Operating System-1 by Adi.pdf

Introduction to Operating System Part-1 by Dr. K. Adisesha

1. Introduction
to
Operating Systems -1
PROF. K. ADISESHA

2. Introduction
to
Operating System
OS Concepts
Functions of OS
Applications of OS
Types of OS
Properties of OS
2
Operating System

3. Introduction
Prof. K. Adisesha (Ph. D)
3
Operating System:
Anoperatingsystemisaprogramthatactsasaninterfacebetweentheuserandthe
computerhardwareandcontrolstheexecutionofallkindsofprograms.
➢SomepopularOperatingSystemsincludeLinuxOperatingSystem,Windows
OperatingSystem,VMS,OS/400,AIX,z/OS,etc.

4. Introduction
Prof. K. Adisesha (Ph. D)
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Operating System:
AnOperatingSystem(OS)isaninterfacebetweenacomputeruserandcomputer
hardware..
➢Anoperatingsystemisasoftwarewhichperformsallthebasictaskslike:
❖Filemanagement
❖Memorymanagement
❖Processmanagement
❖Handlinginputandoutput
❖Controllingperipheraldevicessuch
asdiskdrivesandprinters.

5. Introduction
Prof. K. Adisesha (Ph. D)
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Operating System:

6. Operating System
Prof. K. Adisesha (Ph. D)
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Functions of Operating system :
Theoperatingsystemisavitalcomponentofthesystemsoftwareinacomputersystem..
➢FollowingaresomeofimportantfunctionsofanoperatingSystem.
❖ProcessorManagement
❖MemoryManagement
❖DeviceManagement
❖FileManagement
❖Security
❖Controloversystemperformance
❖Jobaccounting
❖Errordetectingaids
❖Coordinationbetweenothersoftwareandusers

7. Operating System
Prof. K. Adisesha (Ph. D)
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Processor Management:
Inmultiprogrammingenvironment,theOSdecideswhichprocessgetstheprocessor
whenandforhowmuchtime,thisfunctioniscalledprocessscheduling.
➢AnOperatingSystemdoesthefollowingactivitiesforprocessormanagement:.
❖Keepstracksofprocessorandstatusofprocess.
❖Theprogramresponsibleforthistaskisknownastrafficcontroller.
❖Allocatestheprocessor(CPU)toaprocess.
❖De-allocatesprocessorwhenaprocessisnolongerrequired.

8. Operating System
Prof. K. Adisesha (Ph. D)
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Memory Management:
MemorymanagementreferstomanagementofPrimaryMemoryorMainMemory.
Mainmemoryisalargearrayofwordsorbyteswhereeachwordorbytehasitsown
address.
➢AnOperatingSystemdoesthefollowingactivitiesformemorymanagement:
❖Keepstracksofprimarymemory,i.e.,whatpartofitareinusebywhom,whatpart
arenotinuse.
❖Inmultiprogramming,theOSdecideswhichprocesswillgetmemorywhenand
howmuch.
❖Allocatesthememorywhenaprocessrequestsittodoso.
❖De-allocatesthememorywhenaprocessnolongerneedsitorhasbeen
terminated.

9. Operating System
Prof. K. Adisesha (Ph. D)
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Device Management:
AnOperatingSystemmanagesdevicecommunicationviatheirrespectivedrivers.
➢AnOperatingSystemdoesthefollowingactivitiesfordevicemanagement:
❖Keepstracksofalldevices.ProgramresponsibleforthistaskisknownastheI/O
controller.
❖Decideswhichprocessgetsthedevicewhenandforhowmuchtime.
❖Allocatesthedeviceintheefficientway.
❖De-allocatesdevices.

