computing and the web operating systems. overview n what is an operating system n booting the...
TRANSCRIPT
OverviewOverview What is an Operating SystemWhat is an Operating System Booting the ComputerBooting the Computer User InterfacesUser Interfaces Files and File ManagementFiles and File Management Input and Output of InformationInput and Output of Information Memory Limitations: Cache and Virtual MemoryMemory Limitations: Cache and Virtual Memory Context Switching and MultitaskingContext Switching and Multitasking Operating Systems for the Networked WorldOperating Systems for the Networked World
What is an Operating What is an Operating System?System?A collection of programs that manages and controls A collection of programs that manages and controls software, and coordinates the various hardware software, and coordinates the various hardware components to perform tasks requested by the usercomponents to perform tasks requested by the user
Isolate the hardware Isolate the hardware from users and from users and direct manipulation direct manipulation by applicationsby applications
What if the OS wasn’t there?What if the OS wasn’t there? Programs “poked” into RAM via switchesPrograms “poked” into RAM via switches First program loaded “read” other programsFirst program loaded “read” other programs Next program added “device support”Next program added “device support” Devices could then be used to read in larger Devices could then be used to read in larger
programs like BASICprograms like BASIC
Overall process was tedious and slow (could Overall process was tedious and slow (could take up to 30 minutes)take up to 30 minutes)
You wouldn’t want to shut off the computerYou wouldn’t want to shut off the computer
BIOS to the rescueBIOS to the rescue BIOS is the Basic Input Output SystemBIOS is the Basic Input Output System Collection of programsCollection of programs Provides the capability of Provides the capability of
communicating with peripheral devicescommunicating with peripheral devices– KeyboardKeyboard– Disk drivesDisk drives– MonitorMonitor
Allows the rest of the operating system Allows the rest of the operating system to be read in from the disk driveto be read in from the disk drive
Stored in ROM so it is always thereStored in ROM so it is always there
What is an Operating What is an Operating System?System? A collection of programs that carry out A collection of programs that carry out
six basic functionssix basic functions– Booting the ComputerBooting the Computer– Provides the User InterfaceProvides the User Interface– Provides File ManagementProvides File Management– Handles Input and Output OperationsHandles Input and Output Operations– Manages MemoryManages Memory– Provides Context Switching & MultitaskingProvides Context Switching & Multitasking
Examples of Operating Systems:Examples of Operating Systems:Windows (98, NT, ME, XP), MS-DOS, CPM, Mac OS X, UNIX, OS/2, Windows (98, NT, ME, XP), MS-DOS, CPM, Mac OS X, UNIX, OS/2,
LINUX, VMS, PALM OS, SOLARISLINUX, VMS, PALM OS, SOLARIS
Booting the ComputerBooting the Computer Process of automatically running a Process of automatically running a
program in ROM which in turn loads the program in ROM which in turn loads the operating system into RAM and turns operating system into RAM and turns control over to it.control over to it.
Cold Boot – booting up when the power Cold Boot – booting up when the power was originally offwas originally off
Warm Boot – booting up when the Warm Boot – booting up when the power was originally on (re-booting)power was originally on (re-booting)– Gets a fresh copy of the operating systemGets a fresh copy of the operating system
Multiple Operating Systems – Multiple Operating Systems – partitioning the hard drive for each OSpartitioning the hard drive for each OS
User InterfacesUser Interfaces The user interface is the part of the Operating The user interface is the part of the Operating
System that the user sees and interacts withSystem that the user sees and interacts with Different types of interfaces for different purposesDifferent types of interfaces for different purposes
– GUIGUI– CLICLI
GUI – Graphical user interfaceGUI – Graphical user interface– Mouse oriented and utilizes icons and buttonsMouse oriented and utilizes icons and buttons– Allows symbolic manipulation of programs and filesAllows symbolic manipulation of programs and files
CLI – Command line interfaceCLI – Command line interface– Instructions are given by typing commands on the Instructions are given by typing commands on the
keyboardkeyboard– Requires technical understanding of commandsRequires technical understanding of commands– Not user friendly or intuitiveNot user friendly or intuitive
Files and File ManagementFiles and File Management A file is a collection of [data] that is A file is a collection of [data] that is
treated as a single unittreated as a single unit– A pictureA picture– A spread sheetA spread sheet– A documentA document– A programA program
A file has a unique nameA file has a unique name– Filename Filename .. Extension Extension
Extensions are used to associate files Extensions are used to associate files with programswith programs
Files and File ManagementFiles and File Management There are two basic types of file There are two basic types of file
systemssystems– Flat file structureFlat file structure– Hierarchical file structureHierarchical file structure
Flat file structureFlat file structure– Organizes files in one flat listOrganizes files in one flat list– No subdivision or grouping possibleNo subdivision or grouping possible– Like dumping all of your papers in a pile on Like dumping all of your papers in a pile on
the top of your deskthe top of your desk– Difficult to manage and keep track of filesDifficult to manage and keep track of files
Files and File ManagementFiles and File Management Hierarchical file structureHierarchical file structure
