operating system process by sami-kaifi

8/7/2019 operating system process by sami-kaifi

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IN THE NAME OF

ALLAH,THE MOST GRACIOUS,THE MOST MERCIFUL


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ASSIGNMENTON

Process creationProcess terminationSystem calls


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Submitted to:

Sir Asif JavedSubmitted by:

Sami Ullah KaifiRoll No:

BS(IT)-08-16

Course:Operating System

Department of Information TechnologyInstitute of Computing

Bahauddin Zakariya University(Multan)


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Process creation

Process Creation: To create a processOS needs these three components

1. An executable program2. Data3. Context information

All information the operating system needs tointerleave and restart a process.

When OS receives a request to create aprocess, it builds the data structures andallocates a space for this process in memory.


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Process Creation: Demand for a process

In a batch environment, request for a job activates the OSto create a process.

In an interactive environment, when a user logs on the

system, a new process is initiated.

Operating system can also create a process on behalf of anapplication, i.e. for an application requesting to print a file,so that the printing request can continue independentlyfrom the application.

A process or a server (like socket) can request a newprocess for each client it handles (spawning).


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There are many reasons for process termination:

Batch job issues halt instruction

User logs offProcess executes a service request to terminateError and fault conditionsNormal completionTime limit exceededMemory unavailableBounds violation; for example: attempted access of (non-existent) 11thelement of a 10-element arrayProtection error; for example: attempted write to read-only file

Process Termination


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Arithmetic error; for example: attempted division by zeroTime overrun; for example: process waited longer than a specifiedmaximum for an eventI/O failureInvalid instruction; for example: when a process tries to execute data(text)

Privileged instructionData misuseOperating system intervention; processes terminate (cascadingtermination)for example: to resolve a deadlockParent terminates so childParent request


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oSystem calls provide an interface between the process an the operatingsystem.

oSystem calls allow user-level processes to request some services from theoperating system which process itself is not allowed to do.

oIn handling the trap, the operating system will enter in the kernel mode,where it has access to privileged instructions, and can perform the desired

service on the behalf of user-level process. It is because of the criticalnature of operations that the operating system itself does them every timethey are needed.

System Calls


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oFor example, for I/O a process involves a system call telling theoperating system to read or write particular area and this request issatisfied by the operating system.

System programs provide basic functioning to users so that they donot need to write their own environment for program development(editors, compilers) and program execution (shells).

In some sense, they are bundles of useful system calls.


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By sami ullah kaifi

operating system process by sami-kaifi

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