《電子與通信工程專業(yè)英語》課件第17章

Unit17ComputerHardwareFundamentalsNEWWORDSANDPHRASES

NOTES

EXERCISES

參考譯文

EXTENSIVETEXT

1.Thecentralprocessingunit

Thecentralprocessingunit(CPU)istheheartofthecomputersystems.Amongotherthings,itsconfigurationdetermineswhetheracomputerisfastorslowinrelationtoothercomputers.TheCPUisthemostcomplexcomputersystemcomponent,responsiblefordirectingmostofthecomputersystemactivitiesbasedontheinstructionsprovided.Asonecomputergenerationhasevolvedtothenext,thephysicalsizeoftheCPUhasoftenbecomesmallerandsmaller,whileitsspeedandcapacityhaveincreasedtremendously.Indeed,thesechangeshaveresultedinmicrocomputersthataresmallenoughtofitonyourdeskoryourlap.

TheCPUcomprisesthecontrolunitandthearithmetic/logicunit(ALU).

Thecontrolunitisresponsiblefordirectingandcoordinatingmostofthecomputersystemsactivities.Itdeterminesthemovementofelectronicsignalsbetweenmainmemoryandthearithmetic/logicunit,aswellasthecontrolsignalsbetweentheCPUandinput/outputdevices.

Justasacarisuselesswithoutgas,acomputerisnotmuchgoodwithoutsoftwareinstructions.Whenweusesoftware,weareworkingwithhighlevelinstructionsthataretobecarriedoutbythecontrolunit.Theseinstructionsareconvertedbyalanguageprocessorintoalowlevelformofinstructionsthatthecomputercanworkwithmachinelanguage,theonlylanguagethattheCPUcanunderstand.Inmachinelanguage,dataandinstructionsarerepresentedinbinaryform(0sand1s).Oncetheinstructionshavebeenconvertedintothisform,theycanberetrievedfrommainmemoryandinterpretedbythecontrolunit.Accordingtoeachspecificinstruction,thecontrolunitissuesthenecessarysignalstoothercomputersystemcomponentsasneededtosatisfytheprocessingrequirements[1].Thiscouldinvolve,forexample,directingthatdataberetrievedfromadiskstoragedevice,“telling”theprintertoprinttheletteryoujustwrote,orsimplydirectingthearithmetic/logicunittoaddtwonumbers[2].

WithouttheALU,computerswouldnotbeabletodomostofthetasksthatwefinduseful.TheALUperformsallthearithmeticandlogicalfunctionsthatis,itadds,subtracts,multiplies,divides,anddoescomparisons.Thesecomparisons,whicharebasically“l(fā)essthan”,“greaterthan”,and“equalto”,canbecombinedintoseveralcommonexpressions,suchas“greaterthanorequalto”.Theobjectiveofmostinstructionsthatusecomparisonsistodeterminewhichinstructionshouldbeexecutednext.

TheALUcontrolsthespeedofcalculationsandsoreceivesagreatdealofattentionfromcomputerusers.Oldermicrocomputers’speedsareusuallymeasuredinmilliseconds(1thousandthofasecond).Newermicrocomputers’speedsaremeasuredinnanoseconds(1billionthofasecond).Ifananosecondwereequaltooneminute,thenaminutewouldbeequalto1900years!

2.Computerhardware

Computerhardwarecanbedividedintofourcategories:inputhardware,storagehardware,processinghardware,andoutputhardware.

1)

Inputhardware

Thepurposeofinputhardwareistocollectdataandconvertitintoaformsuitableforcomputerprocessing.Themostcommoninputdeviceisakeyboard.Itlooksverymuchlikeatypewriterkeyboard.Itskeysarearrangedinthetypicaltypewriterlayout.Therearealsoanumberofadditionalkeys.Theycanbeusedtoenterspecialcomputerrelatedcodes.Althoughitisn’ttheonlytypeofinputdeviceavailable,thecomputerkeyboardistheonethatismostgenerallyusedbythebusinesscommunity.