– Organizes files in a tree like structureOrganizes files in a tree like structure– Subdivision is achieved via subdirectories Subdivision is achieved via subdirectories
(usually depicted as folders)(usually depicted as folders)– Similar to filing cabinets with drawers and Similar to filing cabinets with drawers and
folders within themfolders within them– Easy to manage and keep track of filesEasy to manage and keep track of files– The folders become part of the naming The folders become part of the naming
convention for the fileconvention for the file
C:\Windows\System32\Regedit.exeC:\Windows\System32\Regedit.exe
Input and Output SupportInput and Output Support I/O support provides basic support to I/O support provides basic support to
read and write information to peripheral read and write information to peripheral devicesdevices
Specialized devices may require special Specialized devices may require special software called a device driversoftware called a device driver– Device drivers are usually provided by the Device drivers are usually provided by the
manufacturer of the specialized hardwaremanufacturer of the specialized hardware– Device drivers provide enhanced features that Device drivers provide enhanced features that
the operating system doesn’t know aboutthe operating system doesn’t know about I/O support also provides error handling I/O support also provides error handling
in case of device failuresin case of device failures
Memory ManagementMemory Management Real vs Virtual MemoryReal vs Virtual Memory Computers have a physical amount of Computers have a physical amount of
RAMRAM All memory in the computer is “owned” All memory in the computer is “owned”
by the operating systemby the operating system The operating system allocates memory The operating system allocates memory
to programs as they need itto programs as they need it The operating system reclaims memory The operating system reclaims memory
when programs are done with itwhen programs are done with it
Memory ManagementMemory Management The user starts up several more programsThe user starts up several more programs
Memory ManagementMemory ManagementThe user wants to start a program that is 35M, but only 20M is freeThe user wants to start a program that is 35M, but only 20M is free
Memory ManagementMemory ManagementWindows will clear out 15M of memory that hasn’t been used in a while and Windows will clear out 15M of memory that hasn’t been used in a while and
load the programload the program
Memory ManagementMemory Management The process of swapping memory in and The process of swapping memory in and
out creates the illusion that you have out creates the illusion that you have more than there really is (Virtual Memory)more than there really is (Virtual Memory)– Too much swapping is bad (poor performance)Too much swapping is bad (poor performance)– Windows hides the disk file from the userWindows hides the disk file from the user
Pagefile.sysPagefile.sys It is usually around 1.5 times the size of real It is usually around 1.5 times the size of real
memorymemory
Other uses of memoryOther uses of memory– Disk cacheDisk cache– RAM diskRAM disk– I/O buffersI/O buffers
Context Switching & Context Switching & MultitaskingMultitasking Context switching allows several application Context switching allows several application
programs to be in RAM at one time. The user programs to be in RAM at one time. The user controls which program is the current one.controls which program is the current one.– The user switches back and forth between programsThe user switches back and forth between programs
Multitasking allows several application Multitasking allows several application programs to be in RAM at one time. Each is programs to be in RAM at one time. Each is allowed CPU time as needed, all under the allowed CPU time as needed, all under the control of the CPU.control of the CPU.– Allows programs to continue to run in the back Allows programs to continue to run in the back
groundground
MS-DOS / Windows 3.1 / Windows XPMS-DOS / Windows 3.1 / Windows XP
OS for the Networked WorldOS for the Networked World Parallel processing / multiprocessing takes Parallel processing / multiprocessing takes
place on a computer with more than 1 CPUplace on a computer with more than 1 CPU– Requires more complex operating systemRequires more complex operating system– Utilizes special programming techniquesUtilizes special programming techniques
Distributed processing utilizes a network to Distributed processing utilizes a network to decentralize and distribute the computing decentralize and distribute the computing needs over several dispersed computersneeds over several dispersed computers– SETI screen saverSETI screen saver
Client / server computing – the server Client / server computing – the server provides data and programs for the clientsprovides data and programs for the clients– Web server and web browsersWeb server and web browsers
OS for the Networked WorldOS for the Networked World Real Time processing – involves human Real Time processing – involves human
interaction with the computer in a situation in interaction with the computer in a situation in which quick or timely return of results is which quick or timely return of results is importantimportant– ATMATM– Airline reservation systemAirline reservation system
Process control – is the control of a process by a Process control – is the control of a process by a computer. It usually requires input to be computer. It usually requires input to be accepted by the CPU, processed, and then a task accepted by the CPU, processed, and then a task is executed based upon the processed input. is executed based upon the processed input. – Automobile electronic ignition systemAutomobile electronic ignition system– Missile guidance systemMissile guidance system– Usually require “feed back”Usually require “feed back”