计算机操作系统期末考试题集锦.doc
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计算机操作系统期末考试题集锦.doc
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操作系统填空题及答案
1、Anoperatingsystemis(program)thatmanagesthecomputerhardware.Thehardwaremustprovideappropriate(mechanisms)toensurethecorrectoperationofthecomputersystemandtopreventuserprogramsfrominterferingwiththeproperoperationofthesystem.
2、Acomputersystemcanbedividedroughlyintofourcomponents:
thehardware,the(operatingsystem),theapplicationprograms,and(users)。
3、Multiprocessorsystemshavethreemainadvantages:
(increasedthroughput),economyofscale,increasedreliability.
4、Inordertoensuretheproperexecutionoftheoperatingsystem,wemustbeabletodistinguishbetweentheexecutionofoperating-systemcodeand(user-definedcode).weneedtwoseparatemodesofoperation:
usermodeand(kernelmode).
5、Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionwithfilemanagement:
(Creatinganddeletingfiles),Creatinganddeletingdirectoriestoorganizefiles,Supportingprimitivesformanipulatingfilesanddirectories,Mappingfilesonto(secondarystorage),Backingupfilesonstable(nonvolatile)storagemedia.
6、Fiveservicesprovidedbyanoperatingsystemthataredesignedtomakeitmoreconvenientforuserstousethecomputersystemare(Program),I/Ooperations,File-systemmanipulation,(Communications)andErrordetection.
7、Thetwomodelsofinterprocesscommunicationaremessage-passingmodelandthe(share-memoryFF)model.
8、Systemcallsallow(running)processestorequestservicesoftheoperatingsystem.
9、Thethreemajoractivitiesofanoperatingsysteminregardtosecondary-storagemanagementareFree-spacemanagement,Storageallocationand(Diskscheduling).
10、Systemcallscanbegroupedroughlyintofivemajorcategories:
processcontrol,(filemanagement),devicemanipulation,(Informationmaintenance),andcommunications.
11、A(process)canbethoughtofasaprograminexecutionwhichwillneedcertainresources-suchasCPUtime,memory,files,andI/Odevices-toaccomplishitstask.
12、Twocommontechniquesforloadingexecutablefilesare(double-clicking)aniconrepresentingtheexecutablefileandenteringthenameoftheexecutablefileonthe(commandline).
13、Asaprocessexecutes,itchangesstatefromnewstate,(runningstate),waitingstate,(readystate),terminatedstate.
14、Theobjectiveofmultiprogrammingistohavesomeprocessrunningatalltimes,tomaximize(CPU)utilization.
15、Asprocessesenterthesystem,theyareputintoa(job)queue,whichconsistsofallprocessesinthesystem.
16、Thelong-termscheduler,or(jobscheduler),selectsprocessesfromthispoolandloadsthemintomemoryforexecution.
17、The(short-term)scheduler,orCPUscheduler,selectsfromamongtheprocessesthatarereadytoexecuteandallocatestheCPUtooneofthem.
18、Theprimarydistinctionbetweenthelong-termschedulerandtheshort-termschedulerschedulersliesin(frequency)ofexecution.
19、Whenaninterruptoccurs,thesystemneedstosavethecurrent(context)oftheprocesscurrentlyrunningontheCPUsothatitcan(restore)thatcontextwhenitsprocessingisdone,essentiallysuspendingtheprocessandthen(resuming)it.
20、Thecontextisrepresentedinthe(PCB)oftheprocess;itincludesthevalueoftheCPUregisters,the(processstate)andmemory-managementinformation.
21、SwitchingtheCPUtoanotherprocessrequiresperformingastatesaveofthecurrentprocessandastaterestoreofadifferentprocess.Thistaskisknownasa(contextswitch).
22、Aprocessmaycreateseveralnewprocesses,viaacreate-process(systemcall),duringthecourseofexecution.Thecreatingprocessiscalledaparentprocess,andthenewprocessesarecalledthe(children)ofthatprocess.
23、Aprocessterminateswhenitfinishesexecutingitsfinalstatementandaskstheoperatingsystemtodeleteitbyusingthe(exit())systemcall.
24、Aprocessisindependentifitcannotaffectorbeaffectedby(theotherprocesses)executinginthesystem.
25、Theadvantagesofprocesscooperationinclude(information),computationspeed-up,modularityandconvenience.
26、Withindirectcommunication,themessagesaresenttoandreceivedfrommailboxes,orportswhichcanbeviewedabstractlyasanobjectintowhichmessagescanbeplacedbyprocessesandfromwhichmessagescanberemoved.
27、Messagepassingmaybeeitherblockingor(nonblocking)alsoknownas(synchronous)andasynchronous.
28、Whethercommunicationisdirectorindirect,messagesexchangedbycommunicatingprocessesresideinatemporaryqueues.Basically,suchqueuescanbeimplementedinthreeways:
(Zerocapacity),(Bounded)andunboundedcapacity.
29、A(thread)isabasicunitofCPUutilization;ItcomprisesathreadID,aprogramCounter,aregisterset,andastack.
