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1、Unit1ComputerandComputerScienceSectionA:ComputerOverviewIntroductionAcomputerisanelectronicdevicethatcanreceiveasetofinstructions,orprogram,andthencarryoutthisprogrambyperformingcalculationsonnumericaldataorbymanipulatingotherformsofinformation.Themodernworldofhightechnolog
2、ycouldnothavecomeaboutexceptforthedevelopmentofthecomputer.Differenttypesandsizesofcomputersfindusesthroughoutsocietyinthestorageandhandlingofdata,fromsecretgovernmentalfilestobankingtransactionstoprivatehouseholdaccounts.Computershaveopenedupanewerainmanufacturingthroughth
3、etechniquesofautomation,andtheyhaveenhancedmoderncommunicationsystems.Theyareessentialtoolsinalmosteveryfieldofresearchandappliedtechnology,fromconstructingmodelsoftheuniversetoproducingtomorrow’sweatherreports,andtheirusehasinitselfopenedupnewareasofconjecture.Databaseserv
4、icesandcomputernetworksmakeavailableagreatvarietyofinformationsources.Thesameadvancedtechniquesalsomakepossibleinvasionsofpersonalandbusinessprivacy.Computercrimehasbecomeoneofthemanyrisksthatarepartofthepriceofmoderntechnology.HistoryThefirstaddingmachine,aprecursorofthedi
5、gitalcomputer,wasdevisedinthe1642bytheFrenchscientist,mathematician,andphilosopherBlaisePascal.Thisdeviceemployedaseriesoften-toothedwheels,eachtoothrepresentingadigitfrom0to9.Thewheelswereconnectedsothatnumberscouldbeaddedtoeachotherbyadvancingthewheelsbyacorrectnumberofte
6、eth.Inthe1670stheGermanphilosopherandmathematicianGottfriedWilhelmLeibnizimprovedonthismachinebydevisingonthatcouldalsomultiply.TheFrenchinventorJoseph-MarieJacquard,indesigninganautomaticloom,usedthin,perforatedwoodenboardstocontroltheweavingofcomplicateddesigns.Duringthe1
7、880stheAmericanstatisticianHermanHollerithconceivedtheideaofusingperforatedcard,similartoJacquard’sboards,forprocessingdata.Employingasystemthatpassedpunchedcards,overelectricalcontacts,hewasabletocompilestatisticalinformationforthe1890UnitedStatescensus.TheAnalyticalEngine
8、Alsointhe19thcentury,theBritishmathematicianandinventorCharlesBabbageworkedoutthep
