshavethesameprecedence,thentheoperatorontheleft-handsideisevaluatedfirst.The

prioritylevelsforoperatorsareasfollows:

Theassignmentoperatorhasthelowestprecedence.

26.5.6ConditionalExpressionsConditional expressions can result in oneof twovalues baseddependingon acondition.Thesyntaxis:

Iftheexpressionistruethenvaluelisexecutedelsevalue2isexecuted.Forexample:

Thiswillassignthestring‘positive’tosignifthevalueofvalisgreaterthanorequalto0,elseitwillassign‘negative’.

26.5.7StringOperatorsThenormalcomparisonoperators,suchas<,>,>=,==,andsoon,canbeusedwith strings. In addition, the concatenation operator (+) can be used toconcatenatetwostringvaluestogether.Forexample:

willresultinthestring

26.6JavaScriptstatementsJavaScript statements are similar toCandallowagreat deal of control of theexecutionofascript.Thebasiccategoriesare:•Conditionalstatements,suchasif…else.•Repetitivestatements,suchasfor,while,breakandcontinue.•Comments,usingeithertheC++styleforsingle-linecomments(//)or

standardCmulti-linecomments(/*…*/).•Objectmanipulationstatementsandoperators,suchasfor…in,new,

this,andwith.

26.7ConditionalstatementsConditionalstatementsallowaprogramtomakedecisionsontheroutethroughaprogram.

26.7.1If…ElseA decision is made with the if statement. It logically determines whether aconditionalexpressionisTRUEorFALSE.ForaTRUE,theprogramexecutesone block of code; a FALSE causes the execution of another (if any). Thekeywordelse identifies the FALSEblock.Braces are used to define the startandendoftheblock.Relationship operators (>,<,>=,<=,==, ! =) yield a TRUE or FALSE from

theiroperation.Logicalstatements(&&,||,!)canthengroupthesetogethertogivetherequiredfunctionality.If theoperationisnotarelationship,suchasbitwiseoranarithmeticoperation,thenanynon-zerovalueisTRUEandazeroisFALSE.Thefollowingisanexamplesyntaxoftheifstatement.Ifthestatementblock

hasonlyonestatementthebraces({})canbeexcluded.

Thefollowingisanexampleformatwithanelseextension.

Itispossibletonestif…elsestatementstogivearequiredfunctionality.Inthenextexample,statementblock1isexecutedifexpression1isTRUE.IfitisFALSE then the program checks the next expression. If this is TRUE theprogramexecutesstatementblock2,elseitchecksthenextexpression,andsoon.IfallexpressionsareFALSEthentheprogramexecutesthefinalelsestatementblock,inthiscase,statementblock4:

26.8Loops26.8.1For()Manytaskswithinaprogramarerepetitive,suchaspromptingfordata,countingvalues, and soon.Thefor loopallows theexecutionofablockofcode foragivencontrolfunction.Thefollowingisanexampleformat;ifthereisonlyonestatementintheblockthenthebracescanbeomitted.

where:

startingcondition — thestartingvaluefortheloop;

testcondition — iftestconditionisTRUEtheloopwillcontinueexecution;

operation — theoperationconductedattheendoftheloop.

26.8.2While()Thewhile() statementallowsablockofcode tobeexecutedwhilea specifiedcondition is TRUE. It checks the condition at the start of the block; if this isTRUEtheblockisexecuted,elseitwillexittheloop.Thesyntaxis:

If the statement block contains a single statement then the braces may beomitted(althoughitdoesnoharmtokeepthem).

26.9CommentsComments are authornotations that explainwhat a scriptdoes.Comments areignoredbytheinterpreter.JavaScriptsupportsJava-stylecomments:•Commentsonasinglelineareprecededbyadouble-slash(//).•Multilinecommentscanbeprecededby/*andfollowedby*/.Thefollowingexampleshowstwocomments:

26.10Functions

JavaScriptsupportsmodulardesignusingfunctions.AfunctionisdefinedwithaJavaScriptwiththefunctionreservedwordandthecodewithinthefunctionisdefinedwithincurlybrackets.Thestandardformatis:

wheretheparameters(param1,param2,andsoon)arethevaluespassedintothefunction.Notethatthereturnvalue(val)fromthefunctionisonlyrequiredwhenavalueisreturnedfromthefunction.JavaScript26.2givesanexamplewithtwofunctions(add()andmult()).In

this case the values value1 and value2 are passed into the variables a and bwithin the add() function, the result is then sent back from the function intovalue3.

Table26.6ExampleJavaScript

26.11ObjectsandpropertiesJavaScript is based on a simple object-oriented paradigm,where objects are aconstructwithpropertiesthatareJavaScriptvariables.Eachobjecthaspropertiesassociatedwithitandcanbeaccessedwiththedotnotation,suchas:

26.12DocumentobjectsThe document object contains information on the currently opened document.HTML expressions can be displayed with the document.write() ordocument.writeln()functions.Thestandardformatis:

whichdisplaysoneormoreexpressionstothespecifiedwindow.Todisplaytothecurrentwindowthedocument.write()isused.Ifadisplaytoaspecifiedwindowthenthewindowreferenceisdefined,forexample:

isusedtooutputtothemywinwindow.The document object can also be used to display HTML properties. The

standardHTMLformatis:

TheseandotherpropertiescanbeaccessedwithinaJavaScriptwith:

Table26.7showsanexample.

Table26.7ExampleJavaScript

26.13EventhandlingJavaScripthaseventhandlerswhich,onacertainevent,causesotherevents tooccur.Forexample,ifauserclicksthemousebuttononacertainmenuoptionthen the event handler can be made to carry-out a particular action, such asaddingtonumberstogether.Table26.8outlinessomeeventhandlers.

Table26.8Exampleeventhanders

26.14WindowobjectsThewindowobjectisthetop-levelobjectfordocumentsandcanbeusedtoopenandclosewindows.

26.14.1WindowAlertThealertwindowshowsanalertmessagetotheusers.Itsformatis:

Table26.9ExampleJavaScript

26.14.2OpeningAndClosingWindowsWindows are opened with window.open() and closed with window.close().Examplesare:

or to open a window it is possible to simply use open() and to close thecurrentwindowtheclose()functionisused.Thestandardformatis:

wherewinVar is thenameofanewwindowwhichcanbeused to refer toagiven

window.winNameisthewindownamegiventothewindow;featuresisacomma-separatedlistwithanyofthefollowing:

26.14.3WindowConfirmThewindowconfirmisusedtodisplayaconfirmdialogueboxwithaspecifiedmessageandtheOKandCancelbuttons.IftheuserselectstheOKbuttonthenthe function returns a TRUE, else it returns a FALSE. Table 26.10 gives anexample of the confirmwindow. In this casewhen theExit button is selectedthenthefunctionConfirmExit() iscalled.In thisfunctiontheuser isaskedtoconfirm the exit with the confirm window. If the user selects OK then thewindowisclosed(ifitistheonlywindowopenthenthebrowserquits).

Table26.10ExampleJavaScriptwithconfirmwindow

26.14.4WindowPromptThewindowpromptdisplaysapromptdialogboxwhichcontainsamessageandaninputfield.Itsstandardformatis:

26.15Objectmanipulationstatementsandoperators

JavaScript has several methods in which objects can be manipulated. Theseinclude: the new operator, the this keyword, thefor…in statement, and thewithstatement.

26.15.1ThisKeywordThethiskeywordisusedtorefertothecurrentobject.Thegeneralformatis:

JavaScript 26.5 gives an example of the this keyword. In this case this isused to pass the property values of the input form. This is then passed to thefunctioncheckval()whentheonBlureventoccurs.

26.15.2NewOperatorThenewoperator isused todefineanewuser-definedobject typeorofoneofthe pre-defined object types, such as array, Boolean, date, function andmath.JavaScript26.6givesanexamplewhichcreatesanarrayobjectwith6elementsandthenassignsstringstoeachofthearray.NotethatinJavathefirstelementofthearrayisindexedas0.

Typicallythenewoperatorisusedtocreatenewdataobjects.Forexample:

26.15.3For…InThefor…instatementisusedtoiterateavariablethroughallitsproperties.Ingeneralitsformatis:

26.15.4WithThe with statement defines a specified object for a set of statements. Awithstatementlooksasfollows:

For example JavaScript 26.7 contains calls to the Math object for the PIpropertyandcosandsinmethods.JavaScript26.8thenusesthewithstatementtodefinetheMatchobjectisthedefaultobject.

26.16Exercises26.16.1.ExplainhowJavadiffersfromJavaScript.26.16.2.ExplainthemainadvantagesofusingJavaratherthanahigh-level

language,suchasC++orPascal.26.16.3.ImplementtheJavaScriptsinthetextandtesttheiroperation.26.16.4.WriteaJavaScriptinwhichtheuserentersavalueandthescript

calculatesthesquareofthatvalue.26.16.5.WriteaJavaScriptinwhichtheuserinitiallyenterstheirname.The

scriptshouldthentesttheenterednameandifitisnot‘FRED’,‘BERT’or‘FREDDY’thenthebrowserexits.

27

Java(Introduction)

27.1Introduction

Java has the great advantage over conventional software languages in that itproduces code which is computer hardware independent. This is because thecompiled code (called bytecodes) is interpreted by the WWW browser.Unfortunatelythisleadstoslowerexecution,butasmuchofthetimeisspentingraphicaluser interfaceprograms, toupdate thegraphics, thentheoverheadis,asfarastheuserisconcerned,notagreatone.The other advantages that Java has over conventional software languages

include:•ItisamoredynamiclanguagethanC/C++andPascal,andwasdesignedto

adapttoanevolvingenvironment.Itisextremelyeasytoaddnewmethodsandextralibrarieswithoutaffectingexistingapplets.ItisalsousefulinInternetapplicationsasitsupportsmostofthestandardimageaudioandvideoformats.

•Ithasnetworkingfacilitiesbuiltintothelanguage(supportforTCP/IPsockets,URLs,IPaddressesanddatagrams).

•WhileJavaisbasedonCandC++itavoidssomeofthedifficultareasofC/C++code(suchaspointersandparameterpassing).

•Itsupportsclient/serverapplicationswheretheJavaappletsrunontheserverandtheclientreceivestheupdatedgraphicsinformation.InthemostextremecasetheclientcansimplybeagraphicsterminalwhichrunsJavaappletsoveranetwork.Thesmall‘black-box’networkedcomputerisoneofthefoundingprinciplesofJava,anditishopedinthefuturethatsmallJava-basedcomputerscouldreplacethecomplexPC/workstationforgeneralpurposeapplications,likeaccessingtheInternetorplayingnetworkgames.This‘black-box’computerconceptisillustratedinFigure27.1.

FIGURE27.1 Internetaccessing

Most existingWeb browsers are enabled for Java applets (such as InternetExplorer3.0andNetscape2.0andlaterversions).Figure27.2showshowJavaappletsarecreated.Firstthesourcecodeisproducedwithaneditor,nextaJavacompilercompilestheJavasourcecodeintobytecode(normallyappendingthefile name with .class). An HTML page is then constructed which has thereference to theapplet.After thisa Java-enabledbrowserorappletviewercanthenbeusedtoruntheapplet.

FIGURE27.2 ConstructingJavaapplets

TheJavaDevelopmentKit (JDK) isavailable, free, fromSunMicrosystemsfrom the WWW site http://java.sun.com. This can be used to compile Javaappletsandstandaloneprograms.ThereareversionsforWindowsNT/95,MacorUNIX-basedsystemswithmanysampleapplets.Table27.1showsthemainfilesusedinthePCversion.Figure27.3showsthe

directory structure of the JDK tools. The Java compiler, Java interpreter andappletviewerprogramsarestoredinthebindirectory.OnthePC,thisdirectory

isnormallysetupinthePATHdirectory,sothattheJavacompilercanbecalledwhiletheuserisinanotherdirectory.Thefollowingisatypicalsetup(assumingthatthehomedirectoryisC:\JAVA):

Table27.1JDKprograms

File Description

Javac.exe Javacompiler

Java.exe Javainterpreter

Appletviewer.exe Appletviewerfortestingandrunningapplets

classes.zip Itisneededbythecompilerandinterpreter

javap.exe Javaclassdisassembler

javadoc.exe Javadocumentgenerator

jbd.exe Javadebugger

FIGURE27.3 DirectorystructureofJDK

Thelibdirectorycontainstheclasses.zipfilewhichisazipped-upversionof the Javaclass files.These class files are stored in thedirectoriesbelow thesrc/java directory. For example, the io classes (such as File.java andInputStream.java) are used for input/output in Java, theawt classes (such asPanel.javaandDialog.java)areusedtocreateandmaintainwindows.Theseandotherclasseswillbediscussedlater.Theincludedirectorycontainsheader files for integratingC/C++programs

withJavaappletsandthedemodirectorycontainssomesampleJavaapplets.

27.1.1AppletTagAnappletiscalledfromwithinanHTMLscriptwiththeAPPLETtag,suchas:

whichloadsanappletcalledTest.classandsets theappletsize to200pixelswideand300pixelshigh.Table27.2discussessomeoptionalparameters.

Table27.2OtherappletHTMLparameters

27.1.2AppletViewerAusefulpartoftheJDKtoolsisanappletviewerwhichisusedtotestappletsbefore theyare runwithin thebrowse.Theappletvieweron thePCversion isAppletViewer.exeandthesuppliedargumentistheHTMLfilethatcontainstheapplettag(s).Itthenrunsalltheassociatedappletsinseparatewindows.

27.2CreatinganappletJavaapplet27.1showsasimpleJavaappletwhichdisplaystwolinesoftextandHTMLscript27.1showshowtheappletintegratesintoanHTMLscript.First the Java applet (j1.java) is created. In this case the edit program is

used.Thedirectory listingbelow shows that the files created arej1.java andj1.html(NotethatWindowsNT/95displaysthe8.3filenameformatonthelefthandsideofthedirectorylistingandthelongfilenameontherighthandside).

NexttheJavaappletiscompiledusingthejavac.exeprogram.Itcanbeseenfromthelistingthat,iftherearenoerrors,thecompiledfileisnamedj1.class.Thiscanthenbeused,withtheHTMLfile,torunasanapplet.

27.3AppletbasicsJavaapplet27.1recapsthepreviousJavaapplet.ThissectionanalyzesthemainpartsofthisJavaapplet.

27.3.1ImportStatementsThe import statement allows previously written code to be included in theapplet.Thiscode is stored inclass libraries (orpackages),whicharecompiledJavacode.FortheJDKtools,theJavasourcecodefortheselibrariesisstoredinthesrc/javadirectory.EachJavaappletcreatedbeginswith:

Theseincludetheawtandappletclasslibraries.Theawtclassprovidecodethat handles windows and graphics operations. The applet in Java script 27.1usesawtcode, forexample,displays the ‘This is ..’messagewithin theappletwindow. Likewise the applet uses the applet code to let the browser run theapplet.ThedefaultJavaclass librariesarestored in theclasses.zip file in thelib

directory.Thisfileisinacompressedformandshouldnotbeunzipbeforeitisused.Thefollowingisanoutlineofthefile.

Table27.3liststhemainclasslibrariesandsomesamplelibraries.

Table27.3Classlibraries

ItcanbeseenthatupgradingtheJavacompilerissimple,asallthatisrequiredistoreplacetheclasslibrarieswithnewones.Forexample,ifthebasiclanguageisupgraded thenjava.lang.* files issimplyreplacedwithanewversion.Theuser can also easily add new class libraries to the standard ones. A completelistingoftheclassesisgiveninAppendixA.

27.3.2AppletClassThestartoftheappletcodeisdefinedintheform:

whichinformstheJavacompilertocreateanappletnamedj1thatextendstheexistingApplet class.Thepublickeywordat the startof the statementallowsthe Java browser to run the applet, while if it is omitted the browser cannotaccessyourapplet.Theclasskeyword isused tocreatingaclassobjectnamedj1 thatextends

theappletclass.Afterthistheappletisdefinedbetweentheleftandrightbraces(groupingsymbols).

27.3.3AppletFunctions

FunctionsallowJavaappletstobesplit intosmallersub-taskscalledfunctions.Thesefunctionshavetheadvantagethat:•Theyallowcodetobereused.•Theyallowfortop-leveldesign.•Theymakeappletdebuggingeasieraseachfunctioncanbetestedinisolation

totherestoftheapplet.Afunctionhasthepublickeyword,followedbythereturnvalue(ifany)and

the name of the function.After this the parameters passed to the function aredefinedwithinroundedbrackets.Recappingfromthepreviousexample:

This functionhas thepublickeywordwhichallowsanyuser toexecute thefunction.Thevoidtypedefinesthatthereisnothingreturnedfromthisfunctionandthenameofthefunctionispaint().Theparameterpassedintothefunctionis g which has the data type of Graphics. Within the paint() function thedrawstring()functioniscalled.Thisfunctionisdefinedinjava.awt.Graphicsclass library (this library has been included with the import java.awt. *statement.Thedefinitionforthisfunctionis:

whichdrawsastringofcharactersusingthecurrentfontandcolour.Thex,ypositionisthestartingpointofthebaselineofthestring(str).It should be noted that Java is case sensitive and the names givenmust be

referedtointhecasethattheyaredefinedas.

27.4Stand-aloneprogramsAJavaprogramcanalsoberunasastand-aloneprogram.ThisallowstheJavaprogramtoberunwithoutabrowserandisnormallyusedwhentestingaJavaapplet.Themethodofoutputtothescreenis:

which prints amessage (message) to the display.This type of debugging ismessy as these statements need to be manually inserted in the program. It islikely that later versions of the JDK toolkit will contain a run-time debuggerwhichwillallowdeveloperstoviewtheexecutionoftheprogram.Torunastand-aloneprogramthejava.exeprogramisusedandtheuseradds

outputstatementswiththeSystem.out.println()function.NotethatthereisnooutputfromappletwiththeSystem.out.println()function.Java stand-alone program 27.1 gives a simple example of a stand-alone

program.Thepublicstaticvoidmain(Strings[]args)definesthemainfunction.Sample run27.3 showshow the Javaprogram iscreated (withedit)andthencompiler(withjavac.exe),andthenfinallyrun(withjava.exe).

27.5JavareservedwordsLikeanyprogramminglanguage,Javahasvariousreservedwordswhichcannotbeusedasavariablename.Thesearegivennext:

27.6AppletvariablesVariablesareusedtostorednumericvaluesandcharacters.InJavaallvariablesmust be declaredwith their data type before they can be used. The Java datatypesaresimilartoC/C++types,andarestatedinTable27.4.

Table27.4Javadatatypesandtheirrange

Type Storage(bytes) Range

boolean TrueorFalse

byte 1 −128to127

char 2 Alphabeticcharacters

int 4 −2,147,483,648to2,147,483,647

short 2 −32,768to32,767

long 4 −2,147,483,648to2,147,483,647

float 4 ±3.4×10(T−38to±3.4×1038

double 8 ±1.7×10−308to±1.7×10308

27.6.1ConvertingNumericDataTypesJava is a strongly typed language and various operations follow standardconversionsfordatatypes.Ifthedeveloperwantstoconvertfromonedatatypetoanother(suchasfromanintegertoadouble)thenthedatatypeconversionisused where the converted data type is defined within rounded brackets. Forexample:

convertstheadditionofyandztoaninteger.

27.6.2ThePaint()ObjectThepaint()objectistheobjectthatiscalledwhenevertheappletisredrawn.Itwillthusbecalledwhenevertheappletisrunandthenitiscalledwhenevertheappletisredisplayed.

27.7JavaoperatorsThetablebelowrecapstheJavaoperatorsfromthepreviouschapter.

27.8MathematicaloperationsJava has a basic set of mathematics functions which are defined in thejava.lang.Mathclass library.Table27.5outlines thesefunctions.Anexampleofthefunctionsinthislibraryisabs()whichcanbeusedtoreturntheabsolutevalue of either a double, an int or a long value. Java automatically picks therequired format and the return data type will be of type of the value to beoperatedon.

Table27.5Functionsdefinedinjava.lang.Math

Function Description

doubleabs(doublea) Returnstheabsolutedoublevalueofa.

floatabs(floata) Returnstheabsolutefloatvalueofa.

intabs(inta) Returnstheabsoluteintegervalueofa.

longabs(longa) Returnstheabsolutelongvalueofa.

doubleacos(doublea) Returnsthearccosineofa,intherangeof0.0throughPi.

doubleasin(doublea) Returnsthearcsineofa,intherangeofPi/2throughPi/2.

doubleatan(doublea) Returnsthearctangentofa,intherangeof–Pi/2throughPi/2.

doubleatan2(doublea,

doubleb)

Convertsrectangularcoordinates(a,b)topolar(r,theta).

doubleceil(doublea) Returnsthe’ceiling’orsmallestwholenumbergreaterthanorequaltoa.

doublecos(doublea) Returnsthetrigonometriccosineofanangle.

doubleexp(doublea) Returnstheexponentialnumbere(2.718…)raisedtothepowerofa.

doublefloor(doublea) Returnsthe’floor’orlargestwholenumberlessthanorequaltoa.

double

IEEEremainder(double

f1,doublef2)

Returnstheremainderoff1dividedbyf2asdefinedbyIEEE754.

doublelog(doublea) Returnsthenaturallogarithm(basee)ofa.

doublemax(doublea,

doubleb)

Takestwodoublevalues,aandb,andreturnsthegreaternumberofthetwo.

doublemax(floata,float

b)

Takestwofloatvalues,aandb,andreturnsthegreaternumberofthetwo.

intmax(inta,intb) Takestwointvalues,aandb,andreturnsthegreaternumberofthetwo.

max(longa,longb) Takestwolongvalues,aandb,andreturnsthegreaternumberofthetwo.

doublemin(doublea,

doubleb)

Takestwodoublevalues,aandb,andreturnsthesmallestnumberofthetwo.

floatmin(floata,float

b)

Takestwofloatvalues,aandb,andreturnsthesmallestnumberofthetwo.

intmin(inta,intb) Takestwointegervalues,aandb,andreturnsthesmallestnumberofthetwo.

longmin(longa,longb) Takestwolongvalues,aandb,andreturnsthesmallestnumberofthetwo.

doublepow(doublea,

doubleb)

Returnsthenumberaraisedtothepowerofb.

doublerandom() Generatesarandomnumberbetween0.0and1.0.

doublerint(doubleb) Convertsadoublevalueintoanintegralvalueindoubleformat.

longround(doublea) Roundsoffadoublevaluebyfirstadding0.5toitandthenreturningthelargestintegerthatislessthanorequaltothisnewvalue.

intround(floata) Roundsoffafloatvaluebyfirstadding0.5toitandthenreturningthelargestintegerthatislessthanorequaltothisnewvalue.

doublesin(doublea) Returnsthetrigonometricsineofanangle.

doublesqrt(doublea) Returnsthesquarerootofa.

doubletan(doublea) Returnsthetrigonometrictangentofanangle.

Asthefunctionsarepartof theMathclass theyareprecededwith theMath.

classmethod.Forexample:

Java stand-alone program 27.2 shows a few examples of mathematicaloperationsandSamplerun27.4showsasamplecompilationandrunsession.Javahasalsotwopre-definedmathematicalconstants.Theseare:•Piisequivalentto3.14159265358979323846.•Eisequivalentto2.7182818284590452354.

27.9Loops

27.9.1For()AswithC/C++andJavaScriptthestandardformatforafor()loopis:

where:

Javaapplet27.2 showshowafor() loopcanbeused todisplay thesquareandcubeof thevalues from0 to9.Notice that the finalvalueofiwithin thefor()loopis9becausetheendconditionisi<10(whileiislessthan10).

27.9.2While()Thewhile()statementallowsablockofcodetobeexecutedwhileaspecifiedcondition is TRUE. It checks the condition at the start of the block; if this isTRUEtheblockisexecuted,elseitwillexittheloop.Thesyntaxis:

If the statement block contains a single statement then the braces may beomitted(althoughitdoesnoharmtokeepthem).

27.10ConditionalstatementsConditionalstatementsallowaprogramtomakedecisionsontheroutethroughaprogram.

27.10.1If…ElseAswithC/C++andJavaScriptthestandardformatforaif()descisionis:

Thefollowingisanexampleformatwithanelseextension.

Javaapplet27.3usesafor()loopandtheif()statementtotestifavalueislessthan,equaltoorgreaterthan5.Theloopisusedtorepeatthetest10times.

The random() function is used to generate a value between 0 and 1, thereturnedvalueisthenmultipliedby10soastoconverttointoavaluebetween0and10.Thenitisconvertedtoanintegerusingthedatatypemodifier(int).Theif()statementisthenusedtotestthevalue.

27.11Exercises27.11.1.WriteaJavaappletwhichdisplaysthefollowingtableofpowers.

27.11.2.WriteaJavaappletwhichdisplaysthefollowingtableofsquarerootvaluesfrom1to15.

Value Squareroot

1 1

2 1.414214

3 1.732051

4 2

5 2.236068

6 2.44949

7 2.645751

8 2.828427

9 3

10 3.162278

11 3.316625

12 3.464102

13 3.605551

14 3.741657

15 3.872983

27.11.3.WriteaJavaappletwhichdisplay20randomnumbersfrombetween0and20.

27.11.4.WriteaJavaappletthatsimulatestherollingoftwodice.Asampleoutputis:

Dice1: 3

Dice2: 5

Total: 8

28

Java(Extendedfunctions)

28.1Introduction

Chapter27discussedtheJavaprogramminglanguage.Thischapterinvestigatesevent-drivenprograms.Themaineventsare:•Initializationandexitfunctions(init(),start(),stop()anddestroy

()).•Repaintingandresizing(paint()).•Mouseevents(mouseUp(),mouseDown()andmouseDrag()).•Keyboardevents(keyUp()andkeyDown()).

28.2InitializationandexitfunctionsJavahasvariousreservedfunctionswhicharecalledwhenvariouseventoccur.Table 28.1 shows typical initialization functions and their events, and Figure28.1illustrateshowtheyarecalled.

Table28.1Javainitializationandexitfunctions

Function Description

publicvoid

init()

Thisfunctioniscalledeachtimetheappletisstarted.Itistypicallyusedtoadduser-interfacecomponents.

publicvoid

start()

Thisfunctioniscalledaftertheinit()functioniscalled.Itisalsocalledwhenevertheuserreturnstothepagecontainingtheappletandthuscanbecalledmanytimesasopposedtotheinit()functionwhichwillonlybecalledwhentheappletisfirststarted.Thus,codewhichistobeexecutedonlyonceisnormallyputintheinit()function,andcodewhichmustbeexecutedeverytimetheappletisaccessedshouldbeinsertedintothestart()function.

publicvoid

stop()

Thisfunctioniscalledwhentheusermovesawayfromthepageonwhichtheappletresides.Itisthustypicallyusedtostopprocessingwhiletheuserisnotaccessingtheapplet.Typicallyitisusedtostopanimationoraudiofiles,ormathematicalprocessing.Thestart()functionnormallyrestartstheprocessing.

publicvoid

paint

(Graphics

g)

Thisfunctioniscalledwhentheappletisfirstcalledandwhenevertheuserresizesormovesthewindows.

publicvoid

destroy()

Thisfunctioniscalledwhentheappletisstoppedandisnormallyusedtoreleaseassociatedresources,suchasfreeingmemory,closingfiles,andsoon.

FIGURE28.1 Javainitializationandexitfunctions

Javaapplet28.1gives an exampleusing theinit() andstart() functions.Thevariablei isdeclaredwithin theappletand it is set toavalueof5 in theinit()function.Thestart()functionthenadds6ontothisvalue.Afterthisthepaint()functioniscalledsothatitdisplaysthevalueofi(whichshouldequal11).

28.3MouseeventsMost Java applets require some user interaction, normally with the mouse orfrom the keyboard. Amouse operation causes mouse events. The three basiceventswhicharesupportedinJavaare:•mouseUp().•mouseDown().•mouseDrag().Java applet 28.2 uses the three mouse events to display the current mouse

cursor.Eachofthefunctionsmustreturnatruevaluetoidentifythattheeventhasbeenhandledsuccessfully(thereturntypeisofdata typeBooleanthus thereturn could only be a true or a false). In the example applet, onmoving themousecursorwiththeleftmousekeypresseddownthemouseDrag()functionisautomaticallycalled.Thexandycoordinateofthecursorisstoredinthexandyvariablewhentheeventoccurs.Thisisusedinthefunctionstobuildamessagestring(inthecaseofthedrageventthestringnameisMouseDragMsg).

28.4MouseselectionInmany applets the user is prompted to select an object using themouse. Toachievethisthexandypositionoftheeventistestedtodetermineifthecursoriswithinthedefinedarea.Javaapplet28.3isaprogramwhichallowstheusertopress themouse button on the applet screen. The applet then uses themouse

eventstodetermineifthecursoriswithinagivenareaofthescreen(inthiscasebetween 10,10 and 100,100). If the user is within this defined area then themessage displayed is HIT, else it is MISS. The graphics functiong.drawRect(x1,y1,x2,y2)drawsarectanglefrom(x1,y1)to(x2,y2).

28.5KeyboardinputJavaprovidesfortwokeyboardevents,theseare:•keyUp().Iscalledwhenakeyhasbeenreleased.•keyDown().Iscalledwhenakeyhasbeenpressed.The parameters passed into these functions are event (which defines the

keyboardstate)andanintegerKeypressedwhichdescribesthekeypressed.

Theeventcontainsanidentificationastothetypeofeventitis.Whenoneofthe function keys is pressed then the variable event.id is set to the macroEvent.KEY_ACTION(asshowninJavaapplet28.5).Otherkeys,suchastheCtrl,AltandShiftkeys,setbitsintheevent.modifiervariable.ThetestfortheCtrlkeyis:

ThisteststheCTRL_MASKbit;ifitisa1thentheCTRLkeyhasbeenpressed.Javaapplet28.5showsitsuses.

