Operating Systems Structure

Mr. S. V. Viraktamath

SDMCET, Dharwad

svvitc2011@gmail..com

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Introduction

• An OS may be viewed from several vantage

points

• 3 view points User, Programmers and OS

designer.

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System Components

• Most of the systems share the goal of

supporting the system components listed:

– Process Management

– Main Memory management

– File management

– I/O system management

– Secondary storage management

– Protection system

– Command interpreter system

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• Process Management

– Process?, Resources needed for process

– Program is not a process

– Program is passive and process is active entity

• Creating and deleting both user and system processes

• Suspending and resuming processes

• Providing mechanisms for process synchronization

• Providing mechanisms for process communication

• Providing mechanisms for deadlock handling

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• Main Memory management

–Mem large array of words/bytes

–Each word/byte has a its own address

• Keeping track of which parts of memory are

currently being used and by whom

• Deciding which processes are to be loaded into

memory when memory space becomes available

• Allocating and de-allocating memory space as

needed

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• File management

– It is a visible component of OS

– File is collection of related information defined by

its creator.

– OS responsibility

• Creating and deleting files

• Creating and deleting directories

• Mapping files onto secondary storage

• Backing up files on stable (nonvolatile) storage media

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• Secondary storage Management

– To execute program it should be in main memory

– Most of the system uses disks as storage medium

– Hence proper management of disc storage is imp

– Free-space management

– Storage allocation

– Disk scheduling

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• Protection System

– Concurrent execution of multiple processes

– Processes must be protected

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Operating system services

• OS provides services to programs & to the users of those programs.

– Program Execution

– I/O Operation

– File system Manipulation

– Communication

– Error detection

– Resource allocation

– Accounting

– Protection

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System Calls

• System calls provide the interface between a process and the OS.

• How system calls are used Ex.

• Read a data from a file copy them to another file.

– Need names of two files.

– Can read from user by using system calls

– Create a file

– Read a file

– Write a file

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Types of system calls

• Process control

– end, abort

– load, execute

– create process, terminate process

– get process attributes, set process attributes

– wait for time

– wait event, signal event

– allocate and free memory

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• File management

– create file, delete file

– open, close

– read, write, reposition

– get file attributes, set file attributes

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• Device management

– request device, release device

– read, write, reposition

– get device attributes, set device attributes

– logically attach or detach devices

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• Communications

– create, delete communication connection

– send, receive messages

– transfer status information

– attach or detach remote devices

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Virtual Machines

• Virtual?

• Virtual Memory

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