10. Operating System
Prof. K. Adisesha (Ph. D)
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File Management:
Afilesystemisnormallyorganizedintodirectoriesforeasynavigationandusage.
Thesedirectoriesmaycontainfilesandotherdirections.
➢AnOperatingSystemdoesthefollowingactivitiesforfilemanagement:
❖Keepstrackofinformation,location,uses,statusetc.Thecollectivefacilitiesare
oftenknownasfilesystem.
❖Accesstothefileforreadandwrite.
❖AllocatesthefileforI/Odevices.
❖De-allocatesthefileformstoragedevices

11. Operating System
Prof. K. Adisesha (Ph. D)
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Applications of Operating System:
FollowingaresomeoftheimportantactivitiesthatanOperatingSystemperforms.
➢Security:Bymeansofpasswordandsimilarothertechniques,itpreventsunauthorized
accesstoprogramsanddata.
➢Controloversystemperformance:Recordingdelaysbetweenrequestforaservice
andresponsefromthesystem.
➢Jobaccounting:Keepingtrackoftimeandresourcesusedbyvariousjobsandusers.
➢Errordetectingaids:Productionofdumps,traces,errormessages,andother
debugginganderrordetectingaids.
➢Coordinationbetweenothersoftwareandusers:Coordinationandassignmentof
compilers,interpreters,assemblersandothersoftwaretothevarioususersofthe
computersystems.

12. Operating System Types
Prof. K. Adisesha (Ph. D)
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Types of Operating System:
Operatingsystemsaretherefromtheveryfirstcomputergenerationandtheykeep
evolvingwithtime.
➢Varioustypesofoperatingsystemswhicharemostcommonlyusedare:
❖Batchoperatingsystem
❖Time-sharingoperatingsystems
❖DistributedoperatingSystem.
❖NetworkoperatingSystem
❖RealTimeoperatingSystem

13. Operating System Types
Prof. K. Adisesha (Ph. D)
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Batch operating system:
Abatchoperatingsystemgrabsallprogramsanddatainthebatchformandthen
processesthem.
➢Eachuserprepareshisjobonanoff-linedevicelikepunchcardsandsubmitsittothe
computeroperator.
➢Tospeedupprocessing,jobswithsimilarneedsarebatchedtogetherandrunasagroup.
➢TheproblemswithBatchSystemsareasfollows−
❖Lackofinteractionbetweentheuserandthejob.
❖CPUisoftenidle,becausethespeedofthemechanicalI/Odevicesisslowerthanthe
CPU.
❖Difficulttoprovidethedesiredpriority.

14. Operating System Types
Prof. K. Adisesha (Ph. D)
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Batch operating system:
Theusersofabatchoperatingsystemdonotinteractwiththecomputerdirectly.
➢Themainaimofusingabatchprocessingsystemistodecreasethesetuptimewhile
submittingsimilarjobstotheCPU.
➢Batchprocessingtechniqueswereimplementedintheharddiskandcardreadersaswell..
➢ExamplesofBatchSystemsareasfollows−
❖PayrollSystem
❖BankInvoiceSystem
❖TransactionsProcess
❖DailyReport
❖ResearchSegment
❖BillingSystem

15. Operating System Types
Prof. K. Adisesha (Ph. D)
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Time-sharing operating systems:
Time-sharingisatechniquewhichenablesmanypeople,locatedatvariousterminals,
touseaparticularcomputersystematthesametime.
➢Time-sharingormultitaskingisalogicalextensionof
multiprogramming.
➢Processor'stimewhichissharedamongmultipleusers
simultaneouslyistermedastime-sharing.
➢MultiplejobsareexecutedbytheCPUbyswitchingbetweenthem,
buttheswitchesoccursofrequentlyenabling,theuserstoreceivean
immediateresponse.
➢TheoperatingsystemusesCPUschedulingandmultiprogramming
toprovideeachuserwithasmallportionofatime.

16. Operating System Types
Prof. K. Adisesha (Ph. D)
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Time-sharing operating systems:
Computersystemsthatweredesignedprimarilyasbatchsystemshavebeenmodifiedto
time-sharingsystems.
➢AdvantagesofTimesharingoperatingsystemsareasfollows:
❖Providestheadvantageofquickresponse.
❖Avoidsduplicationofsoftware.
❖ReducesCPUidletime.
➢DisadvantagesofTime-sharingoperatingsystemsareasfollows:
❖Problemofreliability.
❖Questionofsecurityandintegrityofuserprogramsanddata.
❖Problemofdatacommunication.