ForfunctionkeystheKeyPressvariablehasthefollowingvalues:

Thus,totestforthefunctionkeysthefollowingroutinecanbeused:

ForcontrolkeystheKeyPressvariablehasthefollowingvalues:

Thus,totestforthecontrolkeysthefollowingroutinecanbeused:

28.6GraphicsimagesJavahasexcellentsupportimagesandsound.ForgraphicsfilesithassupportforGIFandJPEGfiles,eachofwhichisinacompressedform.Theimageobjectisdeclaredwith:

Next the graphics image is associated with the image object with the getImage()function:

where the getCodeBase() function returns the applets URL (such aswww.eece.napier.ac.uk)andthesecondargumentisthenameofthegraphicsfile(inthiscase,myson.gif).Afterthistheimagecanbedisplayedwith:

wheremypicisthenameoftheimageobject,andthexandyvaluesarethecoordinates of the upper-left hand corner of the image. The this keywordassociatesthecurrentobject(inthiscaseitisthegraphicsimage)andthecurrentapplet.Javaapplet28.6givesanappletwhichdisplaysanimage.

28.7GraphicsThejava.awt.Graphicsclasscontainsagreatdealofgraphics-basedfunctions;thesearestatedinTable28.2.

Table28.2Javagraphicsfunctions

Graphicsfunction Description

publicabstractvoid

translate(intx,

inty)

Translatesthespecifiedparametersintotheoriginofthegraphicscontext.Allsubsequentoperationsonthisgraphicscontextwillberelativetothisorigin.Parameters:x–thexcoordinatey–theycoordinate

publicabstractColor

get-Color()

Getsthecurrentcolour.

publicabstractvoid

setColor(Colorc)

Setcurrentdrawingcolour.

publicabstractFont

getFont()

Getsthecurrentfont.

publicabstractvoid

setFont(Fontfont)

Setthecurrentfont.

publicFontMetrics

getFontMetrics()

Getsthecurrentfontmetrics.

publicabstract

FontMetrics

getFontMetrics(Font

f)

Getsthecurrentfontmetricsforthespecifiedfont.

publicabstractvoid

copyArea(intx,int

y,intwidth,int

height,intdx,int

dy)

Copiesanareaofthescreenwhere(x,y)isthecoordinateofthetopleft-handcorner,widthandheightandthewidthandheight,anddxisthehorizontaldistanceanddytheverticaldistance.

publicabstractvoid

drawLine(intx1,int

y1,intx2,inty2)

Drawsalinebetweenthe(x1,y1)and(x2,y2).

publicabstractvoid

fillRect(intx,int

y,intwidth,int

height)

Fillsthespecifiedrectanglewiththecurrentcolour.

public

voiddrawRect(int

x,inty,intwidth,

intheight)

Drawstheoutlineofthespecifiedrectangleusingthecurrentcolour.

Publicabstractvoid

clearRect(intx,

inty,intwidth,

intheight)

Clearsthespecifiedrectanglebyfillingitwiththecurrentbackgroundcolourofthecurrentdrawingsurface.

publicvoid

draw3DRect(intx,

inty,intwidth,

intheight,boolean

raised)

Drawsahighlighted3-Drectanglewhereraisedisabooleanvaluethatdefineswhethertherectangleisraisedornot.

publicvoid

fill3DRect(intx,

inty,intwidth,

intheight,boolean

raised)

Paintsahighlighted3-Drectangleusingthecurrentcolour.

publicabstractvoid

drawOval(intx,int

y,intwidth,int

height)

Drawsanovalinsidethespecifiedrectangleusingthecurrentcolour.

publicabstract

voidfillOval(int

x,inty,intwidth,

intheight)

Fillsanovalinsidethespecifiedrectangleusingthecurrentcolour.

publicabstractvoid

drawArc(intx,int

Drawsanarcboundedbythespecifiedrectanglestarting.ZerodegreesforstartAngleisatthe3-o’clockpositionandarcAnglespecifiestheextentofthearc.ApositivevalueforarcAngleindicatesacounter-clockwiserotationwhilea

y,intwidth,int

height,int

startAngle,int

arcAngle)

arc.ApositivevalueforarcAngleindicatesacounter-clockwiserotationwhileanegativevalueindicatesaclockwiserotation.Theparameter(x,y)specifiesthecentrepoint,andwidthandheightspecifiesthewidthandheightofarectangle

publicabstractvoid

fillArc(intx,int

y,intwidth,int

height,int

startAngle,int

arcAngle)

Fillsapie-shapedarcusingthecurrentcolour.

publicabstractvoid

drawPolygon(int

xPoints[],int

yPoints[],int

nPoints)

Drawsapolygonusinganarrayofxandypoints(xPoints[]andyPoints[]).ThenumberofpointswithinthearrayisspecifiedbynPoints.

publicabstractvoid

fillPolygon(int

xPoints[],int

yPoints[],int

nPoints)

Fillsapolygonwiththecurrentcolour.

publicabstractvoid

drawstring(String

str,intχ,inty)

DrawsthespecifiedStringusingthecurrentfontandcolour.

publicabstract

boolean

drawImage(Image

img,intx,inty)

Drawsthespecifiedimageatthespecifiedcoordinate(x,y).

publicabstractvoid

dispose()

Disposesofthisgraphicscontext.

28.7.1SettingTheColourThecurrentdrawingcolour is set using thesetColor() function. It is usedasfollows:

Coloursaredefinedinthejava.awt.Colorclassandvalidcoloursare:

Anyother24-bitcolourcanbegeneratedwith thefunctionColorwhichhastheformat:

wherer,gandbarevaluesofstrengthfrom0to255.Forexample:

28.7.2DrawingLinesAndCirclesNormally to draw a graphics object the user must plan its layout for thedimension within the object. Figure 28.2 shows an example graphic with therequireddimensions.ThedrawOval()functionusesthetoplevelhandpointforthexandyparametersinthefunctionandthewidthandheightdefinethewidthandheightoftheovalshape.ThusthedrawOval()functioncanbeusedtodrawcircles(ifthewidthisequaltotheheight)orovals(ifthewidthisnotequaltotheheight).Javaapplet28.7showstheJavacodetodrawtheobject.Thisappletuses the setColor() function tomake the circle yellow and the other shapesblue.

FIGURE28.2 Dimensionsofgraphic

28.7.3DrawingPolygonsThe drawPolygon() function can be used to draw complex objects where theobjectisdefinedasagroupof(x,y)coordinates.Javaapplet28.8drawsabasicpictureofacarand thexpointsarrayholds thexcoordinatesandypointsholdtheycoordinates.Figure28.3illustratestheobject.

FIGURE28.3 Coordinatesofgraphic

28.8SoundTheplayingofsoundfilesissimilartodisplayinggraphicsfiles.Javaapplet28.9shows a sample applet which plays an audio file (in this case, test.au).Unfortunately the current version of the Java compiler only supports the AUformat,thusWAVfilesneedtobeconvertedintoAUformat.TheinitializationprocessusesthegetAudioClip()functionandtheaudiofile

is played with the loop() function. This function is contained in thejava.applet.AudioClipclass,thesefunctionsare:

28.9DialogboxesOne of the features of Java is that it supports dialog boxes and checkboxes.Theseareusedwitheventhandlerstoproduceevent-drivenoptions.

28.9.1ButtonsAndEventsJavaapplet28.10createsthreeButtonobjects.Thesearecreatedwiththeadd()functionwhichdisplaysthebuttonintheappletwindow.

Applet 28.10 creates three buttonswhich do not have any action associatedwith them. Javaapplet28.11uses theaction functionwhich iscalledwhenaneventoccurs.Withinthisfunctiontheeventvariableistestedtoseeifoneofthebuttonscausedtheevent.Thisisachievedwith:

If this tests to the true then theMsg string takes on thevalueof theObject,whichholdthenameofthebuttonthatcausedtheevent.

28.9.2CheckboxesTypicallycheckboxesareused toselect fromanumberofoptions.Javaapplet28.12showshowanappletcanusecheckboxes.Asbefore,theactionfunctioniscalledwhenacheckboxchangesitsstateandwithinthefunctionevent.targetparameteristestedforthecheckboxwith:

Ifthisistrue,thenthefunctionDetermineCheckState()iscalledwhichtestsevent.targetforthecheckboxvalueanditsstate(trueorfalse).

28.9.3RadioButtonsThe standard checkboxes allowanynumberofoptions tobe selected.A radiobuttonallowsonlyoneoptiontobeselectedatatime.Thepreviousexamplecanbechangedasfollows:

ThissetsthecheckboxtypetoRadioGroupanditcanbeseenthatonlyoneofthecheckboxesisinitallyset(thatis,‘Post’).

28.9.4Pop-UpMenuChoicesTocreateapop-upmenutheChoiceobjectisinitallycreatedwith:

AfterthisthemenuoptionsaredefinedusingtheaddItemmethod.Javaapplet28.13showsanexampleusageofapop-upmenu.

28.9.5TextInputTextcanbeenteredintoaJavaappletusingtheTextFieldaction.InJavaapplet28.14theTextField(20)definesa20-characterinputfield.

28.10FontsJava is well supported with different fonts. The class library java.awt.FontdefinestheFontclassandthegeneralformatfordefiningthefontis:

Themainfont_typesare:

ThisbookiswritteninTimesRoman.Helveticalooksgoodasaheader,suchasHeader1.Courierproducesamonospacefontwhereallofthecharactershavethesamewidth.TheJavaappletsinthischapterusetheCourierfont.Symbolisnormallyusedwhenspecialsymbolsarerequired.Thefont_attribcaneitherbeBOLD,ITALICorNORMAL.andthefont_sizeisanintegervaluewhichissupportedby the compiler. The font size of this text is 11 andmost normal text varies

between8and12.Javaapplet28.15showsanexampleappletusingdifferentfonts.

28.11Exercises28.11.1.Explainhowthethreemouseeventsoccur.28.11.2.WriteaJavaappletthatcontainsatargetwhichhasareaswithdifferent

pointvalues.Thesepointvaluesare50,100and150.Theprogramshouldaccumulatethescoresofar.AsamplescreenisgiveninFigure28.4(refertoJavaapplet28.3fortheoutlineoftheprogram).

FIGURE28.4

28.11.3.Modifytheprogramin28.11.2sothataRESETbuttonisdisplayed.Whenselectedthepointsvalueshouldberesettozero.

28.11.4.WriteaJavaappletwhichdisplaysasquareatastartingposition(50,50)withawidthandlengthof50units.Theusershouldthenbeabletomovetherectangleup,down,leftorrightusingtheukey(forup),dkey(fordown),1key(forleft)andrkey(forright).Theprogramshouldcontinueuntilthexkeyispressed.

28.11.5.WriteaJavaappletwhichdisplayswhichfunctionkeyorcontrolkey(Cntrl)hasbeenpressed.TheprogramshouldruncontinuouslyuntiltheCntrl-Zkeystrokeispressed.

28.11.6.WriteseparateJavaapplets,usingsimplerectanglesandcircles,todisplaythefollowinggraphics:(a)atelevision(asamplegraphicisshowninFigure28.5)

FIGURE28.5

(b)aface(c)ahouse(d)arobot

28.11.7.LocatethreeGIForJPEGfiles.ThenwriteaJavaappletwhichallowstheusertochoosewhichoneshouldbedisplayed.ThefunctionkeyF1selectsthefirstimage,F2thesecond,andF3thethird.ThefunctionkeyF4shouldexittheapplet.

28.11.8.UsinganappletwhichdisplaysthetextTESTTEXT,determinetheapproximatecolourofthefollowingcoloursettings:(a)color(100,50,10)(b)color(200,200,0)(c)color(10,100,100)(d)color(200,200,200)(e)color(10,10,100)

28.11.9.Writeanappletusingapolygonforthefollowingshapes:(a)aship(asampleisshowninFigure28.6)

FIGURE28.6

(b)atank(c)aplane

28.11.10.Locateasoundfileandwriteanapplicationwhichusesit.28.11.11.WriteaJavaappletwhichdisplaysthefollowing:

NotethatSampleAppletisboldArialtextwithasizeof20andtheothertextisCourierofsizeof14.

28.11.12.WriteaJavaappletinwhichtheuserenterssometext.IftheuserentersEXITthentheprogramwillexit.

PARTFDOS

29

Introduction

29.1Introduction

In1947theinventionofthetransistorcausedagreatrevolution.Infactscientistsat theBellLaboratorieskept its inventionsecret foroversevenmonthsso thatthey could fully understand its operation.On 30 June 1948 the transistorwasfinallyrevealedtotheworld.Unfortunately,aswithmanyothergreatinventions,it received little public attention and even less press coverage (theNew YorkTimesgaveit4½inchesonpage46).Transistorshad, initially,beenmadefromgermanium,which isnota robust

materialandcannotwithstandhightemperatures.Thefirstcompanytoproposeamethod of using silicon transistorswas a geological research company namedTexas Instruments (which had diversified into transistors). Soon manycompanieswereproducing silicon transistors andby1955 the electronicvalvemarket had peaked,while themarket for transistorswas rocketing.The largerelectronic valvemanufacturers, such asWestern Electric, CBS, Raytheon andWestinghouse failed to adapt to the changing market and quickly lost theirmarket share to the new transistor manufacturing companies, such as TexasInstruments,Motorola,HughesandRCA.In 1959, IBM built the first commercial transistorized computer named the

IBM 7090/7094 series. It was so successful that it dominated the computermarket for many years. In 1965, they produced the famous IBM system 360whichwasbuiltwithintegratedcircuits.Thenin1970IBMintroducedthe370system, which included semiconductor memories. Unfortunately, thesecomputerswereextremelyexpensivetopurchaseandmaintain.Around the same time the electronics industrywas producing cheap pocket

calculators. The development of affordable computers happened when theJapanesecompanyBusiconcommissionedasmall,atthetime,companynamedInteltoproduceasetofeighttotwelveICsforacalculator.InsteadofdesigningacompletesetofICs,IntelproducedasetofICswhichcouldbeprogrammedto

perform different tasks. Thesewere the first evermicroprocessors. Soon Intel(short for Integrated Electronics) produced a general-purpose 4-bitmicroprocessor,namedthe4004andamorepowerful8-bitversion,namedthe8080.Other companies, such asMotorola,MOSTechnologies andZilogweresoonalsomakingmicroprocessors.IBM’s virtualmonopoly on computer systems soon started to slip asmany

companies developed computers based around the newly available 8-bitmicroprocessors, namely MOS Technologies 6502 and Zilog’s Z–80. IBM’smain contenders were Apple and Commodore who introduced a new type ofcomputer– thepersonalcomputer(PC).TheleadingsystemsweretheAppleIand theCommodore PET.These spawnedmany others, including the SinclairZX80/ZX81, theBBCmicrocomputer, the Sinclair Spectrum, theCommodoreVic–20andtheclassicAppleII(allofwhichwerebasedonoraroundthe6502orZ-80).IBMrealizedthepotentialofthemicroprocessorandusedIntel’s16-bit8086

microprocessor in their version of thePC. Itwas named the IBMPC and hassincebecometheparentofall thePCseverproduced.IBM’smainaimwas tomake a computer which could run business applications, such as wordprocessors, spread-sheets and databases. To increase the production of thissoftwaretheymadeinformationonthehardwarefreelyavailable.Thisresultedinmanysoftwarepackagesbeingdevelopedandhelpedclonemanufacturerstocopytheoriginaldesign.Sotheterm‘IBM-compatible’wasbornanditquicklybecameanindustrystandardbysheermarketdominance.On previous computers IBM had written most of their programs for their

systems.ForthePCtheyhadastricttimelimit,sotheywenttoasmallcomputercompany called Microsoft to develop the operating system program. Thisprogramwasnamed theDiskOperatingSystem (DOS)becauseof its originalpurposeofcontrollingthediskdrives.Itacceptedcommandsfromthekeyboardanddisplayed themto themonitor.The languageofDOSconsistedofasetofcommandswhichwere entereddirectly by the user and interpreted to performfilemanagement tasks,programexecutionandsystemconfiguration.Themainfunctions of DOS were to run programs, copy and remove files, createdirectories,movewithinadirectorystructureandtolistfiles.Microsoft has since gone on develop industry-standard software such as

MicrosoftWindows Version 3,Microsoft Office andMicrosoftWindows 95.Intel has also benefited greatly from the development of the PC and hasdevelopedalargemarketsharefortheirindustry-standardmicroprocessors,such

asthe80286,80386,80486,PentiumandPentiumProprocessors.

29.2IntroductiontoDOSMostmodernPCseitherrunDOSorallowaccesstoanemulatedversionofit.AllversionofMicrosoftWindowsupto,andincludingMicrosoftWindows3.1,required DOS to be running before Windows could run. Windows 95 andWindowsNTarecompleteoperatingsystemswithinthemselvesanddisplayanemulatedversionofDOS.

29.2.1CheckingTheVersionOfDOS(VER)ThefirstversionofDOSwasreleasedin1981andeachsubsequentreleasehasbeenassignedanewversionnumber.WhenthereisamajorchangeinDOSthenthe first number is changed, such as, Versions 1.0, 2.0, 3.0, and so on. Thesecondnumberchangeswitharelativelyminorchange,suchasversion1.1,1.2,1.3,andsoon.MostversionsofDOSarecompatiblewithpreviousversions.TodeterminetheversionofDOSthatacomputerisrunningthenentertheVER

command,asshowninTestrun29.1.ManycurrentsystemsuseVersion6orrunanemulatedDOSfromWindows95orWindowsNT.DOSversions later thanVersion4have anon-linehelpmanual.Todisplay

thehelppageonacommandthenHELPcommand_nameisentered,asshowninTestrun29.2.

29.2.2CheckingTheDateAndTime(DateAndTime)MostPCshaveanon-boardclockwhichispoweredbyarechargeablebattery.TheDATEcommanddisplaysthecurrentdateandallowstheusertochangethesystemdata,ifrequired.Testrun29.3showsanexample.Ifthedateisdisplayedcorrectlythenthe<ENTER>keyispressed,asshowninTestrun29.3.

IfthisdateisincorrectthenthecorrectdateisenteredattheEnternewdate(dd-mm-yy)prompt.Theexample inTest run29.4 shows that thecurrentdatehas been changed to Sunday 8/9/96. Care must be taken when entering thecurrentdateasthesystemmaybesetuptodisplaythedateinUSAformat,thatis,MM-DD-YY(MONTH,DAYandYEAR).TheTIMEcommanddisplaysthecurrenttime.Aswiththedatecommandthe

user ispromptedas towhether tochange thecurrent time,ornot.Pressing theENTERkeydoesnotchangethecurrenttime.Testrun29.6showsanexampleofchangingthesystemtimefrom10:55amto11:15pm.

29.2.3ClearingTheScreen(Cls)TheCLScommandclearsthescreenandleavesonlyapromptandthecursor.

29.2.4StartingAndStoppingDOSWhenthePCisrestarted,DOSisnormallystartedautomaticallyfromthehard-disk(unlessthesystemhasnohard-disks).SomePCstrytoreadthefloppydisksdrivesfor theDOSsystemfiles. If thishappensmakesure therearenofloppydisksinthedrives.ThemethodofstartingDOSisdescribedasthebootprocedure.Therearetwo

mainmethodsofstarting(orrestartingDOS):•Acoldboot–occursatpower-upandcausesthesystemtostartaself-test

program;•Awarmboot–isexecutedwhentheCtrl,AltandDelkeysarepresseddownsimultaneously(describedasCtrl-Alt-Del).Thisisnormallyrequiredwhenaprogramhascrashedandthesystemhashungup.

The Ctrl-Break keys (or Cntrl-C) are used to interrupt a DOS command.Testrun29.7showshowtheTIMEcommandisinterruptedusingtheCtrland‘Ckeys.

29.3DisksComputers store data on floppy disks, hard-disks and optical disks. The diskdrivesonaPCareidentifiedbythelabelsfromA:toZ:.Itisconventionthattheprimaryhard-diskdriveisdriveC:,theprimaryfloppydriveisA:,andthesecondaryfloppydriveisB:.,asgiveninTable29.1.

Table29.1Diskdriveallocation

DriveAllocation Description

A: Primaryfloppydiskdrive

B: Secondaryfloppydiskdrive

C: Primaryhard-diskdrive

D: Secondaryhard-diskdriveorCD-ROMdrive

Floppy and hard-disks store of information using magnetically fields onseparateconcentricrings–knownastracks.Thesearesubdividedintoblocksof512bits–knownassectors.Therearevariousdifferentformatsforthesetracksand sectors with varying capacities; these are given in Figure 29.2. Differingcapacitiesmayleadtocompatibilityproblems.

FIGURE29.2 Samplefilestructure

Table29.2Floppydiskcapacity

29.4Formattingfloppydisks(FORMAT)Theprimaryhard-diskisnamedC:andtheprimarydiskdriveisnamedA:.IfthePChasanotherfloppydiskdriveitisgiventhenameB:.Otherdrivescanexist,suchasfornetworkdrives,asecondaryhard-disk,aCD-ROMdrive,andsoon.Therearetwomaintypesoffloppydisks.Theseareusuallyreferredtobythe

disksdimensions,asshowninFigure29.2.OriginallyPCsusedthe5.25”floppydisks.Theyareextremelysensitivetophysicaldamage,especiallywhentheyarebent.Dataonthediskcanalsobecorruptedbyexternalparticlesorfingerprints.Thediskcanbeput intoadustcover–althoughitprovides littleprotectiontobeing bent. A better floppy disk uses a sliding metal shutter to protect themagnetic disk, this is the 3.5” disk. It also allows a greater amount of datastorage.A3.5”diskcanbeprotectedfromover-writingstoreddatabyslidingthewrite

protect button, as shown in Figure 29.2. There are two types 3.5” disk types,thesediffer in the amountofdata that canbe safely storedon them.Theyarenamedthedoubledensity(DD)andhighdensity(HD)disk.TheDDdiskhasamaximumcapacityof720KBandtheHDhas1.4MB.Normally,HDdisksaremore reliable thanDD disks, but they costmore to buy. AnHD disk can beidentifiedeitherbytheHDsymbolorbythenotchattheothersideofthewriteprotectslider.

FIGURE29.1 3.5”floppydisks.

29.4.1FormattingA3.5”DiskTheFORMATcommandsetsupthenecessaryformatonthedisksothatfilescanbestored.AsamplesessionisshowninTestrun29.8.

Notice that the message Saving UNFORMAT information is displayed. Thisallowstheusertounformatadiskthathasbeenformattedaccidentally(butonlyifnonewfileshavebeenwrittentothedisk).It is also possible to force the FORMAT command to format with a different

capacity.The/f switchextension isused for thispurpose.Table29.3outlineshowitismodifiedfordifferentcapacities.

Table29.3Floppydiskcapacity

Capacity Command Notes

720K formata:/f:720 DD3.5″floppydisk

1.44M formata:/f:1.44 HD3.5″floppydisk

360K formata:/f:360 DD51/4″floppydisk

1.2M formata:/f:1.2 HD51/4″floppydisk

29.5FilesystemstructureFiles storedata in the formofprograms,documents, spread-sheets, and soon.They are organized into a tree structure. The top of the structure is the rootdirectoryandeachbranchiscalledasubdirectory.Thisstructuremakesfindingfileseasierthanhavingallfilesstoredintheonedirectory.Theroutethroughthetreestructuretoagivenfileisknownasthepathname

and reference to files external to the current directory is possiblebyusing thecorrectpath.Thepathname foragiven file is traced through the tree structurefromtherootdirectorytothelocationofthefile.Test run 29.9 shows an example list of a top-level directory. The prompt

shouldbeset-uptodisplaythecurrentdirectory.Inthiscase,theDOSpromptisC:\>.The top level directory in this case contains various subdirectories such as

DOCS, WINDOWS, PSP and TURBO. Each of these directories contains files and/orsubdirectories. The function of each directory is normally obvious from itsname.Forexample,theDOSdirectorycontainsDOSprogram,helpmanualsandsystemfiles,theWINDOWSdirectorycontainsprogramsforMicrosoftWindows.

Thetop-leveldirectoryistherootdirectory,andisgiventhename\.Asmallsectionof thedirectoryhierarchy isgiven inFigure29.2.Notice that therearefour subdirectories below the root directory and that below theDOCS directorythere are three subdirectories NOTES, CLASSES and ADMIN. There is also onesubdirectory below WINDOWS. To identify the directories a pathname must begiven.Thefullpathnameeachdirectoryis:

AllthesedirectoriesarestoredontheharddiskwhichislabelledasC:,thusthefullpathname,withthediskdrive,ofthedirectoriesare:

Thesepathnamesarethefullpathnamesandareabsolutepathnames.Itisalsopossibletospecifyarelativepathname.Withrelativepathnamethenamegivendoesnothavetheprecedingtop-leveldirectory(\).Forexample,ifweareintheGAMESdirectorytherelativepathnamefortheDATAdirectoryisCHESS\DATAandifweareintheWINDOWSdirectorytherelativepathnamefortheSYSTEMdirectoryissimplySYSTEM.

29.6DOSFilenamesFilesarestoredondiskswithafilenameandanextension.Thefilenamecanbeuptoeightcharacterslongandtheextensionuptothreecharacters.Aperiod(‘.’) separates the filename from the extension. Figure 29.3 shows the standardformat.Theextensionnamegivesanindicationaboutwhattypeoffileitis.

FIGURE29.3 DOSfilenames

The valid characters that can be used for the filename are alphabeticcharacters (‘A’ – ‘Z’), numbers (‘0’ – ‘9’), underscores (‘_’), braces (‘{‘,’}’),parentheses (‘(7)’), tilde (‘~’), caret (’⁁‘), ampersand (‘&’), exclamation point(‘!’), pound sign (‘£’), hyphen (‘-’), and dollar sign (‘$’). Other specialcharacterssuchas(‘*’),(‘?’),(‘:’),(‘;’),(’,’),(‘=’),andsoon.arereservedforspecialfunctions.SomevalidandinvalidfilenamesaregiveninTable29.4.

Table29.4

ExamplesofvalidandinvalidDOSfilenames.

29.7FiletypesMostfilescreatedhaveacertainpurpose;forexampledocumentsfromawordprocessor, spread-sheets, text files. The filename extension adds extrainformationaboutwhattypeoffileitis.CommonfilenameextensionsaregiveninTable29.5.

Table29.5Examplefileextensions

Testrun29.10showsasampleDOSlisting.NoticethatthisdirectorycontainsSystemFiles (.SYS),DOSCommands (.COM and.EXE), Text Files (.TXT) andHelpFiles (.HLP).Theother typical files includeBasicLanguageFiles (.BAS),InitializationFiles(.INI)andListings(.LST).Programswiththe.COM,.EXEor.BATextensioncanbeexecuted.

29.8Listingfiles(DIR)TheDIRcommanddisplaysthecontentsofadirectory.AhelpmanualonDIRisgiveninTestrun29.11.Various switches modify the way the DIR command displays the directory

listing.RefertotheusermanualshowninTestrun29.11foracompletelisting.Testrun29.12showsasamplelistingwithoutswitches.

Table29.6ExampleswitchesfortheDIRcommand

Command Description

DIR/w displaydirectoryinfivecolumns

DIR/p displaysonescreenoflistingatatime

DIR/s displayallsubdirectoriesandfiles

DIR/od displaydirectoryinorderofdate

DIR/1 displaysdirectoriesinlowercase

Test run29.12showsanexamplesessionusingsomeof theformats.Noticethat thebasicDIR commanddisplaysnot only the filename and extension, butalsothefollowing:•Thevolumelabelofthedisk(inthiscase,THINKPAD).

•Thevolumeserialnumber,everydiskdrivehasauniquevolumeserialnumber(3A40–09E8).

•Thecurrentdirectoryname(C:\).•Thedirectorynameorfilename.•Thedatefileorsubdirectorywascreated,orwaslastmodified(forexample,

fortheDOSdirectoryitis05/01/95).•Thetimethefileordirectorywascreated,orwaslastmodified(forexample,

fortheDOSdirectoryitis12:00).•Thenumberoffilesinthedirectory(inthiscase,37).•Thediskspaceusedupbythefilesinthecurrentdirectory(inthiscase,65,

786bytes).•Theamountofavailablediskspace(inthiscase,41,353,216bytes).

The DIR/p displays one screen of directory information and the user ispromptedtoPressandkeytocontinue….Thiscontinuesuntilallthedirectoryinformation is displayed. The DIR/s command is useful for finding files insubdirectories. Several switches can be used at a single time, for example to

display all subdirectories with a pause between each screenful the commandusedisDIR/p/s.Worksheet 14: Note, if you are using Windows NT/95 then select either theMSDOS Prompt or shutdown Windows and select Restart the computer inMSDOSmode.W14.1.DeterminetheDOSversionofthePCyouareusing.

Version:

W14.2.DisplaythecurrentdateonthePC.

Date:

W14.3.DisplaythecurrenttimeofthePC.

Time:

W14.4.Modifythedateandtimeandredisplay.

Newdate:Newtime:

W14.5.Changethedateandtimebacksothattheyshowthecorrectdateand

time.

Completedsuccessfully: YES/NO

W14.6.UsetheCtrl-C(orCtrl-Break)keystrokestoquitfromtheTIMEcommand.

Completedsuccessfully: YES/NO

W14.7.Clearthescreen.

Completedsuccessfully: YES/NO

W14.8.Locatethefollowingkeys(tick,iffound):

Keys

FunctionskeysF1-F10 PageUp/PageDown

Altkey NumLock

Cntrlkey Home/End

CapsLock ESC

HorizontalTAB ScrollLock

Break Delete

W14.9.Displaythefollowingcharacterstothescreen(tick,iffound):

Keys √Keys √

£ \

< :

> (

? )

#

/ |

W14.10.ListallthefilesinthetopleveldirectoryontheC:drive.

