《计算机英语》计算机英语第二章.pptx

计算机英语Chapter2ComputerSystemOrganization11CPU目录2MemorySubsystemCONTENT3I/OSubsystem2almostallmoderncomputers,eachmemorycellisset本句为并列复合句，后边的分句省略与usersaddhigher-qualityReadingMaterialonlytheusercanhearthesoundfromthecomputer.OtherI/ODevicesBecausetheyrequirealotofarmdigitally,insteadlightsource,aintoanaudiocomputerandsoftwarethesoul.在计算机中布尔逻辑定义若干布尔逻辑函Comparedwithinst;instItisusuallydividedintothreeprimarysubsystems:theCPU,thememoryLeadinAcomputersystemconsistsofhardwaresystemandsoftwaresystem.withoutsoftware,hardwareinformation.Hence,hardwareisthebodyofthecomputerandsoftwarethesoul.1InandsoftwarewillbeillustratedinHardwareisthematerialfoundationofthecomputer,butcannotbeinstructedto processdataintothis chapter,wemainlyintroducethecomputerhardwarethefollowingchapter.Computerhardwareis theequipmentinvolvedinthefunctionofacomputerandconsistsofthecomponentsthatcanbephysicallyhandled.Itisusuallydividedintothreeprimarysubsystems:theCPU,thememorysubsysteminterconnectedbybuses,oftenmadeofgroupsofwires.andtheinput/output(I/O)subsystem.Thesethreepartsare31CPU41CPUThecomputerscentralprocessingunit(CPU)istheelectroniccircuitrythatprovidesthecomputationalabilityandcontrolofthecomputer.Internally,theCPUhasthreesections,asshownin2-1.Figure51CPU1ArithmeticandLogicUnitAsitsnameimplies,thearithmeticandlogicunit(ALU)performstwoclassesofoperations:arithmeticaddition,subtraction,multiplicationanddivision.AnycomputercanprogrammedinvolveBooleanlogic2:AND,OR,XORandNOT.ThesecanbeusefulbothforcreatingcomplicatedconditionalstatementsandprocessingBooleanlogic.Mostcomputerscanalsoperformandlogic.Arithmeticoperationsincludebetoperformanyarithmeticoperation.Logicoperationscertain logicoperationsonwords.Astheabovediagramshows,theALUreceivesitsoperandsfromtheregistersetoftheCPUandstoresitsresultsbackinperformswhateverarithmeticorlogicoperationsarerequiredtohelpouttheinstructions.theregisterset.Itcarry61CPU2ControlUnitThecontrolunit,oftencalledacontrolsystem,isafunctionalunitsupervisingtheoperationoftheentireconnectionsbetweenvariousfunctionalunitsofthecomputersysteminterpretsinstructionsincomputersystem.Itmakestheandtheprogramonebyone.Thecontrolunitfetchesinstructionsfrommemoryanddeterminestheirtypesordecodesthem.Itthenbreakseachinstructionintoaseriousofcontrolsignalssystemsinsooperationsthatthecontrolunitgoesthroughtointhatoperatetheotherpartsofthecomputer.Controladvancedcomputersmaychangetheorderofsomeinstructionsimproveastoperformance.Itsnoticeablethatthesequenceofprocessaninstructionisitselflikeashortcomputerprogram.371CPU3RegisterSetTheregistersetstoresintermediatedatausedduringtheexecutionoftheinstructions,whichincludesasetofregistersandabusorothercommunicationmechanism.AregisterisaquicklyaccessiblelocationavailabletoaCPU.Itcanbereadandwrittentohavingconsistentlygreatlyalargermemoryintoregisterswhereitisusedforarithmeticoperationsandismanipulatedortestedbyinstructions.Manipulateddataisbacktomainmuchmorerapidlythanthemainmemoryarea,whichavoidstoaccessmainmemoryeverytimedataisneeded.Sincedataisbeingworkedon,reducingtheneedtoaccessmainmemoryincreasesthecomputersspeed.4Almostallcomputersloaddatafromthenoftenstoredmemory.82MemorySubsystem92MemorySubsystemMemory,alsoknownasinternalmemoryormainmemory,referstothecomputerchipsthatstoreinformationforquickretrievalbytheCPU.Acomputersmemorycanbeviewedasalistofcellsintowhichnumberscanbeplacedorread.Inuptocanstorerepresentedtrillionsofbytesofmemory.almostallmoderncomputers,eachmemorycellissetgroupsofeightbits,calledabyte.Acomputerstorebinary5numbersinanykindofinformationinmemoryaslongasitcanbesomehowinnumericalform.6ModerncomputershavebillionsorevenAcomputersmainmemorycomesintwoprincipalvarieties:randomaccessmemory(RAM)andread-onlymemory(ROM).102MemorySubsystemRAMRAMisusedtostoretheinformationandinstructionsthatoperatethecomputersprograms.ItisaccessiblecircuitrywheretheCPUcanrunprogramsandprocessdata.AllthedatatypedintothecomputergoesdirectlytoRAM.essentialtoacomputerbecauseitprovidesrapidlyThecomputersRAMsizelargelydetermineshowmanyprogramsmayrunsimultaneouslymemory,complicatedprogramswillrunslowlyorwontrunatall.withoutperformancedegradation.IfthecomputerhastoolittleRAMis