《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)計算機

lap n. 膝蓋

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

binary adj. 二進制的

millisecond n. 毫秒

typewriter n. 打字機

etched adj. 被腐蝕的，被蝕刻的，風化的

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. 光標游標；指針，指示器

pixel n. 像素

dotmatrix 點陣

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，控制單元向計算機系統(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)相加的運算。

[3]Thestoredcontentsinmemoryarevolatileandcanvanishveryquickly,asduringapowerfailure.

本句可譯為：當電源出故障時，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。“bank”譯為“存儲體”，是一組芯片，一般九個一組，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

第十七單元計算機硬件基礎

1．中央處理器

中央處理器(CPU)就如同計算機系統(tǒng)的心臟，它的配置決定了計算機運行速度的快慢。中央處理器是計算機部件中最復雜的，基于提供的指令直接負責大多數(shù)計算機系統(tǒng)活動。隨著計算機的更新?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算機。中央處理器包含控制單元和算術(shù)/邏輯單元(ALU)兩部分。

控制單元負責指揮和調(diào)度大部分計算機系統(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/輸出設備間的控制信號流動。

正如沒有汽油無法使用汽車一樣，計算機沒有軟件指令也是不行的。當我們使用軟件時，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轉(zhuǎn)換為計算機能懂的機器語言——低級指令格式。在機器語言中，用二進制數(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行譯碼。針對每條特定的指令，控制單元向計算機系統(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)相加的運算。

如果沒有算術(shù)/邏輯單元，計算機就不可能執(zhí)行許多我們認為有效的任務。算術(shù)/邏輯單元能執(zhí)行所有的數(shù)學和邏輯功能，即加、減、乘、除和比較。這類比較是基礎比較，如“小于”、“大于”和“等于”，可以組成聯(lián)合表達式，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)/邏輯單元控制計算速度，因此要從計算機用戶接收大量信號。早期微機的速度一般用毫秒(千分之一秒)計量。新一代的微機速度則用納秒(十億分之一秒)計量。若把納秒比作一分鐘，則一分鐘就等于1900年！

2．計算機硬件

計算機硬件可分為四類：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)換為適合計算機處理的格式。最常見的輸入設備就是鍵盤。它看起來非常像打字機鍵盤，與典型的打字機鍵位布局一致。還有一組數(shù)字附加鍵，可用于輸入特殊計算機相關代碼。雖然鍵盤并不是可獲得的唯一輸入設備，但是計算機鍵盤是工商業(yè)界最常使用的輸入設備。

2)存儲硬件

存儲硬件按照一定的格式相對永久地存儲計算機指令和數(shù)據(jù)，即關機后數(shù)據(jù)不會丟失，并能在需要處理時方便地找回。存儲硬件以電磁信號或激光蝕刻點的方式存儲數(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、翻譯和引導執(zhí)行計算機提供的軟件指令。處理硬件最常用的部件為中央處理器和主存儲器。

中央處理器如同計算機的大腦，它負責讀和翻譯軟件指令，并處理調(diào)度活動。中央處理器的設計要考慮處理能力和計算機的速度，當然還包括它能有效使用的主存儲器容量。如果你的計算機配備了一個設計良好的中央處理器，你就能在很短的時間內(nèi)完成高復雜度的任務。

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，如果你的計算機存儲器很大，你就能在里面放置更多的簡單軟件指令或高級軟件；一個擁有大存儲器的計算機能勝任處理數(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算機系統(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)。這種設備提供了人與微機的主要的視覺對話方式。當你用鍵盤輸入命令或數(shù)據(jù)時，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)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

計算機系統(tǒng)主機箱稱為系統(tǒng)單元，一般包含有供電電源、系統(tǒng)板和存儲設備(有些存儲設備磁盤驅(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。有些微機內(nèi)的電源還負責給監(jiān)視器供電。

(2)系統(tǒng)板常稱為主板，是微機系統(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所有相關支持電路；④可插入附件的擴展插槽。

(3)存儲設備通常是一個或多個軟驅(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，故常常用于在計算機間拷貝數(shù)據(jù)。

(4)附件：系統(tǒng)板上的擴展插槽允許用戶給計算機系統(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，可使計算機通過電話線或類似的電纜完成數(shù)據(jù)通信；③電池供電時鐘和日歷部件；④附加的打印機接口，可使用戶與多種類型外設通信；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的最大特點就是它只臨時性地存儲數(shù)據(jù)或程序。換句話說，它只在微機開機狀態(tài)進行存儲。一旦關機，RAM中所有的內(nèi)容就立刻消失了。當電源出故障時，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)成即時將你進行的工作存到二級存儲介質(zhì)(如軟盤或硬盤)中的習慣。

對于存儲器，需注意的第二個重要因素是它的容量。RAM芯片的存儲體(存儲體是一組芯片，通常九個一組排成一排)有時位于存儲器擴充插件卡上，適合于安裝在主機機箱內(nèi)并且有時位于主電路板上。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人計算機都配有1

GB左右的RAM，并且允許擴展。擴展RAM和擴展存儲器有兩類方法，選擇哪類方法取決于計算機中微處理器的復雜程度。

2)

ROM

當你打開電源，計算機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，這些對計算機操作起到關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算機內(nèi)部。ROM中存儲的指令可被永久讀取，是非易失的。當計算機斷電后，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?？刹脸删幊讨蛔x存儲器(EPROM)芯片可用專門的紫外線設備改寫；當然，在改寫EPROM內(nèi)的數(shù)據(jù)和程序時，必須將它們從計算機內(nèi)取出來。電可擦除可編程只讀存儲器(EEPROM)芯片不用取出計算機就可以改寫。

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