English for IT and EE-17.ppt

TechnicalEnglish ForInformationScienceandElectronicEngineering Unit17 ComputersandNetworks PartI EvolutionofComputers 3 NewWords 4 NewWords 5 1TheevolutionofcomputersandIT Thebirthofcomputersandinformationtechnologygoesbackmanycenturies Thedevelopmentofmathematicsledtothedevelopmentoftoolstohelpincomputation BlaisePascal in17thcenturyFrance wascreditedwithbuildingthefirstcalculatingmachine 在17世纪的法国BlaisePascal因构建了第一台计算机而获得荣誉 6 1 Inthe19thcentury theEnglishmanCharlesBabbage generallyconsideredthefatherofcomputing designedthefirst analyticalengine Thismachinehadamechanicalcomputing mill and liketheJacquardloomoftheearly19thcentury usedpunchcardstostorethenumbersandprocessingrequirements 类似于19世纪早期的提花织布机 采用穿孔卡片来存储数字和处理要求 7 1 AdaLovelaceworkedonthedesignwithhimanddevelopedtheideaofasequenceofinstructions aprogram ThemachinewasnotcompleteatBabbage sdeathin1871 AdaLovelace和他 CharlesBabbage 致力于设计并提出了指令序列的概念 程序 8 2 Almostacenturylater theideasre emergedwiththedevelopmentofelectro mechanicalcalculatingmachines In1890 HermanHollerithusedpunchcardstohelpclassifyinformationfortheUnitedStatesCensusBureau Atthesametime theinventionofthetelegraphandtelephonelaidthegroundworkfortelecommunicationsandthedevelopmentofthevacuumtube Thiselectronicdevicecouldbeusedtostoreinformationrepresentedasbinarypatterns onoroff oneorzero 9 3 Thefirstelectronicdigitalcomputer ENIAC ElectronicNumericalIntegratorandComputer seeFigure17 1 wasdevelopedfortheU S Armyandcompletedin1946 VonNeumann aPrincetonmathematicsprofessor developedtheideafurther 10 3 Headdedtheideaofastoredcomputerprogram Thiswasasetofinstructionsstoredinthecomputermemory whichthecomputerobeyedtocompletetheprogrammedtask 11 4 Fromthisstage computersandcomputerprogrammingevolvedrapidly Themovefromvacuumtubestotransistorssignificantlyreducedthesizeandcostofthemachines andincreasedtheirreliability 从真空管发展到晶体管 大大减小了计算机的尺寸和成本 并提高了可靠性 12 4 Thencameintegratedcircuittechnology whichhasreducedthesize andcost ofcomputers Inthe1960s thetypicalcomputerwasatransistor basedmachinethatcosthalfamilliondollars andneededalarge air conditionedroomandanon siteengineer Thesamecomputerpowernowcosts 2 000andsitsonadesk Ascomputersbecamesmallerandcheaper theyalsobecamefaster madepossiblebyasingleintegratedcircuitcalledachip 需要一个大空调房和一名现场工程师 13 5Evolutionofmicroprocessors microcomputers Theevolutionofmicrocomputersfollowstheevolutionofintegratedcircuit orchip technology Thistechnologyallowscomputerlogictobe burntinto thelayersofachip 计算机逻辑被 烧入 芯片层中 14 5 A5mm2chipcancontainallthelogicneededforacomputerprocessortorunprograms Thistechnologicalbreakthroughmadepossibleamassivereductioninthesizeofcomputers especiallycomparedtotransistor basedlogic wherecomponentswerewiredontoboards 1Thesizereductionenabledlogicswitchingatmanymillionsoftimesasecond 这一技术突破使得计算机的尺寸大大缩小 特别是相比于元件连接在电路板上的晶体管逻辑电路 15 6 Large scaleintegratedcircuitsappearedintheearly1970s Thedevelopmentthatallowedtheprocessortofitonachipalsoallowedchipstobeusedformemory