17. Operating System Types
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Distributed operating System:
Distributedsystemsusemultiplecentralprocessorstoservemultiplereal-time
applicationsandmultipleusers.Dataprocessingjobsaredistributedamongthe
processorsaccordingly.
➢Theprocessorscommunicatewithoneanotherthroughvariouscommunicationlines.
➢Thesearereferredaslooselycoupledsystemsordistributedsystems.
➢Processorsinadistributedsystemmayvaryinsizeandfunction.
➢Theseprocessorsarereferredassites,nodes,computers,andsoon.
➢Examples:Solaris,OSF/1,Micros,
DYNIX,Locus,Mach

18. Operating System Types
Prof. K. Adisesha (Ph. D)
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Distributed operating System:
Distributedsystemsusemultiplecentralprocessorstoservemultiplereal-time
applicationsandmultipleusers.Dataprocessingjobsaredistributedamongthe
processorsaccordingly.
➢Theadvantagesofdistributedsystemsareasfollows−
❖Withresourcesharingfacility,auseratonesitemaybeabletousetheresourcesavailable
atanother.
❖Speeduptheexchangeofdatawithoneanotherviaelectronicmail.
❖Betterservicetothecustomers.
❖Reductionoftheloadonthehostcomputer.
❖Reductionofdelaysindataprocessing.

19. Operating System Types
Prof. K. Adisesha (Ph. D)
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Network operating System:
ANetworkOperatingSystemrunsonaserverandprovidestheserverthecapabilityto
managedata,users,groups,security,applications,andothernetworkingfunctions.
➢Theprimarypurposeofthenetworkoperatingsystemistoallowsharedfileandprinteraccess
amongmultiplecomputersinanetwork,typicallyalocalareanetwork(LAN),aprivate
networkortoothernetworks.
➢Therearetwobasictypesofnetworkoperatingsystems:
❖Peer-to-PeerNetworkOperatingSystems
❖Client/ServerNetworkOperatingSystems
➢Examplesofnetworkoperatingsystemsinclude:
❖MicrosoftWindowsServer2003,MicrosoftWindowsServer2008,
❖UNIX,Linux,MacOSX,NovellNetWare,andBSD.

20. Operating System Types
Prof. K. Adisesha (Ph. D)
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Network operating System:
ANetworkOperatingSystemrunsonaserverandprovidestheserverthecapabilityto
managedata,users,groups,security,applications,andothernetworkingfunctions.
➢Theadvantagesofnetworkoperatingsystemsareasfollows:
❖Centralizedserversarehighlystable.
❖Securityisservermanaged.
❖Upgradestonewtechnologiesandhardwarecanbeeasilyintegratedintothesystem.
❖Remoteaccesstoserversispossiblefromdifferentlocationsandtypesofsystems.
➢Thedisadvantagesofnetworkoperatingsystemsareasfollows:
❖Highcostofbuyingandrunningaserver.
❖Dependencyonacentrallocationformostoperations.
❖Regularmaintenanceandupdatesarerequired..

21. Operating System Types
Prof. K. Adisesha (Ph. D)
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Real Time operating System:
Areal-timesystemisdefinedasadataprocessingsysteminwhichthetimeinterval
requiredtoprocessandrespondtoinputsissosmallthatitcontrolstheenvironment.
➢Thetimetakenbythesystemtorespondtoaninputanddisplayofrequiredupdated
informationistermedastheresponsetime.
➢Inthismethod,theresponsetimeisverylessascomparedtoonlineprocessing.
➢Real-timesystemsareusedwhentherearerigidtimerequirementsontheoperationofa
processorortheflowofdataandreal-timesystemscanbeusedasacontroldeviceina
dedicatedapplication.
➢Areal-timeoperatingsystemmusthavewell-defined,fixedtimeconstraints,otherwisethe
systemwillfail.

22. Operating System Types
Prof. K. Adisesha (Ph. D)
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Real Time operating System:
Therearetwotypesofreal-timeoperatingsystems.
➢Hardreal-timesystems
❖Hardreal-timesystemsguaranteethatcriticaltaskscompleteontime.
❖Inhardreal-timesystems,secondarystorageislimitedormissingandthedataisstoredin
ROM.
❖Inthesesystems,virtualmemoryisalmostneverfound.
➢Softreal-timesystems
❖Softreal-timesystemsarelessrestrictive.
❖Softreal-timesystemshavelimitedutilitythanhardreal-timesystems.
❖Example:Multimedia,virtualreality,AdvancedScientificProjectslikeundersea
explorationandplanetaryrovers,etc.

