《信息工程專業(yè)英語》課件第2章

Unit2TheBasicsofComputerSystem2.1Text2.2ReadingMaterials

2.1Text

TheVonNeumannArchitectureofComputerSystemAllcomputerssharethesamebasicarchitecture,whetheritisamainframeoraPalmPilot.Allhavememory,anI/Osystem,andarithmetic/logicunit,andacontrolunit.ThistypeofarchitectureisnamedVonNeumann’sArchitectureafterthemathematician,JohnVonNeumannwhoconceivedofthedesign.

JohnVonNeumannbeginshis“PreliminaryDiscussion”withabroaddescriptionofthegeneral-purposecomputingmachinecontainingfourbasiccomponents.Theseareknownasrelatingtoarithmetic,memory,control,andconnectionwiththehumanoperator.Inotherwords,thearithmetic/logicalunit(ALU),thememory,thecontrolunit(CU),andtheinput-output(I/O)devicesthatweseeintheclassicalmodelofwhatacomputer“l(fā)ookslike”.VonNeumannArchitectureofComputerSystemisshowninFig2.1.Fig2.1VonNeumannArchitectureofComputerSystem

Memory

ComputerMemoryisthesubsystemthatservesastemporarystorageforallprograminstructionsanddatathatarebeingexecutedbythecomputer.ItistypicallycalledRAM(RandomAccessMemory).Memoryisdividedupintocells,eachcellhavingauniqueaddresssothatthedatacanbefetched.

Arithmetic/logicalunit(ALU)

Thissubsystemistoperformallarithmeticoperationsandcomparisonsforequality.IntheVonNeumann’sarchitecture,thearithmetic/logicalunit(ALU)andtheControlUnit(CU)areseparatecomponents,butinmodernsystemstheyareintegratedintotheprocessor.TheALUhas3sections,theregister,theALUcircuitry,andthepathwaysinbetween.TheregisterisbasicallyastoragecellthatworkslikeRAMandholdstheresultsofthecalculations.ItismushfasterthanRAMandisaddressesdifferently.TheALUcircuitryisthatactuallyperformsthecalculations,anditisdesignedfromAND,OR,andNOTgatesjustasanychip.

ControlUnit(CU)

Thecontrolunitisresponsibleforfetchingthenextprograminstructiontoberunfrommemory,decodeittodeterminewhatneedstobedone,andthenissuethepropercommandtotheALU,memoryandI/Ocontrollerstogetthejobdone.Thesestepsaredonecontinuouslyuntilthelastlineofaprogramisdone,whichisusuallyQUITorSTOP.

Input-output(I/O)devices

Thisisthesubsystemthatallowsthecomputertointeractwithotherdevicesandcommunicatetotheoutsideworld.Italsoisresponsibleforprogramstorage,suchasharddrivecontrol.

Technicalwordsandphrases

memory n.內(nèi)存，存儲(chǔ)器

subsystem n.子系統(tǒng)；次要系統(tǒng)

execute vt.實(shí)行；執(zhí)行

fetch vt.取來；接來；到達(dá)；吸引

processor n.處理器；[電腦]處理程序

register n.寄存器

decode vt.[計(jì)][通信]譯碼，解碼

basicarchitecture 基本架構(gòu)

aPalmPilot 一臺(tái)掌上電腦

bedividedupinto 被劃分為

ALU(arithmetic/logicunit) 算術(shù)/邏輯單元

CU(controlunit) 控制單元

I/O(input-output)system 輸入/輸出系統(tǒng)

RAM(RandomAccessMemory) 隨機(jī)存取存儲(chǔ)器

ANDgates 與門

ORgates 或門

NOTgates 非門

Note:JohnVonNeumann約翰·馮·諾依曼，美籍匈牙利人，開創(chuàng)了現(xiàn)代計(jì)算機(jī)理論，其體系結(jié)構(gòu)沿用至今，早在20世紀(jì)40年代他就已預(yù)見到計(jì)算機(jī)建模和仿真技術(shù)對(duì)當(dāng)代計(jì)算機(jī)將產(chǎn)生的意義深遠(yuǎn)的影響。

2.1.1Exercises

1.PutthePhrasesintoEnglish

(1)人工操作；

(2)唯一的地址；

(3)算數(shù)運(yùn)算；

(4)寄存器；

(5)任何芯片；

(6)正確的命令。

2.PutthePhrasesintoChinese

(1)general-purposecomputingmachine;

(2)humanoperator;

(3)classicalmodel;

(4)temporarystorage;

(5)programinstructionsanddata;

(6)harddrivecontrol.

