操作系统期中作业(答案)精编版

操作系统期中作业(答案)PAGEPAGE3操作系统期中作业姓名：___学号：专业：一、Foreachofthefollowingstatements,ChoosingTrueorFalseBinarysemaphoresarethosethatareusedbynomorethantwothreads.FTheBanker'salgorithmisawayofpreventingdeadlock.FAmulti-levelindexedfilepermitsfasterrandomaccessthanacontiguouslyallocatedfile.FAnatomicoperationisamachineinstructionorasequenceofinstructionsthatmustbeexecutedtocompletionwithoutinterruption.TDeadlockisasituationinwhichtwoormoreprocesses(orthreads)arewaitingforaneventthatwilloccurinthefuture.FStarvationisasituationinwhichaprocessisdeniedaccesstoaresourcebecauseofthecompetitiveactivityofother,possiblyunrelated,processes.TWhileaprocessisblockedonasemaphore'squeue,itisengagedinbusywaiting.FMutualexclusioncanbeenforcedwithageneralsemaphorewhoseinitialvalueisgreaterthan1.FAprinterisanexampleofalogicalresource.FVersionsofOS/360arestillwidelyusedtoday.FWhenanexecutingprocessisstoppedbythescheduler,itissaidtobeblocked.FInterruptsareusedtoachieveatypicaltimesharingOS.T二、MultipleChoiceQuestionsForeachofthefollowingquestions,Thereisonlyonecorrectanswer.Whatisthepurposeofsystemcalls?a)Systemcallsallowuser-levelprocessestogainresourcesfromtheoperatingsystem.b)Systemcallsarethestandardinterfacebetweenauserprocessandakernelprocess.c)Systemcallsallowuser-levelprocessestorequestservicesoftheoperatingsystem.d)Thereisnorealpurposetosystemcalls.Threadsbelongingtothesameprocesssharethea)stack b)datasectionc)registerset d)threadIDInMany-to-Onethreadmodel,Whatwouldhappenifathreadinamultithreadedprocessmakesablockingsystemcall?a)theotherthreadsoftheprocesswouldcontinuetorunb)theentireprocesswouldgetblockedc)theblockingthreadwillgetkilledd)theblockingthreadwillnevergettorunagainWhichofthefollowingOperatingsystemsusespreemptivescheduling?a)MacOS8 b)Windows3.xc)Windows2000 d)DOS6.0Ameasureofthenumberofprocessescompletedpertimeunitiscalleda)throughput b)waitingtimec)responsetime d)CPUutilizationOneoftheproblemswithpriorityschedulingisa)aging b)starvationc)processdeath d)averagewaitingtimeInatime-sharingsystem,whichofthefollowingisthebestcriterionforCPUscheduling.a)MinimizeCPUutilization b)MaximizeCPUutilizationc)Maximizesystemthroughput d)Minimizeresponsetime.TheinitialvalueofsemaphoreSis2.ifthevalueis-1atpresent,howmanyprocessesareblockedonthissemaphore.a)1b)2c)3d)4Asystemisinadeadlock,ifitsresourceallocationgrapha)containsacycle b)doesn’tcontainacyclec)containsacycleandthereisjustoneinstanceofeveryresourced)hasatleastoneoutgoingedgefromanyoneoftheprocessnodesPreemptionofresourcescanbeenforcedtopreventoccurrenceofdeadlocks,butthiscan’tbeappliedtoalltheresourcetypes,aspreemptionmightleavetheresourceinanundeterminedstate.Whichofthefollowingresourcescan’thencebepreempted?a)CPUregisters b)memoryspacec)tapedrive d)alloftheaboveAsystemissaidtobe___________ifitcancontinuetofunctionevenwhenanodeornodesinthesystemfail.a)networked b)distributedc)realtime d)fault-tolerantWhichofthefollowingactivityneedsnospecialhardwaresupport?a)Processscheduling b)timermanagementc)memorymapping d)interruptsystemWhichofthefollowingstatementaboutprocessesisincorrect?a)Aprocessisdynamic.b)Aprocesshasalifetime.c)Aprocessisasetofinstructions.d)Multipleprocessesmayexecuteconcurrently.三、Considerthefollowingsetofprocesses:ProcessBurst-TimePriorityP1 15 4P2 3 8P3 7 5P4 5 2P5 1 6P6 2 6TheprocessesareassumedtohavearrivedintheorderP1,P2,P3,P4,P5,P6,allattime0.UseFCFS,SJF,RoundRobin(quantumis2),Priority(lownumbershavehighpriority).Foreachofthealgorithms:1DrawaGanttchart2.Whatistheaveragewaitingtimeforeachoftheschedulingalgorithms？3.Whatistheaverageturnaroundtimeforeachoftheschedulingalgorithms？Answer:FCFS: P1P2P3P4P5P6151825303133AWT=(0+15+18+25+30+31)/6=19.83ATT=(15+18+25+30+31+33)/6=25.33SJF:P5P6P2P4P3P1AWT=(18+3+11+6+0+1)/6=6.5ATT=(33+6+18+11+1+3)/6=12Round-Robin(quantum=2):P1P2P3P4P5P6P1P2P3P4P1P3P4P1P3P1AWT=(18+11+19+8+9)/6=13.83ATT=(33+14+26+23+9+11)/6=19.33Priority:P4P1P3P5P6P2AWT=(5+30+20+0+27+28)/6=18.33ATT=(20+33+27+5+28+30)/6=23.83Twoconcurrentprocesseshaveinput,computingandprintingactions,respectively.ThatissaidI1,C1,P1forthe1stprocess,andI2,C2,P2forthe2ndprocess.Theirprecedentialrelationshipisshowninthefigure,i.e.I2musthappenafterI1,C2musthappenafterC1andI2,etc.Pleasedescribethesynchronizationrelationshipoftwoprocessesbymeansofsemaphoresandrelatedwait/signaloperations.I1I1I2C1C2P1P2Semaphore:s1,s2,s3:=0;P1: P2: { { I1； wait(s1)； signal(s1)； I2 C1； wait(s2)；signal(s2)； C2 ；P1； wait(s3)；signal(s3)； P2；} }五、TherearethreecooperativeprocessesP1,P2,andP3.Theyreaddata,denotedasa、bandc,fromthesameinputdevice，asshowninfigurebelow.Theinputdeviceisanexclusiveaccessdevice.Thefirstdatum(a)mustbereadbyprocessP1,theseconddatum(b)isreadbyprocessP2,andthethirddatum(c)