操作系统习题

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1、技术资料1.1Whatarethethreemainpurposesofanoperatingsystem?Answer:•Toprovideanenvironmentforacomputerusertoexecuteprogramsoncomputerhardwareinaconvenientandefficientmanner.•Toallocatetheseparateresourcesofthecomputerasneededtosolvetheproblemgiven.Theallocationprocessshouldbeasfairandefficientaspos

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

3、ally,operatingsystemsforbatchsystemshavesimplerrequirementsthanforpersonalcomputers.Batchsystemsdonothavetobeconcernedwithinteractingwithauserasmuchasapersonalcomputer.Asaresult,anoperatingsystemforaPCmustbeconcernedwithresponsetimeforaninteractiveuser.Batchsystemsdonothavesuchrequirements.Ap

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

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

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

7、.Ifthesystemdoesnotcompleteataskinacertaintimeframe,itmaycauseabreakdownoftheentiresystemitisrunning.Thereforewhenwritinganoperatingsystemforareal-timesystem,thewritermustbesurethathisschedulingschemesdon’tallowresponsetimetoexceedthetimecons