《信息工程专业英语》课件第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“lookslike”.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.内存，存储器

subsystem n.子系统；次要系统

execute vt.实行；执行

fetch vt.取来；接来；到达；吸引

processor n.处理器；[电脑]处理程序

register n.寄存器

decode vt.[计][通信]译码，解码

basicarchitecture 基本架构

aPalmPilot 一台掌上电脑

bedividedupinto 被划分为

ALU(arithmetic/logicunit) 算术/逻辑单元

CU(controlunit) 控制单元

I/O(input-output)system 输入/输出系统

RAM(RandomAccessMemory) 随机存取存储器

ANDgates 与门

ORgates 或门

NOTgates 非门

Note:JohnVonNeumann约翰·冯·诺依曼，美籍匈牙利人，开创了现代计算机理论，其体系结构沿用至今，早在20世纪40年代他就已预见到计算机建模和仿真技术对当代计算机将产生的意义深远的影响。

2.1.1Exercises

1.PutthePhrasesintoEnglish

(1)人工操作；

(2)唯一的地址；

(3)算数运算；

(4)寄存器；

(5)任何芯片；

(6)正确的命令。

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.

2.1.2参考译文

所有的计算机都有着相同的基本架构，无论是大型机或掌上电脑都有存储器、I/O系统、算术/逻辑单元以及一个控制单元。这种架构被命名为冯·诺依曼体系结构，由数学家约翰·冯·诺依曼构思设计。冯·诺依曼通过广泛描述通用计算机包含的四个基本组成部分着手开始他的“初步探索”。这些基本组成部分和算术、存储器、控制有关，同时也与人工操作密切相连。换言之，算数/逻辑单元(ALU)、存储器、控制单元(CU)和输入输出(I/O)设备，这些就是电脑的经典模型。计算机系统冯·诺依曼结构如图2.1所示。

存储器

电脑的存储器是为电脑执行的所有程序指令和数据提供临时储存的子系统。它通常被称为RAM(RandomAccessMemory，随机存取存储器)。存储器被划分为很多区间，每个区间有一个唯一的地址，可以读取数据。

数学/逻辑单元(ALU)

该子系统正确执行所有的算术运算和比较。在冯·诺依曼体系结构中，算术/逻辑单元(ALU)和控制单元(CU)是单独的组件，但在现代系统中，它们被集成在处理器中。ALU由3个部分组成：寄存器、ALU电路，以及它们之间的通路。该寄存器基本上是一个像RAM的存储单元，并存储计算结果。其运算速度较RAM快得多而且地址不同。ALU电路实际就是执行计算，它和任何芯片一样是由与门、非门、或门设计而成的。

控制单元(CU)

控制单元负责从内存中获取下一个程序的指令，对其进行解码，以确定需要做什么工作，然后发出正确的命令ALU，由存储器和I/O控制器完成这项工作。这些步骤是连续进行的，直到程序的最后一行由QUIT或STOP完成。

输入-输出(I/O)装置

这是一个允许计算机与其他设备交互、与外界通信的子系统。它也负责存储程序，如硬盘驱动器控制。

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