个人计算机中英文翻译.docx
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个人计算机中英文翻译.docx
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个人计算机中英文翻译
个人计算机中英文翻译
姓名:
岳群杰班级:
信安2006级3班学号:
05
Personalcomputer
Whatispersonalcomputer
Therehavebeenmanykindsofcomputersystemsaccordingtotheirsize,suchassu-percomputers,mainframecomputers,minicomputersandpersonalmputersarespecial,highcapacitycomputersusedbyverylargeorganizationprincipallyforresearchpurposes,amongwhichareoilexplorationandworldwideweatherfo-recasting.Mainframecomputers(ormainframes)arelarge,powerfulcomputersthatmanypeoplecanuseatthesametime.Theyarealsoexpensivesystemsthatareusedforverylargeprocessingtasksandperformmanyimportantbusinessandgovernmentapplicatoions.Minicomputersaresmallerandmorecompactsystems,andfeweropra-torscanusethemcomparedwithamainframecomputer.Theyareusuallyfoundinmedium-sizebusinessesorindivisionswithinalargeorganization,forexampleingov-vernmentdepartment.
Personalcomputers-alsocalledmicrocomputers-aresmall,self-containedcomputersthatfitonadesktopandusuallyonlyusedbyonearetheleastexepensivetype,andarewidelyusedinbusinessforabusinessforavarietyoftasks,suchasword–processing,smalldatabasemanagement,andarealsousedashomecomputers,forfamilybudgetingandsimilarjobs,aswellasforgames.
Protablecompuers
Anotherimportantdevelopmentinpersonalcomputertechnologyisthattheportablecomputershavebeenwidelyused.Asmall,portablepersonalcomputerislightandsmallenoughtoholdonyourlap.Thecomputerissmallerthanaluggagebutlargerthananotebook,andisalsocalledalaptopornotebookcomputer.Aportablecomputerusuallyweighsbetweenthreetoeightpounds,andwhenfoldedshutisaboutthesizeofasmallbriefcase.Soitofferstheuserconsiderablefreedom.Theusercanworkhiscomputerontrain,oronanairplane,oronsafariinAfrica.
Portablecomputerscanbepluggedinorrunonbatteries,althoughthebatteriesmustberechargedveryfewhours.Batterypowerisacriticalbottleneck,computersuseathin,manceandblockingfurtherproductcomputeruseathin,
lightweightdisplayscreencalledaflat-paneldisplayoraLCDmonitor,ratherthanthecathoderaytubetechnologyoflargepersonalcomputers.Portablecomputerdisplaysvarywidelyinquality.Typically,theirdisplayscreensshowfewerlinesthandisplaysonlargerpersonalcomputersandcanbedifficulttoreadinbrightlight.Portablecomputersareself-containedunits,havingtheirownCPUs,memory,andmanyhavemodemsandCD-ROMdrivesaswell.
Whilemoreexpensivethanadesktopcomputerwithequivalentcomputingpower,aportablecomputervanbeidealforthego-userwhoneedsasecondpersonalcomputerwhenheisoutofdesktopcomputers,sincetheycannotbeexpandedormodifiedeasilyshouldyourcomputingneedschange.Also,thedisplayisinferiortostandardvideographicsarray(VGA)displays,althoughactivematrixdisplaysalmostcompetewellexceptforsize.
Thefirstportablecomputers,suchastheOsborneⅠandCompaqⅡ,arebestdescribedas“luggeables”.Thesecomputersweighedinatmorethan25poundsandcouldnotcarriedcomfortablyformorethanashortdistance.Today?
sportablecomputers,thelaptopandnotebookcomputersaremuchsmallerandlighter.
SystemsUsingMiscroprocessors
Electronicsystemsareusedforhandlinginformationinthemostgeneralsense;thisinformationmaybetelephoneconversation,instrumentreadingoracompany?
saccounts,butineachcasethesamemaintypesofoperationareinvolved;theprocessing,storageandtransmissionofinformation.Inconventionalelectronicdesigntheseoperationsarecombinedatthefunctionlevel;forexampleacounter,whetherelectronicormechanical,storesthecurrentcountandincrementsitbyoneasrequired.Asystemsuchasanelectronicclockwhichemployscountershasitsstorageandprocessingcapabilitiesspreadthroughoutthesystembecauseeachcounterisabletostoreandprocessnumbers.
Presentdaymicroprocessorbasedsystemsdepartfromthisconventionalapproachbyseparatingthethreefunctionsofprocessing,storage,andtransmissionintodifferentsectionsofthesystem.ThispartitioningintothreemainfunctionswasdevisedbyVonNeumannduringthe1940s,andwasnotconceivedespeciallyformicrocomputers.Almosteverycomputerevermadehasbeendesignedwiththisstructure,anddespitetheenormousrangeintheirphysicalforms,theyhaveallbeenofessentiallythesamebasicdesign.
