CP0302 03-Jan-2011 RM01 Introduction

8/4/2019 CP0302 03-Jan-2011 RM01 Introduction

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IntroductionIntroduction

What is an Operating System?What is an Operating System?

Mainframe SystemsMainframe Systems Desktop SystemsDesktop Systems

Multiprocessor SystemsMultiprocessor Systems

Distributed SystemsDistributed Systems Clustered SystemClustered System

RealReal --Time SystemsTime Systems

Handheld SystemsHandheld Systems

Computing EnvironmentsComputing Environments


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What is an Operating System?What is an Operating System?

A program that acts as an intermediaryA program that acts as an intermediary

between a user of a computer and thebetween a user of a computer and thecomputer hardware.computer hardware.

Operating system goals:Operating system goals:

Execute user programs and make solving userExecute user programs and make solving user

problems easier.problems easier.

Make the computer system convenient to use.Make the computer system convenient to use.

Use the computer hardware in an efficientUse the computer hardware in an efficientmanner.manner.


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Computer System ComponentsComputer System Components

1.1. HardwareHardwareprovides basic computing resources (CPU,provides basic computing resources (CPU,

memory, I/O devices).memory, I/O devices).2.2. Operating systemOperating systemcontrols and coordinates the use ofcontrols and coordinates the use of

the hardware among the various application programsthe hardware among the various application programs

for the various users.for the various users.3.3.Applications programsApplications programsdefine the ways in which thedefine the ways in which thesystem resources are used to solve the computingsystem resources are used to solve the computingproblems of the users (compilers, database systems,problems of the users (compilers, database systems,

video games, business programs).video games, business programs).4.4. Users (people, machines, other computers).Users (people, machines, other computers).


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Abstract View of SystemAbstract View of SystemComponentsComponents


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Operating System DefinitionsOperating System Definitions

Resource allocatorResource allocatormanages andmanages andallocates resources.allocates resources.

Control programControl programcontrols thecontrols theexecution of user programs andexecution of user programs and

operations of I/O devices .operations of I/O devices .

KernelKernelthe one program running at allthe one program running at alltimes (all else being applicationtimes (all else being application

programs).programs).


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Mainframe SystemsMainframe Systems Reduce setup time by batching similar jobsReduce setup time by batching similar jobs

Automatic job sequencingAutomatic job sequencingautomaticallyautomatically

transfers control from one job to another.transfers control from one job to another.

First rudimentary operating system.First rudimentary operating system.

Resident monitorResident monitor

initial control in monitorinitial control in monitor

control transfers to jobcontrol transfers to job

when job completes control transfers pack towhen job completes control transfers pack to

monitormonitor


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Memory Layout for a Simple BatchMemory Layout for a Simple Batch

SystemSystem


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MultiprogrammedMultiprogrammed Batch SystemsBatch SystemsSeveral jobs are kept in main memory at the same time, and theCPU is multiplexed among them.


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OS Features Needed forOS Features Needed for

MultiprogrammingMultiprogramming I/O routine supplied by the system.I/O routine supplied by the system.

Memory managementMemory managementthe system mustthe system mustallocate the memory to several jobs.allocate the memory to several jobs.

CPU schedulingCPU schedulingthe system mustthe system must

choose among several jobs ready to run.choose among several jobs ready to run.

Allocation of devices.Allocation of devices.


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TimeTime--Sharing SystemsSharing SystemsInteractiveInteractive

ComputingComputing The CPU is multiplexed among several jobs that areThe CPU is multiplexed among several jobs that are

kept in memory and on disk (the CPU is allocated tokept in memory and on disk (the CPU is allocated to

a job only if the job is in memory).a job only if the job is in memory).

A job swapped in and out of memory to the disk.A job swapped in and out of memory to the disk.

OnOn--line communication between the user and theline communication between the user and the

system is provided; when the operating systemsystem is provided; when the operating system

finishes the execution of one command, it seeks thefinishes the execution of one command, it seeks the

nextnext control statementcontrol statement from the userfrom the users keyboard.s keyboard.

OnOn--line system must be available for users to accessline system must be available for users to access

data and code.data and code.


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Desktop SystemsDesktop Systems Personal computersPersonal computerscomputer system dedicated to acomputer system dedicated to a

single user.single user.

I/O devicesI/O deviceskeyboards, mice, display screens, smallkeyboards, mice, display screens, smallprinters.printers.

User convenience and responsiveness.User convenience and responsiveness.

Can adopt technology developed for larger operatingCan adopt technology developed for larger operating

systemsystem often individuals have sole use of computeroften individuals have sole use of computerand do not need advanced CPU utilization ofand do not need advanced CPU utilization ofprotection features.protection features.