3.Translation

(1)Memoryisdividedupintocells,eachcellhavingauniqueaddresssothatthedatacanbefetched.

(2)IntheVonNeumann’sarchitecture,thearithmetic/logicalunit(ALU)andtheControlUnit(CU)areseparatecomponents,butinmodernsystemstheyareintegratedintotheprocessor.

(3)Thecontrolunitisresponsibleforfetchingthenextprograminstructiontoberunfrommemory,decodeittodeterminewhatneedstobedone,andthenissuethepropercommandtotheALU,memoryandI/Ocontrollerstogetthejobdone.

2.1.2參考譯文

所有的計(jì)算機(jī)都有著相同的基本架構(gòu)，無論是大型機(jī)或掌上電腦都有存儲(chǔ)器、I/O系統(tǒng)、算術(shù)/邏輯單元以及一個(gè)控制單元。這種架構(gòu)被命名為馮·諾依曼體系結(jié)構(gòu)，由數(shù)學(xué)家約翰·馮·諾依曼構(gòu)思設(shè)計(jì)。馮·諾依曼通過廣泛描述通用計(jì)算機(jī)包含的四個(gè)基本組成部分著手開始他的“初步探索”。這些基本組成部分和算術(shù)、存儲(chǔ)器、控制有關(guān)，同時(shí)也與人工操作密切相連。換言之，算數(shù)/邏輯單元(ALU)、存儲(chǔ)器、控制單元(CU)和輸入輸出(I/O)設(shè)備，這些就是電腦的經(jīng)典模型。計(jì)算機(jī)系統(tǒng)馮·諾依曼結(jié)構(gòu)如圖2.1所示。

存儲(chǔ)器

電腦的存儲(chǔ)器是為電腦執(zhí)行的所有程序指令和數(shù)據(jù)提供臨時(shí)儲(chǔ)存的子系統(tǒng)。它通常被稱為RAM(RandomAccessMemory，隨機(jī)存取存儲(chǔ)器)。存儲(chǔ)器被劃分為很多區(qū)間，每個(gè)區(qū)間有一個(gè)唯一的地址，可以讀取數(shù)據(jù)。

數(shù)學(xué)/邏輯單元(ALU)

該子系統(tǒng)正確執(zhí)行所有的算術(shù)運(yùn)算和比較。在馮·諾依曼體系結(jié)構(gòu)中，算術(shù)/邏輯單元(ALU)和控制單元(CU)是單獨(dú)的組件，但在現(xiàn)代系統(tǒng)中，它們被集成在處理器中。ALU由3個(gè)部分組成：寄存器、ALU電路，以及它們之間的通路。該寄存器基本上是一個(gè)像RAM的存儲(chǔ)單元，并存儲(chǔ)計(jì)算結(jié)果。其運(yùn)算速度較RAM快得多而且地址不同。ALU電路實(shí)際就是執(zhí)行計(jì)算，它和任何芯片一樣是由與門、非門、或門設(shè)計(jì)而成的。

控制單元(CU)

控制單元負(fù)責(zé)從內(nèi)存中獲取下一個(gè)程序的指令，對(duì)其進(jìn)行解碼，以確定需要做什么工作，然后發(fā)出正確的命令A(yù)LU，由存儲(chǔ)器和I/O控制器完成這項(xiàng)工作。這些步驟是連續(xù)進(jìn)行的，直到程序的最后一行由QUIT或STOP完成。

輸入-輸出(I/O)裝置

這是一個(gè)允許計(jì)算機(jī)與其他設(shè)備交互、與外界通信的子系統(tǒng)。它也負(fù)責(zé)存儲(chǔ)程序，如硬盤驅(qū)動(dòng)器控制。

2.2ReadingMaterials

AbbreviatedasOS,anoperatingsystemisapowerful,andusuallylarge,programthatcontrolsandmanagesthehardwareandothersoftwareonacomputer.

ThemostpopularoperatingsystemstodayincludeversionsofMicrosoftWindows(likeWindows10,Windows8,Windows7,WindowsVista,andWindowsXP),Apple’sMacOS,andflavorsoftheopensourceoperatingsystemLinux.

Windows10(Fig2.2)isthenameforthenextMicrosoftWindowsoperatingsystem.TheinternalMicrosoftcodenameforWindows10isThresholdandthepresumednamewasWindows9butMicrosoftdecidedtoskipthatnumberaltogether.Windows10willintroduceanupdatedStartMenu,anotificationcenter,andsupportforvirtualdesktops.It’salsorumoredthatMicrosoftwillremovetheCharmsBarinWindows10,firstintroducedinWindows8.CortanamayalsobeavailableasanappinWindows10,evenfortraditionalcomputers.Whilethisisnotconfirmed,I'vealsoheardthatWindows10maybeafreeupgradeforWindows8owners.