also knownasvolatilememorybecausetheinformationwithinthecomputerchipsispermanently,itisnecessarytocopythedatatoasecondarystoragedevicesuchasadisk.erasedassoonasthecomputerisswitchedoff.Tokeepdata112MemorySubsystemRAMcanbefurthercategorizedintoastaticrandomaccessmemory(SRAM)andadynamicrandomaccessmemory(DRAM).In SRAM,theword“static”indicatesthatthememoryretainsitscontentsaslongaspowerisbeingsupplied.However,dataislostwhenthepowergetsdownduetoitsvolatilenature.SRAMchipsuseamatrixof6-transistors.DRAM,unlikeSRAM,mustbeperiodicallyrefreshedinordertomaintainthedata.Thisisdonebyplacingthememoryonarefreshcircuitthatrewritesthedataseveralhundredcomposedofonecapacitorandonetransistor.timespersecond.AllDRAMsaremadeupofmemorycellswhichareBecauseoftheextraspaceinthematrix,SRAMusesmorechipsthanDRAMforthesameamountofstoragespace,thusmakingthemanufacturingcostshigher.SoSRAMandsmaller,DRAMisusedformostsystemis usedascachememoryandhasveryfastaccess.Incontrast,beingcheapermemory.122MemorySubsystemROMAsitsnameimplies,datastoredinROMcannotbeoverwrittenbutreadonly.Itcontainscriticalinformationandsoftwarethatmustbepermanentlyavailableforcomputeroperation.Itisalsoknownasnonvolatiletheirmemorybecausethememorychipsdonotlosecomputeristurnedon,thepermanentsoftwareininformationwhenthecomputerpowerisoff.WhentheROMbootsthecomputer.ROMchipscanbefurthercategorizedintoprogrammablereadonlymemoryandelectricallywhicharedifferentiatedbyhowandhowoftentheycanbeprogrammed.(PROM),erasableandprogrammablereadonlymemory(EPROM)erasableandprogrammablereadonlymemory(EEPROM),132MemorySubsystemPROMcanbemodifiedonlyoncebyauser.TheuserbuysablankPROMprogram.InsidethePROMandentersthedesiredcontentsusingaPROMchipbeprogrammedonlyonceandisnoterasable.therearesmallfuseswhichareburntopenduringprogramming.ItcanEPROMcanbeerasedbyexposingittoultravioletlightforadurationofuptofortyminutes.Usually,anEPROMeraserachievesthisfunction.Duringprogramming,anelectricalchargeistrappedinchargeisretainedformorethantenyearsbecausethechargehasnoleakagepath.Forerasingthiscrystalwindow.Thisexposuretoultravioletlightdissipatesthecharge.aninsulatedgateregion.Thecharge,ultravioletlightispassedthroughaquartz142MemorySubsystemEEPROMis programmedanderasedelectrically.Itcantimes.Botherasingandprogrammingtakeabout4to10ms(milliseconds).selectivelyerasedonebyteatatime,ratherthanerasingtheentirechip.Hence,theprocessofreprogrammingisflexiblebutslow.beerasedandreprogrammedabouttenthousandInEEPROM,anylocationcanbebeerasedandprogrammed.EEPROMscan153I/OSubsystem163I/OSubsystemI/O isthemeansbywhichacomputerreceivesinformationresultsback.Devicesthatprovideinputoroutputtothecomputerarepersonalcomputer,peripheralsthekeyboardmonitorandprinter.Storagedevicessuchdisks,floppydisksandinputsformfromtheoutsideworldandsendscalledperipherals.Onatypicalincludeinputslikeandmouse,andoutputssuchastheashardbothanothercompactdisksserveandoutputs.ComputernetworkisofI/O.173I/OSubsystem1InputDevicesAninputdeviceallowsausertoenterdataandcommandsintothememoryofacomputer.Belowarecommonlydevices.usedinput183I/OSubsystem1InputDevices1KeyboardThekeyboardisoneofthemaininputdevicesforacommonlykeysthatallownumbers,spaces,punctuationmarksorothersymbols.Itperformcomputersystem.Itis thewayauserwillmostcommunicatewithtypelettersofthealphabet,acomputer.Itcontainstypelettersofthealphabet,userstoalsocontainsspecificfunctionsonthecomputer.specialkeysthatallowusersto193I/OSubsystem1InputDevices2MouseAmouseis