30、A(traditional)(orheavyweight)processhasa(single)threadofcontrol.Ifaprocesshasmultiplethreadsofcontrol,itcanperformmorethanonetaskatatime.
31、Thebenefitsofmultithreadedprogrammingcanbebrokendownintofourmajorcategories:
(Responsiveness),(Resource),Economy,Utilizationofmultiprocessorarchitecture.
32、CPU(scheduling)isthebasisofmulti-programmedoperatingsystems.ByswitchingtheCPUamong(processes),theoperatingsystemcanmakethecomputermoreproductive.
33、Processexecutionconsistsofacycleof(CPUexecution)andI/Owait.Processesalternatebetweenthesetwostates.
34、DispatchermodulegivescontroloftheCPUtotheprocessselectedbythe(short-term)scheduler;Thisfunctioninvolves:
(switchingcontext),switchingtousermode,jumpingtotheproperlocationintheuserprogramtorestartthatprogram.
35、Thetimeittakesforthedispatchertostoponeprocessandstartanotherrunningisknownasthe(dispatchlatency).
36、ManycriteriahavebeensuggestedforcomparingCPUschedulingalgorithms.Thecriteriaincludethefollowing:
(CPUutilization),throughput,(turnaroud)time,waitingtime,(Responsetime).
37、TheSJFalgorithmcanbeeither(preemptive)ornonpreemptivewhichgivesminimum(averagewaiting)timeforagivensetofprocesses.
38、Amajorproblemwithpriorityschedulingalgorithmsisindefiniteblocking,orstarvation.Asolutiontotheproblemis(aging).
39、The(roundrobin)schedulingalgorithmisdesignedespeciallyfor(time-sharingsystem).ItissimilartoFCFSscheduling,butpreemptionisaddedtoswitchbetweenprocesses.
40、Asituationlikethis,whereseveralprocessesaccessandmanipulatethesamedataconcurrentlyandtheoutcomeoftheexecutiondependsontheparticularorderinwhichtheaccesstakesplace,iscalleda(racecondition).
41、Considerasystemconsistingofnprocesses{PO,PI,...,Pn-1).Eachprocesshasasegmentofcode,calleda(critical),inwhichtheprocessmaybechangingcommonvariables,updatingatable,writingafile,andsoon.
42、Asolutiontothecritical-sectionproblemmustsatisfythefollowingthreerequirements:
(Mutualexclusion),Progressand(Boundedwaiting).
43、Ingeneral,wecanstatethatanysolutiontothecritical-sectionproblemrequiresasimpletool-a(lock).Aprocessmustacquireitbeforeenteringacriticalsection.
44、Thevarioushardware-basedsolutionstothecritical-sectionproblemarecomplicatedforapplicationprogrammerstouse.Toovercomethisdifficulty,wecanuseasynchronizationtoolcalleda(semaphore).
45、AsemaphoreSisanintegervariablethat,apartfrominitialization,isaccessedonlythroughtwostandardatomicoperations:
(wait())and(signal()).
46、Themaindisadvantageofthesemaphoredefinitiongivenhereisthatitrequires(busywaiting).
47、Dispatcherobjectsmaybeineitherasignaledstateoranonsignaledstate.A(signaledstate)indicatesthatanobjectisavailableandathreadwillnotblockwhenacquiringtheobject.
48、Sometimes,awaitingprocessisneveragainabletochangestate,becausetheresourcesithasrequestedareheldbyotherwaitingprocesses.Thissituationiscalleda(deadlock).
49、Asystemconsistsofafinitenumberofresourcestobedistributedamonganumberof(competingprocesses).Theresourcesarepartitionedintoseveraltypes,eachconsistingofsomenumberofidentical(instances).
50、Underthenormalmodeofoperation,aprocessmayutilizearesourceinonlythefollowingsequence:
(Request),use,(Release).
60、Multithreadedprogramsaregoodcandidatesfordeadlockbecausemultiplethreadscancompetefor(sharedresources).
61、Deadlockcanariseiffourconditionsholdsimultaneously:
Mutualexclusion
(Holdandwait),Nopreemption,(Circularwait).
62、Deadlockscanbedescribedmorepreciselyintermsofadirectedgraphcalleda(systemresourceallocation)graph.ThisgraphconsistsofasetofverticesVandasetofedgesE.
63、Themainpurposeofacomputersystemistoexecuteprograms.Theseprograms,togetherwiththedatatheyaccess,mustbein(mainmemory)(atleastpartially)duringexecution.
64、Mainmemoryand(registers)areonlystorageCPUcanaccessdirectly.
65、Thebaseregisterholdsthesmallestlegal(physicalmemoryaddress);thelimitregisterspecifiesthesizeoftherange.
66、Addressbindingofinstructionsanddatatomemoryaddressescanhappenatthreedifferentstages:
(Compiletime),Loadtime,(Executiontime).
67、Logicalandphysicaladdressesarethesameincompile-timeand(load-time)address-bindingschemes;logicalandphysicaladdressesdifferin(execution-time)address-bindingscheme.
68、InMMUscheme,thevalueintherelocationregisterisaddedtoeveryaddressgeneratedbyauserprocessatthetimeit
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