2)

Storagehardware

Thepurposeofstoragehardwareistoprovideameansofstoringcomputerinstructionsanddatainaformthatisrelativelypermanent,thatis,thedataisnotlostwhenthepoweristurnedoffandeasytoretrievewhenneededforprocessing.Storagehardwarestoresdataaselectromagneticsignalsorlaseretchedspot,commonlyondiskortape,ratherthanonpaper.

3)

Processinghardware

Thepurposeofprocessinghardwareistoretrieve,interpret,anddirecttheexecutionofsoftwareinstructionsprovidedtothecomputer.ThemostcommoncomponentsofprocessinghardwarearetheCPUandmainmemory.

TheCPUisthebrainofthecomputer.Itreadsandinterpretssoftwareinstructionsandcoordinatestheprocessingcoordinateactivitiesthatmusttakeplace.ThedesignoftheCPUaffectstheprocessingpowerandspeedofthecomputer,aswellastheamountofmainmemoryitcanuseeffectively.WithawelldesignedCPUinyourcomputer,youcanperformhighlysophisticatedtasksinaveryshorttime.

Mainmemory(alsocalledinternalmemory,primarystorage,orjustmemory)canbethoughtofasanelectronicdesktop.Themoredesksurfaceyouhaveinfrontofyou,themoreyoucanplaceonit.Similarly,ifyourcomputerhasalotofmemory,youcanplacemoresimplesoftwareinstructionorsophisticatedsoftware;acomputerwithalargememoryismorecapableofholdingthethousandsofinstructionthatarecontainedinthemoresophisticatedsoftwareprograms.Alargememoryalsoallowsyoutoworkwithandmanipulategreatamountsofdataandinformationatonemanipulatetime.

4)

Outputhardware

Thepurposeofoutputhardwareistoprovidetheuserwillthemeanstoviewinformationproducedbythecomputersystem.Informationisoutputineitherhardcopyorsoftcopyform.Hardcopyoutputcanbeheldinyourhandexamplesarepaperwithtext(wordsornumbers)orgraphicsprintedonit.Softcopyoutputisdisplayedonamonitor,atelevisionlikescreenonwhichyoucanreadtextandgraphics.

3.Monitorandsystemunit

1)

Monitor

Thetermmonitorisusedinterchangeablywithscreen,videodisplayscreen,andcathoderaytube(CRT).Thisoutputdeviceprovidesyourprincipalvisualcontactwiththemicrocomputersystem.Whenyouentercommandsordatafromthekeyboard,youseetheresultsonthemonitor.Acolormonitor,oftenreferredtoasanRGB(forred,green,blue)monitor,candisplaytextandgraphicsinvariouscolors.Mostofthecapabilitiesofthemonitor,includingimageclarityandtheabilitytodographics,aredeterminedbythesophisticationofthevideodisplaycircuitboard,ifany,containedwithinthesystemunit.Inanycase,theuserneedstheappropriatesoftwaretotakeadvantageofamonitor’scapabilitiesincludingtheabilitytodisplaygraphics.

2)

Systemunit

Themaincomputersystemcabinet,calledthesystemunit,usuallyhousesthepowersupply,thesystemboard,andthestoragedevices(althoughsomestoragedevicesdiskdrives,forexampleareoftenhousedincabinetsoutsidethesystemunit).Theseelementscanbedefinedasfollows:

(1)

Thepowersupplyprovideselectricalpowertoallcomponentshousedinthesystemunit.Insomemicrocomputers,italsoprovidespowertothemonitor.

(2)

Thesystemboard,alsoknownasthemotherboard,isthemaincircuitboardofthemicrocomputersystem.Itnormallyincludes①themicroprocessorchip;②mainmemorychips;③allrelatedsupportcircuitry,and④theexpansionslotswhereadditionalcomponentscanbepluggedin.