May run several different types of operating systemsMay run several different types of operating systems

(Windows,(Windows, MacOSMacOS, UNIX, Linux), UNIX, Linux)


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Parallel SystemsParallel Systems Multiprocessor systems with more than on CPU inMultiprocessor systems with more than on CPU in

close communication.close communication. Tightly coupled systemTightly coupled systemprocessors share memory and aprocessors share memory and a

clock; communication usually takes place through theclock; communication usually takes place through theshared memory.shared memory.

Advantages of parallel system:Advantages of parallel system: IncreasedIncreased throughputthroughput

EconomicalEconomical

Increased reliabilityIncreased reliability graceful degradationgraceful degradation

failfail--soft systemssoft systems


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Parallel Systems (Cont.)Parallel Systems (Cont.) Symmetric multiprocessing (SMP)Symmetric multiprocessing (SMP)

Each processor runs and identical copy of theEach processor runs and identical copy of the

operating system.operating system. Many processes can run at once withoutMany processes can run at once without

performance deterioration.performance deterioration.

Most modern operating systems support SMPMost modern operating systems support SMP

Asymmetric multiprocessingAsymmetric multiprocessing

Each processor is assigned a specific task;Each processor is assigned a specific task;master processor schedules and allocated workmaster processor schedules and allocated work

to slave processors.to slave processors.

More common in extremely large systemsMore common in extremely large systems


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Symmetric MultiprocessingSymmetric Multiprocessing

ArchitectureArchitecture


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Distributed SystemsDistributed Systems Distribute the computation among several physicalDistribute the computation among several physical

processors.processors.

Loosely coupled systemLoosely coupled systemeach processor has its owneach processor has its own

local memory; processors communicate with onelocal memory; processors communicate with one

another through various communications lines,another through various communications lines,

such as highsuch as high--speed buses or telephone lines.speed buses or telephone lines.

Advantages of distributed systems.Advantages of distributed systems.

Resources SharingResources Sharing

Computation speed upComputation speed upload sharingload sharing

ReliabilityReliability

CommunicationsCommunications


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Distributed Systems (cont)Distributed Systems (cont) Requires networking infrastructure.Requires networking infrastructure.

Local area networks (LAN) or Wide areaLocal area networks (LAN) or Wide areanetworks (WAN)networks (WAN)

May be either clientMay be either client--server or peerserver or peer--toto--

peer systems.peer systems.


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General Structure of ClientGeneral Structure of Client--ServerServer


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Clustered SystemsClustered Systems

Clustering allows two or more systems to shareClustering allows two or more systems to share

storage.storage.

Provides high reliability.Provides high reliability.

Asymmetric clusteringAsymmetric clustering: one server runs the: one server runs theapplication while other servers standby.application while other servers standby.

Symmetric clusteringSymmetric clustering: all N hosts are running the: all N hosts are running the

application.application.


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RealReal--Time SystemsTime Systems Often used as a control device in aOften used as a control device in a

dedicated application such as controllingdedicated application such as controlling

scientific experiments, medical imagingscientific experiments, medical imagingsystems, industrial control systems, andsystems, industrial control systems, and

some display systems.some display systems.

WellWell--defined fixeddefined fixed--time constraints.time constraints.

RealReal--Time systems may be eitherTime systems may be either hardhardoror

softsoftrealreal--time.time.


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RealReal--Time Systems (Cont.)Time Systems (Cont.) Hard realHard real--time:time:

Secondary storage limited or absent, data stored inSecondary storage limited or absent, data stored inshort term memory, or readshort term memory, or read--only memory (ROM)only memory (ROM)

Conflicts with timeConflicts with time--sharing systems, not supportedsharing systems, not supportedby generalby general--purpose operating systems.purpose operating systems.

Soft realSoft real--timetime Limited utility in industrial control of roboticsLimited utility in industrial control of robotics

Useful in applications (multimedia, virtual reality)Useful in applications (multimedia, virtual reality)

requiring advanced operatingrequiring advanced operating--system features.system features.


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Handheld SystemsHandheld Systems

Personal Digital Assistants (Personal Digital Assistants (PDAsPDAs))

Cellular telephonesCellular telephones

Issues:Issues:

Limited memoryLimited memory Slow processorsSlow processors

Small display screens.Small display screens.


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Migration of OperatingMigration of Operating--System ConceptsSystem Concepts

and Featuresand Features


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Computing EnvironmentsComputing Environments

Traditional computingTraditional computing

WebWeb--Based ComputingBased Computing

Embedded ComputingEmbedded Computing

Documents

CP0302 03-Jan-2011 RM01 Introduction