replacingtheexpensiveferritecorememory 这一发展使处理器能安在一个芯片上 也能使芯片用于存储器 代替昂贵的铁氧体磁芯存储器 16 6 Theseadvancesledtothebirthofthemicrocomputer orpersonalcomputer initiallyaimedatthehobbyistmarket Bytheearly1970s machineswerebeingproducedforhomeandofficeuse Ofalltheearlymicrocomputers theAppleandIBM Figure17 2 familiesofmachineshavesurvivedtobecomethemajorplayersinthemarket 17 7 Theoperatingsystemisthesoftwarethatprovidesaninterfacebetweenthehardware thecomputeritself andtheuser Itmanagesthehardwareandenablestheusertocontrolthecomputer MicrosoftdevelopedthefirstoperatingsystemforIBMmachines MSDOS MicrosoftDiskOperatingSystem thegrandfatherofthecurrentDOSandWindowssystems Manymanufacturersdevelopedclones orcopies oftheIBMmachinesthatcouldrunwithMSDOS 18 7 TheIBMfamilyisbasedontheIntel8086familyofchips whichevolvedintothehigh speedPentiumchipslater Atthesametime theAppleComputerCompanystarteditsfamilyofmachines TheyfirstbecamepopularwiththelaunchoftheApple2Ecomputer followedbytheMacintoshseries allbasedontheMotorola68000familyofmicroprocessorchips 19 8 Asthetechnologyevolved thenumberofcircuitsthatcouldgoonachipgrew Verylarge scaleintegration VLSI chipswitchingratesweremeasuredinhundredsofmillionsofswitchingspersecond VLSItechnologyhasenabledpersonalcomputerstohaveaprocessingspeedhundredsoftimesfasterthantheearlychips 随着技术的发展 容纳在一个芯片上的电路数量增加了 20 9 Thisadditionalprocessingpowerwasparalleledbyagrowthinthecapacityandspeedofmemorychips Again automationofmanufacturingandminiaturizationwerethekeyfactors Peripheraldevices hardwarecomponentsthatprovidethemeansforinput outputandstorage alsodevelopedinspeedandothercapabilitiestokeeppacewiththeincreasedfunctionofthecomputersthemselves 2 外围设备 提供输入 输出 存储手段的硬件设备 也在速度和其他功能方面得到发展以保持与计算机本身功能的同步增长 21 9 Monitors printersandstoragedevicesallevolvedrapidlywithbothimprovedapplicationofexistingtechnologyandtheintroductionofnewtechnologies Therewereevennewclassesofperipheraldevices suchasscannersandsoundsynthesizers whichfurtherenhancedandbroadenedthewaysinwhichcomputerscouldbeused 22 10 Forexample therewasatransitionfromearlymonochromemonitorsforoutputdisplayoftextonlytocolormonitorswithgraphicscapability Thestoragecapacityofdiskdriveshasincreaseddramatically fromdriveswhosecapacitywasmeasuredinkilobytes 1000bytes tothosewhosecapacityismeasuredingigabytes 1 000 000 000bytes 从仅仅用于文本输出显示的单色显示器到有图形显示功能的彩色显示器的变迁 23 11 Themotherboardisthemaincomponentofanycomputer containingthemicroprocessorandmemorychips Italsocontainsthebus ahigh speedlinkthatenablesalltheperipheraldevicesattachedtoyourmachinetocommunicatewitheachotherandthemicroprocessor 使所有外围设备连到你的机器的高速链接 以使外设相互通信以及和微处理器通信 24 11 Someperipheralsareintheformofcircuitboardsthatplugintothemotherboardbus whileothersareexternaldeviceswhichconnectusingacable Mostperipheralshavesomeonboardlogic 插入母板总线的电路板 25 12 Mostremarkableinthismassiveincreaseinthepowerandversatilityofmicrocomputersisthefactthatithasbeenachievedatnopriceincreasetotheuser becauseofmanufacturingimprovementsmadepossiblebyautomationandminiaturization 