(3)

Thestoragedevicesareusuallyoneormorefloppydiskdrivesandhighcapacityharddiskdrives.Afloppydisk,ordiskette,isathinplasticdiskenclosedinapaperorplasticcoveringthatcanbemagneticallyencodedwithdata.Harddisksarerigiddiskscapableofstoringmuchmoredatathanafloppydisk.(Andharddiskdrivesaccessdatafasterthanfloppydiskdrivesdo.)Harddisksaremoreexpensivethanfloppydisks.Sincemostharddisksarepermanentlyinstalledinthesystemunit,floppydisks,whichcanbecarriedaround,areoftenusedtomovedatafromonecomputertoanother.

(4)

Additionalcomponents:Theexpansionslotsonthesystemboardallowuserstoaddnewcomponentstotheircomputersystem.Themostpopularaddoncomponentincludes:①amemorycardcontainingmainmemorychipsthatgiveyouadditionalmainmemory;②aninternalmodemtofacilitatedatacommunicationbetweencomputersoverphonelinesandsimilarcables;③abatterypoweredclockandcalendarmechanism;④additionalprinterportsthatallowyoutocommunicatewithseveraltypesofoutputdevices;and⑤videodisplayboards.

4．RAMandROM

Therearetwowellknowntypesofmemorychips.OnetypeiscalledRAM.TheothertypeisROM.

1)

RAM

RAM(randomaccessmemory)chipsholdtheprogramanddatathattheCPUispresentlyprocessing.Thatis,itistemporaryorvolatilestorage.

TheprincipalfunctionofRAMistohold:①Dataforprocessing;②Instructionsforprocessingthedatathatis,theprogram;③Informationthatis,processeddatawaitingtobeoutputorsenttosecondarystoragesuchasafloppydiskinadiskdrive.

OneofthemostimportantfactstoknowaboutRAMisthatthepartofitscontentisheldonlytemporarily.Inotherwords,itisstoredonlyaslongasthemicrocomputeristurnedon.Whenyouturnthemachineoff,thecontentsimmediatelyvanish.Thestoredcontentsinmemoryarevolatileandcanvanishveryquickly,asduringapowerfailure[3].Itisthereforeagoodpracticetorepeatedlysaveyourworkinprocesstosecondarystoragemediumsuchasfloppydiskorharddisk.

Thenextimportantfacttoknowaboutmemoryisthatitscapacity.ThebanksofRAMchips(agroupofchips,usuallynine,arrangedinarow)[4]aresometimesonamemoryexpansioncard,whichfitsinsidethesystemcabinetandsometimesareonthemaincircuitboard.TheamountofdatathatcanbestoredinRAMismeasuredinbytes.MostdesktopPCssoldtodayhaveabout1GBofRAMandallowtheadditionofmorememory.TwotypesofmemoryareusedtoincreaseRAMexpandedmemoryandextendedmemory.Thetypeusedisinfluencedbythesophisticationofmicroprocessorinyourmachine.

2)

ROM

Howdoesyourcomputerknowwhattodowhenyouturniton?Howdoesitknowtocheckoutyourhardwarecomponents(suchasthekeyboardorthemonitor)toseethattheyhavebeenconnectedcorrectly?Instructionstoperformsuchoperations,whicharecriticaltotheoperationofcomputer,arestoredpermanentlyonareadonlymemory(ROM)chipinstalledbythemanufacturerinsidethecomputer.TheROMchipretainsinstructionsinapermanentlyaccessible,nonvolatileform.Whenthepowerinthecomputeristurnedoff,theinstructionsstoredinROMwillnotbelost.

CertaintypesofROMchipgiveusersaddedflexibility.Programmablereadonlymemory(PROM)chipsallowyoutoputyourowndataandprogramsonthem.Erasableprogrammablereadonlymemory(EPROM)chipscanbechangedbyusingaspecialultravioletlightdevice;however,youhavetotakeEPROMchipsoutofthecomputertochangethedataandprogramsonthem.Electricallyerasableprogrammablereadonlymemory(EEPROM)chipscanbechangedwithouttakingthemoutofthecomputer.