Notesomeofcontents:FILES:DIRECTORIES:

W14.11.Whichofthefollowingarevalidnamesforfiles(tick):

Filename Valid(√) Invalid(√)

MY_FILE.DAT

DOC1,DOC

TEMP.$$$

WORK∼1.BAT

WORK??.BAT

TAX:1.DOC

$1.WP

W14.12.ForthefilestructuregiveninFigureW14.1completethetablegivennext(thefirstonehasbeencompleted):

FIGUREW14.1 Filestructure

Directory Fullpathname

ADMIN C:\DOCS\ADMIN

MEMO

BERT

BATCH

WINDOWS

SYSTEM

W14.13.ForthefilestructuregiveninFigureW14.2determinethefullpathnamesforthefilesgivennext(thefirstonehasbeencompleted):

FIGUREW14.2 Filestructure

FILE Fullpathname

T_SHEET.DOC C-\DOCS\ADMIN\T_SHEET.DOC

P_SHEET.DOC

MEMOI.DOC

XCOPY.EXE

MESSAGE.BAT

MOUSE.SYS

W14.14.UsingtheDIRcommandlistallthefilesontheharddisk(C:).UsetheCNTRL-Ckeystroketoexit.

Completedsuccessfully: YES/NO

W14.15.Whatistheprobablefunctionofthefollowingfiles:

File ProbableFunction

ADMIN.DOC DocumentFile

TAX91.WK1

DOSHELP.BAK

CONFIG.SYS

XCOPY.HLP

FIG1.PCX

GORILLA.BAS

HELP.TXT

W14.16.DeterminefromtheDIRlistingthesizeofthefollowingfilesontheharddisk:

FILE Sizeoffile(Bytes)

COMMAND.COM

CONFIG.SYS

AUTOEXEC.BAT

\DOS\XCOPY.EXE

\DOS\FC.EXE

W14.17.DeterminefromtheDIRlistingthedatethatthefollowingfileswere

lastmodified:

FILE Datelastmodified

COMMAND.COM

CONFIG.SYS

AUTOEXEC.BAT

\DOSkXCOPY.EXE

\DOS\FC.EXE

W14.18.Determinetheamountofdiskspacethatisremainingontheharddisk.

Diskspace:

W14.19.Determinetheamountofdiskspaceusedupbyallthefilesinthe\DOSdirectory:

DiskspaceusedbyDOSdirectory:W14.20.Determinethenumberoffilesinthe\DOSdirectory(orthe

\WINDOWSdirectoryifthereisno\DOSdirectory):DiskspaceusedbyDOSdirectory:

Numberoffiles:

W14.21.StatewhatthefollowingDIRcommandsdo(trythemout):

Command Function

dir/b Listsdirectoriesanddisplaysonlythenameofthefile/directory(barelisting)

dir/1

dir/on

dir/os

dir/od

W14.22.Rebootthecomputerusingawarm-boot.

Completedsuccessfully: YES/NO

W14.23.Rebootthecomputerusingacold-boot.

Completedsuccessfully: YES/NO

30

DOSFileSystem/Editor

30.1Changingdirectory(CDorCHDIR)

Thechangedirectorycommand,CD (orCHDIR)allows theuser tomovearoundthefilesystem.Table30.1showsafewsamplecommandsandSamplesession30.1showsasamplesession.Atthebeginningofthissessiontheuserisinthetopleveldirectory(C:\).TheDIR/Wcommandlistscontentsofthedirectoryacrossthe screen in five columns. In this case the main directory contains asubdirectorynamed\DOCS.TochangethecurrentdirectorytothisdirectorytheCDDOCScommandlineisused.Next,contentsofthisdirectoryarelistedusingDIR/W.

Table30.1ExamplesoftheCDcommand

Example Description

CD.. changedirectorytotheoneabovethecurrentdirectory

CD\ changedirectorytothetop-leveldirectory

CD\docs\notes\dos changedirectorytothedirectory\DOCS\NOTES\DOS

CDnotes changedirectorytothesubdirectoryNOTES

In the \DOCS directory there are nine subdirectories. Each of thesesubdirectorieshavetheirownfunction;forexample, lecturenotesarestoredintheNOTESdirectoryandgeneraladministrationdocumentsarestoredintheADMINdirectory.NotethatthefullpathnamefortheNOTESdirectoryisC:\DOCS\NOTES.Next,theuserchangesthecurrentworkingdirectorytotheDOCSdirectoryand

thentotheDOSsubdirectory.Thereareseveralfilesinthisdirectoryincludingthefiles DOS.DOC and DOS_S1.DOC. The full pathname of the file DOS.DOC isC:\DOS\DOCS\NOTES\DOS\DOS.DOC.

30.2Makingadirectory(MKDIRorMD)TheMKDIR (orMD)commandcreatessubdirectories.Samplesession30.2showsasamplesessionwherethesubdirectoryTEMPiscreatedinthetop-leveldirectory.

30.3Viewingafile(TYPE)The TYPE command views the contents of a file. A text file uses a standardalphabetknownasASCII.Non-ASCIIfilescontaindatawhichcannotbeviewedbytheuser.Samplesession30.3showsthelistingofthefileCONFIG.SYSwhichisinthetop-leveldirectory.NotethatthisfilecontainsinformationontheinitialstartupenvironmentofthePC.

30.4Wild-cards(*or?)Wild-cards are special characters which can be used to substitute variouscharactersinafilename.Therearetwowild-cardsusedinDOS,theseare:

*replacesanynumberofcharacters?replacesonlyonecharacterSamplesession30.4showsasamplesession.Theuserstarts inthetop-level

directoryandlistsallfilesordirectorieswhichstartwiththeletter‘d’(usingtheDIR d* command).Next the user changes the directory to \DOS.When in thisdirectory the user lists the files which have a SYS file extension (using DIR*.SYS).Next,all fileswhichbeginwith the letter ‘c’are listed(usingDIRC*).Finally,allfileswhichbeginwiththeletter‘m’haveanysecondletterfollowedbytheletters‘av’andwithanyfileextensionarelisted(usingDIRm?av.*).

30.5CreatingatextfileDOS Version 5.0/6.0 andWindows 96 have a text editor named EDIT. Thiseditor isuseful tocreate text filesbutcannotbeusedwith softwareprograms.For this reason an integrated development environment (IDE) editor will beused..TheexampleusedinthissectionisBorlandC++Version3.0,asshowninFigure30.1.

FIGURE30.1 BorlandC++Version4.0mainscreen.

Many networks allows access to the compiler through a menu option. Oncomputerswherethecompilerisinstalledonthelocalharddisk,thentypicalset-

upsaregiveninTable30.1.FortheBorlandproducts(TurboPascal/BorlandC/TurboC)afileisentered

bysimplyenteringtextintotheeditwindow.ThemainmenuoptionsareFile,Edit, Run, Compile, Options, Debug. Once the file text has been enteredthenitissavedbyusingtheFile→Saveoption.AsadefaultCfilesaregiveaCextension, C++ are given a CPP extension, and Pascal files are automaticallyassignedaPASextension.ToloadapreviouslysavedfiletheFile→Openoptionisused.

Table30.2IDEpackages

IDE Programtorun Typicalhomedirectory

BorlandC++Version4 BC.EXE C:\BORLAND\BIN

TurboCVersion2 TC.EXE C:\TC

TurboPascal TURBO.EXE C:\TURBO

30.8DeletingFiles(DELorERASE)The DEL and ERASE commands delete files. Wild-cards can be used to replacefilenames, if required. Sample session 30.5 shows a sample sessionwhere thefile TEST3.TXT is deleted from the TEMP directory. Next, all the files with a TXTextensionaredeleted.As an extra safeguard against accidentally deleting, or selectively deleting

files the /P switch can be used. Notice in Sample session 30.6 the user ispromptedtodeleteeachofthefilesindividually.

30.9Copyingfiles(COPY)TheCOPYcommandisusedtocopyfiles.TheformatoftheCOPYcommandisgivennext:

whereSOURCEisthenameofthefiletocopyandDESTINATIONisthenameofthefile,ordirectory,tocopyto.InSamplesession30.7theusercreatesadirectorynamedTEMP.Next,theuser

changesthedirectorytotheTEMPsubdirectory.Notethatthisdirectoryisempty.A file namedTEST1.TXT is created using theDOS editor (EDIT).After this it islistedusingtheTYPETEST1.TXTcommandline.Next the directory is listed using DIR and then the COPY command is used to

copy thenewcreated file toTEST2.TXT.Adirectory listing(DIR) then showsthattherearenowtwofilesinthisdirectory(TEST1.TXTandTEST2.TXT).Next,thefirstfile(TEST1.TXT)isdeletedusingERASEcommand.

Worksheet15:W15.1.Gotothetop-leveldirectory,thenmovearoundthefilesystemlooking

invariousdirectories.Trytodeterminethelikelyfunctionofthedirectories.

Directory Likelyfunction

C-\DOS DOSdirectorycontainingsomeDOScommands,helpfunctions,systemfiles,andsoon

W15.2.FindallthefileswhichhavetheDOCextensionontheharddisk(hint.usetheDIR/Scommand).

File(*.DOC) Directory

DOS.Doe C:\NOTES\DOeS\DOS

FindallthefilesontheharddiskwiththeBATextension.

File(*.BAT) Directory

AUTOEXEC.BAT C:\

W15.3.CreateadirectorynamedTEMPontheharddisk.

Commandused:

W15.4.Gointothedirectoryyouhavejustcreated.

Commandused:

W15.5.CreateafilenamePROG1.C(ifyouindenttouseC)orPROG1PAS(ifyouindendtousePascal)fromtheIDEeditor,enterthefollowingtextandsavethefile.

W15.6.CheckthatthefilejustcreatedexistsusingtheDIRcommandDoesitexist:YES/NOW15.7.ViewthecontentsofthisfileusingTYPE.

Arethecontentscorrect:Yes/NO

W15.8.CopythisfileintoafilenamedPROG2.C(orPROG2.PASifthefilecreatedisPROG1.PAS)usingtheCOPYcommand.

Commandused:

W15.9.VerifythattheCOPYcommandhasworkedbylistingthedirectory.

Hasthefilebeencopiedcorrectly:YES/NO

W15.10.ViewthecontentsofthenewlycreatedfileusingTYPE.

Arethecontentscorrect:YES/NO

W15.11.Insertadiskintooneofthediskdrivesandformatafloppydisk(ifyouhaveone).

Commandused:YES/NO

W15.12.GotothefloppydiskandcopythefilePROG1.C(orPROG1.PAS)fromtheC:\TEMPdirectoryandconfirmthatithascopiedcorrectly.

Commandused:

W15.13.DeterminetheVolumelabeloftheharddiskyouareusing.

Volumelabel:

W15.14.DeterminethenamesthatDOSwilluseforthefollowingfiles/directories:

Filename DOSfilenameactuallygiven

MYFILE421.TEXT MYFILE.TEX

DOC$1001.D

ACC9192.WK1

BACKUP.$$11

DOCS.FRED.1

MEMOFRED.200

W15.15.Copythefollowingfilesthatshouldbeinthetop-leveldirectoryontheharddisk.

Copyfrom Copyto

AUTOEXEC.BAT AUTOEXEC.OLD

CONFIG.SYS CONFIG.OLD

Filescopiedokay:YES/NO

W15.16.MakeadirectorynamedOLDBATSandcopythefilesCONFIG.OLDandAUTOEXEC.OLDintothisdirectory.

Filescopiedokay:YES/NO

PARTGWindows3.x

31

Introduction

31.1Introduction

AmodernPersonalComputer(PC)consistsofakeyboard,amonitor,amouse,afloppy disk drive, a hard disk drive and a system unit. An operating systemallowstheusertoaccessthesedevicesinaneasy-to-usemanner,asillustratedinFigure31.1.MicrosoftDOS(DiskOperatingSystem)isatext-basedsysteminwhich commands are entered via the keyboard to perform operations such ascopyingfilesandrunningprograms.

FIGURE31.1 Usinganoperatingsystemtoaccesshardware

Microsoft Windows is a program which presents an easy-to-use graphicalinterface to the PC hardware. It uses windows, icons, menus and pointers(WIMPs) to access application programs, disk drives, file systems, and so on.Most operations are conductedusing amouse insteadof keyboard commands.The user is presented with a series of icons which represent applicationprograms. It is far simpler to use than DOS as the information is presentedgraphically.AmajordisadvantageofDOSis that thesyntaxandformatof thetextcommandrequirestoberemembered.

Windows has gone through three major transformations, from the originalVersion 1.0 to themostwidely available version toVersion 3.1 (andVersion3.11)andnowtoWindows95/NT.It isinstalledonalmosteverynewPCsoldand is becoming the de-facto standard for PC packages. This and the nextchapterdiscussWindows3.1/3.11.

31.2RunningWindowsWindows 3.x is a program which is run from DOS. It will either startautomaticallywhenthePCisswitchedon,orcanberunbytypingWINattheDOSpromptandpressing<RETURN>.

31.3WindowsdesktopAfterWindowsisstartedthescreendisplaystheMicrosoftstart-upscreenforashorttime.Thisdisplaystheversionnumberofthesoftware.ThemainWindowsdesktop is displayed after this. On top of the desk is the Program Managerwindow. It contains a number of windows and icons within it. Programs andapplicationsareplacedintogroups.Thesegroupscontainiconswhichrelatetotheprogram.Theinactivewindowsaredisplayedasgroupicons.Therearefourofthese,asshowninFigure31.2.Awindowismadeactivebydoubleclickingonthegroupicon.Thisexpandsthewindowtoitsnormalform.

FIGURE31.2 Maindesktopscreen

Aprogramwhichhasbeenrunningbutiscurrentlypausedisshownasaniconat the bottom of the screen. In the example screen in Figure 31.3 there are 4activegroups,theseare:Accessories,Main,MsofficeandApplications.WithintheAccessories group there are 12 programs, these are: Write, Paintbrush,Terminal, Notepad, Recorder, Cardfile, Calculator, Clock, Object

Packager,CharacterMapper,MediaPlayerandSoundRecorder.

FIGURE31.3 Abasicgroupwindow

Thecurrentactivewindowhasabluetitlebarswhilstaninactivewindowhasagreytitlebar.Onlyiconswithinanactivewindowcanbeselected.

31.4WindowitemsWindowsaremadeuptofourmainparts,theseare:•Maintitlebar.Everywindowhasanidentificationtitleatthetopofit,as

showninFigure31.3.•Menubar.Somewindowshavemenuoptionstochoosefrom,asshownin

Figure31.4.Hot-keysareoftenunderlined.

FIGURE31.4 Menubaronawindow

•Scrollbar.Whenonlypartofawindowisdisplayedascrollbar(oftencalledathumbnail)willappear.Holdingdownthemousebuttononthesmallsquarewithinthescrollbarmovesthecontentsofthewindow.

•Controlmenubox.AsshowninFigure31.3.

31.5MousecontrolsThemousecontrols thepointeraround the screenand the leftmousebutton isused either to run an application, if it is an icon, or to single click to select awindoworfile,asshowninFigure31.5.

FIGURE31.5 Maindesktopscreen

31.6ProgramManagermenusTheProgramManagerwindowhas4menuoptions:File,Options,WindowsandHelp.Table31.1 shows themainoptions and the sub-options.For example, ifthe File menu options is selected a sub-menu (a pull-down menu) shows theoptions:,New,Open,Move,Copy,Delete,Properties,RunandExitWindows.

Table31.1Menuoptions

31.6.1QuittingWindowsToexitWindows,firsttheFileoptionisselectedfromProgramManager.Next,movethemousepointerdownto theExitWindowsoptionandselect itwithasingleclickoftheleftmousebutton,asshowninFigure31.6.

FIGURE31.6 QuittingWindows

31.6.2GettingHelpThe best method of getting help is to refer to the user manual. If that is notavailable then there ison-linehelp. If theHelpmenuoption is selectedon theProgramManagermenudisplaystheoptionsContents,SearchforHelpon,HowtouseHelp,WindowsTutorialandAboutProgramManager.

31.7MovingandresizingawindowTheoptionsusedtochangethewindowssizeare:•Maximizingawindow.Awindowcanbemadetofillthecompletescreenby

selectingthe atthetopright-handcornerofthescreen.•Minimizingawindow.Awindowcanbeminimizedtoaniconusing•Makingawindowsmaller.Ifawindowisfillingthecompletescreenitcan

bemadeintoasmallerwindowbyselecting•Movingawindow.Awindowcanbemovedbyplacingthemousepointeron

thebluetitlebar.Theleftmousebuttonispresseddownwhilemovingthewindowtoitsrequiredposition,thenthemousebuttonisreleased.

•Resizingawindow.Awindowcanberesizedbyplacingthemousepointereitheratoneofthecornersorthesides.Thepointershapeshouldchangewhenitisplacedovertheborderofthewindows.Toexpand(orcontract)thewindowverticallythemousepointerisplacedeitheratthetopor

bottomborder.Themouseisthenpressedwhilemovingtheborderofthewindows.Whentherequiredpositionisfoundthemousebuttonisreleased.Asimilaroperationcanbeconductedtoexpand(orcontact)horizontally.

31.8ClosingawindowwiththeControlmenuThe Control menu is activated by selecting the top left-hand button on thewindow. This menu contains the options: Restore, Move, Size, Minimize,Maximize,Close,Switchto.TheRestore,Move,Size,MinimizeandMaximizeoptionsmimicoperationsthatareconductedbythemouse.AusefuloptionistheClosewhichexitsfromthewindowandclosesitdown,thisisshowninFigure31.7.

FIGURE31.7 Controlmenu

31.9ExercisesConductthefollowingstepsfillingintherequiredinformation.31.9.1.SwitchPCon.Completedsuccessfully[]31.9.2.StartMicrosoftWindowsandwhenitshowstheinitialstart-upscreen

observetheversionnumberofthesoftware.

31.9.3.IdentifyeachoftheactiveandinactivegroupswithintheProgram

Manager.

31.9.4.Identifyallprogramswithinthreeofthegroups.

31.9.5.ResizetheProgramManagerwindowsothatitfillsthescreen.Tickboxifcompletedsuccessfully.

Completedsuccessfully[]31.9.6.ResizetheProgramManagerwindowsothatitisshownatitsnormal

positiononthescreen.Completedsuccessfully[]

31.9.7.IconizetheProgramManagerwindowandthenrestoreittoitsnormalposition.

Completedsuccessfully[]31.9.8.ExpandtheProgramManagerwindowhorizontally,thenrestoreittoits

normalposition.Completedsuccessfully[]31.9.9.ContracttheProgramManagerwindowsvertically,thenrestoreittoits

normalposition.Completedsuccessfully[]31.9.10.Findthefollowingapplicationprograms,runthemandthenexit.Tick

boxifcompletedsuccessfully.

31.9.11.ExitfromWindowsusingtheFilemenuoptionintheProgramManager.

31.9.12.StartWindowsagainandthistimeexitusingtheControlmenu.Operationsused:

31.9.13.Thereisanon-linehelpfacilitywithinWindows.ToselectthisusetheHelpmenuoptionwithintheProgramManager.Usethisfacilitytofindhelponthefollowingtopics.

quittingwindows:—————————deletinggroups:—————————startingapplications:—————————deletingprograms:—————————

32

FileManagement

32.1Introduction

TheMain groupcontains important applicationprogramswhich allow theuseraccess to the file system, to setup a different environment, to setup differentcomputerhardware,gainaccesstoDOS,etc.ItcontainsControlPanel,PrintManager, File Manager, ClipBook Viewer, MS-DOS Prompt, Windows

Setup,PIFEditorandSysedit.TheiconscontainedwithinMainareshowninFigure32.1.

FIGURE32.1 Maingroup

ControlPanelsetsuptheWindowsenvironmentandcanbeusedtochangethe colours of the windows, the fonts used, etc. The Print Manager programchecksthestatusoffileswhichhavebeenprinted.FileManagerallowsaccesstothe file system and can be used to copy or move files from one directory toanotherorfromonediskdrivetoanother.TheMS-DOSPromptprogramgivesaDOSwindow.

32.2FilemanagerThefilemanagerisidentifiedbythefilingcabineticon.Itisopenedbydouble

clickingthecabineticon.Filesanddirectoriesaredisplayedwiththeirfilenameand an icon which indicates the file type. It employs a select, drag and puttechniquewhereafile(ordirectory),onceselected,canbedraggedintoanotherdirectory or onto any disk drive.Note that the filemanager inWindows 3.11differs slightly from the filemanager inWindows 3.1. Figure 32.2 shows theWindows3,11filemanager.Themaindifferenceistheiconstotherightofthecurrentdiskdrivename.

FIGURE32.2 Filemanager

A directory is identified with the icon. Files have three main iconsassociatedwiththem.Applicationprogramsareidentifiedwitha adocumentfile by and any other filewith a . Figure 32.3 shows a sample directorylisting.

FIGURE32.3 Filemanager

Adocumentfile isa filewhichwhendoubleclickedwillstartanassociatedapplication.Table 32.1 shows some typical file extensions and the applicationwhich is run when the file is double clicked. For example, a file with a docextensionwill run awordprocessor, abmpextensionwill start thepaintbrushpackage,andsoon.

Table32.1Fileassociatedwithapplication

Fileextension Description Applicationstarted

wav Soundfile Soundpackage

txt Textfile Notepad

doc Document Wordprocessor

wk3 Lotus123worksheet Lotus123

wri Writedocument Write

hlp Helpfile Windowshelp

pcx Graphicsfile Paintbrush

xls MicrosoftExcellworksheet MicrosoftExcell

ppt MicrosoftPowerpointpresentation MicrosoftPowerpoint

bmp Bit-mappedgraphicsfile Paintbrush

32.2.1SelectingADriveAdiskdrive is selectedwitha singleclickononeof thedisk iconsabove thedirectorylistingorbyselectingDisk→Selectdrive….IntheexampleinFigure32.4therearethreedrives,afloppydiskontheA:drive,ahard-diskontheC:driveandaCD-ROMontheD:drive.Ifthereareanynetworkdrivesthesewillalsobedisplayed.

FIGURE32.4 Displayingdirectory

32.2.2SelectingADirectoryAdirectoryisselectedbyasingleclickonthedirectoryicon(oronthedirectoryname).Theopen file icon ( ) then showswhichdirectory is currentlyopen;thedirectorydisplaywindowdisplaysthecontentsofthisdirectory.Anexampleof changing the currentdirectory is shown inFigure32.5. In this example theuserhas selected to list thecontentsof the top-leveldirectoryon theC:drive.Next themousepointer isplacedover thedocsdirectorywhichis thenopenedwith a single click of the leftmouse button.After this the admin directory isopened.Adirectorycanbeclosedbysinglemousebuttonclickwhenitisopen

(anotherclickwillopenitagain).

FIGURE32.5 Selectingdiskformatoption

32.2.3FormattingADiskAfloppydiskmustbe formattedbefore it can store files.Somedisks arepre-formattedwhen theyarepurchased,butothers required tobe formattedbeforetheyareused.Caremustbetakenwhenformattingadiskasthecurrentcontentsofthediskwillbeerased.To format a disk first insert it into the floppy disk drive. Next select

Disk→Format disk … from themenu, as shown in Figure 32.5.When this isselectedWindowswill prompt the user for the drivewhich the disk has beenenteredandthecapacityofthedisk.BydefaultthisislikelytobesettoA:and1.44MB(fora3.5 inchfloppydiskdriveontheA:drive),respectively.If thedrive differs from the default or its format differs then change the options bypullingdowntheDiskInortheCapacityoptions.Figure32.6shows themainsteps thatare taken to format thedisk.First the

diskcapacityanddrivenamearepromptedfor.WhenthesearecorrecttheOKbutton is selected. Next a Format Disk window is displayed. Within thiswindowthecurrentstatusofthediskformattingoperationisdisplayed(from0to100%complete).Whencomplete,awindowwithamessageCreatingrootdirectory will be displayed. After this the formatted disks’ capacity isdisplayedandtheuserispromptedastowhetheranotherdiskistobeformatted.Ifnomoredisks are tobe formatted then theNo option is selectedelseYes isselected.NotethattheCanceloptiononanyoftheformatstatuswindowscanbeselectedtocanceltheformatprocess.

FIGURE32.6 Formattingafloppydisk

32.2.4MovingFilesOnTheSameDiskDriveMicrosoftWindows uses a select, drag and drop procedure when copying ormovingfilesordirectories.Movingfiles(copyingthembutdeletingtheoriginalfile) can be achieved by moving the mouse pointer over the file and thendraggingtheicon,whilekeepingtheleftmousebuttonhelddown,thenplacingit in thedesireddirectory.Figure32.7 showsan exampleof the file acc2.wk1beingdraggedintothedirectoryC:\DOCS\BUSINESS.

FIGURE32.7 Copyingormovingafileonthesamediskdrive

32.2.5CopyingFilesOnTheSameDiskDriveCopying files toanew location is achievedbyholdingdown theCtrlkeyanddraggingthefiletothedesireddirectory,seeFigure32.8.

FIGURE32.8 Deleteconfirmation

32.2.6CopyingFilesToADifferentDiskDriveCopying filesordirectories toadiskdrive isachievedbysimplydragging thefile or directory icon to the drive icon. This is similar tomoving files on the

same disk drive but in this case the file will not be deleted on the sourcedirectory.

32.2.7MovingFilesToADifferentDiskDriveMovingfilesordirectoriestoanotherdiskdriveisachievedbysimplydraggingthe file or directory icon, while pressing the Shift key, and dragged it to therequireddriveicon.

32.2.8DeletingFilesWhenafileisnolongerrequireditcanbedeleted.Thisisachievedbyclickingonthefile tobedeletedandpressingtheDelkeyonthekeyboard.Amessageaskingforconfirmationshouldappear,asshowninFigure32.8.IfthefileistobedeletedthentheOKbuttonisselectedelseCancel.Theconfirmationwindowfordeletingadirectory isdifferent,anexample is shown inFigure32.9.AftertheuserselectsthedirectorytodeleteaconfirmationisdisplayedwitheitherYesorYes toAll.IftheuserselectsYes theneachfilewithinthedirectorywillbepromptedfordeletionconfirmation.IfYestoAllisselectedthenallfileswithinthedirectory(andsub-directories)willbedeletedwithoutanyconfirmation.

FIGURE32.9 Deletedirectoryconfirmation

32.2.9RunningWindowsAndDOSApplicationsRunningafileisachievedbyplacingthemousepointerovertheapplicationfileand double clicking the left mouse button. If it is a Microsoft Windowsapplication it will be run as a normalWindows application, else if it has anapplication attached to it then the associated application will be run and theselectedfileloadedintoit.Forexample,ifitwereadocumentfile(.DOC)thena

wordprocessorwillbestartedwiththeselecteddocumentloadingintoit.IfaDOS-basedapplicationisselectedthenaDOSscreenwillappearwhich

willthenloadtheprogram(ifitcan).

32.3ExercisesConductthefollowingstepsfillingintherequiredinformation.32.3.1.StartMicrosoftWindows.Completedsuccessfully[]32.3.2.Identifysomeofthedirectoriesandsub-directoriesontheC:driveonthe

PCandcompletethetablegiveninFigure32.10.

FIGURE32.10 DirectorystructureofC:drive

32.3.3.Identifysomeapplicationprogramswithinthe\dosdirectory.Applicationprograms:________________________________________

32.3.4.Identifysomeapplicationprogramswithinthe\windowsdirectory.Applicationprograms:________________________________________32.3.5.Identifysomefileswhichareinthe\WINDOWSdirectorywhichwillrun

applicationprogramsFiles:________________________________________32.3.6.OntheC:drivefind5graphicsfiles(inanydirectory).Files:Files:________________________________________32.3.7.OntheC:drivefind5documentfiles(inanydirectory).Files:Files:________________________________________32.3.8.InsertafloppydiskintheA:driveandformatit.Totaldiskspace:________________________________________32.3.9.CreateadocumentfileeitherbyrunningCardfile(withintheMain

group)orrunningWrite(withinAccessories)orusingawordprocessorsuchasWordforWindowsorAmi-Pro.EntersometextintothedocumentthensaveitintheC:\windowsdirectorywiththenameDOC1.DOC.

Completedsuccessfully[]32.3.10.Verify,withFileManager,thatthisfileisinthe\windowsdirectory.Completedsuccessfully[]32.3.11.CopythefileDOC1.DOCtothefloppydiskintheA:drive.Completedsuccessfully[]32.3.12.Verify,withFileManager,thatthefilehasbeencopiedtotheA:drive.

Ifitisinthewrongplacemoveit.Completedsuccessfully[]32.3.13.CreateadirectoryontheC:drive,namedtemp,belowthetop-level

directoryusingtheFile→CreateDirectorymenuoption.Completedsuccessfully[]32.3.14.Verify,withFileManager,thatthisdirectoryexists.Ifitisinthewrong

placemoveit.Completedsuccessfully[]32.3.15.CopythefileDOC1.DOCtothetempdirectory.Completedsuccessfully[]

32.3.16.Verify,withFileManager,thatthefileisinthetempdirectory.Completedsuccessfully[]32.3.17.Thereisanon-linehelpfacilityforthehelpmanagerwithinWindows.

ToselectthisusetheHelpmenuoptionwithintheFileManager.Usethisfacilitytofindhelponthefollowingtopics.

selectingfiles:———————–sortingfiles:———————–copyingdisks:———————–startingapplications:———————–

PARTHWindows95/NT

33

Windows95/NT

33.1Introduction

Windows NT has provided an excellent network operating system. Itcommunicates directly with many different types of networks, protocols andcomputerarchitectures.WindowsNTandWindows95havethegreatadvantageof other operating systems in that they have integrated network support.Operatingsystemsnowusenetworkstomakepeer-to-peerconnectionsandalsoconnections to servers for access to file systems and print servers. The threemost widely used operating systems are MS-DOS, Microsoft Windows andUNIX. Microsoft Windows comes in many flavours; the main versions areoutlinedbelowandTable33.1listssomeoftheirattributes.

Table33.1Windowscomparisons

•MicrosoftWindows3.xx–16-bitPC-basedoperatingsystemwithlimitedmultitasking.ItrunsfromMS-DOSandthusstillusesMS-DOSfunctionalityandfilesystemstructure.

•MicrosoftWindows95–robust32-bitmultitaskingoperatingsystem

(althoughtherearesome16-bitpartsinit)whichcanrunMS-DOSapplications,MicrosoftWindows3.xxapplicationsand32-bitapplications.