3 在微计算机功能和用途的巨大增长中最令人瞩目的事实是 这种增长在不提高用户承担的价格情况下实现 因为自动化和小型化使得制造工艺的改进成为可能 26 12 Astate of the artpersonalcomputercostsaboutthesametodayasitdidin1980 lessifyouaccountforinflation 今天最新的个人计算机与1980年的价钱差不多 考虑到通货膨胀的话就更低 27 13 Ascomputershavebecomemorepowerful muchofthisadditionalcomputingpowerhasbeenusedupbysoftwarethatmakescomputerseasiertouse 4 随着计算机功能变得更加强大 所增加的大部分计算功能都被使计算机更易使用的软件用足了 28 13 Massmarketingofpersonalcomputersreliesonaproductfortheworkplaceorhomethatdoesnotrequiretheusertoundergoextensivetraining ThesoftwareevolutionbeganwiththeXEROXCompany whichdevelopedagraphicalinterfaceandamousetoselecttheoperationstoperform ratherthanusingcommandkeys 个人计算机的大规模销售依赖于它是用于办公场所或家庭的 不需要对用户进行大量培训的产品 29 13 Theideaofagraphicaluserinterface GUI wastakenonbytheAppleCompanyandusedonitsMacrangeofcomputers These point and click machinessetastandardforusabilitythatwasemulatedbytheWindowsGUInowusedoneverypersonalcomputer 这些 点击 机器制定了一个可用性标准 现在用于每台个人计算机的Windows图形用户界面仿效了这一标准 30 14 Microcomputertechnologyisstillevolving Latercomputerswereenabledtoaccommodatevoiceinputandoutput ThedevelopmentandwidespreaduseofpowerfulcommunicationstoolsforcomputersledtothemasspopularizationoftheInternet whichisfuelinganothergrowthspurtintheindustryanditstechnology 5 强有力的通信工具的开发和广泛使用使互联网大为普及 又引起了 计算机 工业和相关技术的新一轮发展高潮 31 14 Continuingsuccessinthemarketplacedependsonthecontinualdevelopmentofsoftwaretomakemachinesbotheasiertouseandmoreversatile Microcomputersoftwareisdevelopinginthedirectionofartificialintelligence 微型机软件正朝着人工智能方向发展 32 14 Oneexampleofthisis smart businesssoftwarethathelpstheusermakedecisionsbyanalyzingdataforpatternsofbehaviorandthenapplyingthosepatternstonewsituations 6 一个例子是 聪明 商务软件 它帮助用户分析行为模式数据并将这些模式用于新的情况 据此作出决策 33 15Usingmicrocomputers Thefirsttoolstobeusedwidelyonmicrocomputerswerewordprocessors spreadsheets anddatabasesystems The bigthree enabledthecomputertobecomeusefulveryquickly asusersdidnotneedspecializedprogrammingknowledge Thewordprocessorhasgrownfromasimpleletter writingtooltoaproductcapableofdesktoppublishing 文字处理 软件 电子表格 和数据库系统 34 15 Thespreadsheethasgrowntoincorporatestandardtoolsforstatisticalandfinancialanalysis customprogramming andproducinghigh qualitygraphics Themicrocomputerdatabasehasgrownfromasimplefile managementtooltoonethathandlescomplexapplicationsacrossmultiplefiles 7 微机数据库已从一个简单的文档管理工具发展成为在多文档之间处理复杂应用的工具 35 16 IntegratedpackageslikeMicrosoftOfficeenabletheapplicationmodulesto talktoeachother Withthesepackages youcandevelopareportinawordprocessorthatincludesgraphsfromspreadsheetsthatweredevelopedfromdataselectedfromdatabaserecords 8 有了这些软件包 你可以在文字处理器中创建报告 其中包括由电子表格所产生的图 电子表格又是根据数据库中选择的数据制作的 36 16 Furthertothat youcannowcreatea living document Asdatainthespreadsheetchanges thereportchanges Linksbetweenthetoolsareembeddedinthedocument TheMicrosoftversionofthisiscalled ObjectLinkingandEmbedding 37 16 YoumayaddotherpicturesfromgraphicallibrariesandimportmaterialsviatheInternetusingbuilt incommunicationssoftware