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OPERATING SYSTEMS (THEORY)

LECTURE - 2

K.ARIVUSELVAN

Assistant Professor Senior SITE

VIT University

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PROCESS MANAGEMENT

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Program

A program consists of:

Code: machine instructions

Data: variables stored and manipulated in memory

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Preparing a Program

static libraries

(libc, streams)

compiler/assembler Linker

file

.

Executable file

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PROCESS

Program in Execution

You mi ht think of it as

The collection of data structures that fully describes how far the

execution of the program has progressed.

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PROCESS

A Process includes 4 Segments:

DATA: Holds program variables

HEAP: Holds intermediate computation data generated

during run time

STACK: Holds

=> oca var a es

=> Temporaries & Procedure Calls

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Process in Memory

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Processes in Memory

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PROGRAM PROCESS

Instructions in any Instruction execution in machine

Passive Entity

{Content of file stored on

Active Entity

{Contains program counter,s ecif in next instruction tos

execute}

Resides in the Secondary

storageResides in Main memory

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PROCESS IMAGE

o ect on o , ,

Process IdentificationParent & Child ID

Process StateInformation

Content ofprocessor register PCB

Information

User Stack

Priority, State

ser ress pace

(Code& Data)

Shared Address Space

The Collection of attributes is called as Process Control Block

(PCB) or Task Control Block (TCB)

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The Process image is stored on the disk as contiguous block,

this block may be:=> Fixed Size (Pages)

=> Variable Size (Segments)

Process 2

.

-

PImg-2

Process n

Primary Process Table

PImg-n

Process

Image

The address of each Process image is stored on Primary

Process Table

* To maintain the process, its image must be brought into main memory

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Process Images in Main Memory

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Structure of PCB

en er n que prov e y on processcreation

StateNew, Ready, Running, Suspend,Terminated

PriorityMay be Internal (Set by OS) or

External (depends on external

factors) Program CounterAddress of next instruction to be

executed

Includes Pointer to the

= emory o n er

=> Data associated with this process

=> Memory block shared with other process

Context Data Data present in Registers, while process

is executing

I/O Status

Includes

=> I/O requests,I/o devices asssigned to this

process

=> List of Files in use by the process

Accounting Includes the amountn orma on => Amount of processor time used

=> Time limits`