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Mongolia International University Operating System Operating System and Utility Programs and Utility Programs Chapter 2 Chapter 2 B.M.H B.M.H

Computers4 Ch2

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Page 1: Computers4 Ch2

Mongolia International University

Operating System Operating System and Utility Programsand Utility Programs

Chapter 2Chapter 2

B.M.HB.M.H

Page 2: Computers4 Ch2

Computers MIU

Computer SystemComputer System

HardwareHardware Input deviceInput device Processor (CPU)Processor (CPU) Output deviceOutput device Storage (secondary storage)Storage (secondary storage)

SoftwareSoftware System SWSystem SW Application SWApplication SW

People People

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Learning ObjectivesLearning Objectives

OS for large computer systemsOS for large computer systems The method of resource allocation The method of resource allocation

Utility ProgramsUtility Programs

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MainframesMainframes

Large, fast and fairly Large, fast and fairly expensive computersexpensive computers

Used by business or Used by business or governmentgovernment to provide to provide centralized storagecentralized storage

EX) IBM 4381, 9300, EX) IBM 4381, 9300, 3090, Cyber 1803090, Cyber 180

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OS for large computersOS for large computers

Large computer - mainframesLarge computer - mainframes Around about twice as long as PCsAround about twice as long as PCs Owned by businesses and universitiesOwned by businesses and universities Used by many people at onceUsed by many people at once Present special (sharing) problems Present special (sharing) problems

Program, CPU, memory, storage, printer

OS : take care of these things behind the OS : take care of these things behind the scenesscenes So that User can share the computerSo that User can share the computer’’s resourcess resources

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Resource AllocationResource Allocation

Allocated?Allocated? Shared resourcesShared resources (Allocate : give something to somebody for special purpose)(Allocate : give something to somebody for special purpose)

Resources allocationResources allocation : the process of assigning computer : the process of assigning computer

resources to certain programsresources to certain programs

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Resource AllocationResource Allocation

Sharing Sharing a CPUa CPU Sharing Sharing a Memorya Memory Sharing Sharing Storage ResourcesStorage Resources Sharing Sharing Printing ResourcesPrinting Resources

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Sharing the CPUSharing the CPU

Most computers have a single Most computers have a single CPU.CPU. All programs must share it.All programs must share it.

The sharing processThe sharing process Controlled by the OSControlled by the OS Two approaches to sharingTwo approaches to sharing

Multiprogramming Time-sharing Multiprocessing

(Resource allocation)

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MultiprocessingMultiprocessing

The use of a powerful computer with The use of a powerful computer with multiple CPUsmultiple CPUs

Multiple programs can run Multiple programs can run simultaneouslysimultaneously, each using its own , each using its own processorprocessor

(Resource allocation)

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MultiprogrammingMultiprogramming

Only Only one Central Processing Unitone Central Processing Unit

Two or more programs are executed in the Two or more programs are executed in the same time frame, same time frame, concurrentlyconcurrently But not exactly at the same instantBut not exactly at the same instant Taking turns ; one program runs for a while, and Taking turns ; one program runs for a while, and

then another one runsthen another one runs

Event-drivenEvent-driven Programs share resources based on events that take Programs share resources based on events that take

place in the programs.place in the programs.

(Resource allocation)

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MultiprogramminMultiprogrammingg

Implemented by OS through a system of Implemented by OS through a system of interruptsinterrupts InterruptsInterrupts

A signal that causes normal program processing to be suspended temporarily.

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Time-SharingTime-Sharing

A special case of multiprogrammingA special case of multiprogramming

Time-drivenTime-driven To give each user a time sliceTo give each user a time slice The OS doesnThe OS doesn’’t wait for completion of an t wait for completion of an

eventevent At the end of the time slice, the resources are taken

away from the user and given to someone else

(Resource allocation)

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Sharing MemorySharing Memory

Memory managementMemory management The process of The process of

allocating memory to programs and keeping the programs in memory separate from one

another Methods Methods

Partitions (or regions) Foreground and background Virtual storage

(Resource allocation)

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PartitionsPartitions

Some systems simply divide memory Some systems simply divide memory into separate areas (partitions or into separate areas (partitions or regions)regions) Each of which can hold a programEach of which can hold a program

Sharing Memory

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Foreground and Foreground and BackgroundBackground

Large all-purposed computers divide the Large all-purposed computers divide the memory into foreground and backgroundmemory into foreground and background

In a time-sharing environmentIn a time-sharing environment ForegroundForeground

For programs that have higher priority : Interactive program (with the user at a terminal awaiting

response) Receive more CPU time

BackgroundBackground For programs with less pressing schedules lower priorities and less CPU time

Sharing Memory

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Virtual Storage (1)Virtual Storage (1)

Many computer systems uses this technique Many computer systems uses this technique