Fig2.2InterfaceofWindows10

WhilenoofficialreleasedatehasbeenannouncedbyMicrosoft,Windows10isrumoredtobereleasedonorclosetoApril,2015.Windows10,oncereleased,willbethesuccessortoWindows8,Microsoft’smostcurrentversionofWindows.It’sverylikelythatWindows10willbereleasedinthreephases,similartohowWindows8wasreleased.FirstisWindows10EnterpriseTechnicalPreview,whichisabetareleaseforsoftwareandhardwaremakers,aswellastesters.

ThisversionofWindows10wasmadeavailableonOctober1,2014.SecondwilllikelybeaWindows10ConsumerPreview,ormaybeWindows10RC(ReleaseCandidate),whichisanalmost-ready,limited-time-useversionthatMicrosoftwillreleaseforfreetoawideraudience,inreturnforfeedback.Thisshouldbereleasedinearly2015.ThethirdandfinalreleasewillbethefinalcopyofWindows10,whichwillbereferredtoatMicrosoftandtocomputermakersasWindows10RTM(ReleasetoManufacturing).ThisistheversionofWindows10youwillbeabletopurchaseinApril,2015.

Windows10maybethelastmajorversionofWindowsever,withsmaller,moreincremental,improvementsmadeviaupdatesintothefuture.

2.2.2ComputerLanguages

MostCommonComputerLanguages

Thepopularityanduseofcomputerprogramminglanguagesvariesovertime,butthereareafewthathaveremainedwidelyusedforanumberofyears.Programminglanguagesareusedwithinmanydifferentcontexts,includingwebanddesktopapplications.Manyprogrammersareproficientinmorethanonelanguage,andtheavailablelanguagesaresuitedtodifferenttypesoftask.Likenaturallanguages,programminglanguagesvaryintermsofsyntaxaswellasvocabulary.

Java

Javahasremainedthemostwidelyusedlanguageforsometime.Javacanbeusedtodevelopapplicationsfortheweb,desktopandlaptopPCs,andformobiledevicesrunningmanydifferentplatformssuchasAndroid.JavaisdevelopedbySunMicrosystems,nowpartofOracle,andfeaturessimilarstructurestoolderlanguagessuchasC.Javaapplicationsaretypicallycreatedusingobject-orienteddevelopment,throughwhichapplicationresponsibilitiesaredividedupbetweenwell-definedobjects.

C

TheClanguagewasoriginallydevisedinthelate1960sandisusedtodevelopoperatingsystemsaswellasapplications.Inadditiontobeingoneofthemostusedcomputerlanguageshistorically,ChasinfluencedmanyotherpopularlanguagesincludingJava,C++andC#,anditssyntaxfeaturescanbeseenthroughoutprogrammingresources.Cisanimperativelanguage,carryingoutrequiredfunctionalitythroughaseriesofimperativeinstructions.

C++

C++wasinitiallydesignedinthelate1970sasanalternativetoC,withadditionalfeatures.C++hascharacteristicsofbothhigh-andlow-levelprogramminglanguages.High-levelprogramminginvolvesagreaterdegreeofabstraction,whereaslow-levelprogrammingcontainsmoredirectreferencestotheimplementationofaprogramwithinasystem.C++hascontinuedtobeusedbymanyprogrammers,tocreatebothsystemsandapplications.

C#

C#wasreleasedin2000,andwasinitiallyintendedtoprovideobject-orienteddevelopmentwithinMicrosoft’s.NETframework.C#canbeusedforotherprogrammingmethods,includingimperativeandfunctionaltechniques.C#isprimarilyusedinwebcontexts,todevelopInternetapplicationsandcomponents,butcanalsobeusedforsoftwareapplications.ProgrammerswhoarefamiliarwithCandC++typicallyfindC#easiertolearn,duetothesimilaritiesinsyntax.

PHP

PHP(officiallyPHP:HypertextPreprocessor)isoneofthemostwidelyusedserver-sidescriptinglanguagesontheweb.PHPcanbeusedtobuildpowerfulwebapplicationsinconjunctionwithHTMLandotherservertechnologiessuchasdatabases.PHPisusedtobuildwebsites,buildingHTMLstructureswhentheuserrequestsapageataparticularwebaddressandsendingthepagecontenttotheuser’sbrowser,whereitcanberenderedandinteractedwith.

