操作系统习题集

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

2、cientaspossible.•Asacontrolprogramitservestwomajorfunctions:(1)supervisionoftheexecutionofuserprogramstopreventerrorsandimproperuseofthecomputer,and(2)managementoftheoperationandcontrolofI/Odevices.1.2Whatarethemaindifferencesbetweenoperatingsystemsformainframecomputersandperson

3、alcomputers?Answer:Generally,operatingsystemsforbatchsystemshavesimplerrequirementsthanforpersonalcomputers.Batchsystemsdonothavetobeconcernedwithinteractingwithauserasmuchasapersonalcomputer.Asaresult,anoperatingsystemforaPCmustbeconcernedwithresponsetimeforaninteractiveuser.Ba

4、tchsystemsdonothavesuchrequirements.Apurebatchsystemalsomayhavenottohandletimesharing,whereasanoperatingsystemmustswitchrapidlybetweendifferentjobs.1.3Listthefourstepsthatarenecessarytorunaprogramonacompletelydedicatedmachine.Answer:a.Reservemachinetime.b.Manuallyloadprograminto

5、memory.c.Loadstartingaddressandbeginexecution.d.Monitorandcontrolexecutionofprogramfromconsole.1.4Wehavestressedtheneedforanoperatingsystemtomakeefficientuseofthecomputinghardware.Whenisitappropriatefortheoperatingsystemtoforsakethisprincipleandto“waste”resources?Whyissuchasyste

6、mnotreallywasteful?Answer:Single-usersystemsshouldmaximizeuseofthesystemfortheuser.AGUImight“waste”CPUcycles,butitoptimizestheuser’sinteractionwiththesystem.1.5Whatisthemaindifficultythataprogrammermustovercomeinwritinganoperatingsystemforareal-timeenvironment?Answer:Themaindiff

7、icultyiskeepingtheoperatingsystemwithinthefixedtimeconstraintsofareal-timesystem.Ifthesystemdoesnotcompleteataskinacertaintimeframe,itmaycauseabreakdownoftheentiresystemitisrunning.Thereforewhenwritinganoperatingsystemforareal-timesystem,thewritermustbesurethathisschedulingschem

8、esdon’tallowresponsetimetoexceedthetimeconstrai