23. Operating System -Services
Prof. K. Adisesha (Ph. D)
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Operating System -Services:
AnOperatingSystemprovidesservicestoboththeusersandtotheprograms.
➢Itprovidesprogramsanenvironmenttoexecute.
➢Itprovidesuserstheservicestoexecutetheprogramsinaconvenientmanner.
➢CommonservicesprovidedbyanoperatingSystemare:
❖Programexecution
❖I/Ooperations
❖FileSystemmanipulation
❖Communication
❖ErrorDetection
❖ResourceAllocation
❖Protection

24. Operating System -Services
Prof. K. Adisesha (Ph. D)
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Program execution:
Operatingsystemshandlemanykindsofactivitiesfromuserprogramstosystem
programs,theseactivitiesareencapsulatedasaprocess.
➢Aprocessincludesthecompleteexecutioncontext(codetoexecute,datatomanipulate,
registers,OSresourcesinuse).
➢Followingaretheactivitiesofanoperatingsystemwithrespecttoprogrammanagement:
❖Loadsaprogramintomemory.
❖Executestheprogram.
❖Handlesprogram'sexecution.
❖Providesamechanismforprocesssynchronization.
❖Providesamechanismforprocesscommunication.
❖Providesamechanismfordeadlockhandling.

25. Operating System -Services
Prof. K. Adisesha (Ph. D)
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File system manipulation:
Afilerepresentsacollectionofrelatedinformation.Computerscanstorefilesonthe
disk(secondarystorage),forlong-termstoragepurpose.
➢Afilesystemisnormallyorganizedintodirectoriesforeasynavigationandusage.
➢Thesedirectoriesmaycontainfilesandotherdirections.
➢Followingarethemajoractivitiesofanoperatingsystemwithrespecttofilemanagement:
❖Programneedstoreadafileorwriteafile.
❖Theoperatingsystemgivesthepermissiontotheprogramforoperationonfile.
❖Permissionvariesfromread-only,read-write,deniedandsoon.
❖OperatingSystemprovidesaninterfacetotheusertocreate/deletefiles.
❖OperatingSystemprovidesaninterfacetotheusertocreate/deletedirectories.
❖OperatingSystemprovidesaninterfacetocreatethebackupoffilesystem.

26. Operating System -Services
Prof. K. Adisesha (Ph. D)
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I/O Operation:
AnI/OsubsystemcomprisesofI/Odevicesandtheircorrespondingdriversoftware.
Drivershidethepeculiaritiesofspecifichardwaredevicesfromtheusers.
➢AnOperatingSystemmanagesthecommunicationbetweenuseranddevicedrivers:
❖I/OoperationmeansreadorwriteoperationwithanyfileoranyspecificI/Odevice.
❖OperatingsystemprovidestheaccesstotherequiredI/Odevicewhenrequired.

27. Operating System -Services
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Communication:
Incaseofdistributedsystemswhichareacollectionofprocessorsthatdonotshare
memory,peripheraldevices,oraclock,theoperatingsystemmanagescommunications
betweenalltheprocesses.
➢TheOShandlesroutingandconnectionstrategies,andtheproblemsofcontentionandsecurity.
➢Followingarethemajoractivitiesofanoperatingsystemwithrespecttocommunication:
❖Twoprocessesoftenrequiredatatobetransferredbetweenthem
❖Boththeprocessescanbeononecomputerorondifferentcomputers,butareconnected
throughacomputernetwork.
❖Communicationmaybeimplementedbytwomethods,eitherbySharedMemoryorby
MessagePassing..

28. Operating System -Services
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Error handling:
Errorscanoccuranytimeandanywhere.AnerrormayoccurinCPU,inI/Odevicesor
inthememoryhardware.
➢Followingarethemajoractivitiesofanoperatingsystemwithrespecttoerrorhandling:
❖TheOSconstantlychecksforpossibleerrors.
❖TheOStakesanappropriateactiontoensurecorrectandconsistentcomputing.

29. Operating System -Services
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Resource Management:
Incaseofmulti-userormulti-taskingenvironment,resourcessuchasmainmemory,
CPUcyclesandfilesstoragearetobeallocatedtoeachuserorjob.
➢Followingarethemajoractivitiesofanoperatingsystemwithrespecttoresource
management:
❖TheOSmanagesallkindsofresourcesusingschedulers.
❖CPUschedulingalgorithmsareusedforbetterutilizationofCPU.

30. Operating System -Services
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Protection:
Protectionreferstoamechanismorawaytocontroltheaccessofprograms,processes,
oruserstotheresourcesdefinedbyacomputersystem.
➢Followingarethemajoractivitiesofanoperatingsystemwithrespecttoprotection:
❖TheOSensuresthatallaccesstosystemresourcesiscontrolled.
❖TheOSensuresthatexternalI/Odevicesareprotectedfrominvalidaccessattempts.
❖TheOSprovidesauthenticationfeaturesforeachuserbymeansofpasswords.

31. Operating System -Properties
Prof. K. Adisesha (Ph. D)
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Properties of Operating System:
OperatingSystemreferstoamechanismtoaccesstheprograms,processes,orusersto
theresourcesdefinedbyacomputersystem.
➢FollowingarethepropertiesofOperatingSystem:
❖Batchprocessing.
❖Multitasking
❖Multiprogramming
❖Interactivity
❖RealTimeSystem
❖DistributedEnvironment
❖Spooling

32. Operating System -Properties
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Batch processing:
BatchprocessingisatechniqueinwhichanOperatingSystemcollectstheprograms
anddatatogetherinabatchbeforeprocessingstarts.
➢Anoperatingsystemdoesthefollowingactivitiesrelatedtobatchprocessing:
❖TheOSdefinesajobwhichhaspredefinedsequenceofcommands,
programsanddataasasingleunit.
❖TheOSkeepsanumberajobsinmemoryandexecutesthemwithoutany
manualinformation.
❖Jobsareprocessedintheorderofsubmission,i.e.,firstcomefirstserved
fashion.
❖Whenajobcompletesitsexecution,itsmemoryisreleasedandtheoutput
forthejobgetscopiedintoanoutputspoolforlaterprintingorprocessing.

33. Operating System -Properties
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Batch processing:
BatchprocessingisatechniqueinwhichanOperatingSystemcollectstheprograms
anddatatogetherinabatchbeforeprocessingstarts.
➢Advantages
❖Batchprocessingtakesmuchoftheworkoftheoperatortothecomputer.
❖Increasedperformanceasanewjobgetstartedassoonasthepreviousjobisfinished,
withoutanymanualintervention.
➢Disadvantages
❖Difficulttodebugprogram.
❖Ajobcouldenteraninfiniteloop.
❖Duetolackofprotectionscheme,onebatchjobcanaffectpendingjobs.:

34. Operating System -Properties
Prof. K. Adisesha (Ph. D)
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Multitasking:
MultitaskingiswhenmultiplejobsareexecutedbytheCPUsimultaneouslyby
switchingbetweenthem.
➢AnOperatingSystemdoesthefollowingactivitiesrelatedtomultitasking:
❖Theusergivesinstructionstotheoperatingsystemortoaprogramdirectly,andreceivesan
immediateresponse.
❖TheOShandlesmultitaskinginthewaythatitcanhandlemultipleoperations/executesmultiple
programsatatime.
❖MultitaskingOperatingSystemsarealsoknownasTime-sharingsystems.
❖Eachuserhasatleastoneseparateprograminmemory.

35. Operating System -Properties
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Multiprogramming:
Sharingtheprocessor,whentwoormoreprogramsresideinmemoryatthesametime,is
referredasmultiprogramming.
➢Multiprogrammingassumesasinglesharedprocessor.
➢MultiprogrammingincreasesCPUutilizationbyorganizingjobsso
thattheCPUalwayshasonetoexecute.
➢AnOSdoesthefollowingactivitiesrelatedtomultiprogramming:
❖Theoperatingsystemkeepsseveraljobsinmemoryatatime.
❖Thissetofjobsisasubsetofthejobskeptinthejobpool.
❖Theoperatingsystempicksandbeginstoexecuteoneofthejobsinthememory.
❖Multiprogrammingoperatingsystemsmonitorthestateofallactiveprogramsandsystemresources
usingmemorymanagementprogramstoensuresthattheCPUisneveridle,unlesstherearenojobs
toprocess

