-操作系统精髓与设计原理(第五版)+课后题答案1

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1、Chapter2OperatingSystemOverviewReviewQuestions2.1Convenience:Anoperatingsystemmakesacomputermoreconvenienttouse.Efficiency:Anoperatingsystemallowsthecomputersystemresourcestobeusedinanefficientmanner.Abilitytoevolve:Anoperatingsystemshouldbeconstructedinsuchawayastopermitt

2、heeffectivedevelopment,testing,andintroductionofnewsystemfunctionswithoutinterferingwithservice.2.5Theexecutioncontext,orprocessstate,istheinternaldatabywhichtheoperatingsystemisabletosuperviseandcontroltheprocess.Thisinternalinformationisseparatedfromtheprocess,becausethe

3、operatingsystemhasinformationnotpermittedtotheprocess.Thecontextincludesalloftheinformationthattheoperatingsystemneedstomanagetheprocessandthattheprocessorneedstoexecutetheprocessproperly.Thecontextincludesthecontentsofthevariousprocessorregisters,suchastheprogramcounteran

4、ddataregisters.Italsoincludesinformationofusetotheoperatingsystem,suchasthepriorityoftheprocessandwhethertheprocessiswaitingforthecompletionofaparticularI/Oevent.Problems2.1Theanswersarethesamefor(a)and(b).Assumethatalthoughprocessoroperationscannotoverlap,I/Ooperationscan

5、.1Job:TAT=NTProcessorutilization=50%2Jobs:TAT=NTProcessorutilization=100%4Jobs:TAT=(2N–1)NTProcessorutilization=100%2.4Asystemcallisusedbyanapplicationprogramtoinvokeafunctionprovidedbytheoperatingsystem.Typically,thesystemcallresultsintransfertoasystemprogramthatrunsinker

6、nelmode.Chapter3ProcessDescriptionandControlReviewQuestions3.5Swappinginvolvesmovingpartorallofaprocessfrommainmemorytodisk.WhennoneoftheprocessesinmainmemoryisintheReadystate,theoperatingsystemswapsoneoftheblockedprocessesoutontodiskintoasuspendqueue,sothatanotherprocessm

7、aybebroughtintomainmemorytoexecute.3.10Theusermodehasrestrictionsontheinstructionsthatcanbeexecutedandthememoryareasthatcanbeaccessed.Thisistoprotecttheoperatingsystemfromdamageoralteration.Inkernelmode,theoperatingsystemdoesnothavetheserestrictions,sothatitcanperformitsta

8、sks.Problems3.1•Creationanddeletionofbothuserandsystemprocesses.Theprocessesinthesystemca