•MicrosoftWindowsNT–robust32-bitmultitaskingoperatingsystemwithintegratednetworking.NetworksarebuiltwithNTserversandclients.AswithMicrosoftWindows95itcanrunMS-DOS,MicrosoftWindows3.xapplicationsand32-bitapplications.

33.2Servers,workstationsandclientsMicrosoftWindowsNTisa32-bit,pre-emptive,multitaskingoperatingsystem.One of the major advantages it has over UNIX is that it can run PC-basedsoftware.AWindowsNTnetworknormallyconsistsofaserverandanumberofclients.Theserverprovidesfileandprintserversaswellaspowerfulnetworkingapplications, such as electronic mail applications, access to local and remoteperipherals,andsoon.TheWindowsNTclientcaneither:•Operateasastand-aloneoperatingsystem.•Connectwithapeer-to-peerconnection.•ConnecttoaWindowsNTserver.Apeer-to-peerconnectioniswhenonecomputerlogsintoanothercomputer.

Windows NT provides unlimited outbound peer-to-peer connections andtypicallyupto10simultaneousinboundconnections.

33.3WorkgroupsanddomainsWindowsNTassignsuserstoworkgroupswhicharecollectionsofuserswhoaregrouped together with a common purpose. This purpose might be to shareresources such as file systems or printers, and each workgroup has its ownuniquename.WithworkgroupseachWindowsNTworkstationinteractswithacommon group of computers on a peer-to-peer level. Each workstation thenmanagesitsownresourcesanduseraccounts.Workgroupsareusefulforsmallgroups where a small number of users require to access resources on othercomputers.A domain in Windows NT is a logical collection of computers sharing a

common user accounts database and security policy. Thus each domain musthaveatleastoneWindowsNTserver.

Windows NT is designed to operate with either workgroups or domains.Figure33.1illustratesthedifferencebetweendomainsandworkgroups.

FIGURE33.1 Workgroupsanddomains

Domainshavetheadvantagesthat:•Eachdomainformsasingleadministrativeunitwithsharedsecurityanduser

accountinformation.Thisdomainhasonedatabasecontaininguserandgroupinformationandsecuritypolicysettings.

•Theysegmenttheresourcesofthenetworksothatusers,bydefault,canviewallnetworksforaparticulardomain.

Useraccountsareautomaticallyvalidatedbythedomaincontroller.Thisstopsinvalidusersfromgainingaccesstonetworkresources.

33.4WindowsNTuserandgroupaccountsEachuserwithin a domainhas a user account and is assigned to oneormoregroups.Eachgroupisgrantedpermissionsforthefilesystem,accessingprinters,andsoon.Groupaccountsareusefulbecausetheysimplifyanorganizationintoa single administrative unit. They also provide a convenient method ofcontrollingaccessforseveraluserswhowillbeusingWindowsNTtoperformsimilartasks.Byplacingmultipleusersinagroup,theadministratorcanassignrightsand/orpermissionstothegroup.

EachuseronaWindowsNTsystemhasthefollowing:•Ausername(suchasfred_bloggs).•Apassword(assignedbytheadministratorthenchangedbytheuser).•Thegroupsinwhichtheuseraccountisamember(suchas,staff).•Anyuserrightsforusingtheassignedcomputer.Each time a user attempts to perform a particular action on a computer,

Windows NT checks the user account to determine whether the user has theauthoritytoperformthataction(suchasreadthefile,writetothefile,deletethefile,andsoon).Normallytherearethreemaindefaultuseraccounts:Administrator,Guestand

an‘InitialUser’account.ThesystemmanagerusestheAdministratoraccounttoperformsuchtasksasinstallingsoftware,adding/deletinguseraccounts,settingupnetworkperipherals,installinghardware,andsoon.Guestaccountsallowoccasionaluserstologonandbegrantedlimitedrights

onthelocalcomputer.Thesystemmanagermustbesurethat theaccessrightsarelimitedsothathackersorinexperienceduserscannotdodamagetothelocalsystem.The ‘InitialUser’ account is createdduring installationof theWindowsNT

workstation.Thisaccount,assignedanameduring installation, isamemberoftheAdministrator’s group and therefore has all theAdministrator’s rights andprivileges.After the systemhas been installed theAdministrator can allocate newuser

accounts,eitherbycreatingnewuseraccounts,orbycopyingexistingaccounts.

33.5FilesystemsWindowsNTsupportsthreedifferenttypesoffilesystem:•FAT(fileallocationtable)–asusedbyMS-DOS,OS/2andWindowsNT/95.

Asinglevolumecanbeupto2GB.•HPFS(highperformancefilesystem)–aUNIX-stylefilesystemwhichis

usedbyOS/2andWindowsNT.Asinglevolumecanbeupto8GB.MS-DOSapplicationscannotaccessfiles.

•NTFS(NTfilesystem)–asusedbyWindowsNT.Asinglevolumecanbeupto8GB.MS-DOSapplications,themselves,cannotaccessthefilesystembuttheycanwhenrunwithWindowsNT.

TheFATfilesystemiswidelyusedandsupportedbyavarietyofoperatingsystems, suchasMS-DOS,WindowsNTandOS/2. If a system is touseMS-

DOSitmustbeinstalledwithaFATfilesystem.

33.5.1FATThe standardMS-DOS FAT file and directory-naming structure allows an 8-character file name and a 3-character file extension with a dot separator (.)betweenthem(the8.3filename).Itisnotcasesensitiveandthefilenameandextensioncannotcontainspacesandotherreservedcharacters,suchas:

WithWindowsNTandWindows95 theFATfile systemsupports long filenameswhichcanbeup to255characters.Thenamecanalsocontainmultiplespacesanddotseparators.Filenamesarenotcasesensitive,butthecaseoffilenames is preserved (a file named FredDocument.XYz will be displayed asFredDocument.XYz but canbe accessedwith anyof the characters in upper orlowercase).Each file in the FAT table has four attributes (or properties): read-only,

archive,systemandhidden(asshowninFigure33.2).TheFATusesalinkedlistwhere thefile’sdirectoryentrycontains itsbeginningFATentrynumber.ThisFATentryinturncontainsthelocationofthenextclusterifthefileislargerthanonecluster,oramarkerthatdesignatesthisisincludedinthelastcluster.Afilewhichoccupies12clusterswillhave11FATentriesand10FATlinks.

FIGURE33.2 Fileattributes

ThemaindisadvantagewithFATisthatthediskissegmentedintoallocatedunits (orclusters).On large-capacitydisks thesesectorscanbe relatively large(typically512bytes/sector).Diskswithacapacityofbetween256MBand512MBuse16 sectorsper cluster (8KB)anddisks from512MB to1GBuse32sectors per cluster (16KB).Drives up to 2GBuse 64 sectors per cluster (32KB).Thusifthediskhasacapacityof512MBtheneachclusterwillbe8KB.Afilewhichisonly1KBwillthustakeup8KBofdiskspace(awastageof7KB),anda9KBfilewilltakeup16KB(awastageof7KB).Thusafilesystemwhich has many small files will be inefficient on a cluster-based system. Afloppydisknormallyuse1clusterpersector(512bytes).Windows 95 andWindowsNT support up to 255 characters in file names;

unfortunately,MS-DOS andWindows 3.xx applications cannot read them. Toaccommodatethis,everylongfilenamehasanautogeneratedshortfilename(inthe form XXXXXXXX.YYY). Table 33.2 shows three examples. Theconversiontakesthefirstsixcharactersofthelongnamethenaddsa~numbertothenametogiveitauniquename.Filenameswiththesameinitialsixcharactersareidentifiedwithdifferentnumbers.Forexample,ProgramFilesandProgramDirectory would be stored as PROGRA~1 and PROGRA~2, respectively. Samplelisting33.1showsalistingfromWindowsNT.Theleft-handcolumnshowstheshortfilenameandthefarright-handcolumnshowsthelongfilename.

Table33.2

Filenameconversions

Longfilename Shortfilename

ProgramFiles PROGRA∼1

Triangular.bmp TRAING∼1.BMP

Fredte∼1.1 FRED.TEXT.1

33.6RunningWindows95andNTWindows95andNTareoperating systems in theirown right and thusdonotrequireDOS.TheversionofDOSwhichisruninWindow95/NTisanemulatedversion.SometimesWindowsNT/95developsaproblemwhenstartingthecomputer.

Ifthisoccursthenitcanbestartedinasafemode,whichdoesnotloadnetworksupport and using the default settings (VGA monitor, no network, Microsoftmousedriver,andtheminimumdevicedriversrequiredtostartWindows).ThisisachievedbypressingtheF8keywhenWindowsisbeingbooted.Normallytheuser then selects Settings and then Control Panel to change the systemssettings.Oftentheproblemwiththesystemstart-upistodowitheitherAUTOEXEC.BAT

or CONFIG.SYS files. If this is the case the Command Prompt Only operationsettingcanbeselectedwhenstartingthecomputer.Thisoptionbypassesthetwosystemfiles.Otherwise,theStep-by-StepConfirmationcanbeselected,whichallowstheusertoloadaspecificsystemdriver.Anothermethod of fixing the system is to boot the systemwith a bootable

DOSdisk.Theuser can then try to fix the system.Note that this canonly bedoneifthediskhasbeenformattedasFAT.

33.7BasicWindowsNT/95There are many enhancements on Windows NT/95 as opposed to previousversions.Themaindifferencesare:

• Startbuttonandtaskbar.ThetaskbarappearsatthebottomofthescreenanditcontainstheStartbutton,whichcanbeusedtoquicklystartaprogram.Thetaskbaralsoshowstheprogramswhicharecurrentlyrunninganditcanthusbeusedtoswitchbetweenprograms.

• Folders.Documentsandprogramsarestoredinfolders.InDOSandpreviousversionsofWindowsthesefolderswerecalleddirectories.

•Thedesktop.ThedesktopistheareaofscreenwhichappearswhenWindowsisstarted.Figure33.3showsanexample.Itcanbecustomizedbyaddingprogramshortcuts,documents,printers,andthelayoutandstyleofthebackground.Toadjustsettingssuchasdesktopcolourandbackground,useyourrightmousebuttontoclickanywhereonthedesktop,andthenclickProperties.Figure33.4showsanexampleofthePropertieswindow.

FIGURE33.3 Exampledesktopscreen

FIGURE33.4 Exampledesktopscreen

• NetworkNeighborhood.Windows95/NThasextensivesupportfornetworking.IfanetworkispresentthentheNetworkNeighborhoodiconappearsonyourdesktop.Theusercanthenbrowsetheentirenetworkbydouble-clickingtheicon.

• MyComputer.TheMyComputericonallowsquickandeasyaccesstothecomputer.Theusercanbrowsethroughthefilesandfoldersbydouble-clickingtheMyComputericon.

• WindowsExplorer.Thisisaprogramthatallowstheusertoviewboththehierarchyoffoldersonyourcomputerandallthefilesandfoldersineachselectedfolder.Itistypicallyusedtocopyandmovefiles,wherefilescanbedraggedintoaspecificfolder.

•Properties.EachiconwhichappearsinWindows95/NThasassociatedproperties.Itviewsthepropertiesthentherightmousebuttonclicksontheitem,andthenclicksPropertiesfromthepop-upmenu.

•Shortcutmenus.Ashortcutmenuisdisplayedwhentheuserclickstheright

mousebuttononanitem.Thismenuallowstheusertoopen,copyordeletetheitem.

•Close,Minimize,andMaximizebuttons.Eachwindowhasaclosebuttonintheupper-rightcornerwhich,whenclicked,willclosethewindow

andquittheprogram.Thewindowscanalsominimizeormaximize .Thecurrentactivewindowhasabluetitlebarwhilstaninactivewindowhasa

greytitlebar.Onlyiconswithinanactivewindowcanbeselected.

33.8MousecontrolsThemousecontrolsthepointeraroundthescreen.AswithpreviousversionsofWindows,adoubleclickoftheleftmousebuttononaniconisusedtoeitherrunanapplicationandasingleclicktoselectawindoworfile.

33.9QuittingWindowsThe usermust shutWindows down before switching off the computer. To dothistheuserselectstheShutDown…optionfromtheStartbar.Thentheuserwillbegivenanumberofoptions,asshowninFigure33.5.Iftheuseristoquitand switchoff then theShutdown the computeroption is selected andYes isselected.

FIGURE33.5 QuittingWindows

33.9.1GettingHelpThe best method of getting help is to refer to the user manual. If that is notavailablethenthereison-linehelp.Theon-linemanualisavailablebyselectingthehelpmanualicon.

33.10MovingandresizingawindowTheoptionusedtochangethewindowssizeare:•Maximizingawindow.Awindowcanbemadetofillthecompletescreenby

selectingthe atthetopright-handcornerofthescreen.•Minimizingawindow.Awindowcanbeminimizedtoaniconusing•Makingawindowsmaller.Ifawindowisfillingthecompletescreenitcan

bemadeintoasmallerwindowbyselecting•Movingawindow.Awindowcanbemovedbyplacingthemousepointeron

thebluetitlebar.Theleftmousebuttondownispressedwhilemovingthewindowtoitsrequiredposition,thenthemousebuttonisreleased.

•Resizingawindow.Awindowcanberesizedbyplacingthemousepointereitheratoneofthecornersorthesides.Thepointershapeshouldchangewhenitisplacedovertheborderofthewindows.Toexpand(orcontract)thewindowverticallythemousepointerisplacedeitheratthetoporbottomborder.Themouseisthenpressedwhilemovingtheborderofthewindows.Whentherequiredpositionisfoundthemousebuttonisreleased.Asimilaroperationcanbeconductedtoexpand(orcontract)horizontally.

33.11ClosingawindowwiththeControlmenuTheControlmenuisactivatedbyselectthetopleft-handbuttononthewindow.Thismenucontainstheoptions:Restore,Move,Size,Minimize,MaximizeandClose. The Restore, Move, Size, Minimize and Maximize options mimicoperationsthatareconductedbythemouse.AusefuloptionistheClosewhichexitsfromthewindowandclosesitdown;thisisshowninFigure33.6.

FIGURE33.6 Controlmenu

33.12StartTheStartbuttonat thebottomleft-handside isusedtoquicklyrunapplicationprograms.AnexampleStartbarisshowninFigure33.7.

FIGURE33.7 Examplestartoptions

33.13MyComputerTheMyComputerwindowallowsaccesstolocaldisks,suchasthefloppydiskand hard disks, printers,CD-ROM, and so on. Figure 33.8 shows an examplewindow.

FIGURE33.8 ExampleMyComputer

33.14RunningDOSWindowsNT/95runsanemulatedversionofDOS.ThisistypicallyusedtorunDOS-basedprogramandalsotorunDOScommands.Figure33.9showshowaDOSwindow is initiated. It can either run in awindow or full-screen. Figure33.10showsasampleDOSwindow.

FIGURE33.9 SelectingMS-DOSPrompt

FIGURE33.10 DOSwindow

33.15Windows95/NTnetworkdrivesWindowsNTand95displays thecurrentlymountednetworkdriveswithin thegroupMyComputer. Figure 33.11 shows driveswhich are either local (C:D:andE:)ormountedusingNetWare(F:G:andsoon).WindowsNTand95alsoautomatically scan the neigbouring networks to find network servers. Anexample is shown in Figures 1.12 and 1.13. Figure 33.13 shows the currentlymountedservers(suchas,EECE_l)andbyselectingtheGlobalNetworkiconalltheotherconnectedlocalserverscanbeshown.

FIGURE33.11 Mountednetworkandlocaldrives

FIGURE33.13 Localneighbourhoodservers

FIGURE33.12 Networkneighbourhood

33.16ExercisesConductthefollowingstepsfillingintherequiredinformation.33.16.1.Windowsversion.Windows95[]WindowsNT[]Other[]33.16.2.Networkedcomputer.Yes[]No[]33.16.3.Identifyeachoftheiconsonthedesktop:33.16.4.SelectMyComputerandresizeitsothatitfillsthescreen.Ticboxif

completesuccessfully.Completedsuccessfully[]

33.16.5.ResizeMyComputersothatitisshownatitsnormalpositiononthescreen.

Completedsuccessfully[]33.16.6.IconizeMyComputerandthenrestoreittoitsnormalposition.Completedsuccessfully[]33.16.7.ExpandMyComputerhorizontally,thenrestoreittoitsnormal

position.Completedsuccessfully[]33.16.8.ContractMyComputerwindowvertically,thenrestoreittoitsnormal

position.Completedsuccessfully[]33.16.9.Findthefollowingapplicationprograms,runthemandthenexit.Tic

boxifcompletesuccessfully.

33.16.10.OpenaDOSwindowandmovearoundthefilesystem.Listsomeofthedirectoriesonthesystem:

33.16.11.ExitfromWindows.Completedsuccessfully[]33.16.12.StartWindowsagain.Completedsuccessfully[]33.16.13.Thereisanon-linehelpfacilitywithinWindows.Toselectthis,use

theHelpmenuoptionwithintheProgramManager.Usethisfacilitytofindhelponthefollowingtopics.

Quittingwindows:_____________________

Deletingfolders:_____________________Startingapplications:______________________Deletingprograms:______________________

34

ExtraWindows

34.1Savingimportantset-upfiles

Windows 3.x and Windows 95/NT store important program configurationinformationinINIfile.Thesearenormallyeitherstoredinthedefaultwindowsdirectory or in the home directory of the application. The important files forWindowsconfigurationare:•SYSTEM.INI.Thiscontainsinformationontheconfigurationofvarious

programsandalsoprogramswhichareinitiatedwhenWindowsisstarted.

•WIN.INI.Thiscontainsinformationofthedesktop,suchasthegroupswhicharedisplayed,theirpositiononthedesktopandtheirsize.

Itisimportanttobackuptheinitializationfilesasthesecanbeeasilymodifiedby mistake. Initialization files have a INI extension and are stored in the\WINDOWS directory.Tomake a backupof these files create a directorynamedINIasasubdirectoryofthe\WINDOWSdirectorycancopytheseINIfilesintoit.Ifoneofthesefilesismodifiedbymistakeit isasimpletasktocopyanolderversionback into the\WINDOWSdirectory.Thisprocedure is shown inTest run34.1.

34.2RunningaprogramwhenWindowsstartsupProgramscanbeinitiatedwhenWindowsisstarted.Typicalprogramswhichcanbeloadedaretheclock,awordprocessor,aspreadsheetoracalendar.Thiscanbe achieved by selecting the following folder: Selecting Windows→StartMenu→Programs→StartUpThenthestartupitemisaddedbyeitherdraggingitintotheStartUpfolderor

byselectingFile→New.

FIGURE34.1 AddingtotheStartUpfolder

InWindows3.1itisselectedby:•TheapplicationiconcanbeinsertedintotheStartUpgroupsothatitwill

automaticallystartwhenwindowsisstarted.TocreateanewStartUpgroup,selectFile>NewfromProgramManager,asillustratedinFigure34.2.NextselectagroupandnameitStartUp.Iconscanthenbedraggedfromanothergroupintothisone.

FIGURE34.2 CreatingaStartUpgroup

Oncethestartupgrouphasbeeninitiatedanemptywindowshouldbedisplayed.Tomoveaprogrampointtoitwiththecursorthenholdthe

firstmousekeydownanddragitintotheStartUpgroup.Iftheprogramistobecopied(andnotmoved)thenholddowntheCtrlkeyastheiconisdragged.Figure34.2showsaStartUpwindowswiththeCalendarandClock.

AprogramcanalsobeautomaticallystartedbyeditingtheWIN.INIfilesothattheprogramname is insertedafter therun=directive.Forexample, to run theclockandWordforWindowsthefollowingcanbeinserted:

Toloadaprogramwhichisminimized(thatis,itwillappearasaniconatthebottom of the screen) the load= directive is used. For example, to start theprogramsWord forWindows 6.0 andcardfile the following can be insertedintotheWIN.INIfile

34.3CapturingWindowsscreenTherearetwohotkeysset-upinWindowstocapturescreens:•PrintScreenkeycapturesacompletescreen.•Alt-PrintScreencapturesonlythecurrentwindow.These captured screens are put into the clipboard. Figure 34.3 shows the

ClipboardViewerscreenafterascreenhasbeencapturedfromMicrosoftWordforWindows2.0.Thecontentsoftheclipboardcanbeimportedintoadocumentorother applicationbypasting.This can eitherbedoneby selecting thePastefromamenuorCtrl-V.

FIGURE34.3 ContentsofClipboardViewerafterascreenhasbeencaptured

34.4SwappingbetweenapplicationsThe Alt-TAB hot key can be used to switch between one application andanother.Forexample:

1.Runanapplication.2.PressAlt-TABtocyclethroughtheWindowsapplicationsonthedesktop.

Thenameoftheapplicationappearsatthetopofthescreen.Figure34.4 showsanexampleof swappingbetweenaWindows screenand

anotherapplication.

FIGURE34.4 Swappingbetweenapplications

34.5TerminatingprogramswhichhavecrashedIf a programhas crashed it cannormally be terminatedusing theCtrl-Alt-Delkeystrokes.IfWindowsisstillrunningitwilldisplayabluescreenwhichasksthe user to either press <RETURN> if the program is to be terminated to useCtrl-Alt-Deltorebootthesystem.Normallyit isonlyrequiredtoterminatethecrashedprogramsopress<RETURN>.

34.6WindowsfileextensionsWindowsusesalargenumberoffiletypes.Table34.1givesthebasicfiletypeextensions.

Table34.1Fileextensions

34.7Exercises34.7.1.StartthecalculatorprogramandthenpressCtrl-Alt-Del.Confirmthata

similarscreentotheoneshowninFigure34.5.Nextshutdowntheprogram.

FIGURE34.5 Closinganapplication

Completedsuccessfully[]34.7.2.IdentifysomeINIfilesandtheapplicationprogramthattheyarelikelyto

belinkedto.Completedsuccessfully[]34.7.3.ListsomeoftheWIN.INIandSYSTEM.INIfiles.Identifysomeofthe

linesinthesefiles.Completedsuccessfully[]34.7.4.RuntheCalculatorandNotepadprograms(fromtheAccessoriesgroup)

andusetheAlt-TABkeystroketoswapbetweentheseapplications.Completedsuccessfully[]

34.7.5.WiththeCalculatorprogram,determinethefollowing:(i)54×32

(ii)1043254(iii)√l63Completedsuccessfully[]

34.7.6.WiththeNotepadprogram,createafilecalledMYFILE.TXTandaddthefollowingtext:

Completedsuccessfully[]34.7.7.QuittheCalculatorandNotepadprograms.Completedsuccessfully[]34.7.8.LocatetheMYFILE.TXTfileandopenittoseethatitcontainsthe

enteredtext.Completedsuccessfully[]34.7.9.ClosetheNotepadprogram.Completedsuccessfully[]34.7.10.Fromtheoperatingsystem,changethenameofMYFILE.TXTto

MYFILE2.TXT.Completedsuccessfully[]34.7.11.Fromtheoperatingsystem,copytheMYFILE2.TXTfileinto

MYFILE3.TXTfile.Completedsuccessfully[]34.7.12.FormatafloppydiskandcopytheMYFILE2.TXTfileontoit.Completedsuccessfully[]

PART IUNIX

35

IntroductiontoUNIX

35.1Introduction

UNIX is an extremely popular operating system and dominates in the high-powered,multitaskingworkstationmarket. It is relatively simple touseand toadminister,andalsohasahighdegreeofsecurity.UNIXcomputersuseTCP/IPcommunications to mount disk resources from one machine onto another. Itsmaincharacteristicsare:•Multi-user.•Pre-emptivemultitasking.•Multi-processing.•Multi-threadedapplications.•Memorymanagementwithpaging(organizingprogramssothattheprogram

isloadedintopagesofmemory)andswapping(whichinvolvesswappingthecontentsofmemorytodiskstorage).

The two main families of UNIX are UNIX System V and BSD (BerkeleySoftwareDistribution)Version4.4.SystemVistheoperatingsystemmostoftenusedandhasdescendedfromasystemdevelopedbytheBellLaboratoriesandwasrecentlysoldtoSCO(SantaCruzOperation).PopularUNIXsystemsare:•AIX(onIBMworkstationsandmainframes).•HP-UX(onHPworkstations).•Linux(onPC-basedsystems).•OSF/1(onDECworkstations).•Solaris(onSunworkstations).Aninitiativebyseveralsoftwarevendorshasresultedinacommonstandard

fortheuserinterfaceandtheoperationofUNIX.Theuserinterfacestandardisdefined by the common desktop environment (CDE). This allows softwarevendors to write calls to a standard CDEAPI (application specific interface).ThecommonUNIXstandardhasbeendefinedasSpec1170APIs.Compliancewith the CDE and Spec 1170 API is certified by X/Open, which is a UNIX

standardorganization.

35.2LoginintothesystemInorder toconnect to thesystemavaliduser IDandapasswordare required.Theseareassignedinitiallybythesystemmanager.InSamplesession35.1theuserbill_b logsinwiththecorrectpassword.IftheuserIDandpasswordarevalid then system messages are then displayed in a start-up screen (such assystem shut-downs, holiday arrangements, and so on) and the command lineprompt is displayed (in this case[51:miranda:/net/castor_win/local_user/bill_b]%). The computer is nowreadyforacommand.

35.3DirectorystructureFilesareusedtostorepermanentinformationwhichareusedbyprograms.Theinformation could be schematics, text files, documents, and so on. In order tofacilitatetherecoveryoffilestheyarearrangedintodirectoriesinastructurethatissimilartoanofficefilingsystem.TheUNIXfiledirectorystructuretakestheformofatreewiththerootdirectoryatthehighestlevel.Thistoplevel,orrootdirectory, is given the name /.An example of a directory system is shown inFigure35.1. In this case thereare5 sub-directoriesbelow the root level, these

are bin, usr, etc, dev and user. Below the usr directory there are 3 sub-directories, theseare lib, admandbin. In thiscase,all theusersof the systemhave been assigned to a sub-directory below the users directory, that is,bill_b,fred_aandalan_g.

FIGURE35.1 Basicdirectorystructure

The full pathname of the bill_b directory is /users/bill_b and the fullpathname of the adm directory is usradmin. Files can be stored within adirectorystructure.Figure35.2showsanexamplestructure.

FIGURE35.2 Basicdirectorystructureshowingfileswithindirectories

Inthiscase,thefullpathnameoftheFORTRANfileprog.ftnis:

andthefullpathnameofthecdirectoryis:

Files and sub-directories canalsobe referred to ina relativemanner,wherethedirectoryisnotreferencetothetop-level(itthusdoesnothaveapreceding/).Forexample,iftheuserwasinthebill_bdirectorythentherelativepathfortheCprogramfile1.cis:

35.4On-linemanualUnix provides an on-line manual to give information on all the UNIX

commands.Togetinformationmancommand-nameisused,suchas:

Examples are man 1s, man cd, and so on. Sample session 35.2 shows anexampleofthehelpmanualforthe1scommand.

35.5ChangingdirectoryThepwdcommandcanbeusedtodeterminethepresentworkingdirectory.andthe cd command can be used to change the current working directory.Whenchangingdirectoryeitherthefullpathnameortherelativepathnameisgiven.Ifa/precedesthedirectorynamethenitisafullpathname,elseitisarelativepath.Somespecialcharactersequencesareusedtorepresentotherdirectory,suchasthedirectoryabovethecurrentdirectoryisspecifiedbyadoubledot(..).Thustomovetothedirectoryabovethecommandcd..canbeused.Ifthecd

command is usedwithout any preceding directory specifier then the directorywillbechangedtotheuser’shomedirectory.Someexamplecommandsessionsaregivennext.

35.6ListingdirectoriesThelscommandliststhecontentsofadirectory.Ifnodirectory-nameisgiventhen it lists thecontentsof thecurrentdirectory.Sample session35.3 showsatypicalsession.In[5]theusermovestothedirectoryaboveandin[11]theusermovebacktothehomedirectory.

Thebasicdirectorylistinggivesnoinformationaboutthesizeoffiles,ifitisadirectory,andsoon.Tolistmoreinformationthe–1optionisused.Anexamplesession is shown in Sample session 35.5. In [15] the user requests extendedinformationonthefiles.

Otheroptionscanbeusedwithls;togetafulllistusetheon-linemanual.InSamplesession35.1itwasseenthatotherpossibleextensionsareabcdfgilmnopqrstuxACFHLR1.Examplesofusageare:

Itisalsopossibletospecifymorethanoneextension,suchas1s–drwhichlistsonlydirectoriesinreverseorder.

35.7FileattributesUNIXprovidessystemsecuritybyassigningeachfileanddirectorywithasetofattributes. These give the privileges on the file usage and their settings aredisplayedwiththe1s–1command.Inthecaseof[15]inSamplesession35.4,theuseruses1s–1togetextendedinformation.Thedirectorylistinggivessixmainfields;theseare:•Fileattributes.•Ownerofthefiles.Person(userID)whoownsthefile.•Groupinformation.Thegroupnamedefinesthenameofthegroupthegroup

theattributesconcern.•Sizeoffile.Thesizeofthefileinbytes(8bits).•Dateandtimecreatedorlastmodified.Thisgivesthedateandtimethefile

waslastmodified.Ifitwasmodifiedinadifferentyearthentheyearanddatearegiven,butnotimeinformationisgiven.

•Filename.Figure35.3definestheformatoftheextendedfilelisting.Thefileattributes

contain the letters r, w, x which denote read, write and executable. If theattribute exists then the associated letter is placed at a fixed position, else a –appears.Thedefinitionoftheseattributesareasfollows:

FIGURE35.3 Extendedfilelisting

•Read(r).Thisfilecanbecopied,viewed,andsoon,butitcannotbemodified.

•Write(w).Thisfilecanbecopied,viewedandchanged,ifrequired.Executable(x).Itispossibletoexecutethisprogram.

Thefileattributessplitintofourmainsections.Thefirstpositionidentifiesifit is a directory or a file.A d character identifies a directory, else it is a file.Positions 2–4 are the owner attributes, positions 5–7 are the groups attributesandpositions8–10are the restof theworld’s attributes.Table35.1 lists someexamples.

