资源描述：
《习题操作系统课件》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、Lla.Stealingorcopyingone'sprogramsordata;usingsystemresources(CPU,memory,diskspace,peripherals)withoutproperaccounting.b.Probablynot,sinceanyprotectionschemedevisedbyhumanscaninevitablybebrokenbyahuman,andthemorecomplexthescheme,themoredifficultitist
2、ofeelconfidentofitscorrectimplementation.1.3Whcntherearcfewotherusers,thetaskislarge,andthehardwareisfast,timc-sharingmakcssense.Thefullpowerofthesystemcanbebroughttobearontheusefsproblem・Theproblemcanbesolvedfasterthanonapersonalcomputer.Anothercase
3、occurswhenlotsofotherusersneedresourcesatthesametime.Apersonalcomputerisbestwhenthejobissmallenoughtobeexecutedreasonablyonitandwhenperformanceissufficienttoexecutetheprogramtotheusefssatisfaction.L5Symmetricmultiprocessingtreatsallprocessorsasequals
4、,andI/OcanbeprocessedonanyCPU・AsymmetricmultiprocessinghasonemasterCPUandtheremainderCPUsareslaves・Themasterdistributestasksamongtheslaves,andI/Oisusuallydonebythemasteronly.Multiprocessorscansavemoneybynotduplicatingpowersupplies,housings,andperiphe
5、rals.Theycanexecuteprogramsmorequicklyandcanhaveincreasedreliability.Theyarealsomorecomplexinbothhardwareandsoftwarethanuniprocessorsystems.1.12Anoperatingsystemforamachineofthistypewouldneedtoremainincontrol(ormonitormode)atalltimes・Thiscouldbeaccom
6、plishedbytwomethods:a.Softwareinterpretationofalluserprograms(likesomeBASIC,Java,andLISPsystems,forexample).Thesoftwareinterpreterwouldprovide,insoftware,whatthehardwaredoesnotprovide.b.Requiremeantthatallprogramsbewritteninhigh-levellanguagessothata
7、llobjectcodeiscompiler-produced.Thecompilerwouldgenerate(eitherin-lineorbyfunctioncalls)theprotectionchecksthatthehardwareismissing・1.17a.Batch.Jobswithsimilarneedsarebatchedtogetherandrunthroughthecomputerasagroupbyanoperatororautomaticjobsequencer.
8、PerformanceisincreasedbyattemptingtokeepCPUandI/Odevicesbusyatalltimesthroughbuffering,off-lineoperation,spooling,andmultiprogramming・Batchisgoodforexecutinglargejobsthatneedlittleinteraction;itcanbesubmittedandpickeduplater.b.Interactive.Thissystemi
