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1、ChapterTwoDATAMANIPULATIONChapterSummaryThischapterintroducestheroleofacomputer'sCPU.Itdescribesthemachinecycleandthevariousoperations(or,and,exclusiveor,add,shift,etc.)performedbyatypicalarithmetic/logicunit.Theconceptofamachinelanguageispresentedintermsofthesimpleyetrep
2、resentativemachinedescribedinAppendixCofthetext.ThechapteralsointroducessomealternativestothevonNeumannarchitecturesuchasmultiprocessormachinesandartificialneuralnetworks.Theoptionalsectionsinthischapterpresentamorethoroughdiscussionoftheinstructionsfoundinatypicalmachine
3、language(logicalandnumericaloperations,shifts,jumps,andI/Ocommunication),ashortexplanationofhowacomputercommunicateswithperipheraldevices,andalternativemachinedesigns.ThemachinelanguageinAppendixCinvolvesonlydirectandimmediateaddressing.However,indirectaddressingisintrodu
4、cedinthelastsection(PointersinMachineLanguage)ofChapter7afterthepointerconcepthasbeenpresentedinthecontextofdatastructures.Comments1.MuchofComment1regardingthepreviouschapterispertinentherealso.Thedevelopmentofskillsinthesubjectsofmachinearchitectureandmachinelanguageprog
5、rammingisnotrequiredlaterinthebook.Instead,whatoneneedsisanimageoftheCPU/mainmemoryinterface,anunderstandingofthemachinecycleandmachinelanguages,anappreciationofthedifferenceinspeedsofmechanicalmotioncomparedtoCPUactivities,andanexposuretothelimitedrepertoireofbitmanipula
6、tionsaCPUcanperform.2.Tomoststudentsatthisstagethetermsmillisecond,microsecond,nanosecond,andpicosecondmerelyrefertoextremelyshortandindistinguishableunitsoftime.Infact,mostwouldprobablyaccepttheincorrectstatementthatactivitieswithinacomputerareessentiallyinstantaneous.On
7、ceastudentofminewrotearecursiveroutineforevaluatingthedeterminantofamatrixinaninterpretedlanguageonatime-sharingsystem.Thestudenttriedtotesttheprogramusingan8by8matrix,butkeptterminatingtheprogramafteraminutebecause"itmustbeinaloop."Thisstudentleftwithanunderstandingofmic
8、rosecondsasrealunitsoftimethatcanaccumulateintosignificantperiods.3.Asubtlepointthatcanaddsignif