Table35.1Examplefileattributes

Attributes Description

-r-x–x— Thisfilecanbeexecutedbytheownerandhisgroup(e.g.staff,students,admin,research,system,andsoon).Itcanbeviewedbytheownerbutno-oneelse.Nootherprivilegesexist.

drwxr-xr-x Thisdirectorycanbecannotbewrittentobythemembersofgroupandothers.Allotherprivilegesexist

-rwxrwxrwx Thisfilecanbereadandwrittentobyeveryoneanditcanalsobeexecutedbyeveryone(bewareofthis).

35.7.1ChangingAttributesOfAFileAswehaveseen,fileshavecertainattributessucharead/writeprivileges,andsoon.Thechmodcommandcanbeusedbytheownerofthefiletochangeanyofthe

fileattributes.Ageneralformatisgivennext.

wheresettingsdefinehowtheattributesaretobechangedandwhichpartoftheattributetochange.Thecharacterswhichdefinewhichparttomodifyareu(user),g(group),o(others),ora(all).Thecharactersforthefileattributesareasign (+, – or =) followed by the characters r, w, x. A ‘+’, specify that theattributeistobeadded,aspecifiesthattheattributeistobetakenaway.The‘=’definestheactualattributes.Someexamplesaregivennext:

InSamplesession35.5[20]theownerofthefilechangestheexecuteattributefortheuser.

35.8Specialcharacters(*,?and[])Thereareseveralspecialcharacterswhichaidaccesstofiles.ThesearestatedinTable35.2.

Table35.2Specialcharacters

Char Description

? matchesanysinglecharacterinafilename.

* matcheszeroormorecharactersinafilename.

[] matchesonecharacteratatime,thesecharactersarecontainedinthesquaredbrackets.

Samplesession35.6showsafewsampleusesofwildcards. In[24] theuserlistsallthefileswhichbeginwiththeletter‘m’.In[26]alltwoletterfilenamesbeginningwith‘c’arelisted.Thenin[27]thefileswhichbeginwiththeletters‘a’,‘b’or‘c’arelisted.

Notethat[a–c]represents[abc]and[1–9]represents[123456789].

35.9ListingcontentsofafileThecommandtolistthecontentsofafileiscat,itsformis:

Samplesession35.7showshowit isused. Ifafile is larger thanonescreenfullitispossibletostopthetextfromscrollingbyusingCntl-S(⁁S)tostopthetextandCntl-Q(^Q)tostart.

35.10MakingandremovingdirectoriesTomakeadirectorythemkdircommandisused,itsformis:

toremoveadirectorythermdircommandisused,itsformis:

Inbothcasesthefullpathnameorrelativepathnamecanbegiven.

35.11Copying,renamingandremovingThecommandtocopyfilesisthecpcommand.Thestandardformatis:

andthecommandtorename(ormove)iscalledmv.Itsstandardformatis:

Files are erased, or deleted, using the rm command. Sample session 35.8showssomeusesofthesecommands.

35.12StandardinputandoutputThe standard input device for a program is via the keyboard and the standardoutput is to themonitor. InUNIX all input output devices are communicatedwiththroughadevicefile,whicharestoredinthe/devdirectory.Forexample,each connected keyboard to the system (including remote computers) has adifferent device name.To determinewhich is your terminal pathname use thettycommandasshowninSamplesession35.9.

35.12.1RedirectionItispossibletodirecttheinputand/oroutputfromaprogramtoanotherfileordevice.

RedirectingoutputTheredirectionsymbol(>)redirectstheoutputofaprogramtoagivenfile(oroutputdevice).Thisoutputwillnotappearonthemonitor(unlessitisredirectedtoit).Samplesession35.10showshowtheoutputfromadirectorylistingcanbesendtoafilenameddirlist(see[57]).Thecontentsofthisfilearethenlistedin[58].

Theredirectionofoutputisparticularlyusefulwhenaprocessisrunningandanoutputtothescreenisnotrequired.Anotheradvantageofredirectionisthatitispossibletokeepapermanentcopyofaprogram’sexecution.Tocreateatextfilethecatcommandisusedwiththeredirection,asshown

next.ThefileisclosedwhentheuserusestheCNTRL-Dkeystroke,asshowninSamplerun35.11.If the user does notwant the output to appear on the screen then it can be

redirectedtothefilecalleddevnull.Thisisthesystemswastepaperbasketanditwillautomaticallybedeleted.

RedirectinginputTheinputcanberedirectedwiththeredirectsymbol(<).Thefilegivenafterthesymbolistakenastheinput.Forexample:

Inthiscasetheprogramprog1takesitsinputfromthefileinputfile,andnotfromthekeyboard.

35.12.2PipesThepipeallowstheoutputofoneprogramtobesenttoanotherastheinput.Thesymbolusedistheverticalbar(|)anditsstandardformis:

This notation means that the output of program_a is used as the input toprogram_b.Thepipehelps in commandswhere a temporary file/s needs tobecreated. For example, to find out who is logged into the system the who –acommand can be used. If names in a file need to be sorted alphabetically thesortcommandcanbeused.Thustosorttheusersonthesystemalphabeticallywecanuse:

Itispossibletoachievethiswithonelineusingpipes.

35.13CompilingCprogramsThecccommandisusedtocompileandlinkaprogram.IftherearenoerrorsintheCsourcecodethen,bydefault,afilenameda.outwillbeproduced.Thiscanthen be executed. If another executable filename is required then the -ofilename option can be used. Sample session 35.14 shows how the C filefile.ciscompiledandlinkedtoanexecutablefilenamedfile.

35.14DisplayingthetimeanddateThe command to display the date is simply date. This is shown in Samplesession35.15.

35.15WheretofindthingsUNIXhasvariousdefaultdirectorieswhichstore standardcommandprogramsandconfigurationfiles.Someofthesearedefinedinthefollowingsections.

35.15.1/BinThe/bindirectorycontainsmostofthestandardcommands,suchascompilers,UNIXcommands,programdevelopmenttools,andsoon.Examplesare:•FORTRANandCcompilers,f77andcc.•commandssuchasar,cat,manutilities.

35.15.2/Dev

The /dev directory contains special files for external devices, terminals,consoles,lineprinters,diskdrives,andsoon.

35.15.3/EtcThe/etcdirectorycontains restrictedsystemdataandsystemutilityprogramswhicharenormallyusedby the systemmanager.These includepassword file,login,andsoon.Examplesare:

35.15.4/LibThe /lib directory contains system utilities and FORTRAN and C runtimesupport,systemcallsandinput/outputroutines.

35.15.5/TmpTemporary (scratch) files used by various utilities such as editors, compilers,assemblers.Thesearenormallystoredinthe/tmpdirectory.

35.15.6UsradmTheusradmstoresvariousadministratorsfiles,suchas:

35.15.7UsrbinTheusrbincontainslessusedutilityprograms,suchas:

35.15.8UsrincludeTheusrincludedirectorycontainsC#includeheaderfiles,suchas:

35.15.9UsrlibTheusrlibdirectorycontainslibraryroutinesandsetupfiles,suchas:

35.15.10UsrmanTheusrmancontainsthemanualpages,suchas

35.16Exercises35.17.1.Gotoyourhomedirectory.

35.17.2.Displaythecurrentsystemdate.

35.17.3.Displaytheon-linehelpmanualforthefollowingcommands:

Completedsuccessfully:YES/NO35.17.4.Listalltheuserscurrentlyloggedintothesystem.

35.17.5.Createadirectorynamedsrcinyourhomedirectory.35.17.6.Gointothedirectorysrcandcreateasub-directorynamedcprogs.35.17.7.Gointothecprogsdirectoryandcreateafilenamedfile1.cusingcat

(orthesystemeditor).Enterthefollowingtextandsavethefile.

35.17.8.Listthefileyouhavejustcreated.Completedsuccessfully:YES/NO35.17.9.Changethenameofthisfiletofile2.c.Completedsuccessfully:YES/NO

35.17.10.Makeacopyofthisfileandnameitfile3.c.Completedsuccessfully:YES/NO35.17.11.Changethefileattributesofthisfilesothatthepubliccannotread

fromorwritetothisfile.35.17.12.Createanothernamedfile2.candenterthefollowingsourcecode.

35.17.13.Concatenatethetwofilestogether.Calltheresultantfilesrc.lis.Completedsuccessfully:YES/NO35.17.14.CompileandrunthetwoCprogramsjustcreated.Completedsuccessfully:YES/NO35.17.15.Removethefilesrc.lisCompletedsuccessfully:YES/NO35.17.16.Investigatethefollowingcommands/utilities:

35.17.17.Locatethefollowingutilityfilesanddeterminetheirusage.

35.17.18.Sketcharoughoutlineofthedirectorystructureofthesystem.

35.17SummaryTable35.3listssomestandardUNIXcommands.

Table35.3Commandssummary

Command Description

mansubject on-linemanualonsubject

ls listofadirectory(−1longlisting;–aall;–rreverselisting.

cd changedirectory

mv movefile

cp copyfile

mkdir makedirectory

pwd presentworkingdirectory

cat concatenateafile/s

>file redirectoutputtofile

<file redirectinputfromfile

36

UNIXCommands

36.1Processcontrol

UNIX is amultitasking,multiuseroperating system,wheremany tasks canberunningatacertaintime.Typicallythereareseveralprocesseswhicharestartedwhenthecomputerisrebooted;thesearenameddaemonprocessesandtheyrunevenwhenthereisnouserloggedintothesystem.

36.1.1Ps(ProcessStatus)Thepscommandprintsinformationaboutthecurrentprocessstatus.Thebasicpslistgivesalistofthecurrentjobsoftheuser.AnexampleisgiveninSamplesession36.1.

The informationprovidedgives theprocess identificationnumber (PID), theterminalatwhichtheprocesswasstarted(TTY),theamountofCPUtimeusedandthecommandlinethatwasentered(CMD).Aprocesscanbestoppedusingthekillcommand.Alonglistingisachievedusingthe–1optionandforacompletelistingofall

processesonthesystemthe–aoptionisused,asshowninSamplesession36.2.

ThecolumnheadedSgives thestateof theprocess.AnS identifies that theprocess is sleeping (the system is doing something else),W specifies that thesystemiswaitingforanotherprocesstostopandRspecifiesthattheprocessiscurrentlyrunning.Insummary:•Rprocessisrunning.•Tprocesshasstooped.•Dprocessindiskwait.•Sprocessissleeping(thatis,lessthan20secs.).•Iprocessisidle(thatis,longerthan20secs.).UID is the user identity number. PRI is the priority of the process.A high

numbermeansalowpriority.

36.1.2Kill(SendASignalToAProcess,OrTerminateAProcess)Thekillcommandsendsasignaltoaprocess.Thegeneralformatis:

Theprocessidisthenumbergiventotheprocessbythecomputer.Thiscanbefoundbyusing thepscommand.Thesigvaluedefines theamountof strengththatisgiventothekillprocessandthestrongestvalueisa–9.Theownerofaprocess can kill his own, but only the superuser can kill any process. Samplesession36.3givesanexamplesession.

36.1.3At(ExecuteCommandsAtLaterDate)Theatcommandwhenusedinconjunctionwithanothercommandwillexecutethatcommandatsomelatertime.Thestandardformatis:

wheretimeisgivenusingfrom1to4digits,followedbyeither‘a’,‘p’,‘n’or‘m’foram,pm,noonormidnight,respectively.Ifnolettersaregiventhena24-hour clock is assumed. A 1-or 2-digit time is assumed to be given in hours,whereasa3-or4-digit time is assumed tobehoursandminutes.Acolonmayalsobeincludedtoseparatethehoursfromtheminutes.TheDate can be specified by themonth followed by the day-of-the-month

number,suchasMar31.AWeekcanbegiveninsteadofthedayandmonth.Forexample,tocompileaprogramatquarterpasteightatnight:

andtosendfredamessageat14:00:

To remove all files with the .o extensions from the current directory onSeptember9that1noon.

To list all jobs that are waiting to executed at some later time use the –1option.

Toremove jobs fromtheschedule the–roptioncanbeusedandgiving thejobnumber.

36.1.4Nice(RunACommandAtALowPriority)Thenicecommandrunsacommandatalowpriority.Thestandardformatisasfollows:

Thelowestpriorityis–20andthedefaultis–10.Samplesession36.9givesasamplesession.

36.2CompilersThetwomaincompilersonUNIXsystemsareC(cc)andFORTRAN(f77).

36.2.1Cc(CCompiler)ThecccommandistheClanguagecompilerandisusedtoconvertaCprograminto binary code. It can also link several binarymodules together tomake anexecutablefile.Fileswiththeextension.caretakenasCprogramsandwhenaCprogramis

compiled theresultingbinarymodule(theobjectcode) isplaced in thecurrentdirectory.Ifa–coptionisnotusedthebinarycodewillbecalleda.out.Ifthe–coptionisusedthebinarycodewill takethenamegiven,themodulesproducedwillhavea.oextension.Optionsare:–c.producesinglebinarymodule(objectcode)withtheextension.o.–o.outfitthisoptionisusedtogivethenamefortheoutputfile.–g.producedebuginformationforusewithadebugger(suchasdbx).In Sample session 36.11, the first example of the C program progl.c is

compiled;theresultingfileproducediscalleda.out.Thisfilecanbeexecutedas required. The second type of compilation (cc –c *.c) compiles all the Cprograms and produces an object module with a .o extension. These objectmodulescanbelinkedtogetherusingthecompiler.Thelastexample(cc–oprogprog1.oprog2.o) linkstogethertheobjectmodulesforprog1.candprog2.c.Theexecutableprogram,inthiscase,willbecalledprog.

36.2.2F77(FORTRANCompiler)The FORTRAN compiler f 77 is used to compile and/or link FORTRANprograms.Thesourcefileisassumedtohavethe.fextension.Ifthe–coptionischosenthecompiledmodulewillhavethe.oextension;thisisanobjectmodule.Samplesession36.11givessomeexamples.

36.2.3Dbx(DebuggerForC,FORTRANAndPascal)The dbx utility is a source-level debugger for C, FORTRAN and Pascal. Itallows the user to trace a program’s execution and list variables. The generalformatis:

Somecommandsfordbxare:

run runsthecurrentprogram.

step stepthroughtheprogramexecutiononelineatatime.

cont continueprogramexecutionwhereitstopped.

print printcontentsofavariablesuchasprintinput_value.

list listnexttenlinesofcodeifnoargumentsaregiven;tolistfromlinestarttolineenduselistlinestart,lineend.

lineend.

help gethelpinformation.

trace traceprogramexecution.

quit exitdbx.

36.2.4Lint(CProgramVerifier)Thelint utility isused toverifyCprograms. It attempts todetectbugs,non-portablewarnings and anywasteful use ofC code.The basicC compiler,cc,doeslittleruntimecheckingorinefficiencychecking.Torunthelintprogram:

Samplesession36.12givesasamplesession.

36.3FilemanipulationcommandsUNIX has a number of file manipulation commands, some of which weredefinedinthepreviouschapterandmanyothersaregiveninthissection.

36.3.1Cp(CopyFiles)Thecpcommandwillcopyagivenfileordirectorytoagivenfileordirectory.Thereareseveraloptionsthatcanbeused:–iusesinteractivemode,theuserispromptedwheneverafileistobe

overwritten.Theuseranswers‘y’or‘n’.–rusesrecursivemode,thecpcommandallfilesincludingeachsubdirectoryit

encounters.Thefollowingexamplewillcopyafilecalledfile1intoafilecalledfile2.

Note that if file2 were a directory then file2 would be copied into thatdirectory.

Ifyouwanttocopyawholedirectoryandallsubdirectoriesthe–roptionisused. In the next example the whole directory structure of usrstaff/bill iscopiedintothedirectoryusrstaff/fred:

Tocopyafileintoadirectory:

36.3.2Is(ListDirectory)The ls command lists the contents of a directory. A summary of the variousoptionsaregivenbelow:

–a listsallentriesincludingfilesthatbeginwitha.(dot)

–l listsfilesinthelongformat.Informationgivenincludessize,ownership,groupandtimelastmodified.

–r listsinreversealphabeticorder.

–t listsbytimelastmodified(latestfirst)insteadofname.

–l listsoneentryperline.

–F marksdirectorieswithatrailingslash(/),executableswithatrailingstar(*).

–R recursivelylistssubdirectoriesencountered.

Samplesession36.16givessomeexamples.

36.3.3File(DetermineFileType)Thefilecommandisused to testa file for its typesuchasaCprogram, textfile,binaryfile,andsoon.Samplesession36.17givesatypicalsession.Typical

filetypesinclude:•mc68020demandpagedexecutable.•Cprogramtext.•ASCIItext.•Empty.•Archiverandomlibrary.•Symboliclink.•Executableshellscript.

36.3.4Du(DiskUsage)The du command lists the size of a directory and its subdirectories. If nodirectorynameisgiventhecurrentdirectoryisassumed.Twooptionsaregivennext:

36.3.5Cat(ConcatenateAndDisplay)The cat command concatenates and displays the given files to the standardoutput,whichisnormallythescreen(althoughthisoutputcanbechangedusingtheredirectionsymbol).Forexample,tolistafiletothescreen:

Toconcatenatetwofilestogether(file1.txtandfile2.txt)andputthemintoafilecalledfile3.txt:

If no filename is given then the input is taken from the standard input,normallythekeyboard.Ifaredirectsymbolisusedthenthisinputwillbesenttothegivenfile.Theendoftheinputisgivenbya⁁D(acontrol-D).Forexample:

36.3.6Compress,Uncompress(CompressAndExpandFiles)ThecompresscommandusestheadaptiveLempel-Zivcodingtoreducethesizeof a file. A.Z is added onto the filename so that it can be identified. Samplesession36.21showsanexample.

Thecontentsofthecompressedfilesareinacodedformsothattheycannotbe viewed by a text editor. The uncompress command can be used touncompress a compress file. Only files with the extension .Z can beuncompressed.

36.3.7Chmod(ChangeMode)FilesinUNIXhavevariousattributes;theseattributescanbesetorresetwiththechmodcommand.Theattributesare:

Owner Group Public

rwx rwx rwx

Theowneristhepersonwhocreatedthefileandthegroupisacollectionofseveralusers,suchasresearch,development,production,admingroups,andsoon.Thepublicisforeveryoneelseonthesystem.Therattributestandsforreadprivilegeandifitissetthenthefilecanberead

(that is, listed or copied) by that type of user.Thew attribute stands forwriteprivilegeandif it issetthenthefilecanbewrittento(thatis, listed,copiedormodified)bythattypeofuser.Thexattributestandsforexecuteprivilegeandifitissetthenthefilecanbeexecuted(thatis,itcanberun)bythattypeofuser.Forexample-rw-r–r–isafilethattheownercanreadorwritebutthegroup

andthepubliccanonlyreadthisfile.Anotherexampleis-r-x–x–x;withthese

attributestheownercanonlyreadthefile.No-oneelsecanreadthefile.No-onecan change the contents of the file.Everyone can execute the file.Thels -allistinggivesthefileattributes.

Thereareseveralways tochange theattributes.Thegeneral format isgivenbelow:

Thepermissioncanbesetbyusingtheoctalsystem.Ifanattributeexistsa1is set, if not it is set to a 0. For example,rw-r–r– translates to 110 100 100,whichis644inoctal.Forexample:

Tomakethefilefile.txtintorw-rw-r–:

TomakethefileRun_proginto–x–x—:

Theothermethodusedissymbolicnotation,thesearelistednext:

u userpermission

o others(public)permission

= assignapermission

– takeawaypermission

w writeattribute

g grouppermission

a allofuser,groupandotherpermissions+addapermission

r readattribute

x executeattribute

Forexample,tochangethefileRun_listsothatitcanbeexecutedbyalluse:

To take away readprivilege for all fileswith the .c extension for thegroupuse:

36.3.8Df(DiskSpace)Thedfcommandallowsyoutolisttheusageofthediskandallothermounteddiskdrives.Samplesession36.28givessomeexamples.

36.3.9Diff(DifferencesBetweenFiles)Thediffcommandshowsthedifferencebetweentwofilesortwodirectories.

Therearevariousoptionsusedandthesearesummarizednext:–iignoresthecaseofletters(suchas‘b’issameas‘B’).–wignoreallblanks(suchasfred=16.2issameasfred=16.2).Someexamplesarenext.Intheoutputlistingthe<characterreferstothefirst

file given and the > character refers to the second file given. A c refers to achange,adtoalinedeletedandanareferstotextthathasbeenappended.Thelinenumbersofthefirstfilealwaysappearfirst.

36.3.10Mv(MoveFiles)Themvcommandmovesfilesordirectoriesaroundthefilesystem.Thestandardformatsare:

Therearethreedifferentpermutations.Theseare:•Movingafileintoanotherfile(likerenaming).•Movingadirectoryintoanotherdirectory(likerenaming).•Movingafileintoanotherdirectory.Theoptionsthatcanbeusedare:

–i filesaremovedinteractively.Whenafileistobemovedthesystemwillprompttheuserastowhetherhewantstomovethefile.Iftheansweris’y’thefilewillbemoved,elseitwillnotbemoved.

–f forcemode;overrideanyrestrictions.

Samplesession36.30showsexamples.

36.3.11More(PageAFile)The more command allows the user to print one page of text at a time to thestandardoutput.Itpausesattheendofthepagewiththeprompt‘–More–’atthebottomofthepage.Samplesession36.31showssomeexamples.

36.3.12Rm(RemoveFilesOrDirectories)Thermcommandremoves filesordirectories.Toremoveadirectorywhich isemptythermdircommandcanbeused.Therearevariousoptions,suchas:

–f forcemode;removefileswithoutaskingquestions

–r recursivemode;deletecontentofadirectory,itssubdirectoriesand

thedirectoryitself;

–i interactivemode;asksquestionastowhethereachfileistobedeleted.

Samplesession36.32givessomeexamples.

36.3.13In(MakeLinks)TheIncommandmakesasoftlinktoafileordirectory.Whenthelinknameisusedthesystemwillgototheplaceindicatedbythelink.Thegeneralformatis:

Samplesession36.33showssomeexample.

36.3.14Find(FindFile)The find command searches recursively through a directory structure to findfilesthatmatchcertaincriteria.Itusesapathnamefromwheretostartseaching;thisisthefirstargumentgivenafterfind.Thenameofthefileisspecifiedafterthe–nameargumentandiftheuserwantsthefilesfoundprintedtothestandardoutputthe–printisspecifiedattheend.Samplesession36.34givesanexampleoffindingafilecalledfred.f,startingfromthecurrentdirectory.

Samplesession36.35showsasearchofthefilepasswd,startingfromthetop-leveldirectory.

Thewild-cardcharactercanbeusedinthenamebutthismustbeinsertedin

invertedcommas(”“).Samplesession36.36givesanexampleofsearchforallCfilesstartingwiththe/usr/staff/billdirectory.

Otherextensionscanbeusedsuchas–a timewhichdefines the timeof lastaccess.Theargumentfollowing–atimeisthenumberofdayssinceithasbeenaccessed.Samplesession36.37givesanexampleofsearchingforall.ofilesthathavenotbeenusedwithin10days.

36.3.15Grep(SearchAFileForAPattern)The grep commandwill search through given files looking for a given stringpattern. There are various options which can be used, a summary of these isgivenbelow:–vprintlinesthatdonotmatch;–xdisplayonlylinesthatmatchexactly;

–cdisplaycountofmatchinglines;–iignorecase.Samplesession36.38givessomeexamplesandthestandardformatis:

36.3.16Head(DisplaysFirstFewLinesOfAFile)Theheadcommandprintsthetopnlinesofafile.Thedefaultnumberis10linesandSample2.39givesexamples.Theformatisasfollows:

36.3.17Tail(DisplayLastPartOfFile)The tail command displays the last part of a file, where the first argumentdefines thenumberof lines tobedisplayed.Forexample, todisplay the last4linesofthefilefile1.txt:

36.3.18Wc(WordCount)Thewcutilitycountsthewords,charactersandlinesinafile.Ifseveralfilesaregiventhenthesumtotalof thefileswillbegiven.Thereare threeoptions thatcanbeused;thesearec,wand1,whichstandforcharacters,wordsandlines.

Ifnofilenameisgiventhenthekeyboardistakenastheinputandacontrol-Dendsthefileinput.Examplesare:

36.4Othercommands36.4.1Ar(ArchiveAndLibraryMaintainer)TheArCommandIsUsedToCreateAndMaintainLibrariesAndArchives.ALibraryIsAFileWhichContainsCompiledPrograms.TheseFilesAreCalledObjectModulesAndAreSelf-ContainedModules.TheObjectModulesHaveTheExtension.O.TheLibrariesAreUsedInTheLinkingProcess.

ThereAreCertainStandardLibrariesOnTheSystem;TheseIncludeTheStandardMathsLibraryAndStandardInput/OutputLibrary(NormallyFoundIn/Usr/Lib).

There are various options usedwith ar; these are given in Table 36.1. Forexample,tocreateanarchive

Table36.1aroptions

Option Description

d deletethenamedfilesfromthearchive

r replacethenamedfilesfromarchive

t listthecontentsofanarchive

x extractafilefromanarchive

c createanarchive

v extendedlistingoffile

Thentolistthearchive:

andtoextractafilefromthearchive:

Thenaddingallfileswith.cextension:

andlistingthearchiveagain:

Toextractafile:

andtocreatealibrarywith.oobjectmodules:

Archivesareusefulforkeepingmanyfilestogetherintheonefile.Thismakesthemusefulforprinting,storingontape,andsoon.ThesearestandardlibrariesontheUNIXsystem,suchas:

36.4.2Banner(MakePosters)Thebanner command prints thewords given on the screen in large letters.AsamplesessionisshowninSamplesession36.42.Themaximumlettersononelineisten.Itsstandardformis:

36.4.3Cal(Calendar)Thecalcommanddisplaysacalendarforagivenyearand/ormonth.Theyearmayvaryfrom1to9999andifnomonthoryearisgiventhecurrentmonthwillbe printed. Sample session 36.43 shows an example of displaying the currentmonthandSamplesession36.44displaysawholeyear.

36.4.4Chpass(ChangePassword)The chpass command is used to change the current login password. Samplesession36.45showsanexample.

36.4.5Date(DisplayOrSetDate)Thedatecommandeithergivesthecurrentdateandtimeorcanbeusedtosetthe current date and time (although only the superuser can do this). If noargumentsaregiventhenthecurrentdateandtimeisprinted.Ifavalidargumentisgiventhenthecurrenttimeischanged.Thegeneralformatisgivenbelow:

whereyyistheyear,mmisthemonth,ddisthedayofmonth,hhisthehour(24hourclock),mmistheminuteandssistheseconds(optional).It is possible to leave out various field such as the year and the seconds.

Samplesession36.46givessomeexamples.

36.4.6Echo(EchoArguments)Theechocommandwritesitsargumenttothestandardoutput.AC-likestandardis used for printing. Sample session 36.47 shows a few examples and thecharactersusedaregivenbelow:

36.4.7Finger(DisplayInformationOnUsers)The finger command gives information on a given user. This informationincludes:•Loginname.•Fullname.•Terminalname.•Idletime.•Logintime.•Officelocation.•Phonenumber,ifknown.Thefilesusedare:

36.4.8Ftp(FileTransferProgram)TheftputilityisthestandardFileTransferProtocol.Itisusedtotransferfilestoandfromaremotenetwork.Theformatis:

36.4.9Ipr(PrintFile)Thelprcommandspoolsafiletotheprinter.

36.4.10Mail(InteractiveMail)Themail utility is used to send and receivemessages from/to other users.Tosend mail the user’s name is simply specified after the program name. Forexample,tosendmailtoauserfred:

Whenever thecontrol-D(⁁D)keystroke isused then themessage issent toaspecifiedrecipient.Otheruserscanbesentthesamemailbysimplygivingtheirusernameasoneofthearguments,suchas:

Tosendafilewhichhasmailtheredirectsymbol(<)isused,suchas:

Whenreadingmail thesystemwill typically tell theuserwhen there ismailwaitingtoberead,suchas:

Thentoreadthemailthemailprogramisrun,suchas:Thentoreadthemailthemailprogramisrun,suchas:

Themail responsewithaquestionmark (?) isused to indicate that themailprogramiswaitingontheusertoenteracommand.Possibleoptionsare:

? displayhelpinformation

q quit

x exitwithoutchangingmail

p print

sfile savetofile

d deletemail

+ next(nodelete)

muser mailuser

36.4.11Passwd(ChangeLoginPassword)The passwd command is used to change the current password. Each user’spasswordisstoredinacodedforminetcpasswd.Eachnewpassword’smustbeat least5 characters long if they includeupper and lowercase,or6 if theyaremonocase.Samplesession36.53showsanexample.

36.4.12Pwd(PresentWorkingDirectory)

The pwd command prints the pathname of the current working directory.Examplesare:

36.4.13Rlogin(RemoteLogin)Therlogincommandallowstheuser to logintoaremotemachine.Theformatis:

36.4.14Sleep(SuspendExecutionForAnInterval)The sleep command is used to suspend to command for a given time. Thestandardformatis:

wherethetimeisinseconds.Samplesession36.55showsanexample.

36.4.15Spell(FindSpellingErrors)The spell utility finds spelling errors. TheUNIX dictionary resides in the file/usr/diet/words.Theformatisgivenbelow.

Therearevariousoptionsused:

-b Britishspelling(suchascolourinsteadofcolor).

-v verbose,fulllisting.

-X listseveryplausiblestemfordoubtfulwords.

Samplesession36.56showsanexample.

36.4.16Stty(SetTerminalOptions)Thesttycommandsetsuptheterminalcharacteristics.Therearetwomaintypesofoptions;thesearetogglesandsettings.Thestandardformatisgivenbelow.

Varioussettingsare:

even allowevenparity

odd allowoddparity

echo echoeverycharactertoscreen

icase convertcapitalletterstolowercase

tabs preservetabs

ek seteraseandshellcharactersto#and@

erasec seterasecharactertoc(usuallyB/S)

killc ,.setkillcharactertoc(usually@)

300,1200,andsoon setbaudrate

Samplesession36.57givesexamples.

