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OperatingSystem Overview

Dr. Muhammed J. Al-Muhammed

Operating

Systems:Internals

and

DesignPrinciples

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Operating System A program that controls the execution of

application programs

An interface between applications andhardware

Main obectives of an OS!

"onvenience #$ciency Ability to evolve

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and Software

Infrastructure

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Operating SystemServices

'rogram development! dierent servicessuch editors and debuggers to help programmers increating their programs

'rogram execution! loading data andinstructions to memory, initialization of IO devices,scheduling

Access ()O devices! niform interface, hidesdetails so the programmer can access these devicesusing simple read!write"

"ontrolled access to *les! #uthorization,sharing, caching"+

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Operating SystemServices

System access ,for shared or publicsystems! $rotection, authorization, resolvecon%icts

#rror detection and response! ardware errors! memory error or device failure Software errors! arithmetic errors/ access

forbidden memory locations/ allocation errors

Accounting collect statistics ,billing monitor performance

used to anticipate future enhancementsOperating systems are among the most comple&0Operating System

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'ey Interfaces

(nstruction set architecture ,(SA! isthe interface between hardware and the software"

(wo interfaces) user IS# *small+ and OS IS#*larger+

Application binary interface ,A1(!maes program portability possible"

Application programming interface,A'(! (he #$I gives a program access to thehardware resources and services available in a

system through the user IS# supplemented withhi h-level lan ua e *H..+ librar calls" sin an

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(he /ole of an OS

A computer is a set of resources

for the movement/ storage/ andprocessing of data

3he OS is responsible for

managing these resources

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Operating System

as Software3he operating system control

mechanism is unusual in two way

5unctions in the same way as ordinary computersoftware , provides instructions for the processor.owever/ the OS directs the processor to useresources and timing the execution of otherprograms.

5re6uently relin6uishes control and must dependon the processor to allow it to regain control

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OperatingSystem

as8esourceManager

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0volution of

Operating SystemsA maor OS will evolve over time

for a number of reasons!ardwareupgrades

:ew types of

hardware:ewservices

5ixes

;indows D$ released in %

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indowsArchitecture

2%

Operating System

"omponents of

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"omponents of

indows #xecutive

contains the core OS services

Bernel controls execution of the processors

ardware Abstraction Iayer ,AI maps between generic hardware commands and responses and

those uni6ue to a speci*c platform

Device Drivers dynamic libraries that extend the functionality of the #xecutive

indowing and Hraphics System implements the H( functions

2&

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ser-Mode 'rocesses

5our basic types are supported byindows!

2+

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Client!Server 6odelindows OS services/

environmentalsubsystems/ andapplications are allstructured using theclient)server model

"ommon in distributed

systems/ but can beused internal to a singlesystem

'rocesses communicatevia 8'"

#dvantages

it simpli*es the #xecutive

it improves reliability it provides a uniform

means for applications tocommunicate withservices via 8'"s without

restricting @exibility it provides a suitable

base for distributedcomputing

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(hreads and S6$ 3wo important characteristics of indows are its

support for threads and for symmetric

multiprocessing ,SM' OS routines can run on any available processor/ and diEerentroutines can execute simultaneously on diEerent processors

indows supports the use of multiple threads of executionwithin a single process. Multiple threads within the sameprocess may execute on diEerent processors simultaneously

Server processes may use multiple threads to process re6uestsfrom more than one client simultaneously

indows provides mechanisms for sharing data and resourcesbetween processes and @exible interprocess communication

capabilities

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>indows Ob

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WindowsKernel

27

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>indows E

"hanges and improvements! 0ngineering improvements

the system is now built in layers which can be separately tested

$erformance improvements amount of memory re6uired has been reduced

/eliability improvements

user-mode heap is more tolerant of memory allocation errors by")" programmers

0nergy eGciency

many improvements have been made Security

1itIoc>er is now easier to set up and use

(hread improvements

can support hundreds of "'s

Dynamic 5air Share Scheduling ,D5SS29

Operating System

(raditional 2ID

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(raditional 2IDSystems

ere developed at 1ell Iabs and became operational on a 'D'-4 in ;94ages

ighly modular and easily con*gured

4+

Operating System

6odular

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6odular

6onolithic 'ernel (ncludes virtually all of the

OS functionality in onelarge bloc> of code that

runs as a single processwith a single address space

All the functionalcomponents of the >ernelhave access to all of its

internal data structuresand routines

Iinux is structured as acollection of modules

.oadable 6odules

8elatively independent bloc>s

A module is an obect *le whosecode can be lin>ed to andunlin>ed from the >ernel atruntime

A module is executed in >ernelmode on behalf of the currentprocess

ave two importantcharacteristics!

Dynamic lin>ing

Stac>able modules40

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.inu&

'ernel

6odul

es

42

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.inu& 'ernel Components

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.inu& 7server 7irtual

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.inu& 7server 7irtual

6achine #rchitecture Open-source/ fast/

lightweight approach toimplementing virtual

machines on a Iinuxserver

Only a single copy of theIinux >ernel is involved

Supports a number ofseparate virtual servers #ach virtual server is

isolated from the others &nvolves four elements"49

Operating System

nu& server

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#rchitecture

7