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1、SOLUTIONSTOCHAPTER1PROBLEMS1.Anoperatingsystemmustprovidetheuserswithanextended(i.e.,virtual)machine,anditmustmanagetheI/Odevicesandothersystemresources.2.MultiprogrammingistherapidswitchingoftheCPUbetweenmultipleprocessesinmemory.ItiscommonlyusedtokeeptheCPUbusywhileoneormoreprocessesaredoingI/
2、O.3.Inputspoolingisthetechniqueofreadinginjobs,forexample,fromcards,ontothedisk,sothatwhenthecurrentlyexecutingprocessesarefinished,therewillbeworkwaitingfortheCPU.Outputspoolingconsistsoffirstcopyingprintablefilestodiskbeforeprintingthem,ratherthanprintingdirectlyastheoutputisgenerated.Inputspooli
3、ngonapersonalcomputerisnotverylikely,butoutputspoolingis.4.TheprimereasonformultiprogrammingistogivetheCPUsomethingtodowhilewaitingforI/Otocomplete.IfthereisnoDMA,theCPUisfullyoccupieddoingI/O,sothereisnothingtobegained(atleastintermsofCPUutilization)bymultiprogramming.NomatterhowmuchI/Oaprogram
4、does,theCPUwillbe100percentbusy.Thisofcourseassumesthemajordelayisthewaitwhiledataarecopied.ACPUcoulddootherworkiftheI/Owereslowforotherreasons(arrivingonaserialline,forinstance).5.Secondgenerationcomputersdidnothavethenecessaryhardwaretoprotecttheoperatingsystemfrommalicioususerprograms.6.Itiss
5、tillalive.Forexample,IntelmakesPentiumI,II,andIII,and4CPUswithavarietyofdifferentpropertiesincludingspeedandpowerconsumption.Allofthesemachinesarearchitecturallycompatible.Theydifferonlyinpriceandperformance,whichistheessenceofthefamilyidea.7.A25×80charactermonochrometextscreenrequiresa2000-byte
6、buffer.The1024×768pixel24-bitcolorbitmaprequires2,359,296bytes.In1980thesetwooptionswouldhavecost$10and$11,520,respectively.Forcurrentprices,checkonhowmuchRAMcurrentlycosts,probablylessthan$1/MB.8.Choices(a),(c),and(d)shouldberestrictedtokernelmode.9.Personalcomputersystemsarealwaysinteractive,o
7、ftenwithonlyasingleuser.Mainframesystemsnearlyalwaysemphasizebatchortimesharingwithmanyusers.Protectionismuchmoreofanissueonmainframesystems,asisefficientuseofallresources.10.Everynanosecondoneinstructionemergesfromthepipelin