NEWWORDSANDPHRASES

configuration n. 構(gòu)造，結(jié)構(gòu)，配置

tremendously adv. 非常地

microcomputer n. 微(型)計(jì)算機(jī)

lap n. 膝蓋

coordinate n. 坐標(biāo)(系)；協(xié)同，協(xié)調(diào)；交叉索引；并列

binary adj. 二進(jìn)制的

millisecond n. 毫秒

typewriter n. 打字機(jī)

etched adj. 被腐蝕的，被蝕刻的，風(fēng)化的

interchangeably adv. 可交替地

diskette n. 磁盤

volatile adj. 可變的，不穩(wěn)定的

exterior adj. 外部的

n. 外部

archive vt. 存檔

n. 檔案文件

spin vt.,vi. 旋轉(zhuǎn)，紡，紡紗

n. 旋轉(zhuǎn)

cursor n. 光標(biāo)游標(biāo)；指針，指示器

pixel n. 像素

dotmatrix 點(diǎn)陣

inkjet 墨水噴射,噴墨

thermal adj. 熱的，熱量的

NOTES

[1]Accordingtoeachspecificinstruction,thecontrolunitissuesthenecessarysignalstoothercomputersystemcomponentsasneededtosatisfytheprocessingrequirements.

本句可譯為：針對每條特定的指令，控制單元向計(jì)算機(jī)系統(tǒng)其他部件發(fā)出必要的控制信號，以滿足處理需求。

[2]Thiscouldinvolve,forexample,directingthatdataberetrievedfromadiskstoragedevice,“telling”theprintertoprinttheletteryoujustwrote,orsimplydirectingthearithmetic/logicunittoaddtwonumbers.本句可譯為：例如，這可能涉及命令從磁盤存儲器取數(shù)據(jù)，“告知”打印機(jī)打印你剛寫好的信，或簡單地命令算術(shù)/邏輯單元做兩數(shù)相加的運(yùn)算。

[3]Thestoredcontentsinmemoryarevolatileandcanvanishveryquickly,asduringapowerfailure.

本句可譯為：當(dāng)電源出故障時(shí)，RAM存儲器中的內(nèi)容是易失的，并且會消失得非常迅速。

[4]ThebanksofRAMchips(agroupofchips,usuallynine,arrangedinarow)…

在這里，括號里的內(nèi)容就是對“ThebanksofRAMchips”的解釋?！癰ank”譯為“存儲體”，是一組芯片，一般九個(gè)一組，成一行排列。

本句可譯為：RAM芯片的存儲體(存儲體是一組芯片，通常九個(gè)一組排成一排)……

EXERCISES

Ⅰ.

TranslatethefollowingphrasesintoEnglish.

控制單元 電信號 主存 語言處理器

硬盤 電磁信號 顯示器 復(fù)雜的軟件程序

串行口 電路板 圖像顯示屏幕 可編程只讀存儲器

Ⅱ.

TranslatethefollowingphrasesintoChinese.

(1)

centralprocessingunit

(2)

physicalsize

(3)

arithmetic/logicunit

(4)

highlevelinstructions

(5)

binaryform

(6)

diskstoragedevice

(7)

imageclarity

(8)

microprocessorchip

(9)

highcapacityharddiskdrive

(10)

batterypoweredclock

(11)

memoryexpansioncard

(12)

readonlymemory

(13)

erasableprogrammablereadonlymemory

Ⅲ.

TranslatethefollowingparagraphsintoChinese.

(1)

Thecontrolunitisresponsiblefordirectingandcoordinatingmostofthecomputersystemsactivities.Itdeterminesthemovementofe1ectronicsignalsbetweenmainmemoryandthearithmetic/logicunit,aswellasthecontrolsignalsbetweentheCPUandinput/outputdevices.

(2)

Justasacarisuselesswithoutgas,acomputerisnotmuchgoodwithoutsoftwareinstructions.Whenweusesoftware,weareworkingwithhighlevelinstructionsthataretobecarriedoutbythecontrolunit.Theseinstructionsareconvertedbyalanguageprocessorintoalowlevelformofinstructionsthatthecomputercanworkwithmachinelanguage,theonlylanguagethattheCPUcanunderstand.Inmachinelanguage,dataandinstructionsarerepresentedinbinaryform(0sand1s).

