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MODERNOPERATINGSYSTEMSSECONDEDITIONPROBLEMSOLUTIONSANDREWS.TANENBAUMVrijeUniversiteitAmsterdam,TheNetherlandsPRENTICEHALLUPPERSADDLERIVER,NJ07458SOLUTIONSTOCHAPTER1PROBLEMS1.Anoperatingsystemmustprovidetheuserswithanextended(i.e.,virtual)machine,anditmustmanagetheI/Odevicesandothersystemresources.2.MultiprogrammingistherapidswitchingoftheCPUbetweenmultipleprocessesinmemory.ItiscommonlyusedtokeeptheCPUbusywhileoneormoreprocessesaredoingI/O.3.Inputspoolingisthetechniqueofreadinginjobs,forexample,fromcards,ontothedisk,sothatwhenthecurrentlyexecutingprocessesarefinished,therewillbeworkwaitingfortheCPU.Outputspoolingconsistsoffirstcopyingprintablefilestodiskbeforeprintingthem,ratherthanprintingdirectlyastheoutputisgenerated.Inputspoolingonapersonalcomputerisnotverylikely,butoutputspoolingis.4.TheprimereasonformultiprogrammingistogivetheCPUsomethingtodowhilewaitingforI/Otocomplete.IfthereisnoDMA,theCPUisfullyoccupieddoingI/O,sothereisnothingtobegained(atleastintermsofCPUutilization)bymultiprogramming.NomatterhowmuchI/Oaprogramdoes,theCPUwillbe100percentbusy.Thisofcourseassumesthemajordelayisthewaitwhiledataarecopied.ACPUcoulddootherworkiftheI/Owereslowforotherreasons(arrivingonaserialline,forinstance).5.Secondgenerationcomputersdidnothavethenecessaryhardwaretoprotecttheoperatingsystemfrommalicioususerprograms.6.Itisstillalive.Forexample,IntelmakesPentiumI,II,andIII,and4CPUswithavarietyofdifferentpropertiesincludingspeedandpowerconsumption.Allofthesemachinesarearchitecturallycompatible.Theydifferonlyinpriceandperformance,whichistheessenceofthefamilyidea.7.A25×80charactermonochrometextscreenrequiresa2000-bytebuffer.The1024×768pixel24-bitcolorbitmaprequires2,359,296bytes.In1980thesetwooptionswouldhavecost$10and$11,520,respectively.Forcurrentprices,checkonhowmuchRAMcurrentlycosts,probablylessthan$1/MB.8.Choices(a),(c),and(d)shouldberestrictedtokernelmode.9.Personalcomputersystemsarealwaysinteractive,oftenwithonlyasingleuser.Mainframe
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