操作系统习题

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1、1.1Whatarethethreemainpurposesofanoperatingsystem?Answer:•Toprovideanenvironmentforacomputerusertoexecuteprogramsoncomputerhardwareinaconvenientandefficientmanner.•Toallocatetheseparateresourcesofthecomputerasneededtosolvetheproblemgiven.Theallocationprocessshouldbeasfairandefficientaspossible.

2、•Asacontrolprogramitservestwomajorfunctions:(1)supervisionoftheexecutionofuserprogramstopreventerrorsandimproperuseofthecomputer,and(2)managementoftheoperationandcontrolofI/Odevices.1.2Whatarethemaindifferencesbetweenoperatingsystemsformainframecomputersandpersonalcomputers?Answer:Generally,ope

3、ratingsystemsforbatchsystemshavesimplerrequirementsthanforpersonalcomputers.Batchsystemsdonothavetobeconcernedwithinteractingwithauserasmuchasapersonalcomputer.Asaresult,anoperatingsystemforaPCmustbeconcernedwithresponsetimeforaninteractiveuser.Batchsystemsdonothavesuchrequirements.Apurebatchsy

4、stemalsomayhavenottohandletimesharing,whereasanoperatingsystemmustswitchrapidlybetweendifferentjobs.1.3Listthefourstepsthatarenecessarytorunaprogramonacompletelydedicatedmachine.Answer:a.Reservemachinetime.b.Manuallyloadprogramintomemory.c.Loadstartingaddressandbeginexecution.d.Monitorandcontro

5、lexecutionofprogramfromconsole.1.4Wehavestressedtheneedforanoperatingsystemtomakeefficientuseofthecomputinghardware.Whenisitappropriatefortheoperatingsystemtoforsakethisprincipleandto“waste”resources?Whyissuchasystemnotreallywasteful?Answer:Single-usersystemsshouldmaximizeuseofthesystemfortheus

6、er.AGUImight“waste”CPUcycles,butitoptimizestheuser’sinteractionwiththesystem.1.5Whatisthemaindifficultythataprogrammermustovercomeinwritinganoperatingsystemforareal-timeenvironment?Answer:Themaindifficultyiskeepingtheoperatingsystemwithinthefixedtimeconstraintsofareal-timesystem.Ifthesystemdoes

7、notcompleteataskinacertaintimeframe,itmaycauseabreakdownoftheentiresystemitisrunning.Thereforewhenwritinganoperatingsystemforareal-timesystem,thewritermustbesurethathisschedulingschemesdon’tallowresponsetimetoexceedthetimeconstrai