(3)

WithouttheALU,computerswouldnotbeabletodomostofthetasksthatwefinduseful.TheALUperformsallthearithmeticandlogicalfunctionsthatis,itadds,subtracts,multiplies,divides,anddoescomparisons.Thesecomparisons,whicharebasically“l(fā)essthan”,“greaterthan”,and“equalto”,canbecombinedintoseveralcommonexpressions,suchas“greaterthanorequalto”.Theobjectiveofmostinstructionsthatusecomparisonsistodeterminewhichinstructionshouldbeexecutednext.

(4)

Thepurposeofinputhardwareistocollectdataandconvertitintoaformsuitableforcomputerprocessing.Themostcommoninputdeviceisakeyboard.Itlooksverymuchlikeatypewriterkeyboard.Itskeysarearrangedinthetypicaltypewriterlayout.Therearealsoanumberofadditionalkeys.Theycanbeusedtoenterspecialcomputerrelatedcodes.Althoughitisn’ttheonlytypeofinputdeviceavailable,thecomputerkeyboardistheonethatismostgenerallyusedbythebusinesscommunity.

(5)

OneofthemostimportantfactstoknowaboutRAMisthatthepartofitscontentisheldonlytemporarily.Inotherwords,itisstoredonlyaslongasthemicrocomputeristurnedon.Whenyouturnthemachineoff,thecontentsimmediatelyvanish.Thestoredcontentsinmemoryarevolatileandcanvanishveryquickly,asduringapowerfailure.Itisthereforeagoodpracticetorepeatedlysaveyourworkinprocesstosecondarystoragemediumsuchasfloppydiskorharddisk.

參考譯文

第十七單元計(jì)算機(jī)硬件基礎(chǔ)

1．中央處理器

中央處理器(CPU)就如同計(jì)算機(jī)系統(tǒng)的心臟，它的配置決定了計(jì)算機(jī)運(yùn)行速度的快慢。中央處理器是計(jì)算機(jī)部件中最復(fù)雜的，基于提供的指令直接負(fù)責(zé)大多數(shù)計(jì)算機(jī)系統(tǒng)活動。隨著計(jì)算機(jī)的更新?lián)Q代，中央處理器變得越來越小，速度和性能增長迅猛。當(dāng)然，這些變化也產(chǎn)生了足夠適合在桌面和膝上用的微型計(jì)算機(jī)。中央處理器包含控制單元和算術(shù)/邏輯單元(ALU)兩部分。

控制單元負(fù)責(zé)指揮和調(diào)度大部分計(jì)算機(jī)系統(tǒng)活動。它決定了主存和算術(shù)/邏輯單元間的電子信號流動和中央處理器與輸入/輸出設(shè)備間的控制信號流動。

正如沒有汽油無法使用汽車一樣，計(jì)算機(jī)沒有軟件指令也是不行的。當(dāng)我們使用軟件時(shí)，我們使用的是被控制單元執(zhí)行的高級指令。這些指令被語言處理機(jī)轉(zhuǎn)換為計(jì)算機(jī)能懂的機(jī)器語言——低級指令格式。在機(jī)器語言中，用二進(jìn)制數(shù)(0和1)表示數(shù)據(jù)和指令。一旦指令被轉(zhuǎn)換為這種格式，它們就可以從主存中取回并通過控制單元進(jìn)行譯碼。針對每條特定的指令，控制單元向計(jì)算機(jī)系統(tǒng)其他部件發(fā)出必要的控制信號，以滿足處理需求。例如，這可能涉及命令從磁盤存儲器取數(shù)據(jù)，“告知”打印機(jī)打印你剛寫好的信，或簡單地命令算術(shù)/邏輯單元做兩數(shù)相加的運(yùn)算。

如果沒有算術(shù)/邏輯單元，計(jì)算機(jī)就不可能執(zhí)行許多我們認(rèn)為有效的任務(wù)。算術(shù)/邏輯單元能執(zhí)行所有的數(shù)學(xué)和邏輯功能，即加、減、乘、除和比較。這類比較是基礎(chǔ)比較，如“小于”、“大于”和“等于”，可以組成聯(lián)合表達(dá)式，如“大于或等于”。大部分比較指令的作用是確定下面該執(zhí)行哪條指令。

