Unit4HowPCsWork?ContentsLearningObjectives1Words&Expressions2Text3Exercises4Learning

ObjectivesAfteryouhavereadthisunit,youshouldbefamiliarwith:1.WhatCPUcontains?2.Thesystemcomponentofcomputer.

Words&Expressionsfragilea.易碎的,脆的individualn.個人,個體a.個別的,單獨的,個人的electronica.電子的disketten.磁盤,磁碟operandn.操作數(shù)manipulatev.(熟練地)操作,使用(機器等),操縱temporarya.暫時的,臨時的,臨時性pulsen.脈搏,脈沖arithmeticn.算術(shù),算法transistorn.晶體管TextThebasicbuildingblockofamodemcomputerisachip,acomplex,integratedelectroniccircuitetchedonatinysquareofsiliconnobiggerthanafingernail.Sinceindividualchipsarefragileanddifficulttohandle,theyarenormallypackedandmountedonboards.Acomputerisassembledbyslidingtherightboardsintoamachinebox.Oneboardmightholdtheprocessor,whichinfactistheheartofacomputer;anothermightholdmemorystorewhichprovidesthecomputerwithdataandinstructions;whilethethirdmightholdtheelectronicstolinkaparticularinputdeviceoroutputdevicetothesystem.LetususethesystemshowninFigure2-6toshowyouhowatypicalcomputerworks.Acomputeriscontrolledbyastoredprogram,soifweTextwanttouseacomputer,thefirststepiscopyingtheprogramfromdisketteintomemory.Nowtheprocessorcanbeginexecutinginstructions;thedatainputfromthekeyboardarestoredinmemory.Theprocessorprocessesthedataandthenstorestheresultsbackintomemory.Atlast,wecangettheresult.Nowwecanseethatacomputersystemconsistsoffourbasiccomponents.Aninputdeviceprovidesdata.Thedataarestoredinmemory,whichalsoholdsaprogram.Underthecontrolsoftheprogram,thecomputer’sprocessorprocessesthedata.Theresultsflowfromthecomputertoanoutputdevice.Letuscomeclosertothesystemcomponentsonebyone.Beginningwiththeprocessor.Theprocessor,usuallycalledthecentralprocessingunit(CPU)ormainprocessor,istheheartofacomputer.ItistheCPUthatinfactprocessesormanipulatesdataandcontrolsalltherestpartsofthecomputer.Howcanitmanageitsjob?Thesecretissoftware.Withoutaprogramtoprovidecontrol,aCPUcandonothing.HowcanaprogramguidetheCPUthroughtheprocesses?Letusconsiderfromthebasicelementofaprogram-instruction.Aninstructioniscomposedoftwoparts:anoperationcodeandoneormoreoperands(Figure2-7).TheoperationcodetellstheCPUwhattodoandtheoperandstelltheCPUwheretofindthedatatobemanipulated.Theprocessorcontainsfourmajorcomponents(Figure2-8):aclock,aninstructioncontrolunit,anarithmeticandlogicunit(usuallyshortedforALU),andseveralregisters.Theclockgeneratespreciselytimedpulsesofcurrentthatsynchronizetheprocessor’sothercomponents.

Thentheinstructioncontrolunitdeterminesthelocationofthenextinstructiontobeexecutedandfetchesitfromthemainmemory.Thearithmeticandlogicunitperformsarithmeticoperations(suchasadditionandsubtraction)andlogicoperations(suchastestingavaluetoseeifitistrueorfalse),whiletheregistersaretemporarystoragedevicesthatholdcontrolinformation,keydataandsomeintermediateresults.SincetheregistersarelocatedintheCPU,theprocessingspeedisfasterthanthemainmemory.Thenwhichisthekeycomponenttoacomputer’sspeed?Itistheclock!Inmoredetail,itistheclock’sfrequencythatdecidesacomputer’sprocessingspeed.Whenwebuyacomputer,weusuallyconsiderthemainfrequencyfirst,andthatmeanaclock’sfrequency.NowwewilltalkmoreindetailabouttheMicroprocessorsandCentralProcessingUnits(Figure2-9).Microprocessorsarecentralprocessingunitsetchedonatinychipofsiliconand,thus,arecalledmicrochips.Microprocessorscontainmanyelectronicswitches,calledtransistors,whichdeterminewhetherelectriccurrentisallowedtopassthroughornot.Transistorsarethebasicbuildingblocksofmicroprocessors.Asinglemicrochipmaycontainmillionsoftransistors.Whenelectriccurrentisallowedtopassthrough,theswitchison.Thisrepresentsa1bit.Ifthecurrentdoesnotpassthrough,theswitchisoff.Thisrepresentsa0bit.Whenwetalkaboutthecomputer,weusuallymeetthetopic:motherboard.Themaincircuitboardinacomputeriscalledthemotherboard.Itisaflatboardtheholdsallofthekeyelementsthatmakeupthe“brain”ofthesystem,includingthemicroprocessororCPU,RAM(electronicorprimarymemory),andexpansionslotswhicharesocketswhereothercircuitboardscalledexpansionboardsmaybepluggedin.Exercises1.Answerthefollowingquestionaccordingtothetext.(1)HowPCworks?(2)Howmanybasiccomponentsarethereinacomputersystem?(3)WhatisCPU?(4)Howcanitmanageitsjob?2.TranslatethefollowingtermsorphrasesfromEnglishintoChineseandviceversa:key(1)microprocessor(6)操作數(shù)(2)chip(7)操作碼(3)instruction(8)脈沖(4)displayscreen(9)寄存器(5)CPU(10)晶體管3.Fillintheblankswiththeinformationgiveninthetext:

(1) Thebasicbuildingblockofamodemcomputerisachip,acomplex,integratedelectroniccircuitetchedon

nobiggerthanafingernail.(2) Theprocessor,usuallycalled or

,istheheartofacomputer.(3) Aninstructioniscomposedoftwoparts:an

andoneormoreoperands.(4) Microprocessorsarecentralprocessingunitsetchedonatinychipofsiliconand,thus,arecalled

.(5) Themaincircuitboardinacomputeriscalledthe

.key4.Choosethebestonefromtheitemsgivenbelowtocompletethefollowingpassage.

Mobilecomputers-which(1)laptops,notebooks,subnotebooksandhandholds(2)soubiquitousinsuchashorttime,nosurprisetohearwhosay:”Itwilldefinetheleadingedge(3)thenextfiveyearsorso.”Themostremarkable(4)mobilecomputersistheamountofdatastorageandmemorypacked(5)theirtinyboxes.Thesedevicesnotonlyhandlewindowseasilybutalsorunstorage-hungryprograms.(1)A.included B.include C.includes D.haveincluded(2)A.havebecome B.hadbecome C.becoming D.becomes(3)A.from B.for C.to D.about(4)A.at B.to C.for D.above(5)A.under B.to C.into D.ontokey5.MarkthefollowingstatementswithT(true)orF(false)accordingtothetext.(1)Sinceindividualchipsarefragileanddifficulttohandle,theyarenormallypackedandmountedonboards.(2)Theprocessorcontainsfourmajorcomponents:aclock,aninstructioncontrolunit,anarithmeticandlogicunit(usuallyshortedforALU),andseveralregisters.(3)Whenelectriccurrentisallowedtopassthrough,theswitchison.Thisrepresentsa0bit.Ifthecurrentdoesnotpassthrough,theswitchisoff.Thisrepresentsa1bit.(4)itistheclock’sfrequencythatdecidesacomputer’sprocessingspeed.(5)Themaincircuitboardinacomputeriscalledthemotherboard.Itisaflatboardtheholdsallofthekeyelementsthatmakeupthe“brain”ofthesystem.key6.Selecttheoneanswertoeachquestion.(1)A(n)

gathersinputandtransformsitintoaseriesofelectronicsignalsforthecomputertostoreandmanipulate.A.outputdeviceB.inputdeviceC.memoryD.data(2)Inacomputer,mostprocessingtakeplaceinacomponentcalledthe

.A.bus B.memory C.systemunit D.centralprocessingunit(3)Random-accessmemory(RAM)isakindof

storage.A.permanent. B.temporaryC.Flash D.smart(4)ROMisatypeof.A.semiconductor B.slot C.adapter D.network(5)A(n)

typicallycombinesthecapabilityofascanner,printer,fax,andcopyingmachine.A.multifunctionaldevice B. outputdeviceC.inputdevice D. CD-readonlymemory(6)

istheareawheredatacanbeleftonapermanentbasiswhenitisnotimmediatelyneededforprocessing.A. Secondarystorage B. CMOSC. CPU D. Primarystoragekey7.TranslatethefollowingsentencesintoChinese.(1)Thebasicbuildingblockofamodemcomputerisachip,acomplex,integratedelectroniccircuitetchedonatinysquareofsiliconnobiggerthanafingernail.(2)Theprocessorprocessesthedataandthenstorestheresultsbackintomemory.Atlast,wecangettheresult.(3)Nowwecanseethatacomputersystemconsistsoffourbasiccomponents.Aninputdeviceprovidesdata.