36.4.17Tar(TapeArchiver)Thetarutilityallowsfilestobesaved,recoveredorlistedfromatapedrive.Itsstandardformis:

Optionsusedare:

c tocreatetapearchive

t tolisttapearchive

r torecovertapearchive

V completelistingoffilenames

Samplesession36.58showsexamples.

36.4.18Who(UsersLoggedIn)The who command lists all users on the system and which terminal they areusing.Thisinformationisfoundintheetcutmpfile.Iftheargumentsgivenaream i (that is, who am i) then the system prints details about the user. Forexample:

The informationgiven is theusername, terminal logged inonanddate thattheuserloggedin.

36.4.19Write(SendsMessagesToUsers)The write utility sends a message to a specified user. A control-D ends themessageinputandsendsit.Examplesare:

36.5Exercises36.5.1.LoginintheUNIXsystemanddeterminethecurrentprocessesthatthe

useriscurrentlyrunning.36.5.2.Determineallthecurrentprocessesthatarerunningandtheuserwhich

initiatedtheprocess.Identifythestatusoftheprocesses.36.5.3.Usethecat>newfilecommandandthentheCtrl-Zkeystroketo

suspendtheprocess.Showthattheprocesshasbeensuspended.

36.5.4.Killtheprocesswhichhasjustbeensuspended.36.5.5.Usingtheatcommand,runanIs–1atatimeoneminutefromthe

currenttime.36.5.6.Fromthecurrentdirectory,determinethefiletypesofthefiles.36.5.7.Fromthecurrentdirectory,determinethesizeofallthedirectories.36.5.8.Determinethepresentworkingdirectory.36.5.9.Determinethepresentdate.36.5.10.Listthecurrentdirectorysothatdirectorieshaveatrailingslash.36.5.11.Recursivelylistthecurrentdirectory,showingallsubdirectories.36.5.12.Determinetheuserswhoarecurrentlyloggedintothecomputer.36.5.13.Ifthereisauserloggedintothecomputerthensendanelectronic

messagetothem.36.5.14.Usingstty,determinetheterminalcharacteristics.36.5.15.Forthetop-leveldirectory,findalltheCprogramfiles.

37

EditingandTextProcessing

37.1Introduction

UNIX has several command programswhich can be used to edit and processtext.ThesearedefinedinTable37.1.

Table37.1Editingandtextprocessingprograms

Texteditors Textprocessing Textmanipulation

vi,thevisualeditor nroff,formatdocument grep,looksforapattern

ex,lineeditor troff,printformateddocument sort,sortslinesoftext

ed,lineeditor tb1,formattingtables spell,findsspellingerrors

sed,streamtexteditor pic,graphicslanguagefortypesetting

tr,translatescharacters

awk,patternscanningandprocessing

eqn,typesettingmathematics wc,countscharacters,wordsandlinesinafile.

37.2VisualeditorMost UNIX systems have their own text editor which is selected from theGraphical User Interface. The vi editor (pronounced vee-eye) is a text-basededitorandisstandardonallUNIXsystems.ItisnottheeasiesteditortousebutitisavailableonallUNIX-basedsystem.Theeditoriscalledwith:

37.2.1MakingChangesThe vi editor involves using special characters to identify editing commands.The user enters text only when the editor is in insert mode. All charactersenteredthismodeareaddedtothefile.Whennotininsertmodethecharactersare interpreted as editor commands. For example, an ‘x’ keystroke tells theeditortodeleteasinglecharacteranda‘d’followedbya‘w’deletesaword.

InsertmodeTo insert text the user must be in the insert mode. A summary of the maininsertionanddeleteoptionsisgivenbelow.Toinserttext,placethecursoronthecharacteryouwant to insertbefore thenpress ‘i’; thiswillputyou into insertmode.Thetextcanthenbeenteredwithasmanylinesasrequired.Toexitfrominsertmode,theESCkeyispressed,asillustratedinFigure37.1.Thisthenputstheeditorbackintonormalmode.Othermethodsofinsertionaresimilar,suchasan‘a’putsinsertedtextafterthecurrentcursorposition.While‘o’startsanewlineabovethelinetheuseriscurrentlyonand‘o’putsitafterthecurrentline.TheinsertmodecharactersarelistedinTable37.2.

Table37.2Editingandtextprocessingprograms

Option Description

i Enterinserttextmodebeforecursor.TheESCkeyisusedtoexitfrominsertmode.

Enterinsertmodeandcreateanewtextlineabovelineyouareon.

O Enterinsertmodebelowcurrentline.

a Enterinsertmodeaftercursor(thatis,append).

dd Deletewholeline.

X Deleteonecharacter.

dw Deleteword.

db Deletewordbefore.

ns Substitutesncharactersandentersintoinsertmode.

FIGURE37.1 Editandinsertmode

37.2.2DeletingTextDeletingtextisperformedintheeditmode.Thevariousmethodsare:•Deletelines.Asinglelineisdeletedwithtwo‘d’characters,thatis‘d’‘d’.

Todeleteseverallinesthenumberoflinestobedeletedisenteredfirstfollowedbytwo‘d’characters,suchas6‘d’‘d’deletes6lines

•Deletewords.Asingleword(asequenceofcharactersdelimitedbyspaces)isdeletedwitha‘d’followedby‘w’.Aswithdeletelines,severalwordsaredeletedbyenteringthenumberofwordstodeletefollowedbythe‘d’and‘w’characters.

•Deletecharacters.Asinglecharacterisdeletedwiththe‘x’character.Again,ifthischaracterisprecededbyanumberthenanumberofcharactersaredeleted.Forexample,5followedby‘x’deletes5characters.

37.2.3SubstitutingThe ‘s’ character identifies a substitution of characters. First the number ofcharacterstobesubstitutedisenteredandtheeditormarkstheendofthetexttobesubstitutedwitha$.Theeditoristhenputintoinsertmodeandthenewtextis entered followed by the ESC key. For example, to change fred to tom thecursorismovedtothefoffredandthentheusertypes4stom<ESC>.

37.2.4CutAndPaste(YankAndPut)The‘y’‘y’keystrokeisusedtocopyalineoftext(yank)andthe‘p’keystroke(put)isthenusedtoputthistexttoadefinedpartofafile.Thisisequivalenttocopythenpasteoperation.Iftheyankoptionisprecededbyanumberthenthatnumberoflinesareyanked.Forexample7‘y’‘y’stores7linesoftext.Notethatthe‘p’characterputslinesafterthepresentlineand‘P’afterthepresentline.

37.2.5UndoingThevi editor allows the last change to be undone. The keystroke for the lastoperation to be undone is ‘u’ and to restore awhole line the ‘U’ keystroke isused.

37.2.6MovingAroundTherearevariousmethodsofmovingaround theseareoutlined inTable37.3;andaredefinedas:

Table37.3Editingandtextprocessingprograms

Option Description

lor→ movecursorforwardonecursorposition

hor← movecursorbackoneposition

^b backwardsonepage

^f forwardonepage

^d scrolldownfile

^u scrollupfile

kor↓ nextline

jor↑ previousline

Gn gotolinenumbern

W forwardoneword

b backoneword

e endofcurrentword

w wordafterthisword

•Movingcursor.Thecursorcanbeusedwiththearrowkey(←,→,andsoon)iftheyaresupportedbytheterminalbeingused.Ifthekeyboardhasnoarrowkeys(ortheyarenotsupported)thenthecharactersusedare‘h’(left),‘j’(down),‘k’(up)and‘1’(right)keys

•Movingbypage.ThepagecanbemovedbackandforwardusingthePgUpandPgDnkeys,iftheyaresupported.Else,tomovebackwardsbyonepagethe⁁b(pressCntrlandbatthesametime)andtomoveonepageforwardthen⁁f.A⁁uand⁁dallowsthescreentobescrolledupordown,respectively.

•Goingtoaline.Inmanysituationstheuserrequirestogotoaspecificlinenumber(especiallywhencompilingaprogram).Todothisthe‘G’characterisfollowedbythelinenumber.Forexample,‘G’1234goestolinenumber1234.

37.2.7SearchingForStringsThe‘’and‘?’charactersareusedtofindastring.A‘’searchesforwardsforthenextoccurrenceofastring,whereas,‘?’searchesbackfortheoccurrenceofthestring.Thus:

37.2.8GettingOutOfTheEditorAndSavingThere are various options that can be used (depending on what you require).ThesearespecifiedinTable37.4.Theuser’schangesarenotstoredto thefileuntil theuseruseseither‘Z’‘Z’, ‘:’‘w’‘q’or’:’‘w’.Thesediffer in that the‘:’‘w’‘q’and‘Z’‘Z’sequencecausesthechangestobesavedtothefileandquitfromtheeditor,whereas‘:’‘w’saveschangesandtheeditorstaysactive.

Table37.4Methodsofexiting

Option Description

ZZ Exitsfromeditorandsavesallchanges.

:wq<CR> Sameasabove(writeandquit).

:w<CR> Writechangesbutdonotquit.

:wfilename<CR> Writechangestofilename,noquit.

:qexcl<CR> Quitfromeditor,nochanges.

:eexcl<CR> Re-edit,discardingchanges.

Ausercanabandon thechanges thathavebeenmadesince the last savebyusingeither‘:’‘q’‘!’or‘:’‘e’‘!’.Notethat<CR>standsforpressingthereturnkey.

37.2.9Reading-InAndWriting-ToFilesThecommandtoread-infilesis:rfilenameandthecommandtowritethefiletoaspecifiedfile is :w filename.Forexample, :rfred readsinafilecalledfredand:wfred2.txtwritestoafilecalledfred2.txt.

37.2.10UsefulAdvancedEditingFacilitiesTherearemanypowerfultexteditingfacilitiesavailable,someusefulexamplesare:

thischangesalloccurrencesofname1toname2for10lines:

writeslines5to18tofilecalledfred.txt.

37.3ExampleoftexteditingThissectioncontainsapracticalexampleoftextediting.Starttheeditorwith:

thenwhen theeditorhas startedenter ‘i’ toput theeditor into insertmode.Enterthetextgivenbelowandmakethechangesrequired.Ifmistakesaremadeas the text is being typed-in then the back-space keywill delete the previouscharacter,elsewaituntilallthetexthasbeenenteredandthenmaketherequiredmodifications.Thetextis:

Oncethetexthasbeenenteredthenmakethefollowingchanges/operations:(a)Changeloininthetitletolion.Thiscanbedoneinanumberofways,such

as:•MovecursortotheLofLOINpress4×(orxxxx)andthenpressito

enterinsertmodeandentercorrectwordLION.PressESCbuttontoexitfrominsertmode.

•MovecursortotheLofLOINpress4s(substitute4letters)the$signshowstheendofthewordtobesubstituted.Youwillbeininsertmodeautomatically.EnternewtextLIONandpressESCtoreturntonormalmode;

•MovecursortotheLofLIONpressR(overwritemodeandreplace)thiswillautomaticallyputyouintoinsertmode.NextentercorrectLIONandpressESC.

•Foradvancededitinggotostartoftextthentype::s/LOIN/LION/g100<CR>.ThissubstitutesgloballyLOINforLIONfor100lines.

(b)Copythefirst4linesofthesecondparagraphandputtheseafterthe

thirdparagraph.Todothisfirstyank(togetlines)andtheput.First,positionthecursoratanypositiononthelinewhichbeginsthesecondparagraph.Next,getthelinesbyusing4yy(whichgets4linesoruse4Y)thenmovethecursortothelastlineandpressρtoputthelinesbelowlastline.

(c)Deletethesenewlines.Thiscanbedonebymovingthecursortothefirstlineofthenewlinesandthenusing4dd(ordddd)todeletethese4newlines.

(d)Searchforthewordsheepsandchangethistoheaps.Tofindthewordsheepsuse/sheeps<CR>,theeditorwillthenfindthefirstoccurrenceafterthecurrentcursorposition.Ifthewordliesbackwardsfromthecursorthenuse?sheeps<CR>.Oncefoundreplaceitwithheaps.

(e)Searchforthewordstumbled.Howmanyoccurrencesarethere?(f)Writemodifiedtexttothefilelion2.txt.Thisisdonebyusing:w

lion2.txt<CR>.(g)Readthisfileinattheendofthefile.Movethecursortotheendoffile

thenuse:rlion2.txt.Thiswillreadthefilein.(h)Deletethesenewlines.Positionthecursoronthefirstnewlinethenusedd

todeletealine.Repeatthisdeletionwiththerepeatoptionuntilalltherequiredlinesaredeleted.

(i)Findthewordconfusionandchangeittounconfusion,thenundothispressu(theundooption).

(j)Savethetext.Use:wq<CR>.

37.4sededitorThe sed is a non-iterative stream editor. It is useful for editing large files andperformingglobaledits.Thefollowingtextcanbeenteredandoperatedonintheexamplesgiven;callthefileWalrus.

37.4.1GlobalChangingTogloballychangestring1tostring2thefollowingisused:

Forexample,ifweusetheexamplegivenpreviouslytochangehistoher,thefollowingcanbeused:

Wecanseethatonthefifthlinethishasbeenreplacebyther.Toundothisthefollowingcouldbeused:

37.5grepThegrep command searches throughgiven files for a given stringpattern. Itsstandardformatis:

wheretheoptionswhichcanbeusedare:

–v printlinesthatdonotmatch

–v printlinesthatdonotmatch

–X displayonlylinesthatmatchexactly

–c displaycountofmatchinglines

–i ignorecase

Examplesare:

Thegrepistypicallyusedwithapipetosearchtheoutputfromacommand.Forexample, to findeveryoccurrenceof theword set in themanualon theCshell:

whichisequivalentto:

37.6sortThesortutilitysortslinesinthegivenfilesandwritestheoutputtothestandardoutput. It always uses the characters to sort the text and ignores the values ofnumericalvalues.Thestandardformatis:

Asanexample,createthefollowingfileandcallitleague.Itsfunctionisto

list a number of individuals, the number of games they have played and thenumberofpointsscored.Eachfieldisseparatedbyspacesortabs.

To sort the first field, that is the first name, then the sort is used with nooptions.

Next, thesurnamescanbesortedbyaddingthe+1option,whichcauses thesorttoskiptothefirstfield.

ThisisanincorrectsortasSimonRiponcomesbeforeBertRipon.Thereasonthatithasnotsortedthesenamesproperlyisthatithastestedonlythesurname.Totestthefirstfieldafterthesecondthe–2optionisadded.Thusthesort+1–2leaguecommandis interpretedas ‘skip thefirst fieldand thensortbutstopsortingafterthesecondfieldandgobacktothestartoftheline’.

Tosortthethirdfield(thatis,thegamesplayed)thenthe+2noptionisused.Thus sort +2n +1 League is interpreted as ‘skip two fields then sortnumerically,thentheyaresortedbyskippingthefirstfield’.

Tosortinreversetheroptionisused.

Tosortwiththefourthfield(thatis,points):

37.7Exercises37.7.1.Writeacommandusing1s,|andthegrepthatwilldetermineallfiles,in

thecurrentworkingdirectory,whichcontaintheletterr.37.7.2.Usingwho,|andgrep,determinealltheusersonteletypeterminals(that

is,ttyxx).37.7.3.Usingthels-alandgrep,showanyfilewhichhastheattributesrwx-r–

r–.37.7.4.Determineanyusageofthestring“>>”inthemanualoncshandsh.37.7.5.Thefollowingarelistsofteamsandtheirgamesplayed,goalsfor,goals

againstandpoints.Usingthesortutility,determine:(i)Thelistalphabeticallyofteams.

(ii)Theteamssortedbydecendinggoalsfor.(iii)Theteamssortedbyascendinggoalsagainst.(iv)Theteamssortedbypointsthenbygoalsfor.

37.7.6.Usingsortandls–al,listthefilesinthecurrentdirectoryinorderofdecreasingsize.

38

Csh(CShell)

38.1Introduction

The C shell (csh) is one of the interfaces between the user and the UNIXoperatingsystem;othersinclude:•Bourneshell(sh).•Korneshell(ksh).The C shell includes a command interpreter and a high-level programming

language.IthasseveraladvantagesovertheBourneshell,theseinclude:•Variablesaremoreversatile.•Itsupportsarraysofnumbersandstrings.•Improvedprotectionoveraccidentallogout.•Improvedprotectionoveraccidentalfileoverwrite.•Aliasmechanism.•Historymechanismtorecallpastevents.

38.2EnteringtheCShellTheBourneshelland theCshellcanbeusedatany timebutonlyonecanbeusedatatime.Tocall-uptheCshell:

andtheBourneshelliscalled-upusingsh.Normally,theshellatwhichauserisputintoinitiallyissetupintheetcpasswdfile.Thisfilecanonlybechangebythesystemadministrator.Tolistthepasswdfile:

this gives a paged list and the shells are given defined by either binsh orbincsh.Anexcerptfromapasswdfileisgivennext:

In this case, the passwd file has 3 users defined, these are root, fred andfred2. The encrypted password is given in the second field (between the firstandsecondcolon).The third field isauniquenumber thatdefines theuser (inthis case fred is 2 and fred2 is 3). The fourth field, in this case defines thegroup number. The fifth field is simply a comment field and, in this case,containstheuser’snames.Inthenextfieldtheuser’shomedirectoryisdefinedandthefinalfieldcontainstheinitialUNIXshell(inthiscaseitistheCshell).WhenenteringtheCshellthe.cshrcfileisexecuted.ThisfilesetsuptheC

shelltotheneedsoftheuserandisfoundintheuser’shomedirectory.Itcanbefoundbytyping1s–a1intheuser’shomedirectory.Itcanbelistedasfollows:

The.cshrcfilewillbediscussedlater.

38.3LeavingtheCshellAn annoying feature of the Bourne shell is that if the user presses theCONTROL-Dkeystrokebymistakethentheywillbelogged-out.IntheCshellif theignoreeof variable is set then theCONTROL-D (^D) logoutprocess isinactive.AusercanexitfromtheCshellbytypingexit.Tosettheignoreeofvariablejusttype:

This is usually done automatically when entering the shell. An example ofenteringandleavingtheCshellisgivenbelow.

Note:Iftheignoreeofvariableisnotsetthen^DwillexittheCshell.

38.4HistoryThehistorymechanismmaintains a list ofprevious command lines,whicharealso called events. To set the number of events the set history command isused.Forexample,tosetthenumberofstoredeventsto10:

andtorecallthepreviouseventsthehistorycommandistyped:

38.5ReexecutingeventsItispossibletoreexecuteanyeventinthehistorylist.Thereferencetoaneventismadebystartingthelinewitha!.

38.5.1EventNumbersAn event can be reexecuted using the event number. This is achieved by a !followedbytheeventnumber.

Anegativenumberaftertheexclamationmarkreferstoaneventpriortothecurrentevent.

38.5.2ReexecutingPreviousEventTwo exclamation marks (! !) are used to reexecute the previous event. Forexample:

38.5.3EventsUsingTextToexecuteapreviouseventwithtextthenanexclamationmarkfollowedbytextatthebeginningoftheeventcanbeused.Forexample:

38.5.4ChangingLastEventTypicallyausermakesamistakeinacommandlineandwantstoreplaceapartof thecommand linewithanother.Tochangea stringof text in the last eventthen the caret (^) symbol is used. For example ^fred^temp reexecutes the lasteventbutchangesfredfortemp.Forexample:

38.5.5ChangingPreviousEventsTomodify a previous event it is possible to use the :s/old/new to change agiven event. The event is specified by the methods given previously. Forexample:

Thefirstexamplechangesevent13butsubstitutestempforfred.Thesecondexampleexecutesthelasteventbeginningwithcatandsubstitutesyyyforxxx.

38.6Alias

Thealiasmechanismallowsauser tosubstituteagivencommandfora singleword(oralias).Thefollowingarecommonaliases:

Thefirstexampleexecutesthehistorycommandwheneverhisenteredatthecommandline.Thesecondexecutesan1s–a1whendirisentered.Theusercanlistthecurrentlydefinedaliasesbysimplytypingalias,suchas:

Theunaliascommandisusedtoremoveanalias,suchas:

38.7VariablesTheCshellonlyusesstringsanddoesnotusenumbers.Thus,forexample,5isinterpretedas thecharacter5andnotas thenumber5.Tooperateonnumbersthe@isused.

38.7.1VariableSubstitutionThecommandsthatareusedtomanipulatevariablesare:•setenvwhichoperatesonglobalvariables(thatis,systemvariables).•setand@whichoperateonlocalvariablestothecurrentshell.A variable is recognized by a preceding $ followed by the variable name.

Examplesare$fruit,$numbers,andsoon.

38.7.2StringVariablesTheCshelltreatsvariablesasstrings.Todeclareavariablethesetcommandisused.Forexample:

Thiswilldeclarethevariablemynamewhichcontainsthestring“Bill”.Notethataspaceoneithersideofthe=isnecessary.

38.7.3ArraysOfStringsBefore an arraymember is used itmust be declared, that is, set. It is used todeclareeverymemberofthearray.

38.7.4NumericalVariablesThe@ command is used to assign a numeric variable. The format of the@commandis:@variable-nameoperatorexpressionTheoperatorcanbeanyoftheCoperators.Theseare:

Shiftoperators:

Relationship:

Bitwise:

Logical:

Anexampleisgivennext:

38.7.5FilesFilescanbetestedfortheirstatususingthe–noption,thestandardformis:

wherencanbe:d.fileisadirectorye.fileexistsf.fileisaplainfileo.userownsthefiler.userhasreadaccesstofilew.userhaswriteaccesstofilex.userhasexecuteaccesstofilez.fileisempty

Forexample

38.8Specialforms($#,$?and~)The number of elements in an array is determined using the $# operator. Thegeneralformatis:

Todetermineifavariablehasbeendeclaredthe$?canbeused.Thegeneralformatis:

Thevaluereturnedwillbezeroifithasnotbeendeclaredand1ifithasbeendeclared.

The~ (tilde) operator is used to substitute for the full pathname of a givenuser.Forexample:

Thus–fredstandsforuserfred’shomedirectory,andsoon.

38.9ShellvariablesThesevariables canbe set by either the shell or theuser.There are twobasictypes:thefirstisgivenvalues,whereasthesecondiseithersetorunset.

38.9.1SystemVariablesThatTakeAValueThestandardvariablesthattakeonvaluesare:•$argv–Theargvvariablecontainsallthecommandlinearguments.argv

[0]holdsthenameofthecallingprogram,argv[1]containsthefirstargument,andsoon.Forexample,ifthecommandlineis:

Thentheargvvariableswillbe:

•$#argv–containsthenumberofcommandlinearguments.Inthepreviousexamplethiswillbe4.

•$cdpath–Thevariableisusedbythecdcommand.Whenacdcommandwithasimplefilenameisgiven,thenthesystemwillsearchthecurrentworkingdirectory.Ifthefileisnotinthecurrentworkingdirectorythenthesystemwillsearchinthedirectoriesgivenbythecdpathvariable.Ifafileisfoundinanyofthesearchpathsthenthesystemchangestothatdirectory.Itisusuallysetinthe.loginfile,forexample:

•$cwd–fullpathnameofcurrentdirectory.•$history–definesthesizeofthehistorylist.Thisvalueisusuallysetinthe

.cshrcfile,suchas:

•$home–definesthehomedirectoryoftheuser.

•$mail–fileswheretheshellchecksformail.•$path–givesthedirectoriesinwhichthesystemsearchesforexecutables.

Usuallythesearchpathis‘.’,‘/bin’andusr/bin’.Forexample:

•$prompt–Astringthatisprintedbeforeeachcommandisread.Ifa‘!’appearsinthestringthecurrenteventnumberissubstituted.Thedefaultpromptisa%.Anexamplepromptsettingis:

whichwillprintasaprompt:

ifthecurrentdirectoryisusrstaff/bill_b/docs,thecurrenteventwas15andtheuser’snameisbill_b.

•$savehist–containsthenumberofhistoryeventsthatarestoredwhentheuserlogsout.Theseeventsarestoredinthe~/.historyfile.Whentheusernextlogsinthenthecurrenthistorylistwillbeasthesavedeventhistory.

38.9.2SystemVariablesAreSetThestandardvariablesthataresetare:•$filec–enablesfilenamecompletion.Ifitissetthenthefilenameis

completedwhenthe<ESC>keyispressedandthefileisfound.

maybecome:

The<Cntl-D>(^D)characterisusedtolistanyfileswhichmatchthecurrentinput.Forexample:

InthisexamplethefileswhichmatchthefirstthreecharactersFORarelisted.

•$ignoreeof–ifsettheshellignoresthe<Cntrl-D>logoutcommandandexitisusedtoleavetheshell.Itissetwith:

•$noclobber–whensettherearerestrictionsontheredirectiontofiles.Ifa>isgivenandthefileexistsitwillnotbedestroyed.

38.10ShellscriptsA shell script is a file that contains C shell commands. To execute a file themodemustbechangedsothatitcanbeexecuted.Forexample:

NotethatthefirstnonblankcharacterinaCshellscriptmustbea#.ThistellstheshellthatitisaCshellscript.

38.11ControlStructuresTheCshellcontrolstatementsareif,foreach,whileandswitch.

38.11.1IfThegeneralformatoftheifcontrolstructureisgivenbelow.

AnexampleofaCshellscriptusingtheifcontrolstructureis:

Ifthescript’sfilenamewereargtestthenatypicalrunsessionmaybe:

38.11.2If-ThenElseTherearethreedifferenttypesofif-thenelsestructures:

Type1 Type2 Type3

if(expression)thencommands if(expression)thencommands if(expression)thencommands

endif elsecommands elseif(expression)then.

endif .

endif

AnexampleofaShellscriptusingif-thenis:

Ifthefileiscalledgradethenatypicalrunsessionmaybe:

38.11.3ForeachThe foreach structure reads each argument of an argument list in turn. Thestandardformatisasfollows:

Whentheloopisfirstexecutedthenloopindexwillbeassignedthefirstvalueintheargument-list.Thecommandsarethenexecutedandtheloopreturnstothestartandtheloopindexthentakesonthesecondvalueintheargument-list,andsoon.

38.11.4WhileThegeneralformatofthewhileloopis:

The followingshell script isanexamplewhichdetermines the factorialofanumber.

38.11.5SwitchTheswitchstatementcanchoosebetweenseveraldifferentstrings.Thegeneralformatis:

An example of the switch structure which implements a basic calculator isgivennext:

38.12AutomaticallyexecutedCshellscripts(.login.cshrc)Whensomeonelogsontothesystem,orstartsaCshell,threeCshellscriptsarerunatvarioustimes.

38.12.1The.LoginFileThe.loginfileisexecutedwhentheuserlogsontothesystem.Usuallythisfilecontainsterminalandkeyboardcommands.Anexampleofatypical.loginfileisshownbelow.Inthiscase,thesetenvcommandisusedtosetavariableforallshells,thatiscshandsh.Theterminaltypesetupisavt100.

38.12.2The.CshrcFileThe.cshrcfileisexecutedwheneveraCshell isrun.Againit isfoundinthehomedirectoryoftheuser.ItistypicallyusedtosetupparametersusedbytheCshell,suchasthepath,prompt,andsoon.Aquickwayoflistingthe.cshrcfilewhereveryouareis:

Atypical.cshrcfileis:

38.12.3The.LogoutFileThe.logoutfileisautomaticallyexecutedwhentheuserlogsoutofthesystem.It typicallycontainscommandswhich tidyup theuser’sworkareaandalso towritemessages.

38.13Exercises38.13.1.Usinganalias,defineacommandnamedrenamewhichisequivalentto:

38.13.2.Usingthedatecommand,setuserprompttogivethedate.38.13.3.WriteaCshellscriptthatcalculatesthesumofnumbersup-toand

includingthenumbergiven.38.13.4.WriteaCshellscriptnamedadd_dot_C.whichwilladda.ctoany

givenfilename.Forexample:

wouldcausethefilefredtobecomefred.c.38.13.5.Thecommandforfindingagivenfileonthesystemis:

whichsearchesfromthetop-leveldirectoryforthefilecalledfilename.Forexample,tofindprog1.cthefollowingcanbeused:

WriteaCshellscriptwhichiscalledfindfileinwhichtheargumentpassedtoitisthefilename.Forexample,

38.13.6.Thestreameditorsedcanbeusedtoreplaceagivenwordwithanotherword.Theformatofthiscommandisgivenbelow:

Thischangeswordoldforwordnewgloballyinfilecalledfilename.Writeashellscriptcalledreplacewhichgivesthreearguments.Thefirsttwoareforthewordsandthethirdforthefilename.Forexample,toreplacefredforterryinthefilename_file:

38.13.7.WriteaCshellscriptwhichwillgiveinformationaboutagivenfile.Theinformationshouldincludeaccessrights,whetheritisofzerolength,filetype,andsoon.Nametheshellscripttestfile.