算術(shù)/邏輯單元控制計(jì)算速度，因此要從計(jì)算機(jī)用戶接收大量信號。早期微機(jī)的速度一般用毫秒(千分之一秒)計(jì)量。新一代的微機(jī)速度則用納秒(十億分之一秒)計(jì)量。若把納秒比作一分鐘，則一分鐘就等于1900年！

2．計(jì)算機(jī)硬件

計(jì)算機(jī)硬件可分為四類：輸入硬件、存儲硬件、處理硬件和輸出硬件。

1)輸入硬件

輸入硬件用于收集數(shù)據(jù)并將數(shù)據(jù)轉(zhuǎn)換為適合計(jì)算機(jī)處理的格式。最常見的輸入設(shè)備就是鍵盤。它看起來非常像打字機(jī)鍵盤，與典型的打字機(jī)鍵位布局一致。還有一組數(shù)字附加鍵，可用于輸入特殊計(jì)算機(jī)相關(guān)代碼。雖然鍵盤并不是可獲得的唯一輸入設(shè)備，但是計(jì)算機(jī)鍵盤是工商業(yè)界最常使用的輸入設(shè)備。

2)存儲硬件

存儲硬件按照一定的格式相對永久地存儲計(jì)算機(jī)指令和數(shù)據(jù)，即關(guān)機(jī)后數(shù)據(jù)不會丟失，并能在需要處理時(shí)方便地找回。存儲硬件以電磁信號或激光蝕刻點(diǎn)的方式存儲數(shù)據(jù)，通常存儲在盤片或磁帶上，而不是紙上。

3)處理硬件

處理硬件用于檢索、翻譯和引導(dǎo)執(zhí)行計(jì)算機(jī)提供的軟件指令。處理硬件最常用的部件為中央處理器和主存儲器。

中央處理器如同計(jì)算機(jī)的大腦，它負(fù)責(zé)讀和翻譯軟件指令，并處理調(diào)度活動。中央處理器的設(shè)計(jì)要考慮處理能力和計(jì)算機(jī)的速度，當(dāng)然還包括它能有效使用的主存儲器容量。如果你的計(jì)算機(jī)配備了一個(gè)設(shè)計(jì)良好的中央處理器，你就能在很短的時(shí)間內(nèi)完成高復(fù)雜度的任務(wù)。

可以將主存儲器(也稱為內(nèi)存、基本存儲或存儲器)想象成一個(gè)電子桌面。你面前的桌面面積越大，你在桌面上放的東西就越多。同樣的，如果你的計(jì)算機(jī)存儲器很大，你就能在里面放置更多的簡單軟件指令或高級軟件；一個(gè)擁有大存儲器的計(jì)算機(jī)能勝任處理數(shù)千條指令，這些指令包含在更高級的軟件程序中。大容量存儲器還允許在一個(gè)操作周期操作大量數(shù)據(jù)和信息。

4)輸出硬件

輸出硬件的作用是讓用戶按照自己的方式查看計(jì)算機(jī)系統(tǒng)生成的信息。信息以硬拷貝或軟拷貝方式輸出。硬拷貝輸出可以拿在手上看，如上面打印有文本(文字或數(shù)字)或圖的紙。軟拷貝顯示在監(jiān)視器(一個(gè)像電視一樣的屏幕)上，可以在上面顯示文本或圖形。

3．監(jiān)視器和系統(tǒng)單元

1)監(jiān)視器

術(shù)語“監(jiān)視器”常指屏幕、視頻顯示屏和陰極射線管(CRT)。這種設(shè)備提供了人與微機(jī)的主要的視覺對話方式。當(dāng)你用鍵盤輸入命令或數(shù)據(jù)時(shí)，你可以在監(jiān)視器上看到剛輸入的結(jié)果。彩色監(jiān)視器常指RGB(RGB代表紅、綠、藍(lán))監(jiān)視器，它能以多種顏色顯示文本和圖形。監(jiān)視器的大多數(shù)性能(包括圖像清晰度和圖像顯示能力)取決于視頻顯示電路板的高級程度，該電路板一般包含在系統(tǒng)單元中。在任何情況下，用戶需要合理地將軟件與監(jiān)視器的圖像顯示性能相匹配。

