计算机专业英语论文硬件概述.docx

计算机专业英语论文硬件概述.docx

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计算机专业英语论文硬件概述

题目：

计算机硬件概述（Overviewofthecomputerhardwarebased）

学院：

信息技术学院

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XXXXXX

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　　Acomputerisafastandaccuratesymbolprocessingsystem.Itcanaccept,store,processdataandproduceoutputresults.Acomputercanautomaticallyprocessdatawithouthumanintervention.However,itmustbegivenasetofinstructiontoguideit,stepbystep,throughprocesses.Thesetofinstructionsiscalledaprogram,Theprogramisstoredphysicallyinsidethemachine,makingitaprogram.

Allcomputersystemsofinteresttousaresimilar.Theycontainhardwarecomponentsforinput,centralprocessingunitandoutput.Thesystemonthesmall-scaleiscalledamicrocomputerorminicomputer.Continuingupthesizescale,themainframecomputerisonethatmayofferafasterprocessingspeedandagreaterstoragecapacitythanatypicalmini.Finallycomesthesupercomputer,designedtoprocesscomplexscientificapplications，whichisthelargestandfastest.

Althoughthecapacityofcomputers'storagelocationsisvaried，everycomputerstoresnumbers，letters，andothercharactersinacodedform.Everycharacterinthestorageisrepresentedbyastringof0sand1s，theonlydigitsfoundedinthebinarynumberingsystem.BCDandASCIIarepopularcomputercodes.

So,whatpartofcomputerhardwarethatcontainsit?

Computerhardwarehasfourparts:

thecentralprocessingunit（CPU）andmemory,storagehardware,inputhardware,andoutputhardware.

TheCentralProcessingUnit

Pronouncedasseparatelettersitistheabbreviationforcentralprocessingunit.TheCPUisthebrainsofthecomputer.Sometimesreferredtosimplyasthecentralprocessor,butmorecommonlycalledprocessor,theCPUiswheremostcalculationstakeplace.Intermsofcomputingpower,theCPUisthemostimportantelementofacomputersystem.

Onlargemachines,CPUsrequireoneormoreprintedcircuitboards.Onpersonalcomputersandsmallworkstations,theCPUishousedinasinglechipcalledamicroprocessor.Sincethe1970'sthemicroprocessorclassofCPUshasalmostcompletelyovertakenallotherCPUimplementations.

EarlyCPUswerecustom-designedasapartofalarger,sometimesone-of-a-kind,computer.However,thiscostlymethodofdesigningcustomCPUsforaparticularapplicationhaslargelygivenwaytothedevelopmentofmass-producedprocessorsthataremadeforoneormanypurposes.Thisstandardizationtrendgenerallybeganintheeraofdiscretetransistormainframesandminicomputersandhasrapidlyacceleratedwiththepopularizationoftheintegratedcircuit（IC）.TheIChasallowedincreasinglycomplexCPUstobedesignedandmanufacturedtotolerancesontheorderofnanometers.BoththeminiaturizationandstandardizationofCPUshaveincreasedthepresenceofthesedigitaldevicesinmodernlifefarbeyondthelimitedapplicationofdedicatedcomputingmachines.Modernmicroprocessorsappearineverythingfromautomobilestocellphonesandchildren'stoys.

TheCPUitselfisaninternalcomponentofthecomputer.ModernCPUsaresmallandsquareandcontainmultiplemetallicconnectorsorpinsontheunderside.TheCPUisinserteddirectlyintoaCPUsocket,pinsidedown,onthemotherboard.EachmotherboardwillsupportonlyaspecifictypeorrangeofCPUsoyoumustcheckthemotherboardmanufacturer'sspecificationsbeforeattemptingtoreplaceorupgradeaCPU.ModernCPUsalsohaveanattachedheatsinkandsmallfanthatgodirectlyontopoftheCPUtohelpdissipateheat.

TwotypicalcomponentsofaCPUarethefollowing:

Thearithmeticlogicunit（ALU）,whichperformsarithmeticandlogicaloperations.

Thecontrolunit（CU）,whichextractsinstructionsfrommemoryanddecodesandexecutesthem,callingontheALUwhennecessary.

Toproperlyperformitsjob,theCPUmustcompleteacycleoffoursteps.Thefirststepinthiscycleistofetchainstructionfromasoftwareprogram'smemory.OncetheCPUfetchestheinstruction,itssecondstepistodecodetheinstruction.Bydecodingtheinstruction,theCPUisabletoorganizetheinformationfromtheinstructioninamannerthatallowstheCPUtocompletethenextstep,whichisexecuting.

Duringtheexecutionstep,theCPUcompletestheinstruction.Itaccomplishesthisbyfollowingtheinformationgainedduringthedecodingstep.OncetheCPUhasfinishedexecutingtheinstruction,thefinalstepinthiscycleistowrite-backtheresultsthatoccurredduringtheexecutionstep.TheCPUcanwrite-backtheresultstoitsowninternalregister,ortothemainmemoryofthecomputer.

TheControlUnit:

Acontrolunitisoneofthetwocomponentsofthecentralprocessingunit.Thefunctionofthecontrolunitistoextractinformationwhichisstoredinthememoryandtodecodeandexecutethoseinstructions.

