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1、1IntroductionFoundationsofComputerScienceãCengageLearning1DefinetheTuringmodelofacomputer.DefinethevonNeumannmodelofacomputer.Describethethreecomponentsofacomputer:hardware, data,andsoftware.Listtopicsrelatedtocomputerhardware.Listtopicsrelatedtodata.Listtop
2、icsrelatedtosoftware.Discusssomesocialandethicalissuesrelatedtotheuseof computers.Giveashorthistoryofcomputers.ObjectivesAfterstudyingthischapter,thestudentshouldbeableto:21-1TURINGMODELTheideaofauniversalcomputationaldevicewasfirstdescribedbyAlanTuringin193
3、7.Heproposedthatallcomputationcouldbeperformedbyaspecialkindofamachine,nowcalledaTuringmachine.Hebasedthemodelontheactionsthatpeopleperformwheninvolvedincomputation.Heabstractedtheseactionsintoamodelforacomputationalmachinethathasreallychangedtheworld.3Datap
4、rocessorsBeforediscussingtheTuringmodel,letusdefineacomputerasadataprocessor.Usingthisdefinition,acomputeractsasablackboxthatacceptsinputdata,processesthedata,andcreatesoutputdata(Figure1.1).Althoughthismodelcandefinethefunctionalityofacomputertoday,itistoog
5、eneral.Inthismodel,apocketcalculatorisalsoacomputer(whichitis,inaliteralsense).Figure1.1Asinglepurposecomputingmachine4ProgrammabledataprocessorsTheTuringmodelisabettermodelforageneral-purposecomputer.Thismodeladdsanextraelementtothespecificcomputingmachine:
6、theprogram.Aprogramisasetofinstructionsthattellsthecomputerwhattodowithdata.Figure1.2showstheTuringmodel.Figure1.2AcomputerbasedontheTuringmodel5Figure1.3Thesameprogram,differentdata6Figure1.4Thesamedata,differentprograms7TheuniversalTuringmachineAuniversalT
7、uringmachine,amachinethatcandoanycomputationiftheappropriateprogramisprovided,wasthefirstdescriptionofamoderncomputer.ItcanbeprovedthataverypowerfulcomputerandauniversalTuringmachinecancomputethesamething.Weneedonlyprovidethedataandtheprogram—thedescriptiono
8、fhowtodothecomputation—toeithermachine.Infact,auniversalTuringmachineiscapableofcomputinganythingthatiscomputable.81-2VONNEUMANNMODELComputersbuiltontheTuringuniversalmachinestoredataintheirmemo