2.2.3Viruses

TypesofComputerViruses

Youarealreadyawareofwhatcomputersareandwhatfunctionstheyperform.Beingapartofthismodernera,youmustcomeacrosswiththeterm“ComputerVirus”manytimes,whichisthebasiccauseofcomputerinfection.Itcorruptsthecomputerfilesandaffectsitsfunctioning.AviruscanspreadfromonecomputertoanotherbymeansofnetworkorbyanyremovablemediumlikeCDs,DVDs,FloppyandUSBDrives,whichmaycarryvirus.Thespreadingofthemaliciouscodeofthesevirusesisgenerallyfacilitatedbytheinternet.

Avirusisacomputerprogramthatcaneasilyreplicateitselfandcausecomputerinfection.Thissoftwareiswrittendeliberatelytomakeitsentryinacomputerwithoutanynotificationorpermissionoftheuser.Thesenastyprogramsinstallthemselves.Therearevarioustypesofviruses,whichdependsonthemaliciouseffecttheycause.Notallareequallymaliciousbuttheusershouldcheckthatitisremovedassoonaspossible,nomatteritismoreorlessharmful.Themostcommontypesofviruseslistedandexplainedbelow.Justhavealook.

ResidentViruses

Itisoneofthemostcommontypesofvirus,whichresidesinthecomputermemoryalsoknownasRAM.Thefunction,whichitperforms,istoinfectthealreadyinstalledprogramsandtheprograms,whichmayinstalledinfuture.Thisallhappensbyincorporatingamaliciouscodeinthememoryofthecomputer.Theyachievethisbyallocatingaspacefortheminthememoryofthecomputer.Thevirusescanaffecttheotherfilesonlybyestablishingaprocess,whichcanactivatethemaliciouscodetofunction.

Therearevarioustypesofprocesses,whichdevelopedbythevirusestostartitsfunctioning.ThemostcommonofthemisTSR(Terminate-Stay-Resident)interruptfunctionandmanipulationofMCBs(MemoryControlBlocks).TheTSRinterruptfunctioningmethodissimplestforthevirustoarouseinfectionbutthescannerscanalsodetectitveryeasily.Thisinterruptsalltheexecutionsbycorruptingprogramsandfilesthatclosed,openedorrenamed.

Thedetectionisveryeasyasitachievedbyreferringtothelocalharddrive’smap.Theresidentvirusdetectedbyantiviruswithin-depthscanningefficiencyonly.TheexamplesofthistypeofvirusesareMeve,Mrklunky,RandexandCMJ.

OverwriteViruses

ThistypeofvirusesinfectsthewiderangeofoperatingsystemssuchasMacintosh,Linux,Dosandwindows.Thevirusgenerallyattacksafile,whichbecomesitsvictimandafterthis,thevirusoverwritethefilewiththemaliciouscode.Iftheinfectionnotdetectedontime,theinfectedfilecancausedamagetotheotherfilesirreversibly.Thecomputersysteminfectedwithsuchtypeofvirusbecomesinoperableanddonotperformfunctionsnormally.Theinfectedfilescannotdisinfectbuttheonlythingcanhappenistheremovalofthecorruptedfileandrestoringitfromthebackupresource.TheexamplesofthistypeofvirusesareTrivial.88.D,Way,Trj.Reboot.

DirectActionViruses

Whenthisvirusisexecutedinthecomputeritstartsreplicatingandtakingactiononthefilesanddirectories.TheseinfectthefilesinadirectoryandalsothedirectorieshavingthosefilesthatarespecifiedintheAUTOEXEC.BATfilepath.Generally,batchfilesofthistypearelocatedintherootdirectoryoftheharddriveanditalsoperformssomefunctionswhenthecomputerisbooted.

Bootviruses

Thesearetheviruseswhichaffectthebootsectorofthediskettesandtheharddrives.Everyharddriveordiskettehassectorsandthefirstsectorisknownasthebootsector.IthasMBR(MaterBootRecord)whichfunctionstoreadandloadtheOS(OperatingSystem).Ifyoure-bootthecomputerwhilethediskhavingvirusinfectedbootisinthedrivethenitcancauseinfectiontotheharddriveofthesystem.Assoonastheharddrivegetsinfected,allthedisketteswillautomaticallygetinfected.Youcancheckthisvirusbyusingantivirussoftware.

PolymorphicViruses

Thisisoneofthosetypesofviruseswhichareverycomplexthreatstocomputers.Everytometheyinfectthecomputersystem,theyproducecopiesofthemselvesbyencryptingorencodingthemisadifferentway.Allthecopiesarefunctionallyactivebutslightlymodifiedofthepreviousone.Toencryptinadifferentway,theyusedifferentencryption