36. Operating System -Properties
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Multiprogramming:
Sharingtheprocessor,whentwoormoreprogramsresideinmemoryatthesametime,
isreferredasmultiprogramming.
➢Multiprogrammingassumesasinglesharedprocessor.
➢MultiprogrammingincreasesCPUutilizationbyorganizingjobssothattheCPUalwayshas
onetoexecute.
➢AnOSdoesthefollowingactivitiesrelatedtomultiprogramming:
❖Theoperatingsystemkeepsseveraljobsinmemoryatatime.
❖Thissetofjobsisasubsetofthejobskeptinthejobpool.
❖Theoperatingsystempicksandbeginstoexecuteoneofthejobsinthememory.
❖Multiprogrammingoperatingsystemsmonitorthestateofallactiveprogramsandsystemresources
usingmemorymanagementprogramstoensuresthattheCPUisneveridle,unlesstherearenojobs
toprocess

37. Operating System -Properties
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Real Time System & Interactivity:
Real-timesystemsareusuallydedicated,embeddedsystems.
➢Anoperatingsystemdoesthefollowingactivitiesrelatedtoreal-timesystemactivity..
❖Insuchsystems,OperatingSystemstypicallyreadfromandreacttosensordata.
❖TheOperatingsystemmustguaranteeresponsetoeventswithinfixedperiodsoftimeto
ensurecorrectperformance.
Interactivity
➢Interactivityreferstotheabilityofuserstointeractwithacomputersystem.
➢AnOperatingsystemdoesthefollowingactivitiesrelatedtointeractivity−
❖Providestheuseraninterfacetointeractwiththesystem.
❖Managesinputdevicestotakeinputsfromtheuser.Forexample,keyboard.
❖Managesoutputdevicestoshowoutputstotheuser.Forexample,Monitor.
❖TheresponsetimeoftheOSneedstobeshort,sincetheusersubmitsandwaitsfortheresult.

38. Operating System -Properties
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Distributed Environment:
AdistributedenvironmentreferstomultipleindependentCPUsorprocessorsina
computersystem.
➢Anoperatingsystemdoesthefollowingactivitiesrelatedtodistributedenvironment:
❖TheOSdistributescomputationlogicsamongseveralphysicalprocessors.
❖Theprocessorsdonotsharememoryoraclock.Instead,eachprocessorhasitsownlocal
memory.
❖TheOSmanagesthecommunicationsbetweentheprocessors.
❖Theycommunicatewitheachotherthroughvariouscommunicationlines.

39. Operating System -Properties
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Spooling:
Spoolingisanacronymforsimultaneousperipheraloperationsonline.
➢SpoolingreferstoputtingdataofvariousI/Ojobsinabuffer.
➢ThisbufferisaspecialareainmemoryorharddiskwhichisaccessibletoI/Odevices.
➢Advantages
❖Thespoolingoperationusesadiskasaverylarge
buffer.
❖SpoolingiscapableofoverlappingI/Ooperationfor
onejobwithprocessoroperationsforanotherjob.

40. Operating System -Properties
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Spooling:
Spoolingisanacronymforsimultaneousperipheraloperationsonline.
➢SpoolingreferstoputtingdataofvariousI/Ojobsinabuffer.
➢Anoperatingsystemdoesthefollowingactivitiesrelatedtodistributedenvironment.
❖HandlesI/Odevicedataspoolingasdeviceshavedifferentdataaccessrates.
❖Maintainsthespoolingbufferwhichprovidesawaitingstationwheredatacanrestwhilethe
slowerdevicecatchesup.
❖MaintainsparallelcomputationbecauseofspoolingprocessasacomputercanperformI/O
inparallelfashion.
❖Itbecomespossibletohavethecomputerreaddatafromatape,writedatatodiskandto
writeouttoatapeprinterwhileitisdoingitscomputingtask

41. Discussion
Prof. K. Adisesha (Ph. D)
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Queries ?
Prof. K. Adisesha
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