2)系統(tǒng)單元

計(jì)算機(jī)系統(tǒng)主機(jī)箱稱為系統(tǒng)單元，一般包含有供電電源、系統(tǒng)板和存儲設(shè)備(有些存儲設(shè)備磁盤驅(qū)動經(jīng)常是外置的)。這些要素定義如下：

(1)供電電源給所有系統(tǒng)單元內(nèi)的部件供電。有些微機(jī)內(nèi)的電源還負(fù)責(zé)給監(jiān)視器供電。

(2)系統(tǒng)板常稱為主板，是微機(jī)系統(tǒng)的主電路板，通常包含：①微處理器芯片；②主存儲器芯片；③所有相關(guān)支持電路；④可插入附件的擴(kuò)展插槽。

(3)存儲設(shè)備通常是一個(gè)或多個(gè)軟驅(qū)和大容量硬盤。軟盤或磁盤是一種表面覆蓋著一層紙或塑料的很薄的塑料盤片，能把數(shù)據(jù)用磁性的方法編碼在盤片的表面。硬盤是一種硬磁盤，可存儲的數(shù)據(jù)比軟盤多很多。(并且硬盤驅(qū)動器訪問數(shù)據(jù)的速度也比軟盤驅(qū)動器快。)硬盤比軟盤價(jià)格更高。大多數(shù)硬盤都是永久地安裝在系統(tǒng)單元中，而軟盤由于要便于攜帶，故常常用于在計(jì)算機(jī)間拷貝數(shù)據(jù)。

(4)附件：系統(tǒng)板上的擴(kuò)展插槽允許用戶給計(jì)算機(jī)系統(tǒng)添加新的部件。常添加的部件有：含有主存儲器芯片的存儲卡，可為系統(tǒng)提供附加主存；②內(nèi)部調(diào)制解調(diào)器，可使計(jì)算機(jī)通過電話線或類似的電纜完成數(shù)據(jù)通信；③電池供電時(shí)鐘和日歷部件；④附加的打印機(jī)接口，可使用戶與多種類型外設(shè)通信；⑤顯卡。

4．RAM和ROM

眾所周知的存儲器芯片有兩類，一類稱為RAM，另一類稱為ROM。

1)

RAM

RAM(隨機(jī)存取存儲器)芯片保存CPU正在處理的程序和數(shù)據(jù)，即它是一種臨時(shí)或易失性存儲器。

RAM的主要功能是存儲：①要處理的數(shù)據(jù)；②用于處理數(shù)據(jù)的指令，即程序；③信息，即等待被輸出或發(fā)送至二級存儲器(如軟驅(qū)中的軟盤)處理后的數(shù)據(jù)。需注意的是，RAM的最大特點(diǎn)就是它只臨時(shí)性地存儲數(shù)據(jù)或程序。換句話說，它只在微機(jī)開機(jī)狀態(tài)進(jìn)行存儲。一旦關(guān)機(jī)，RAM中所有的內(nèi)容就立刻消失了。當(dāng)電源出故障時(shí)，RAM存儲器中存儲的內(nèi)容是易失的，并且會消失得非常迅速。因此，要養(yǎng)成即時(shí)將你進(jìn)行的工作存到二級存儲介質(zhì)(如軟盤或硬盤)中的習(xí)慣。

對于存儲器，需注意的第二個(gè)重要因素是它的容量。RAM芯片的存儲體(存儲體是一組芯片，通常九個(gè)一組排成一排)有時(shí)位于存儲器擴(kuò)充插件卡上，適合于安裝在主機(jī)機(jī)箱內(nèi)并且有時(shí)位于主電路板上。RAM可存儲數(shù)據(jù)的容量用字節(jié)表示?，F(xiàn)在可購買的大部分個(gè)人計(jì)算機(jī)都配有1