A

JavaClassesjava/java/lang/java/lang/Object.classjava/lang/Exception.classjava/lang/Integer.classjava/lang/NumberFormatException.class java/lang/Throwable.class

java/lang/Class.classjava/lang/IllegalAccessException.class java/lang/StringBuffer.class

java/lang/ClassNotFoundException.classjava/lang/IllegalArgumentException.classjava/lang/Number.classjava/lang/InterruptedException.classjava/lang/String.classjava/lang/RuntimeException.class java/lang/InternalError.class

java/lang/Long.classjava/lang/Character.class java/lang/CloneNotSupportedException.class

java/lang/InstantiationException.class java/lang/VirtualMachineError.classjava/lang/Double.classjava/lang/Error.classjava/lang/NullPointerException.class java/lang/Cloneable.class

java/lang/System.classjava/lang/ClassLoader.classjava/lang/Math.classjava/lang/Float.classjava/lang/Runtime.classjava/lang/StringIndexOutOfBoundsException.class

java/lang/IndexOutOfBoundsException.class java/lang/SecurityException.classjava/lang/LinkageError.classjava/lang/Runnable.classjava/lang/Process.classjava/lang/SecurityManager.classjava/lang/Thread.classjava/lang/UnsatisfiedLinkError.class

java/lang/IncompatibleClassChangeError.classjava/lang/NoSuchMethodError.class java/lang/IllegalThreadStateException.classjava/lang/ThreadGroup.class java/lang/ThreadDeath.classjava/lang/ArraylndexOutOfBoundsException.classjava/lang/Boolean.class

java/lang/Compiler.class java/lang/NoSuchMethodException.classjava/lang/ArithmeticException.class java/lang/ArrayStoreException.classjava/lang/ClassCastException.class java/lang/NegativeArraySizeException.classjava/lang/IllegalMonitorStateException.classjava/lang/ClassCircularityError.class java/lang/ClassFormatError.classjava/lang/AbstractMethodError.class java/lang/IllegalAccessError.classjava/lang/InstantiationError.class java/lang/NoSuchFieldError.classjava/lang/NoClassDefFoundError.class java/lang/VerifyError.classjava/lang/OutOfMemoryError.class java/lang/StackOverflowError.classjava/lang/UnknownError.classjava/lang/Win32Process.classjava/io/java/io/FilterOutputStream.class java/io/OutputStream.class

java/io/IOException.classjava/io/PrintStream.classjava/io/FileInputStream.classjava/ioAnterruptedIOException.classjava/io/File.classjava/io/InputStream.class java/io/BufferedInputStream.class

java/io/FileOutputStream.class java/io/FileNotFoundException.classjava/io/BufferedOutputStream.class java/io/FileDescriptor.classjava/io/FilenameFilter.class java/io/FilterInputStream.classjava/io/PipedInputStream.class java/io/PipedOutputStream.classjava/io/EOFException.class java/io/UTFDataFormatException.classjava/io/DataInput.classjava/io/DataOutput.class java/io/DataInputStream.class

java/io/PushbackInputStream.class java/io/ByteArrayInputStream.classjava/io/SequenceInputStream.class java/io/StringBufferInputStream.classjava/io/LineNumberInputStream.class java/io/DataOutputStream.classjava/io/ByteArrayOutputStream.class java/io/RandomAccessFile.classjava/io/StreamTokenizer.classjava/util/java/util/Hashtable.class java/util/Enumeration.class

java/util/HashtableEnumerator.class java/util/Properties.classjava/util/HashtableEntry.classjava/util/Dictionary.classjava/util/Date.classjava/util/NoSuchElementException.class java/util/StringTokenizer.class

java/util/Random.classjava/util/VectorEnumerator.classjava/util/Vector.classjava/util/BitSet.classjava/util/EmptyStackException.class java/util/Observable.class

java/util/Observer.classjava/util/ObserverList.classjava/util/Stack.classjava/awt/java/awt/Toolkit.class

java/awt/peer/java/awt/peer/WindowPeer.class java/awt/peer/TextFieldPeer.class

java/awt/peer/ContainerPeer.class java/awt/peer/PanelPeer.classjava/awt/peer/CanvasPeer.class java/awt/peer/FramePeer.classjava/awt/peer/ChoicePeer.class java/awt/peer/CheckboxMenuItemPeer.classjava/awt/peer/TextAreaPeer.class java/awt/peer/FileDialogPeer.classjava/awt/peer/TextComponentPeer.class java/awt/peer/ScrollbarPeer.classjava/awt/peer/ButtonPeer.class java/awt/peer/ComponentPeer.classjava/awt/peer/MenuComponentPeer.class java/awt/peer/MenuItemPeer.classjava/awt/peer/CheckboxPeer.class java/awt/peer/MenuPeer.classjava/awt/peer/ListPeer.class java/awt/peer/MenuBarPeer.classjava/awt/peer/LabelPeer.class java/awt/peer/DialogPeer.classjava/awt/Image.classjava/awt/MenuItem.classjava/awt/MenuComponent.classjava/awt/image/java/awt/image/ImageProducer.class java/awt/image/ColorModel.class

java/awt/image/DirectColorModel.class java/awt/image/ImageConsumer.classjava/awt/image/ImageObserver.class java/awt/image/CropImageFilter.classjava/awt/image/ImageFilter.class java/awt/image/FilteredImageSource.classjava/awt/image/IndexColorModel.classjava/awt/image/MemoryImageSource.class java/awt/image/PixelGrabber.classjava/awt/image/RGBImageFilter.class java/awt/FontMetrics.classjava/awt/Checkbox.class java/awt/CheckboxGroup.classjava/awt/MenuContainer.classjava/awt/Menu.classjava/awt/Insets.classjava/awt/MenuBar.classjava/awt/List.classjava/awt/Label.classjava/awt/Component.class java/awt/TextField.class

java/awt/TextComponent.classjava/awt/Dialog.classjava/awt/Font.classjava/awt/Window.classjava/awt/FocusManager.classjava/awt/Panel.classjava/awt/Container.class java/awt/Graphics.class

java/awt/CheckboxMenuItem.classjava/awt/Canvas.classjava/awt/Frame.classjava/awt/Choice.classjava/awt/Event.class

java/awt/TextArea.classjava/awt/AWTError.classjava/awt/Polygon.classjava/awt/FlowLayout.classjava/awt/Point.classjava/awt/FileDialog.class java/awt/Scrollbar.class java/awt/Dimension.class

java/awt/Color.classjava/awt/Button.classjava/awt/LayoutManager.class java/awt/Rectangle.class

java/awt/BorderLayout.class java/awt/GridLayout.classjava/awt/GridBagConstraints.class java/awt/GridBagLayout.classjava/awt/GridBagLayoutInfo.class java/awt/CardLayout.classjava/awt/MediaTracker.class java/awt/MediaEntry.classjava/awt/ImageMediaEntry.classjava/awt/AWTException.classjava/net/java/net/URL.classjava/net/URLStreamHandlerFactory.class java/net/InetAddress.class

java/net/UnknownContentHandler.class java/net/UnknownHostException.classjava/net/URLStreamHandler.class java/net/URLConnection.classjava/net/MalformedURLException.class java/net/ContentHandlerFactory.classjava/net/ContentHandler.class java/net/UnknownServiceException.classjava/net/ServerSocket.class java/net/PlainSocketImpl.classjava/net/SocketImpl.class java/net/ProtocolException.classjava/net/SocketException.class java/net/SocketInputStream.classjava/net/Socket.classjava/net/SocketImplFactory.class java/net/SocketOutputStream.class

java/net/DatagramPacket.class java/net/DatagramSocket.classjava/net/URLEncoder.classjava/applet/java/applet/Applet.class java/applet/AppletContext.class

java/applet/AudioClip.classjava/applet/AppletStub.classsun/sun/tools/sun/tools/debug/sun/tools/debug/BreakpointQueue.class

sun/tools/debug/DebuggerCallback.class sun/tools/debug/RemoteThread.classsun/tools/debug/StackFrame.class sun/tools/debug/RemoteAgent.classsun/tools/debug/AgentConstants.class sun/tools/debug/AgentIn.classsun/tools/debug/RemoteObject.classsun/tools/debug/RemoteStackVariable.classsun/tools/debug/Remote Value.class sun/tools/debug/RemoteClass.classsun/tools/debug/Agent.class sun/tools/debug/RemoteBoolean.classsun/tools/debug/RemoteChar.class sun/tools/debug/RemoteString.classsun/tools/debug/NoSessionException.class sun/tools/debug/Field.class

sun/tools/debug/NoSuchLineNumberException.classsun/tools/debug/RemoteShort.class sun/tools/debug/RemoteThreadGroup.classsun/tools/debug/RemoteInt.class sun/tools/debug/ResponseStream.classsun/tools/debug/RemoteDouble.class sun/tools/debug/LocalVariable.classsun/tools/debug/BreakpointSet.class sun/tools/debug/RemoteStackFrame.classsun/tools/debug/MainThread.class sun/tools/debug/BreakpointHandler.classsun/tools/debug/AgentOutputStream.class sun/tools/debug/RemoteLong.classsun/tools/debug/RemoteFloat.class sun/tools/debug/RemoteArray.classsun/tools/debug/InvalidPCException.class sun/tools/debug/LineNumber.classsun/tools/debug/RemoteField.class sun/tools/debug/NoSuchFieldException.classsun/tools/debug/RemoteByte.class sun/tools/debug/EmptyApp.classsun/tools/debug/RemoteDebugger.classsun/tools/java/sun/tools/java/RuntimeConstants.class sun/tools/java/Constants.class

sun/tools/java/Environment.class sun/tools/java/ClassPath.classsun/tools/java/ClassDeclaration.class sun/tools/java/FieldDefinition.classsun/tools/java/Type.class sun/tools/java/ClassNotFound.classsun/tools/java/ClassType.class sun/tools/java/ClassDefinition.classsun/tools/java/Parser.class sun/tools/java/ClassPathEntry.classsun/tools/java/CompilerError.class sun/tools/java/Identifier.classsun/tools/java/Package.class sun/tools/java/ClassFile.classsun/tools/java/Imports.class sun/tools/java/ArrayType.classsun/tools/java/AmbiguousField.class sun/tools/java/MethodType.classsun/tools/java/Scanner.class sun/tools/java/SyntaxError.classsun/tools/java/BinaryClass.class sun/tools/java/BinaryField.classsun/tools/java/AmbiguousClass.class sun/tools/java/BinaryConstantPool.classsun/tools/java/ScannerInputStream.class sun/tools/java/BinaryAttribute.classsun/tools/java/BinaryCode.class sun/tools/java/BinaryExceptionHandler.classsun/tools/javac/sun/tools/javac/Main.class sun/tools/javac/SourceClass.class

sun/tools/javac/CompilerField.class sun/tools/javac/SourceField.classsun/tools/javac/BatchEnvironment.class sun/tools/javac/ErrorConsumer.classsun/tools/javac/ErrorMessage.class sun/tools/javac/BatchParser.classsun/tools/zip/sun/tools/zip/ZipFile.class sun/tools/zip/ZipEntry.class

sun/tools/zip/ZipFileInputStream.class sun/tools/zip/ZipConstants.classsun/tools/zip/ZipFormatException.classsun/tools/zip/ZipReaderInputStream.class sun/tools/zip/ZipReader.class

sun/tools/tree/sun/tools/tree/ConstantExpression.class sun/tools/tree/LocalField.class

sun/tools/tree/Expression.class sun/tools/tree/IncDecExpression.classsun/tools/tree/SuperExpression.class sun/tools/tree/NaryExpression.classsun/tools/tree/StringExpression.class sun/tools/tree/UnaryExpression.classsun/tools/tree/Context.class sun/tools/tree/ExpressionStatement.classsun/tools/tree/ConditionVars.class sun/tools/tree/Node.classsun/tools/tree/CharExpression.class sun/tools/tree/CaseStatement.classsun/tools/tree/LessExpression.class sun/tools/tree/IntegerExpression.classsun/tools/tree/SubtractExpression.classsun/tools/tree/ArrayAccessExpression.class sun/tools/tree/TryStatement.classsun/tools/tree/BinaryEqualityExpression.class sun/tools/tree/Statement.classsun/tools/tree/AssignSubtractExpression.classsun/tools/tree/FinallyStatement.class sun/tools/tree/ForStatement.classsun/tools/tree/DivRemExpression.class sun/tools/tree/BinaryExpression.classsun/tools/tree/ShiftRightExpression.classsun/tools/tree/AssignMultiplyExpression.classsun/tools/tree/BooleanExpression.classsun/tools/tree/BinaiyAritnmeticExpression.classsun/tools/tree/ThrowStatement.classsun/tools/tree/AssignDivideExpression.classsun/tools/tree/AssignShiftLeftExpression.classsun/tools/tree/NewArrayExpression.class sun/tools/tree/AndExpression.classsun/tools/tree/AssignBitOrExpression.class sun/tools/tree/BreakStatement.classsun/tools/tree/SynchronizedStatement.classsun/tools/tree/PreDecExpression.class sun/tools/tree/CompoundStatement.classsun/tools/tree/DoubleExpression.class sun/tools/tree/ConvertExpression.classsun/tools/tree/NullExpression.class sun/tools/tree/LessOrEqualExpression.classsun/tools/tree/IdentifierExpression.class sun/tools/tree/ReturnStatement.classsun/tools/tree/BitNotExpression.class sun/tools/tree/LongExpression.classsun/tools/tree/VarDeclarationStatement.classsun/tools/tree/MethodExpression.class sun/tools/tree/ThisExpression.classsun/tools/tree/BitOrExpression.class sun/tools/tree/PositiveExpression.classsun/tools/tree/IfStatement.class sun/tools/tree/FloatExpression.classsun/tools/tree/NotEqualExpression.classsun/tools/tree/InstanceOfExpression.class sun/tools/tree/NotExpression.classsun/tools/tree/BitAndExpression.class sun/tools/tree/DivideExpression.class

sun/tools/tree/ShortExpression.class sun/tools/tree/RemainderExpression.classsun/tools/tree/NewInstanceExpression.class sun/tools/tree/SwitchStatement.classsun/tools/tree/AddExpression.class sun/tools/tree/AssignOpExpression.classsun/tools/tree/EqualExpression.class sun/tools/tree/PostIncExpression.classsun/tools/tree/GreaterExpression.class sun/tools/tree/PostDecExpression.classsun/tools/tree/AssignExpression.class sun/tools/tree/WhileStatement.classsun/tools/tree/ContinueStatement.classsun/tools/tree/ConditionalExpression.classsun/tools/tree/AssignAddExpression.classsun/tools/tree/BinaryBitExpression.class sun/tools/tree/CastExpression.classsun/tools/tree/AssignBitXorExpression.classsun/tools/tree/ArrayExpression.classsun/tools/tree/InlineMethodExpression.classsun/tools/tree/InlineNewInstanceExpression.classsun/tools/tree/CodeContext.classsun/tools/tree/AssignShiftRightExpression.classsun/tools/tree/UnsignedShiftRightExpression.classsun/tools/tree/AssignBitAndExpression.classsun/tools/tree/ShiftLeftExpression.class sun/tools/tree/CatchStatement.classsun/tools/tree/IntExpression.class sun/tools/tree/TypeExpression.classsun/tools/tree/CommaExpression.classsun/tools/tree/AssignUnsignedShiftRightExpression.classsun/tools/tree/ExprExpression.classsun/tools/tree/AssignRemainderExpression.classsun/tools/tree/ByteExpression.class sun/tools/tree/BinaryAssignExpression.classsun/tools/tree/DoStatement.class sun/tools/tree/DeclarationStatement.classsun/tools/tree/MultiplyExpression.classsun/tools/tree/InlineReturnStatement.class sun/tools/tree/BitXorExpression.classsun/tools/tree/BinaryCompareExpression.classsun/tools/tree/BinaryShiftExpression.class sun/tools/tree/CheckContext.classsun/tools/tree/PreIncExpression.classsun/tools/tree/GreaterOrEqualExpression.classsun/tools/tree/FieldExpression.class sun/tools/tree/OrExpression.classsun/tools/tree/BinaryLogicalExpression.classsun/tools/tree/NegativeExpression.class sun/tools/tree/LengthExpression.classsun/tools/asm/sun/tools/asm/Assembler.class sun/tools/asm/Instruction.class

sun/tools/asm/LocalVariable.class sun/tools/asm/ArrayData.classsun/tools/asm/LocalVariableTable.classsun/tools/asm/SwitchDataEnumeration.class sun/tools/asm/ConstantPool.classsun/tools/asm/ConstantPoolData.classsun/tools/asm/NameAndTypeConstantData.classsun/tools/asm/NumberConstantData.classsun/tools/asm/FieldConstantData.classsun/tools/asm/TryData.class sun/tools/asm/Label.classsun/tools/asm/SwitchData.class sun/tools/asm/CatchData.classsun/tools/asm/StringExpressionConstantData.classsun/tools/asm/NameAndTypeData.class sun/tools/asm/StringConstantData.classsun/tools/asm/ClassConstantData.classsun/tools/ttydebug/sun/tools/ttydebug/TTY.classsun/tools/javadoc/sun/tools/javadoc/Main.classsun/tools/javadoc/DocumentationGenerator.class

sun/tools/javadoc/HTMLDocumentationGenerator.classsun/tools/javadoc/MIFDocumentationGenerator.classsun/tools/javadoc/MIFPrintStream.classsun/net/sun/net/MulticastSocket.class sun/net/URLCanonicalizer.class

sun/net/NetworkClient.class sun/net/NetworkServer.classsun/net/ProgressData.class sun/net/ProgressEntry.classsun/net/TelnetInputStream.class sun/net/TelnetProtocolException.classsun/net/TelnetOutputStream.class sun/net/TransferProtocolClient.classsun/net/ftp/sun/net/ftp/FtpInputStream.class sun/net/ftp/FtpClient.class

sun/net/ftp/FtpLoginException.class sun/net/ftp/FtpProtocolException.classsun/net/ftp/IftpClient.classsun/net/nntp/sun/net/nntp/NewsgroupInfo.class sun/net/nntp/NntpClient.class

sun/net/nntp/UnknownNewsgroupException.classsun/net/nntp/NntpProtocolException.class sun/net/nntp/NntpInputStream.classsun/net/smtp/sun/net/smtp/SmtpPrintStream.class sun/net/smtp/SmtpClient.class

sun/net/smtp/SmtpProtocolException.classsun/net/www/sun/net/www/auth/sun/net/www/auth/Authenticator.class sun/net/www/auth/basic.class

sun/net/www/content/sun/net/www/content/text/sun/net/www/content/text/Generic.class sun/net/www/content/text/plain.class

sun/net/www/content/image/

sun/net/www/content/image/gif.class sun/net/www/content/image/jpeg.classsun/net/www/content/image/x_xbitmap.classsun/net/www/content/image/x_xpixmap.classsun/net/www/FormatException.class sun/net/www/MessageHeader.classsun/net/www/MeteredStream.class sun/net/www/ProgressReport.classsun/net/www/MimeEntry.class sun/net/www/MimeLauncher.classsun/net/www/MimeTable.class sun/net/www/URLConnection.classsun/net/www/UnknownContentException.classsun/net/www/UnknownContentHandler.classsun/net/www/protocol/sun/net/www/protocol/file/sun/net/www/protocol/file/Handler.class

sun/net/www/protocol/file/FileURLConnection.classsun/net/www/protocol/http/sun/net/www/protocol/http/Handler.class

sun/net/www/protocol/http/HttpURLConnection.classsun/net/www/protocol/http/HttpPostBufferStream.classsun/net/www/protocol/doc/sun/net/www/protocol/doc/Handler.classsun/net/www/protocol/verbatim/sun/net/www/protocol/verbatim/Handler.class

sun/net/www/protocol/verbatim/VerbatimConnection.classsun/net/www/protocol/gopher/sun/net/www/protocol/gopher/GopherClient.class

sun/net/www/protocol/gopher/GopherInputStream.classsun/net/www/http/sun/net/www/http/UnauthorizedHttpRequestException.class

sun/net/www/http/HttpClient.class sun/net/www/http/AuthenticationInfo.classsun/awt/sun/awt/HorizBagLayout.class sun/awt/VerticalBagLayout.class

sun/awt/VariableGridLayout.class sun/awt/FocusingTextField.classsun/awt/win32/sun/awt/win32/MToolkit.class sun/awt/win32/MMenuBarPeer.class

sun/awt/win32/MButtonPeer.class sun/awt/win32/Win32Image.classsun/awt/win32/MScrollbarPeer.class sun/awt/win32/MDialogPeer.classsun/awt/win32/MCheckboxMenuItemPeer.classsun/awt/win32/Win32Graphics.class sun/awt/win32/MListPeer.classsun/awt/win32/MWindowPeer.class sun/awt/win32/MMenuItemPeer.classsun/awt/win32/ModalThread.class sun/awt/win32/MCanvasPeer.classsun/awt/win32/MFileDialogPeer.class sun/awt/win32/MTextAreaPeer.classsun/awt/win32/MPanelPeer.class sun/awt/win32/MComponentPecr.class

sun/awt/win32/MCheckboxPeer.class sun/awt/win32/MLabelPeer.classsun/awt/win32/Win32FontMetrics.class sun/awt/win32/MFramePeer.classsun/awt/win32/MMenuPeer.class sun/awt/win32/MChoicePeer.classsun/awt/win32/MTextFieldPeer.class sun/awt/win32/Win32PrintJob.classsun/awt/image/sun/awt/image/URLImageSource.class sun/awt/image/ImageWatched.class

sun/awt/image/InputStreamImageSource.classsun/awt/image/ConsumerQueue.class sun/awt/image/ImageDecoder.classsun/awt/image/ImageRepresentation.classsun/awt/image/ImageInfoGrabber.class sun/awt/image/XbmImageDecoder.classsun/awt/image/GifImageDecoder.class sun/awt/image/ImageFetcher.classsun/awt/image/PixelStore.class sun/awt/image/JPEGImageDecoder.classsun/awt/image/PixelStore8.class sun/awt/image/ImageFetchable.classsun/awt/image/OffScreenImageSource.class sun/awt/image/PixelStore32.classsun/awt/image/ImageFormatException.classsun/awt/image/FileImageSource.class sun/awt/image/Image.classsun/awt/UpdateClient.class sun/awt/ScreenUpdaterEntry.classsun/awt/ScreenUpdater.classsun/misc/sun/misc/Ref.classsun/misc/MessageUtils.classsun/misc/Cache.classsun/misc/CacheEntry.class sun/misc/CacheEnumerator.class

sun/misc/CEFormatException.class sun/misc/CEStreamExhausted.classsun/misc/CRC16.classsun/misc/CharacterDecoder.class sun/misc/BASE64Decoder.class

sun/misc/UCDecoder.class sun/misc/UUDecoder.classsun/misc/CharacterEncoder.class sun/misc/BASE64Encoder.classsun/misc/HexDumpEncoder.class sun/misc/UCEncoder.classsun/misc/UUEncoder.class sun/misc/Timeable.classsun/misc/TimerTickThread.classsun/misc/Timer.classsun/misc/TimerThread.class sun/misc/ConditionLock.class

sun/misc/Lock.classsun/audio/sun/audio/AudioDataStream.class sun/audio/AudioData.class

sun/audio/AudioDevice.class sun/audio/AudioPlayer.classsun/audio/AudioStream.class sun/audio/NativeAudioStream.classsun/audio/InvalidAudioFormatException.classsun/audio/AudioTranslatorStream.class sun/audio/AudioStreamSequence.class

sun/audio/ContinuousAudioDataStream.classsun/applet/sun/applet/StdAppletViewerFactory.class sun/applet/TextFrame.class

sun/applet/AppletViewerFactory.class sun/applet/AppletViewer.classsun/applet/AppletCopyright.class sun/applet/AppletAudioClip.classsun/applet/AppletSecurity.class sun/applet/AppletThreadGroup.classsun/applet/AppletClassLoader.class sun/applet/AppletPanel.classsun/applet/AppletViewerPanel.class sun/applet/AppletProps.classsun/applet/AppletSecurityException.classsun/applet/AppletZipClassLoader.class

B

ANSI-CFunctionsTableB.1Timefunctions

TableB.2

TableB.2Classificationfunctions

TableB.3Stringfunctions

TableB.4Conversionfunctions

TableB.5Input/outputfunctions

TableB.6Otherstandardfunction

TableB.7Mathfunctions

C

TurboPascalReferenceThefollowingisalistofTurboPascalprocedures.

TurboPascalaccessessomestandardproceduresandfunctionsthroughunits,whicharelibrariesofprecompiledmodules.Forexample,theCrtunitcontainsroutineswhichaccessthetextdisplay.Touseaunittheuseskeywordmustbeincluded in a statement near the top of the program. For example, to use theclrscrfunction:

Thelistingofmodulesinthecrtunitis:

Thelistingofmodulesinthesystemunitis:

Thelistingofmodulesinthedosunitis:

Thelistingofmodulesinthegraphunitis:

Thefollowingisaquickreferencetocommonlyusedfunctions.

Thefollowingisaquickreferencetocommonlyusedprocedures.

D

AssemblyLanguageReferenceD.1AssemblylanguagemnemonicsTableD.1 outlines theAssemblyLanguagemnemonics (in column1) and theequivalentencodedbitvalues(incolumn3).Italsoshowsthenumberofcyclesfora8086processoranda80386processor(columns4and5).Theexplanationoftheencodedbitvaluesisgivenafterthetable.

TableD.1AssemblyLanguagereference

Syntax:

reg Ageneral-purposeregisterofanysize.

segreg Asegmentregisters,suchasDS,ES,SSorCS.

accum Anaccumulatorofanysize:ALorAX(orEAXon386/486).

mem Adirectorindirectmemoryoperandofanysize.

label Alabeledmemorylocationinthecodesegment.

src,dest Asourceofdestinationmemoryoperandusedinastringoperand.

immed Aconstantoperand.

andthebitsarespecifiedby:

d directionbit.Ifset(1)thenthetransferisfrommemorytoregisterorregistertoregister,andthedestinationisaregfield.Ifnotsetthenthesourceisaregisterfieldandthetransferisfromregistertomemory.

w word/bytebit.Ifsetthe16-bitoperandsareused,else8-bitoperandsareused.

s signbit.Ifsetthentheoperandhasasign-bit.

mod mode.Identifiestheregister/memorymode.Theseare:

00 Ifr/mis110thendirectmemoryisused,elsethedisplacementis0andanindirectmemoryoperandisused.

01 Anindirectmemoryoperandisusedwithan8-bitdisplacement.

10 Anindirectmemoryoperandisusedwitha16-bitdisplacement.

11 Atwo-registerinstructionisused;theregfieldspecifiesthedestinationandther/mfieldspecifiesthesource.

regregister.Specifiesoneofthegeneral-purposeregisters.Theseare:

reg 16-bit,ifw=1 8-bit,ifw=0

000 AX AL

001 CX CL

010 DX DL

011 BX BL

100 SP AH

100 SP AH

101 BP CH

110 SI DH

111 DI BH

r/mregister/memory.Specifiesamemoryofregisteroperand.Ifthemodfileis11thentheregisterisspecifiedwiththeregfield(asgivenabove),elseithasthefollowingsettings:

reg Operandaddress

000 DS:[BX+SI+disp]

001 DS:[BX+DI+disp]

010 SS:[BP+SI+disp]

011 SS:[BP+DI+disp]

100 DS:[SI+disp]

101 DS:[DI+disp]

110 DS:[BP+disp]

111 DS:[BX+disp]

Theinstructionencodinghastheform:

where:

Disp displacement.Specifiestheoffsetformemoryoperands.

mmedi register/memory.Specifiestheactualvaluesforconstantvalues

D.2AssemblerdirectivesTableD.2outlinessomeAssemblyLanguagedirectives.

TableD.2AssemblyLanguagereference

Directive Description

.386 Enablesassemblyof386code.

.8086 Enablesassemblyof8086code.

ASSUMEsegreg:name Selectssegregtobethedefaultsegmentregisterforallsymbolsinthenamedsegment.

.CODE Definesthecodesegment.

COMMENT Definesacomment.

.CONST Definesaconstant.

nameDBinit Allocationsandoptionallyinitializesabyteofstorageforeachinit.

nameDWinit Allocationsandoptionallyinitializesawordofstorageforeachinit.

nameDDinit Allocationsandoptionallyinitializesadoublewordofstorageforeachinit.

nameDFinit Allocationsandoptionallyinitializesafarword(6bytes)ofstorageforeachinit.

nameDQinit Allocationsandoptionallyinitializesaquadword(8bytes)ofstorageforeachinit.

.DATA Definethedatasegment.

ELSE DefinesanalternativeblockoftheIFdirective.

END Definestheendofamodule.

ENDIF DefinestheendoftheIFdirective.

EXTERNnames Definesoneofmoreexternalvariables,labelsorsystemswhicharecallednames.

IFexpressionifstatements

ENDIF

DefinestheIFdirective.

INCLUDEfilename Includessourcecode.

.MODELmem_model Definesmemorymodel.

namemodule_name Definesthemodulename.

orgexpress Organizestheprograminmemory.

.stacksize Definesthestacksize.

titletext Definestitle.

D.3CandPascalinterruptsIn Turbo/Borland C there are four main functions to interrupt the processor:int86x(),intdos(),intr()andint86().Thesefunctionsareprototypedintheheader file dos.h. This header file also contains a structure definition thatallows aCprogram togain access to theprocessor’s registers.Parameters arepassed into and out of the interrupt sevice routines via these registers. Theformatofthestructureis:

Registers are accessed either as 8-bit registers (such as AL, AH) or 16-bitregisters(suchasAX,BX).Ifastructurenameregsisdeclared,then:

Thesyntaxofthefunctionint86()takestheformof

wherethefirstargumentoftheparameterlististheinterruptnumber,theinputregisters are passed as the second argument and the output registers the third.Parameters arepassed to the interrupt routineby setting certain input registersandparametersarepassedbackfromtheinterruptintheoutputregisters.In a similiarway Turbo Pascal provides access throught the routine named

Intr().Togainaccesstothisproceduretheusesdos;statementisplacednearthetopoftheprogram.AdatatypenamedRegistershasalsobeenpredefined,asshownbelow.Notethatitispossibletouseeitherthe16-bitregisters(suchasAX,BX)or8-bit(suchasAL,AH):

InProgramD.1, theDOS interrupt21h and function02h (writecharacter totheoutput)isusedtodisplaythecharacter‘A’.Inthiscase,thefunctionnumber02hisloadedintoAHandthecharactertobedisplayedisloadedintoDL.

ProgramD.2showshowaprogramcangainaccess to thesystemdate.Thefunctionusedinthisexampleis2Ah.TestrunD.1givesasamplerun.

E

ASCIICharacterSetANSIdefinedastandardalphabetknownasASCII.ThishassincebeenadoptedbytheCCITTasastandard,knownasIA5(InternationalAlphabetNo.5).Thefollowingtablesdefinethisalphabetinbinary,asadecimal,asahexadecimalvalueandasacharacter.

