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ID:41079883
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页数:20页
时间:2019-08-15
《-操作系统精髓与设计原理(第五版)+课后题答案1》由会员上传分享,免费在线阅读,更多相关内容在工程资料-天天文库。
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
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