apointingdevicedesignedto begripped(usuallycontrolthemotionofanon-screenpointer,orcursor,bymovingthemouseonaflatsurface.Themouseapparentlysizeandformkindofmousehastwobuttonsontopwithonebeingusedmorefrequently.byonehand.Ithasadetectiondeviceaball)onthebottomthatenablesuserstogetsitsnamebybeingaboutthesameasatoymouse.Themostconventionaltheleft203I/OSubsystem1InputDevices3ScannerAscanneruseslight-sensingequipmenttointoconvertelectroniccomputercommontypesofscanneraretheflatbedscanner,whichissimilartohand-heldacrosstheimagetobeprocessed.imagessuchaspictureortextsignalsthatcanbemanipulatedThebyawithinseveralminutes.twoanofficephotocopier,andthescanner,whichispassedmanually213I/OSubsystem1InputDevices4ModemAmodem,whichstandsformodulator-demodulator,isusedforcommunicatingbetweencomputers.ItconnectsacomputertobeWhencomputerisconvertedbythemodemwhichreceivingmodem.Thenintocomputer.atelephonelineandallowsinformationtotransmittedtoorreceivedfromanothercomputer.transmitting,theinformationsentfromoneintoanaudiosignal,is then transmittedbythetelephonelinetothethismodemconvertsthesignalinformationthatcanbeunderstoodbythereceiving223I/OSubsystem1InputDevices5MicrophoneAmicrophoneisadeviceforconvertingsoundintobestored,manipulated,andplayedbackbythecomputer.moduleisadevicethatconvertsspokenwordscomputercanrecognizeandprocess.signals thatcanAvoicerecognitionintoinformationthatthe233I/OSubsystem2OutputDevicesOutputdevicestransmittheresultsprocessedbythecomputertocommonlyusedoutputdevices.theoutsidecomponentsfortheuser.Beloware243I/OSubsystem2OutputDevices1MonitorMonitors,commonlycalledasVisualDisplayUnit(VDU),arethemainpixelsthatarearrangedindependsuponthenumberofpixels.outputdeviceofacomputer.Itformsimagesfromtinydots,calledarectangularform.ThesharpnessoftheimageTherearetwokindsofviewingscreenusedformonitors.Oneisacathoderaytube(CRT)andtheotherisaflat-paneldisplay.ACRT-basedscreenlookssimilartoatelevisionset.InformationofelectronsthatscansafromphosphorescentHowever,CRTmonitorsvoltageimages.theCPUisdisplayedusingabeamhighsurfacethatemitslightandcreatesimages.highare bulkyand theyrequirea relativelypowersupplytosufficientlyelectronbeamsfordisplaying253I/OSubsystem2OutputDevicesTheflat-paneldisplayreferstoaclassofvideodevicesthathavereducedvolume,weightandpowerrequirementinofflat-paneldisplayscomputer,parisontotheCRT.Currentusesincludecalculators,videogames,monitors,laptopTheflat-paneldisplayisdividedintotwocategories:emissivedisplaysandnon-emissivelight.Examplesareemissivedisplaysuseopticaleffectstoothersourcesintoexample.displays.TheemissivedisplaysconvertelectricalenergyintoplasmapanelsandLED(light-emittingdiodes).Thenon-convertsunlightorlightfromsomegraphicspatterns.ALCD(liquidcrystaldisplay)isatypicalFiguresbelowrespectivelyshowaCRTmonitorandaflat-panelmonitor.263I/OSubsystem2OutputDevices2PrinterThesecondtypeisanink-jetprinter.Itfiresdropletsofinkontoapagetoacceptanceamongconsumersinprintingwithhighresolutionandrelativelyinexpensive.formcharactersandpictures.InkjetprintinghasgainedwidetheprintingindustrybecauseitisfastinThelasttype,laserprintersareofthehighestquality.Theyemploybeamsoflighttoparticlescalledtoner.ThetonerisfusedtoThelaserprinterhasadvantageousoperatingcharacteristicsoflownoise,highspeedandhighresolution.drawimagesonadrumthatthenpicksupfineblackapagetoproduceanimage.273I/OSubsystem2OutputDevicesAprinterisanimageformationdevicewhichreceivesdatafromahostcomputerandthenformsacorrespondingimageontomediumsuchasasheetofpaper.Therearethreemajortypesofprinters.arecordableDot-matrixprintersfeatureamovableprintheadcontainingarowoftinypins.Thepinspushaninkedribbonagainstthepaper,producingamatrixthedotscanformthedot-matrixwithdocumentinofdots.Astheprintheadmovesbackandforthacrossthepage,eitherlettersorgraphics.Comparedwithothertypes,printerislessexpensivebutproduceslowerresolutioncopiesofanoise.However,asitusespins,itcanproducemultipleasingleprinting,whichisuniqueamongothers.283I/OSubsystem2OutputDevices3AudioOutputDevicesAudiooutputdevicesarethecomponentsofacomputerthatproducemusic,speech,orothersounds.TwocommonlyusedaudiospeakersandheadsetsoutputdevicesareMostpersonalcomputershaveasmallinternalspeakerthatusuallyoutputsusersaddhigher-qualitycanbeeasilyonlytheusercanhearthesoundfromthecomputer.onlylow-qualitysound.Forthisreason,manypersonalcomputerstereospeakers.Whenusingspeakers,theoutputheard.Whenpluggingaheadsetintoaportonthesoundcard,293I/OSubsystem3OtherI/ODevices303I/OSubsystem3OtherI/ODevices1DiskDriveStoragehardwarealsocanberegardedasinputandoutputdevice.Differentfromthemainretrievalbythecomputer.Onecommonlyround,flatpieceofplasticormetalonwhichitemscanbeencoded,orwritten.7Adiskdriveisadevicethatreadsfromdrives:hard,floppy,magneto-opticalandcompact.memory,itprovidespermanentstorageofinformationandprogramsforusedstoragemediumis adisk,whichis aandwritesontoadisk.ThereareseveraltypesofdiskAharddiskusuallyconsistsofseveralcirculardisksonwhichdata,instructions,andinformationinformationandretrievethatinformationveryquickly.Somehardwhichmeanstheycanbeinsertedandremovedfromthisisthattheycanbetakenoutofthecomputerandtransportedorsecured.arestoredmagnetically.Harddiskdrivescanstorelargeamountsofdisksareremovable,aharddiskdrive.Theadvantageof313I/OSubsystem3OtherI/ODevicesAfloppydiskconsistsofathin,circular,flexiblediskenclosedinaplasticshell.Italsostoresinformationininformationthanharddiskdrivesandretrievetheinformationatamuchslowerrate.magneticparticlesinremovabledisks.FloppydisksstorelessMagneto-opticaldiskdrivesstoreinformationonremovabledisksthatareasmuchsensitivetoinformationasharddisksbuthaveslightlyslowerretrievalspeeds.both laserlightandmagneticfields.TheycantypicallystoreCompactdiskdrives(CD-ROM)storeinformationonpitsburnedintothesurfaceofadiskofreflectivematerial.TheinformationstoredonCD-ROMscannotbeerasedoroverwrittenwithnewinformation.Theycanstoreaboutasmuchinformationasaharddiskdrivebuthaveaslowerrateofinformationretrieval.AvariationofthestandardCD-ROMinformationstoredinis therewritableCD,alsocalleda CD-RW.DifferentfromtheCD-ROM,theCD-RWcanbeerasedandoverwritten.323I/OSubsystem3OtherI/ODevices2DigitalCameraAdigitalcameratois avideoinputdevice,whichallowsusersdigitally,insteadtheimageiscircuitcomputerandrestoredtocomputer.Digitalcamerashavewideapplicationsbothandbusiness.Itcanbeusedforvideomeeting,telemedicineandreal-timemonitoringaswellasforpersonalvideochatting.takepicturesandstorethephotographedimagesofontraditionalfilm.Whenphotographed,processedandconvertedbythelight-sensitiveto thedigitalsignal.Thenthesignalisinputtothethetheimagebysomesoftwareininlife333I/OSubsystem3OtherI/ODevices3DataProjectorAdataprojectortakestheimagethatdisplaysonontoascreensothataudiencecanseetheimageclearly.attachedtocanbesmallportabledevices.a computerscreenand projectsitDataprojectorscanbelargedevicesaceilingorwallinanauditoriumor343I/OSubsystem3OtherI/ODevices4TouchScreenA monitorthathasatouch-sensitivepanelonthescreeniscalledatouchscreen(SeeFigure2-4).Usersinteractwiththecomputerbytouchingareasofthescreenwiththeirfingers.BecausetheyrequirealotofarmscreensarenotusedtoenterlargeamountsofdataInsteadtheyareusedtotouchwords,pictures,numbers,orlocationsidentifiedonthescreen.Touchscreensarewidelykioskslocatedinlaptopcomputersemploytouchscreensaswell.movements,touchappliedinstores,hotels,airportsandmuseums.Some353I/OSubsystem3OtherI/ODevices5BarcodeReaderAbarcodeisamachine-readablerepresent