Called Called virtual memoryvirtual memory Virtual : made to appear to exist by the use of Virtual : made to appear to exist by the use of

computer SWcomputer SW

The programs currently being executed are The programs currently being executed are stored on stored on diskdisk,,

portions of these programs portions of these programs

are brought into are brought into memorymemory as needed. as needed. Memory : real storageMemory : real storage Secondary storage : virtual storageSecondary storage : virtual storage

Sharing Memory

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Virtual Storage (2)Virtual Storage (2)

Paging Paging

one way of virtual storageone way of virtual storage the process of the process of

dividing a program into equal-size pieces ; called pages storing them in equal-size memory spaces ; called page frames

All pages and page framesAll pages and page frames: the same fixed size (ex. 2 or 4 KB)

Sharing Memory

Refer to Fig 2-11Refer to Fig 2-11

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Sharing Storage Sharing Storage ResourcesResources

More than user want to read or write a record More than user want to read or write a record from the same disk pack at the same timefrom the same disk pack at the same time

OSOS Keeps track of which file is whereKeeps track of which file is where Responds to commands to manipulate filesResponds to commands to manipulate files Keeps track of the Input and output requestsKeeps track of the Input and output requests Processes themProcesses them

In the order in which they were received Routes any program instruction to read or write a Routes any program instruction to read or write a

recordrecord

Resource allocation

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Sharing Printing Sharing Printing ResourcesResources

SpoolingSpooling A process for sharing a printerA process for sharing a printer

Moving data and store it for a short time on a disk before it is printed

Each program writes onto a disk each line that is to be printed

The disk file is placed into a queue It is printed when the printer becomes available

Resource allocation

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Mongolia International University

Utility ProgramsUtility Programs

File ManagerFile Manager

Back up and RestoreBack up and Restore

File CompressionFile Compression

DefragmenterDefragmenter

Device DriversDevice Drivers

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Utility Programs (1)Utility Programs (1)

Most of the resource allocation tasks Most of the resource allocation tasks : done by the OS without user involvement: done by the OS without user involvement

Utility Programs Utility Programs : perform explicit services : perform explicit services at the userat the user’’s requests request Utility : a piece of computer SW that performs a Utility : a piece of computer SW that performs a

particular taskparticular task Part of the system software, not part of the OS.Part of the system software, not part of the OS. Some utilities are packaged with OSsSome utilities are packaged with OSs Others can be purchased separatelyOthers can be purchased separately

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Utility Programs (2)Utility Programs (2)

To avoid duplication of effortTo avoid duplication of effort Backing up Backing up Restoring filesRestoring files Compressing files and entire hard disksCompressing files and entire hard disks Locating filesLocating files Searching computer virusesSearching computer viruses

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File manager (1)File manager (1)

Organize and manage files in a Organize and manage files in a hierarchical directory structurehierarchical directory structure organized in a way that makes sense to organized in a way that makes sense to

youyou Directory Directory

: a named area in storage that can contain files and other directories

The newer versions of Windows: Refer to directories as folders

Utility Programs

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File manager (2)File manager (2)

FunctionsFunctions Enable you to create the directory structureEnable you to create the directory structure Display lists of files in directories Display lists of files in directories

; to copy, move, rename, and delete files; and to format and copy diskettes

Utility Programs

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Back up and RestoreBack up and Restore

Make backups of entire hard drives or of Make backups of entire hard drives or of selected directoriesselected directories Backing up files involvesBacking up files involves

Making duplicate copies Storing them in a safe place

These backups could be made toThese backups could be made to Diskettes, high capacity media (CD, tape)

Create the backup files in a specific format to Create the backup files in a specific format to minimize space requirementsminimize space requirements

Needed the restore routine to use themNeeded the restore routine to use them

Utility Programs

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File CompressionFile Compression

Reduces the amount of space of a fileReduces the amount of space of a file Compressed fileCompressed file

Take up less space on diskTake up less space on disk Take less time to transmit across communication lineTake less time to transmit across communication line Must be uncompressed into their original form Must be uncompressed into their original form

before using thembefore using them Ex) PKZIP, WinZip,RAREx) PKZIP, WinZip,RAR

Utility Programs

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DefragmenterDefragmenter

Reorganize the files on the disk Reorganize the files on the disk so that all files are stored in so that all files are stored in contiguous contiguous

locationslocations

Ex) Windows : Disk DefragmenterEx) Windows : Disk Defragmenter

Fragmented: noncontiguous storing because Fragmented: noncontiguous storing because of not enough space.of not enough space.

Utility Programs

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Device Drivers (1)Device Drivers (1)

Allow the OS to communicate with Allow the OS to communicate with peripheralsperipherals Accepts standard commands from the OS Accepts standard commands from the OS Converts them into the proper format Converts them into the proper format

for the device it supportsfor the device it supports

Utility Programs

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Device Drivers (2)Device Drivers (2)

ManufacturesManufactures Provide Provide device driversdevice drivers for their products for their products Installing the product Installing the product

: includes copying the appropriate driver to : includes copying the appropriate driver to your hard driveyour hard drive

Utility Programs