Italsotakeshelpfromthearithmeticlogicunit,wheneverrequired.Thecontrolunitisveryimportantforcomputersfunctioning.Thecontrolunithasoutputswhichtakechargeoftheactivitiesoftheentiredevice.SomeregardthecontrolunittobeanFSMorfinitestatemachinewhichisusedforhardwareandsoftwareapplications.

ControlUnitandMicroprogram:

Therewasatimewhenthemanufacturingofcontrolunitswasadifficultprocess,especiallyindesigningit.Buttodaythescenariohaschanged.Acontrolunitisexecutedintheformofmicroprogramswhichremainincontrolstores.Thereisamicrosequencerwhichchoosesthewordsandcertainportionsofthosewordswhichdirectlymanagethevariouscomputerparts.Thesepartsarearithmeticandlogicunits,buses,instructionregisters,registersandinput/output.Todaythelatestcomputersmaypossesssubsidiarycontrollersforeverysubsystem,whichwouldbesupervisedbythemaincontrolunit.

FunctionsofControlUnit:

Acontrolunitcanbedescribedasasortofcircuitrythatsupervisesandcontrolsthepathofinformationthatrunsovertheprocessorandorganizesthevariousactivitiesofthoseunitsthatlieinsideit.

Itcarriesoutmanytaskssuchasdecoding,fetching,handlingtheexecutionandfinallystoringtheresults.

Itcontrolstheexecutionofinstructionsinasequentialorder.

Itguidestheflowofdatathroughthedifferentpartsofthecomputer.

Itinterpretstheinstructions.

Itregulatesthetimecontrolsoftheprocessor.

Itsendsandreceivescontrolsignalsfromvariousperipheraldevices.

Acontrolunitisamajorcomputerpartwhichhelpsinthefunctioningofthecentralprocessingunitandinturnrunsthewholecomputer.

　　TheArithmetic-LogicUnit:

Anarithmetic-logicunit（ALU）isthepartofacomputerprocessor（CPU）thatcarriesoutarithmeticandlogicoperationsontheoperandsincomputerinstructionwords.Insomeprocessors,theALUisdividedintotwounits,anarithmeticunit（AU）andalogicunit（LU）.SomeprocessorscontainmorethanoneAU-forexample,oneforfixed-pointoperationsandanotherforfloating-pointoperations.（Inpersonalcomputersfloatingpointoperationsaresometimesdonebyafloatingpointunitonaseparatechipcalledanumericcoprocessor.）

Typically,theALUhasdirectinputandoutputaccesstotheprocessorcontroller,mainmemory（randomaccessmemoryorRAMinapersonalcomputer）,andinput/outputdevices.Inputsandoutputsflowalonganelectronicpaththatiscalledabus.Theinputconsistsofaninstructionword（sometimescalledamachineinstructionword）thatcontainsanoperationcode（sometimescalledan"opcode"）,oneormoreoperands,andsometimesaformatcode.TheoperationcodetellstheALUwhatoperationtoperformandtheoperandsareusedintheoperation.（Forexample,twooperandsmightbeaddedtogetherorcomparedlogically.）Theformatmaybecombinedwiththeopcodeandtells,forexample,whetherthisisafixed-pointorafloating-pointinstruction.Theoutputconsistsofaresultthatisplacedinastorageregisterandsettingsthatindicatewhethertheoperationwasperformedsuccessfully.（Ifitisn't,somesortofstatuswillbestoredinapermanentplacethatissometimescalledthemachinestatusword.）

Ingeneral,theALUincludesstorageplacesforinputoperands,operandsthatarebeingadded,theaccumulatedresult（storedinanaccumulator）,andshiftedresults.TheflowofbitsandtheoperationsperformedontheminthesubunitsoftheALUiscontrolledbygatedcircuits.Thegatesinthesecircuitsarecontrolledbyasequencelogicunitthatusesaparticularalgorithmorsequenceforeachoperationcode.Inthearithmeticunit,multiplicationanddivisionaredonebyaseriesofaddingorsubtractingandshiftingoperations.Thereareseveralwaystorepresentnegativenumbers.Inthelogicunit,oneof16possiblelogicoperationscanbeperformed-suchascomparingtwooperandsandidentifyingwherebitsdon'tmatch.

ThedesignoftheALUisobviouslyacriticalpartoftheprocessorandnewapproachestospeedingupinstructionhandlingarecontinuallybeingdeveloped.

Memory

Incomputing,memoryreferstothestateinformationofacomputingsystem,asitiskeptactiveinsomephysicalstructure.Theterm"memory"isusedfortheinformationinphysicalsystemswhicharefast（ieRAM）,asadistinctionfromphysicalsystemswhichareslowtoaccess（iedatastorage）.Bydesign,theterm"memory"referstotemporarystatedevices,whereastheterm"storage"isreservedforpermanentdata.Advancesinstoragetechnologyhaveblurredthedistinctionabit—memorykeptonwhatisconventionallyastoragesystemiscalled"virtualmemory".

Colloquially,computermemoryreferstothephysicaldevicesusedtostoredataorprograms（sequencesofinstructions）onatemporaryorpermanentbasisforuseinanelectronicdigitalcomputer.Computersrepresentinformation