GB左右的RAM，并且允許擴(kuò)展。擴(kuò)展RAM和擴(kuò)展存儲器有兩類方法，選擇哪類方法取決于計(jì)算機(jī)中微處理器的復(fù)雜程度。

2)

ROM

當(dāng)你打開電源，計(jì)算機(jī)如何知道要做什么呢？它如何知道要去檢查硬件部件(如鍵盤或監(jiān)視器)是否連接正常呢？這些操作都是依靠執(zhí)行指令來完成的，這些對計(jì)算機(jī)操作起到關(guān)鍵作用的指令被永久存儲在只讀存儲器(ROM)芯片中，生產(chǎn)商將這種芯片安裝在計(jì)算機(jī)內(nèi)部。ROM中存儲的指令可被永久讀取，是非易失的。當(dāng)計(jì)算機(jī)斷電后，存儲在ROM中的指令不會丟失。某些類型的ROM芯片給用戶提供更多的靈活性?？删幊讨蛔x存儲器(PROM)芯片允許用戶加入自己的數(shù)據(jù)和程序。可擦除可編程只讀存儲器(EPROM)芯片可用專門的紫外線設(shè)備改寫；當(dāng)然，在改寫EPROM內(nèi)的數(shù)據(jù)和程序時(shí)，必須將它們從計(jì)算機(jī)內(nèi)取出來。電可擦除可編程只讀存儲器(EEPROM)芯片不用取出計(jì)算機(jī)就可以改寫。

EXTENSIVETEXT

TheFutureofComputing

Siliconmicroprocessorshavebeentheheartofthecomputingworldformorethan40years.Inthattime,microprocessormanufacturershavecrammedmoreandmoreelectronicdevicesontomicroprocessors.InaccordancewithMoore’sLaw,thenumberofelectronicdevicesputonamicroprocessorhasdoubledevery18months.Moore’sLawisnamedafterIntelfounderGordonMoore,whopredictedin1965thatmicroprocessorswoulddoubleincomplexityeverytwoyears.ManyhavepredictedthatMoore’sLawwillsoonreachitsendbecauseofthephysicallimitationsofsiliconmicroprocessors.

Thecurrentprocessusedtopackmoreandmoretransistorsontoachipiscalleddeep-ultravioletlithography(DUVL),whichisaphotography-liketechniquethatfocuseslightthroughlensestocarvecircuitpatternsonsiliconwafers.DUVLwillbegintoreachitslimitaround2005.Atthattime,chipmakerswillhavetolooktoothertechnologiestocrammoretransistorsontosilicontocreatemorepowerfulchips.Manyarealreadylookingatextreme-ultravioletlithography(EUVL)asawaytoextendthelifeofsiliconatleastuntiltheendofthedecade.EUVLusesmirrorsinsteadoflensestofocusthelight,whichallowslightwithshorterwavelengthstoaccuratelyfocusonthesiliconwafer.

BeyondEUVL,researchershavebeenlookingatalternativestothetraditionalmicroprocessordesign.TwoofthemoreinterestingemergingtechnologiesareDNAcomputersandquantumcomputers.

DNAcomputershavethepotentialtotakecomputingtonewlevels,pickingupwhereMoore’sLawleavesoff.ThereareseveraladvantagestousingDNAinsteadofsilicon.

Aslongastherearecellularorganisms,therewillbeasupplyofDNA.ThelargesupplyofDNAmakesitacheapresource.

Unliketraditionalmicroprocessors,whicharemadeusingtoxicmaterials,DNAbiochipscanbemadecleanly.

DNAcomputersaremanytimessmallerthantoday’scomputers.

DNA’skeyadvantageisthatitwillmakecomputerssmaller,whileatthesametimeincreasingstoragecapacity,thananycomputerthathascomebefore.OnepoundofDNAbasthecapacitytostoremoreinformationthanalltheelectronic