Thewholedocumentisprofessionallypresentedusingawordprocessorormultimediapresentationmanager 38 16 Thewordprocessorcanalsocheckspellingandgrammar aswellascreatethetableofcontentsandindexes Anintegratedpackagemayincludeaprofessionalpresentationmanagerthatallowsyoutodevelopslideshowsthatcanthenbedeliveredonthecomputeroranyscreen 39 17 Client servertechnologyallowsdifferentmicrocomputerstoshareinformation accessfiles printers etc andcommunicatewitheachother Aparalleldevelopment calledworkgroupcomputing hasfocusedonsoftwarethatautomatestheflowofinformationinanorganizationtofacilitateelectronicconferencingandsimilaractivities 平行开发的工作组计算把重心放在软件上 软件使一个组织 机构 中的信息流自动化以便于电子会议和类似的活动 40 18 Inaddition thereareavastnumberofmorespecializedapplicationspackagessuchasCorelDrawforgraphics AutoCADfordesigndrawings andfinancialsoftwaresuchasACCPACforautomatingbookkeepingandaccountingfunctions Newusesforcomputertechnologyarefounddaily inmedicine education theartsandeveryotherfieldofhumanendeavor 为自动记账和结算功能开发的财务软件 如ACCPAC 41 19 Issuesofcompatibilitybetweenplatformsarebeingresolved Mostmajorsoftwareproductscannowprocessthedatacreatedusingthemajorcompetitors products 42 19 Usersneedasmoothtransitionfromoldersoftwareproductstonewones astheyoftenhaveasignificantinvestmentintherecordsthatexistontheircomputers Ingeneral newersoftwarecanautomaticallytranslatedocumentsproducedinearliersoftwareapplications 用户需要从旧版软件产品到新版软件的平稳过渡 因为它们往往在自己计算机的记录上投入很大 PartII LocalAreaNetworks 44 NewWords 45 NewWords 46 NewWords 47 1TheneedforLANs PerhapsthedrivingforcebehindthewidespreaduseofLANsisthedramaticandcontinuingdecreaseincomputerhardwarecosts accompaniedbyanincreaseincomputerhardwarecapability Yearbyyear thecostofcomputersystemscontinuestodropdramaticallywhiletheperformanceandcapacityofthosesystemscontinuetoriseequallydramatically 48 1 Thisongoingtechnologicalrevolutionhasenabledthedevelopmentofapplicationsofastoundingcomplexityandpower Forexample desktopapplicationsthatrequirethegreatpoweroftoday smicroprocessor basedsystemsincludethefollowing 49 1 Imageprocessing Speechrecognition Videoconferencing Multimediaauthoring Voiceandvideoannotationoffiles 50 2 Workstationsystemsnowsupporthighlysophisticatedengineeringandscientificapplications aswellassimulationsystems andtheabilitytoapplyworkgroupprinciplestoimageandvideoapplications 1 现在工作站系统支持极为复杂的工程和科学应用 也支持仿真系统 以及将工作组原则用于图像和视频应用中 51 2 Inaddition businessesarerelyingonincreasinglypowerfulserverstohandletransactionanddatabaseprocessingandtosupportmassiveclient servernetworksthathavereplacedthehugemainframecomputercentersofyesteryear 2 此外 商业事务正在依赖于愈来愈强大的服务器来进行交易和数据库处理 支持已经取代了以往大型中央计算机的大规模的客户 服务器网络 52 3 Allofthesefactorsleadtoanincreasednumberofsystems withincreasedpower atasinglesite officebuilding factory operationscenter andsoon Atthesametime thereisanabsoluterequirementtointerconnectthesesystemstoshareandexchangedataamongsystems andtoshareexpensiveresources 53 4 Theneedtosharedataisacompellingreasonforinterconnection Individualusersofcomputerresourcesdon