The standardASCII character set is a 7-bit character and ranges from 0 to

127.This code is rather limited as it does not contain symbols such asGreekletters, lines, and so on. For this purpose the extended ASCII code has beendefined. This fits into character number 128 to 255. The following 4 tablesdefineatypicalextendedASCIIcharacterset.

Index

—Ω—

Ω,24,275

—1—

100Ω,93

100Mbps,402,412

10Mbps,402

155Mbps,402

16Mbps,402

—2—

24-bitcolour,462

256colours,394

2scomplement,159,222,223,227,277,424

—8—

80286,230,274,476

80386,5,231,232,233,236,243,274,276,476,485,649,653,655

80386DX,230,232

80486,231,232,236,239,241,243,245,252,254,276,415,476,653

8086,229,230,233,234,236,243,244,261,271,274,276,279,476,649,655

8088,230

8255,268

A

AA,245,254

accumulator,233,649,650,651,652,653

accuracy,91,309

active,232,233,268,270,286,295,300,506,507,510,532,597

ADC,21,649

addressbus,4,219,220,226,230–232,236,261,262

addressbussize,226,230

addressablememory,226

addressing

immediate,236

memory,226,236,237

register,236

addressingmemory,244

AIX,549

algorithm,3,129,135,219

alias,557,605,609,619

AM,413

American,391,413

ampersand,108,111,180,345,483

analogue,553

AND,35,36,41,64,96,97,247,423,424,598,611,649

angle,32,33,37,39,98–101,118,119,200,201,376,448

animation,454

ANSI,8,12,15,96,368,391,413,484,495,627

apple,29,229,319,476

ARC,492

archive,529,583,584,590

arctan,32,33,101

arctan(),32

argument,81,86,87,90,108,109,111,162,193,194,205,310,311,440,460,552,580–582,585,586,613,615,616,620

arithmeticoperator,421,422

ARP,391,413

arrayindexing,181

arrayofstrings,148,150,155,156

Arrayofstructures,181

arrays,121

arraysofstrings,610

arrowkeys,294,596

ASCII,24,60,61,67,143,159,160,240,286,363,368,391,413,424,483,493,565,573,586,628

BEL,191,475,549

CR,160,597,598,599

FF,245,252,254,392,393

LF,160

SUB,246,652

ASCIIcharacters,60,61,67,159,240,424,565

ASK,413

aspectratio,376

assemblerdirectives,252,654

assembly,224,239,240,243,265,266,267,655

AssemblyLanguage,5,219,239,243,245,247,259,271,415,649,654,655

asynchronous,413

AT,191,230

attributes,162,163,415,484,525,529,554–556,565,576,603,631

changing,556

au,464,482,485,490–493,499,501,530

audio,410,411,437,454,464,465

AUTOEXEC.BAT,530

averagesprogram,166

averaging,136

B

backspace,24

basepointer,234

BASIC,3,5,219,291–294,296,305,307,308,310,311,317,324,327–329,339,345,352,361,362,371,374,415,483,530,551

BCD,287

bell,549

BellLaboratories,191,475,549

bestpossibleunits,56

binary,3,4,5,63,79,108,159,163,168,169,170,171,210,211,215,216,220,221,222,223,224,225,243,244,265,271,272,273,411,413,415,564,570,573,631,632

address,108

commands,5,415

file,159,163,168,170,171,211,216,573,631

I/O,215

numbers,221

read/write,168

BIOS,263,279,281–284,285,286,287,288

printerinterrupt,286,287

bitshift,233,248,424

bitmapped,159,545

bitwise,35,41,210,247,424–426,447

bitwiseoperator,35,424

black,81,82,83,281,302,387,393,399,437,462

blanklines,173

blue,281,288,302,373,374,387,392,393,398,462,463,507,509,532,534,544

BMP,293,299,371,372,545

bold,385,472

Boolean,307,308,309,310,311,417,418,420,424,434,455

bitwise,247,424

logic,63,102

bootdrive,280,281

BorlandC,238,265–267,291,494,495

BorlandC++,6,291,494,495

Bourneshell,605,606

braces,9,41,68,132,150,179,426,427,428,444,450,483

brackets,122,124

bridge,413

browser,385–389,393,394,401,404,410,411,415–417,431,433,437,438,440,442,444,445

buffer,48,69,144,285

Busicon,229,475

Buttonsettings,313

byte,220

byteenablelines,232

C

C

arrays,121

fileI/O,162

functions,82,123

parameterpassing,107

program,9–12,16,18,19,23,24,26,35,48,91,93,107,111,113,114,145,146,148,159,166,168,172,178–180,223,405,418,552,561,565,570,572–574,592

Cshell,601,605,606,609,610,615–620

C/C++,415,437,439,446,449,450

C++,191–202,205,206,208,211–216,241,266,267,268,291,414–416,421,426,436,437,439,446,449,450,494,495

classtemplate,207

classes,192,195,209

constructors,205,209

datahiding,192

destructors,205

functiontemplates,206

I/Ostreamsupport,192

objects,192,417,429

overloading,192,193

templateclasses,192

virtualfunctions,192

callbyreference,109,111

capacitance,55,73

capacitivereactance,30,31

capacitor,30,63,73,149,150,183

caption,345

captionproperty,324,326,331,334,335,337,338

carriagereturn,160,586,628,632

carryflag,247,248,649,652

caseoptions,54

CBS,475

CD,265,479,491–493,495,515,535

centigrade,27,92–94,331,332

CGI,405

CGIscript,405

changingdirectory,552

characteralphabet,391,413

characterarrays,141,143,144

characterhandling,12,16

characterstrings,175

charactersandnumbers,243

click,362,363,364,372,373,375,377,378

clients,525

clockcycles,273–275

clockperiod,273,275

cls,375,379

cluster,529

CMC,649

COBOL,3,5,415

code

machine,4,5,239,240,415

object,5,6,86

source,5–8,10,13,23,87

colour,49–52,57,58,281,282,288,293,300–302,318,319,373–378,387,392–394,399,461,462,471,513,531,589

colourcode,49,50,51,52,318,319

COM1:,265

combinationallogic,94

combinations,220,296,365

comments,9,13,193,243,426,428

Commodore,229,476

commondialog,352,355,357

compilation,5–7,25,123,447,570

compile,6,7,494,565

compiler,5–8,11,13,16,18,19,23,25,32,86,87,108–110,122,123,181,193,238,310,415–417,438,439,443–445,464,469,494,570,571,572

complexarithmetic,184

complexfunctions,200

compleximpedance,186

complexnumber,37,101,118,184,188,192,199,200,203

complexnumbers,192,199

compress,411,553,554,558,559,560,575

compressed,159

compression,394

computing,229

conditionaljump,249,250

CONFIG.SYS,530

constants,9,13,49,54,113,243,355,357,365,366,447

controlbus,4

controlRegister,268,269

controls,293,302

conversioncharacters,91

conversioncontrolcharacter,24,26

copperwire,10,14

copying,renamingandremoving,558

countingthenumberofcharacters,147

CPU,239,241,245,252,254,567

creatingamenusystem,346

csh

eventnumbers,607

reexecutingevents,607

cube,449

currency,308,309,310

D

DAT,163,166,167,168,488

data

bus,4

definition,253

Register,265,266,267

segment,235,240,253,655

type,9–11,14,25,26,49,81,86–91,108,109,121,122,124,141,145,148,150,160,162,175,176,178,179,191,193,199,205–207,209,237,281,308–312,417,418,444,446,447,451,455

types,10,14,307,308,418

databaseprogram,176,178,186

date,201,280,307,309,310,311,434,477,478,484,485,487,490,554,561,563,568,569,585,586,591,592,619,627

DD,391,477,480,481,655

debugger,6,7,240,255–259,439,445,570,571

DEC,246,549,650

decimal,60,77,79,221–225,227,243,244,309,392,393,420,561,650

decimalpoint,25

decisionsandloops,317

declaration,11,14

declarationofvariables,11,14

degrees,32,33,39,65,100,101,156,462

del,286,346,478,519,544,545

Delphi,291

destinationaddress,234,244

dialogBox,345,354

Digital,265,268,271

Directorystructure,550

diskdrives,4,219,299,416,476,479,500,505,562,577

dividebyzero,44,55,56,70,73,167,168

division,308,421,422,649

do..whileloop,68–70,320

DOC,483,488–492,499,501,519,521,522,530

domains,526,527

DOS,236,243,254,279,280,281,283,285,286,291,476–479,481–485,487,490–499,501,505,506,513,519,525,528–531,535,536,539,541

cls,478

copy,496,500

date,477,563

delete,495,628

dir,484,485,490–493,494–500,563

erase,495,496

exit,280,281,283,285,286

filenames,483

format,479–481

mkdir,493

run,535

services,279

startingandstopping,478

time,477,479,487,563,567,568

type,493,496,500

unformat,480

ver,477

version,280,477,487

DOS-based,243,519

draganddrop,367

E

earth,29

Edinburgh,324

edit,5,294,440,441,445,494,497,593,594,597

editor,5–7,159,166

eece.napier.ac.uk,398,460

EEPROM,4

electronicmail,525

EMspectrum,45

EMwave,45,46,47,55

encapsulation,191

EOF,164

equates,254

equivalentresistance,12,15,20,34,39,40,57,58,79,115,116

error,10,16,19,23,25,44,55,56,72,86,87,142,145,164,165,168,209,213,284,287,310,311,321,373,399,401,617,631,632,633,634,635

errorprocessing,213

escapesequence,24

Ethernet,390,391,402,408,409,411–413,434,435

eventhandling,430

executable,5,7,8,12,16,159,405,411,417,555,556,561,570,573,574

exp(),88,90

Explorer,417,531

exponent,25,160,424

F

Fahrenheit,27,92,331,332

farads,31,55

FAT,528,529

faulttolerance,412

FAX,467,468

FC,490,491

fclose(),163

FDDI,390,402,408,411–413,434,435

DAS,650

feof(),164

FET,78

fflush(),48

fflush(stdin),48,69

fgetc(),164

fgets(),165

file

attributes,163,529,554

binaryread/write,168

binary,159,163,168

I/O,159

pointer,160,162–164

pointers,214

systemstructure,481

system,491,499,505,513,525–529,539,578

systems,505,525,526,528

text,159,160,163,165,166,174

transferprotocol,587

find_nearest_pref(),132

firmware,3,192

floatingpoint,11,14,15,24,25,32,152,160,166–168,174,175,176,178,215,222,308,311

floppydisk,478,479,480,481,500,501,505,515–517,521,529,535,546

fopen(),162,163

forloop,59,63,77,96,155,320,427

forceofattraction,29

formatdescriptor,35

forms,293,323,324,405

formsandcode,324

FORTRAN,3,5,159,219,415,492,551,562,570,571,584,614

fourth,65,129,602,606

fprintf(),165

fputc(),164,165

fputs(),165

frame,298

France,324,330

fread(),168

freediskspace,279,280

frequencies,30

frequency,30,31,32,33,45–47,55,73,98–100,101,153,154

fscanf(),162,164,165

ftp,443,565,587

function

declarations,86

header,81,105,109,111

prototype,84,85,87,88,96,111,115

general,12,15,81,106,428,444,448,488,627

fwrite(),168

G

gateway,405

gateways,261

get_float(),155,181

get_int(),181

get_values(),111,114,166

getchar(),25,26,48,53,69,75,76,147,164

gets(),25,147,165

GIF,159,393,394,416,459,471

globalvariable,82,83,84

gradient,28,29

graphicaluserinterface,593

ground,598

H

hackers,416,528

handshaking,269,270

hardware,3–5,219,229,233,263,279,412,415,437,476,505,513,528

HD,480,481

header,8,9,13,23,25,26,32,44,51,81,86,87,105,106,109,111,192,209,265,266,267,385,386,403,439,469,563

headerfile,8,9,23,25,32,51,86,87,201,439,563

help,533

helpfiles,159

helpmanuals,357,481

hertz,31

hexadecimal,24,25,35,77,79,108,224,225,236,237,243,302,373,374,378,392,393,420,629

hierarchicaldecomposition,82

high-levellanguage,5,219,243,415–417,436

history,605,606

hobbycomputers,3

hosts,562

HPFS,528

HP-UX,549,550

HTML,385–388,390,391–397,399,401–409,413,416–419,429,430,432–436,438,440,441,450,451,455–460,463–468,470

anchors,401

backgroundimages,393

colours,392

definitionlists,391

displayingimages,394

hexadecimalcolours,392

horizontallines,397

inputtypes,407

links,387

lists,388,491

menus,345,409

orderedlists,388

script,386–388,390,391,394–397,399,401–404,406–409,416,440,441,450,451,455–460,463–468,470

tables,403

unorderedlists,388,390

http,387,394,398,416,431,438,443

hubs,412

Hughes,475

Hz,153,154

I

I/O

classes,209

digitalprograms,271

digital,265,268,271

inputtingabyte,265

isolated,261,263

library,208

memorymapped,261,262

outputtingaword,267

stream,192,208,213

streams,208

IBM,229,230,412,475,476,549

ICprogrammers,21

icons,371,372,373,513,514,515,532,538

IDE,265,494,500

IEEE,309,448

if(),41–43,45,49,426,427

if…elsestatements,41,427

images,293,299,393–396,459

impedance,32,73,98,100,101,151,173

impliedaddressing,236

information,4,5,8,9,152,159,209,220,229,243,279,299,312,314,387,391,394,402,403,405,413,415,429,437,476,479,480,483–485,493,505,510,519,526,537,541,545,550,552–554,562,567,570,571,573,586,588,591,620

initializinganarray,132

input/output,4,9,12,16,21,22,23,81,161,162,209,219,233,261,268,416,439,562,583

insertmode,594,595,597,598

integrateddevelopment,6,7,494

Intel,229,230,231,233,415,475,476

Intelmicroprocessors,230,231,233

interface,81,231,232,261,265,291–324,437,446,453,505,549

interfacingwithmemory,262

Internet,411,417,437,438

InternetExplorer,417,437

interrupt

1682h,281

1684h,283

1686h,284

1688h,284

1690h,285,1Ah,287

1693h,279

interrupts,279

IP,234,391,412,413,437,526,549

IPaddress,391,413,437

IPX,412

ISDN,435

J

Java,159,191,403,404,414–418,421,422,428,434,436–472

applet,415,416,418,437–458,460,463–472

compiler,416,417,438,439,443,444,464

script,442

JPE,651

JPEG,159,393,394,459,471

JPG,416

K

kΩ,56

keyboard,4,5,9,12,16,21,22,25,26,48,69,144,192,202,216,219,264,279,281,285,288,431,455,457,476,505,519,559,560,575,582,596,618,632,633

keyboardbuffer,144

keypress,361–363,368,458,459

keystroke,285,286,471,490,546,559,587,591,594,595,606

keywords,5,10,12,15,41,176,179,415,426

Korneshell,605

L

LAN,402,411

length,52–54,141,143,144,148,220,310,371,407,428,471,620,632

libraries,5,9,12,15,23,81,86

library,12,16,25,144,208,352,444,447,469,545,563,573,583,584

LIFO,250

light,13,45,271,273,278,281,393

limitingrangesofinputs,69

linebreak,386,404,412

linker,5,6,7,86

Linux,549

listingcontentsofafile,557

listingdirectories,553

ln(),90

Localandglobalvariables,83

localareanetwork,412

localvariables,81,82,106,610

log(),88,90

logarithms,90

logical,41,308,421,423,426,611

logicaloperator,96,423,424

loginintothesystem,550

longinteger,160,237,308,309,630

longword,220

lostfocus,368

lowercase,12,48,53,58,145,590,628,629,630

LZH,492

M

MΩ,56

MAC,390

MACaddresses,390

machinecode,4,5,239,240,245,246,261,415,416

machinecodeandassemblylanguage,240

macros,5,8,9,53,253,415

main(),82–84,85,168,193

makingandremovingdirectories,557

manganese,52

MASM,253,491,492,493

mathematicalfunctions,12,16,201

memory,3,4,7,11,14,26,107–109,122,144,181,205,215,219,220,221,226,230,232–241,244,246,248,251,259,261–265,268,278,286,291,393,454,526,549,633,651,653–656

address,3,4,26,108,122,144

addressing,226,236,237

cache,230

map,108,109,261–265

segmentation,236

menu,6,7,57,155,186,294–296,300,301,302,345–349,351,353,358,409,430,467,468,494,507–510,512,516,522,534,539,543

menueditor,345,346,347,350

metafile,293,299,371

mF,55

microprocessor,4,5,219,220,229,230,231,262,415,476

Microsoft,159,191,253,262,263,266,267,268,291,310,330,352,417,476,481,505,506,510,514,517,519,525,530,543

Assembler,253

Office,476

VisualC++,191,291

Windows,262,263,291,310,352,476,481,505,510,517,519,525

microwaves,45

MIME,411

model

large,238

small,238

modularprogram,81

module,105,106,118,252,295,296,347,570,571,655,656

modules,292

MOS,229,476

MOSTechnologies,229,476

Motionvideo,159

Motorola,229,415

mouse

control,533

controls,508,533

down,364

up,364

MOV,244,651

moveinstruction,244

movingarounddatainmemory,251

MPEG,410

MS-DOS,513,525,528,529,536,541

multimedia,408,410

multiplechoiceexample,324

multiplication,422

multitasking,416,525,526,549,567

N

NAND,35,36,96

Napier

EECEdepartment,398,460

negative,85,90,145,222,234,235,246,249,311,320,426,462,607,629

negativenumbers,222

nestedloop,96

Netscape,417

network,18,402,408,409,411–413,435,437,479,497,515,525–528,530,531,537,587

networkmanagement,412

networktraffic,412

networking,525,531

NewYorkTimes,475

newline,23,24,165

nF,55

nibble,220

NOR,35,36,64,96,97

NTFS,528

null,143,144,147

numbersandrepresentations,222

O

objectcode,159

objectproperties,323

object-oriented,291

objects,191,192,207,293,297,299,303,340,341,350,362,371,417,429,432,434,435,463,465

octal,24,25,77,224,225,243,420,576,586

OLE,299,330

openingafile,162

operatingsystem,10,21,159,291,401,415,476,505,525,526,528,530,546,549,567,605

operators,307,425

opticaldisks,479

OR,35,36,41,96,97,210,247,278,423,424,457,611,651

ordered,388,389

organization,391,413,527

OS/2,528

OSF/1,549

OSI,390,413

P

paragraph,386,550,598

parallel,11,12,15,19,33,34,39,47–49,57,58,70,79,114–116,151–155,186,194–199,265,283

parallelresistors,19,33,39,57

parallel_impedance(),152

parameterconversion,24

parameterlist,86,106,121,123,125

parameterpassing,81,84,105,106,107,198,437

parameters,24,25,29,52,81,82,84,86,87,89,100,104–106,109,142,152–155,198,201,284,312,316,363,397,404,428,440,444,457,461,463

Pascal,3,5,7,13–16,18,19,21,22,23,26,27,31,32,35,36,41,48,49,53,54,68,88,91,92,93,97,100,104,105,106,113,114,118,119,121,124,132,141,142,150,152,154,159,161,166,168,172,175,176,177,219,225,237,261,266,267,293,307,308,318,320,401,415,436,437,483,494,500,571

arrayroutines,142

arrays,124

compilation,7

fileI/O,161

functions,88

parameterpassing,106

program,13,15,16,18,19,23,36,54,91–93,97,100,113,114,150,161,166,168,172,176,177

string,141,142

stringconversionroutines,142

passingarraystoCfunctions,123

passingarraystofunctions,124

passingbyreference,81

passingbyvalue,81

PC,5,6,7,159,229,230,233,236,240,262,263,272,283,291,415,437,438,440,476,478,479,487,493,505,506,510,520,525,549

PCX,483,490

peer-to-peer,525,526

Pentium,231,233,236,243,276,415,476

permutations,63,96,578

pF,55

pixels,371,377,378,396,397,403,404,433,440

pointervariable,122,124

pointers,81,107–109,110–115,122–124,144,145,147,160,162–164,180,198,214,237,238,437,505

far,237,238

near,238

nearandfar,237,238

withfunctions,109

polygons,463

ports

number,284

PortA,268–270,273,276–278

PortB,268–273,276–278

PortC,268,269,270,278

Postscript,159

power(),87,90

precedence,307,308,425,447

precisionspecifier,25

preemptive,526,549

preemptivemultitasking,526,549

preferredresistorvalue,135,136

presentation,309,401

printservers,525

print_results(),112

printable,628

printerport,287

printf(),23,24,25,53,86,87,91,145,162,165,192,208,629

priority,425,568,570

privatekey,195

procedures,293

processorflags,235

projectfiles,292

prototyped,32,44,86,87,144,199,200,265–267,268

prototypes,86,93,94

publicmember,195

pushandpop,250

putchar(),23,164,165

puts(),9,13,23,24,165

Q

quadraticequation,42–45,56,105,111,113,114,334,335

quadraticequations,111

quadraticroots,334

R

RADAR,492

radians,32,33,38,39,100,101,376,634

radio,45,293,408,431,467

RAM,4,220,263,493

range,3,11,14,70,71,104,132,139,199,223,231,263,301,308,309,310,311,321,336,337,345,374,392,446,448,634,635,636

Raytheon,475

RCcircuit,61–63,151

RCA,475

read_data(),168

readingandwritingonecharacteratatime,171

readln(),154

recast,88

recordsinPascal,175

rectangular,186,448

red,288,302,373,374,392,393,398,462

register,233,235,239–241,244,246,248,251,253,259,265–274,279,281,285,649–655

relationshipoperator,422

repeat..until,59,68,69,70,77,142,161

repeatingprogram,69

resistance,10–15,19,20,23,32–34,39,40,48,49,52–58,69–73,75,76,79,98,100,104,109,114–116,133–136,153,154,196,197,198,208,216,321,338,339

resistancecalculation,336

resistanceofaconductor,52

resistivities,53

resistorcolourcode,49

resize,362,368,369,511,538

return,84

flag,111

statement,84

value,10,84,85,87–89,110,164,165,213,279,315,429,444,630–636

RGB,302,373,374,375,376,377,392

ringnetwork,412

RLseries,32,66,98,99,154,155

RLseriescircuit,32,66,98,99,155

ROM,4,263,265,479,515,535

root,32,43,44,45,55,56,70,105,111–114,200,334,448,449,452,481,482,517,550,560,561,574,576,577,606,635

roottype,111,113,114

RR,302

RS–232,284,435

runningaverageprogram,126

S

sampling,136

scanf(),25,26,35,48,86,87,91,111,145,154,162,165,208,629,632

schematic,31–33,63,95,97,98,151

SCO,549

scrollbar,507

search,8,147,172,305,508,509,581,599,601,613

sectionheader,385

sectors,280,479,529

segment,235–237,239–241,244,245,251–255,280,281,283,286,526,651,653,655

serial,480,481,484–498,541

serialcommunications,284

serialport,283,284,285

seriesRL,98–100

servername,398

servers,525,537,538

shellscripts,615

shellvariables,612

shiftinstructions,247

shift/rotate,247

shortinteger,109

signedinteger,11,14,24,176,178,223,224,227,424

silver,52

Sinclair,229,476

SMTP,443

software,3,4,9,10,13,18,141,191,229,230,236,239,262,412,414,437,476,494,506,510,525,549,550,650

softwareengineers,3

Solaris,549

sort(),129

sortingprogram,129

sound,159,459,464,472

soundfile,159,514

source,5,6,7,8,10,13,23,31,78,82,87,142,234,246,252,367,386,442,518,558,561,565,571,653

sourceaddress,234

specialcharacters,556

specification,3,25,401

speech,413

speedoflight,13,46

SPX,412

SPX/IPX,412

sqrt(),86,87,100

squareroot,32,43

squares,65,299

sscanf(),145

stackpointer,234

standardfunctions,12,16,633

standardinput,559,575,583,632,633

standardinputandoutput,559

standardoutput,559,574,580,586,601,633

standardstringfunctions,144

standards,391,413

statementblock,41,42,59,60,68,318,319,321,427,428,449,450,451

statements,422

repetitive,59,81,105,121,159

static,12,418,445,446,449

statements

logical,41,426

statusregisters,234

stdin,48

stopbit,284,413

straightline,28,29,104,107,111,201

strcat(),144

strcmp(),146

strcpy(),144

stringmanipulation,141

stringvariables,610

strings,141,144,147,420,445

strlen(),144

strlwr(),144

structurechart,85,86,89,98,112,114,115,132,151,181

structures,181,186

arrays,181

dotnotation,176,178

members,175,176,178

pointeroperator,180

structuresandRecords,175

SUB,246,652

subroutinecalls,250

SunMicrosystems,191,415,438

swap,106,107,110,546

swapped,129

switchstatement,49,54,617

switch(),49,54

synchronized,4,220,413,446

synchronous,265

syntax,86,265,266,267,415,417,418,421,425,427,428,450,505

systemdate,280,563

systemtime,279,280,283,287

SYSTEM.INI,541,545

T

TAB,297,488,543,546

tables,403,562,593

tangent(),91

TCP,391,412,413,437,526,549

TCP/IP,391,412,413,437,526,549

TD,403,404,405

television,471

telnet,443

temperatureconversion,332

temperatureconversionprogram,331

terminal,586,618

terminateandstay,280

test,6,7,26,28,29,31,35–37,39,40,45,55,57,58,60,79,86,89,90,92,97,163,167,168,170,185,201,205,206,213,234,271,285,286,321,332,351,428,436,440,449,451,458,459,464,478,569,573,574,602,611

TexasInstruments,475

text,159,212,282,323,326,327,330–336,351–355,364,365,366,368,372,373,468,483,514,545,593

blink,385

editor,166,385,401,494,575,593

file,159,494,514,545

I/O,212

keyword,161

textbackgroundfunction,57

timestepdelay,136

timing,261,273

token,9,254,255,408,412,413

TokenRing,390,402,408,409,412,413,434,435

MAUs,412

tokenrings,412

tolower(),48,53,54

topology,387

TR,403,404,405

tracks,479

traffic,278,412

transientresponse,61

transistor,475

transistors,475

truthtable,63–65,94–97

TurboDebugger,239,241

TurboPascal,5,7,14,15,18,48,237,266,267,494

TXT,483,490,496,497,498,545,546

typekeyword,124,176

typesofroots,45,334

U

UK,398

uncompress,575

uncompressed,575

unconditionaljump,249

UNIX,8,405,438,492,525,528,549,550,552,554,559,562,566,567,570,572,576,584,589,591,593,605,606

banner,584,585

cal,563,565,584,585

cat,557–566,574–580,583,591,600,606–609,615,619

cc,557,561,562,569–572

chmod,556–577,615,616

chpass,585

compilingCprograms,561

cp,557,558,564,566,572,573,612

date,585

dbx,570,571

df,577

diff,578

du,573

echo,586

f77,562,570,571

file,573

find,580

finger,586

grep,581,582,593,600,601,603

head,581,582

kill,567,568,590,609,618

lint,572

In,580

lpr,568,587,608

Is,552–560,564,566,567,570,571,573–577,579,580,589,603,606–609,619

mail,587

more,553–556,565,579,598,605,608,619,655

mv,557,558,566,578,579,619

nice,570

passwd,562,581,588,605,606

pipes,560

processcontrol,567

ps,567,568

redirection,559

rlogin,588,589

rm,558,564,569,571,579,580

sed,557,593,599,600,620

sleep,589

sort,601,603

spell,565,589,593

stty,557,589,590,592,618

tail,582

tar,553,590

wc,582,583,593

who,562,590

write,591

unload,362,369,431

unorderedlists,388,389

upcase,48,49

URL,387,398,405,430,443,460

URLs,437

USA,477

V

varkeyword,106,125,420

variables,81–85,89,96,106–109,111,113,114,121,152,193,197,199,201,253,275,307,309,312,418,419,420,421,429,446,552,571,605,609,610,612–614,655

initialization,12

substitution,609

velocity,71,72

version,229,230,280,310,385,438,439,440,443,464,475,476,477,487,505,506,510,530,537,541

VGA,263,530

video,159,281,282,288,393,411,437

visible,45

VisualBasic,291–294,296,305,307,308,310,311,317,324,327–329,339,345,352,361,362,371,374

controlsandevents,302

files,292

formwindow,296,297

language,305

menubar,294,507

objectbox,300

projectwindow,295,296,302,306

propertieswindow,295,297,300,301,531

toolbox,296,298

visualeditor,567,593,597,607–609,614–616

example,597

insertmode,594,595,597,598

substituting,595

volatile,12,446

voltage,23,31,39,40,61–63,72,73,75,76,104,216,321,337,338,339,341,422

W

WAV,464

wavelength,45,46,55

web,415,416,437

WesternElectric,475

UNIX,562

while(),68,145,146,428,450

white,212,302,387,393,399,462

WIMPs,505

WIN.INI,541–543,545

Windowobjects,432

Windows

capturingascreen,543

closingawindow,510,534

deletingfiles,518

desktop,506

fileextensions,545

Filemanager,513,514,515

formattingadisk,515

help,509,533

maingroup,513,521

movingandresizingawindow,509,533

movingfiles,517

quitting,508,509,533

running,506,519,530

selectingadirectory,515

selectingadrive,515

startup,542

swapping,543,544

terminatingprograms,544

Windows3.x,506,525,529,541

Windows95/NT,159,262,263,291,476,477,505,525,526,528,529,530,531,537,541

DOSwindow,513,536,539

Explorer,531

MyComputer,531,535,537,538

networkneighborhood,531,537

startbutton,531,534

WindowsNT,159,291,438,440,476,477,487,505,525,526,527,528,530,531,537,541

networkdrives,537

WK3,484

WMF,293,299,371

word,220

wordprocessor,159,514

words,60,147,173,246,446,582,584,589,593,594,620

workgroups,526,527

worksheet,18,37,39,56,57,67,79,104,118,139,156,174,188,487,499

workstation,437,526,528,549

workstations,525,549

WP,488

Writingtofiles,165

WWW,191,385,386,387,389–398,401,411,413,415,417,437,438

X

X

xterm,557

X/Open,549

XOR,247,424,653

Z

Zilog,229,476

ZIP,411,442,492