Inamicroprocessorbasedsystemtheprocessingwillbeperformedinthemicroprocessoritself.Thestoragewillbebymeansofmemorycircuitsandthecommunicationofinformationintoandoutofthesystemwillbebymeansofspecial
input/output(I/O)circuits.Itwouldbeimpossibletoidentifyaparticularpieceofhardwarewhichperformedthecountinginamicroprocessorbasedclockbecausethetimewouldbestoredinthememoryandincrementedatregularintervalsbythemicroprocessor.However,thesoftwarewhichdefinedthesystem?
sbehaviorwouldcontainsectionsthatperformedascounters.Theapparentlyratherabstractapproachtothearchitectureofthemicroprocessoranditsassociatedcircuitsallowsittobeveryflexibleinuse,sincethesystemisdefinedalmostentirelyinsoftware.Thedesignprocessislargelyoneofsoftwareengineering,andthesimilarproblemsofconstructionandmaintenancewhichoccurinconventionalengineeringareencounteredwhenproducingsoftware.
Figureillustrateshowthesethreesectionswithinamicrocomputerareconnectedintermsofthecommunicationofinformationwithinthetransferofinformationbetweenitselfandthememoryandinput/ouputexternalconnectionsrelatetotherest(thatisthenon-computerpart)oftheengineeringsystem.
Althoughonlyonestoragesectionhasbeenshowninthediagram,inpracticetwodistincttypesofmemoryRAMandROMareused.Ineachcase,theword”memory”isratherinappropriatesinceacomputermemoryismorelikeafilingcabinetinconcept;informationisstoredinasetofnumbered“boxes”anditisreferencedbytheserialnumberofthe“box”inquestion.
MicrocomputersuseRAM(RandomAccessMemory)intowhichdatacanbewrittenandfromwhichdatacanbereadagainwhenneeded.Thisdatecanbereadbackfromthememoryinanysequencedesired,andnotnecessarilythesameorderinwhichitwaswritten,hencethewaprwssion“random”accessmemory.AnothertypeofROM(ReadOnlyMemory)isusedtoholdfixedpatternsofinformationwhichcannotbeaffectedbythemicroprocessor;thesepatternsarenotlostwhenpowerisremovedandarenormallyusedtoholdtheprogramwhichdefinesthebehaviorofamicroprocessorbasedsystem.ROMscanbereadlikeRAMs,butunlikeRAMstheycannotbeusedtostorevariableinformation.SomeROMshavetheirdatapatternsputinduringmanufacture,whileothersareprogrammablebytheuserbymeansofspecialequipmentandarecalledprogrammableROMs.ThewidelyusedprogrammableROMsareerasablebymeansofspecialultravioletlampsandarereferredtoasEPROMs,shortforErasableProgrammableReadOnlyMemories.Othernewtypesofdevicecanbeerasedelectricallywithouttheneedforultravioletlight,whicharecalledElectricallyErasableProgrammableReadOnlyMemories,EEPROMs.
Themicroprocessorprocessesdataunderthecontroloftheporogram,controllingtheflowofinformationtoandfrommemoryandinput/outputdevices.Someinput/outputdevices
aregeneral-purposetypeswhileothersaredesignedforcontrollingspecialhardwaresuchasdiscdrivesorcontrollinginformationtransmissiontoothercomputers.MosttypesofI/Odevicesareprogrammabletosomeextent,allowingdifferentmodesofoperation,whilesomeactuallycontainspecial-purposemicroprocessorstopermitquitecomplexoperationstobecarriedoutwithoutdirectlyinvolvingthemainmicroprocessor.
Themicroprocessor,memoryandinput/outputcircuitmayallbecontainedonthesameintegratedcircuitprovidedthattheapplicationdoesnotrequiretoomuchprogramordatastorage.Thisisusuallythecaseinlow-costapplicationsuchasthecontrollersusedinmicrowaveovensandautomaticwashingmachines.Theuseofsinglepackageallowsconsiderablecostsavingstobemadewhenarticlesaremanufacturedinlargequantities.Astechnologydevelops,moreandmorepowerfulprocessorsandlargerandlargeramountsofmemoryarebeingincorporatedintosinglechipmicrocomputerswithresultingsavinginassemblycostsinthefinalproducts.Fortheforeseeablefuture,however,tiwillcontinuetobenecessarytointerconnectanumberofintegratedcircuitstomakeamicrocomputerwheneverlargeramountsofstorageorinput/outputarerequired.
Anothermajorengineeringapplicationofmicrocomputersisinprocesscontrol.Herethepresenceofthemicrocomputerisusuallymoreapparenttotheuserbecauseprovisionisnormallymadeforprogrammingthemicrocomputerfortheparticularapplication.Inprocesscontrolthebenefitsoffittingtheentiresystemontoasinglechipareusuallyoutweighedbythehighdesigncostinvolved,becausethissortofequipmentisproducedinsmallerquantities.Moreover,processcontrollersareusuallymorecomplicatedsothatitismoredifficulttomakethemassingleintegratedcircuits.Intheformercasethesystemwouldbeprogrammedinconventionalprogramminglanguagesuchastheonestobeintroducedlater,whileintheothercaseaspecial-purposelanguagemightbeused,forexampleonewhichallowedthefunctionofthecontrollertobedescribedintermsofrelayinterconnections.IneithercaseprogramscanbestoredinRAM,whichallowstobealteredtosuitchangesinapplication,but
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