tworkinisolation Theyneedfacilitiestoexchangemessageswithotherusers toaccessdatafromseveralsourcesinthepreparationofadocumentorforananalysis andtoshareproject relatedinformationwithothermembersofaworkgroup 3 他们需要拥有手段与其他用户交换信息 在准备文件或作分析时访问多处来源的数据 与工作组其他成员共享与项目有关的信息 54 5 Theneedtoshareexpensiveresourcesisanotherdrivingfactorinthedevelopmentofnetworks Thecostofprocessorhardwarehasdroppedfarmorerapidlythanthecostofmassstoragedevices videoequipment printers andotherperipheraldevices 55 5 Theresultisaneedtosharetheseexpensivedevicesamonganumberofuserstojustifythecostoftheequipment Thissharingrequiressomesortofclient serverarchitectureoperatingoveraLANthatinterconnectsusersandresources 这种共享需要工作在连接用户和资源的局域网上的某种客户 服务器结构 56 6LANapplications ThevarietyofapplicationsforLANsiswide ToprovidesomeinsightintothetypesofrequirementsthatLANsareintendedtomeet thefollowingsectionsdiscusssomeofthemostimportantgeneralapplicationareasforthesenetworks 57 7PersonalcomputerLANs AcommonLANconfigurationisonethatsupportspersonalcomputers Withtherelativelylowcostofsuchsystems individualmanagerswithinorganizationsoftenindependentlyprocurepersonalcomputersfordepartmentalapplications suchasspreadsheetandprojectmanagementtools andforInternetaccess 4 由于这种系统相对较低的价格 机构中个别经理人员常为本部门的应用如电子表格和项目管理工具 访问互联网而独立购买个人计算机 58 8 Butacollectionofdepartment levelprocessorswon tmeetallofanorganization sneeds centralprocessingfacilitiesarestillrequired Someprograms suchaseconometricforecastingmodels aretoobigtorunonasmallcomputer Corporate widedatafiles suchasaccountingandpayroll requireacentralizedfacilitybutshouldbeaccessibletoanumberofusers Inaddition thereareotherkindsoffilesthat althoughspecialized mustbesharedbyanumberofusers 59 8 Further therearesoundreasonsforconnectingindividualintelligentworkstationsnotonlytoacentralfacilitybuttoeachotheraswell 5Membersofaprojectororganizationteamneedtoshareworkandinformation Byfarthemostefficientwaytodosoistoestablishanetwork 而且有充足理由将各个智能工作站不仅与中央设备相联 还要彼此相联 60 9 Certainexpensiveresources suchasadiskoralaserprinter canbesharedbyallusersofthedepartmentalLAN Inaddition thenetworkcantieintolargercorporatenetworkfacilities Forexample thecorporationmayhaveabuilding wideLANandawideareaprivatenetwork Acommunicationsservercanprovidecontrolledaccesstotheseresources 61 10 LANsforthesupportofpersonalcomputersandworkstationshavebecomenearlyuniversalinorganizationsofallsizes Eventhosesitesthatstilldependheavilyonthemainframehavetransferredmuchoftheprocessingloadtonetworksofpersonalcomputers Perhapstheprimeexampleofthewayinwhichpersonalcomputersarebeingusedistoimplementclient serverapplications 62 11 Forpersonalcomputernetworks akeyrequirementislowcost Inparticular thecostofattachmenttothenetworkmustbesignificantlylessthanthecostoftheattacheddevice Thus fortheordinarypersonalcomputer anattachmentcostinthehundredsofdollarsisdesirable 链接网络的成本必须大大低于链接设备的成本 63 11 Formoreexpensive high performanceworkstations higherattachmentcostscanbetolerated Inanycase thissuggeststhatthedatarateofthenetworkmaybelimited ingeneral thehigherthedatarate thehigherthecost 64 12Back endnetworks storageareanetworks Back endnetworksareusedtointerconnectlargesystemssuchasmainframes supercomputers andmassstoragedevices Thekeyrequirementhereisforbulkdatatransferamongalimitednumberofdevicesinasmallarea Highreliabilityisgenerallyalsoarequirement Thesearesometypicalcharacteristics 65 12 Highdatarate Tosatisfythehigh volumedemand dataratesof100Mbpsormorearerequired High speedinterface Datatransferoperationsbetweenalargehostsystemandamassstoragedevicearetypicallyperformedthroughhigh speedparallelI Ointerfaces ratherthanslowercommunicationsinterfaces Thus thephysicallinkbetweenstationandnetworkmustbehighspeed 66 12 Distributedaccess Somesortofdistributedmediumaccesscontrol MAC techniqueisneededtoenableanumberofdevicestosharethemediumwithefficientandreliableaccess Limiteddistance Typically aback endnetworkwillbeemployedinacomputerroomorasmallnumberofcontiguousrooms 67 12 Limitednumberofdevices Thenumberofexpensivemainframesandmassstoragedevicesfoundinthecomputerroomgenerallynumbersinthetensofdevices 6 计算机房中昂贵的主机和大容量存储设备的数量一般以几十台计 68 13 Back endnetworksarecommonlyfoundatsitesoflargecompaniesorresearchinstallationswithlargedata processingbudgets Becauseofthescaleinvolved asmalldifferenceinproductivitycanmeanmillionsofdollars 由于涉及的规模 工作效率的微小差别意味着百万美元的差异 69 14 Considerasitethatusesadedicatedmainframecomputer Thisimpliesafairlylargeapplicationorsetofapplications Astheloadatthesitegrows theexistingmainframemaybereplacedbyamorepowerfulone perhapsamultiprocessorsystem 70 14 Atsomesites asingle systemreplacementwon tbeabletokeepup equipmentperformancegrowthrateswillbeexceededbydemandgrowthrates Thefacilitywilleventuallyrequiremultipleindependentcomputers Again therearecompellingreasonsforinterconnectingthesesystems Thecostofsysteminterruptishigh soitshouldbepossible easilyandquickly toshiftapplicationstobackupsystems 7 系统中断的代价是昂贵的 所以应该具有方便而快捷地将应用转移到备份系统的能力 71 14 Itmustbepossibletotestnewproceduresandapplicationswithoutdegradingtheproductionsystem Largebulk storagefilesmustbeaccessiblefrommorethanonecomputer Loadlevelingshouldbepossibletomaximizeutilizationandperformance 72 15 Obviously somekeyrequirementsforback endnetworksaretheoppositeofthoseforpersonalcomputerLANs Highdataratesarerequiredtokeepupwiththework whichtypicallyinvolvesthetransferoflargeblocksofdata Theequipmentforachievinghighspeedsisexpensive Fortunately giventhemuchhighercostoftheattacheddevices suchcostsarereasonable 8 实现高速度的设备是昂贵的 幸亏考虑到联在上面的设备更要贵得多 这种价格还是合理的 73 16 Aconceptrelatedtothatoftheback endnetworkisthestorageareanetwork SAN ASANisaseparatenetworktohandlestorageneeds TheSANuntiesstoragetasksfromspecificserversandcreatesasharedstoragefacilityacrossahigh speednetwork Thecollectionofnetworkedstoragedevicescanincludeharddisks tapelibraries andCDarrays 74 16 MostSANsusefiberchannels InatypicallargeLANinstallation withanumberofserversandperhapsmainframes eachhasitsowndedicatedstoragedevices Ifaclientneeds