英语科普文选合集中英文对照计算机互联网通信优质文档.docx
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英语科普文选合集中英文对照计算机互联网通信优质文档
英语科普文选(中英对照)
计算机与因特网插件指南
Lifeon-linecanbeamuchricherexperiencewhenyouaren'trestrictedtojustwrittenwordsandstillpictures.Evenifyou'renewtotheNet,you'veprobablyheardaobutmultimediaon-line--listeningtoaudio,watchinganimationsandvideos,evenplayinginthree-dimensionalspace.Soundandmovementmakeinformationcomealive.
Toexperienceit,you'llneedspecialpiecesofsoftwarecalledplug-ins.Theterm"plug-in"referstoasmall,add-onpieceofsoftwarewhichextendsthecapabilitiesofyourwebbrowser,likeNetscapeNavigatororMicrosoftExplorer,turningyourcomputerintoaradioorTV.
Whenyouarriveatawebpagewhichcontainsafilerequiringaplug-inwhichyoudon'thave,youwillusuallyreceiveamessageaskingifyouwanttogetitbydownloadingitandinstallingitintoyourcomputer.Mostofthetime,theinstallationwillbeautomatic.
Occasionally,you'llrunintoadownloadedfilewhichneedstobedecompressedorun-zippedbeforeinstallation.Onceinstalled,plug-insrunautomatically,withoutyouhavingtodoanything.
Manymultimediacontrolsstillneedtobeobtainedfromthedeveloperbutareinstalledautomatically.
Shockwaveisagoodexampleofthis.AllyouneedtodoisgototheMacromediasiteandclickonthelinktoinstalltheActiveXcontrol.Theresthappensautomatically.Thenexttimeyougotoa"Shocked"website,theShockwavecontrolloadsandplaysthemovie.
Mostplug-insandcontrolscanbedownloadedforfreeontheInternet,althoughnotallwillworkwitheverysystem.Someofthem,forinstance,onlyworkwithwindows95.
当你不再仅仅限于文字和静止图片时,网上生活会丰富多彩得多。
即使是个因特网新手,你也许听说过在线式多媒体——听音乐、看动画和录像,甚至玩三维游戏。
声音和活动画面使信息变得活灵活现。
要体验这些,你需要叫作“插件”的特殊软件。
术语“插件”指的是一个附加的小软件,他能够扩展你的网络浏览器(比如网景的导航者或微软的探索者)的功能——把你的计算机变成一台收音机或电视机。
当你进入的网页含有需要使用插件程序的文件,而你却又没有这个程序时,通常你会收到一个信息,询问你是否需要下载该程序并安装到你的电脑里。
多数情况下安装是自动运行的。
有时候,你会碰到一个需要在安装前先进行解压缩的下载文件。
一旦安装完毕,插件就会自动运行,无需你做任何事。
许多多媒体的控制程序仍需从开发商处索取,不过都是自动安装的。
Shockwave就是这方面一个很好的例子。
你所需要做的就是到Macromedia网站上点击链接来安装ActiveX控制程序,剩下的事自动就会完成。
下次再到一个需要使Shockwave的网站时,Shockwave控制程序就会自动装载并播放电影。
大多数插件和控制程序可以从因特网上免费下载,尽管并非所有这些程序都会在每一个系统上正常运行。
例如有些就只适用于视窗95。
LocalAreaNetwork(局域网)
Therearetwocategoriesofnetworks:
localareanetworks(LANs)andwideareanetworks(WANs).HereI'dliketomainlytalkaboutLAN.
ALANisasystemofcomputersandassociatedperipheralssuchasPrintersthatarephysicallyconnectedbycablewithinalimitedgeographicalarea-typicallyinanofficebuildingoronacollegecampus.Thetopologyofthenetworkmaybering,starorbus.LANsusefiberopticsorcoaxialcabletoconnectcomputers,andeachcomputermusthavespecialcommunicationssoftwareinstalledoilitsharddisk.SoftwarehasbeendevelopedthatallowscomputerswithdifferentplatformstocoexistandexchangedataonthesameLAN.
AFileServer
Manynetworksaremanagedbyacomputercalledafileserver.Afileserverhasalarge-capacityharddiskandspecialsoftwarethatmanagesaccesstofliesonthenetwork.Itcontrolshowdataanddatabasearesharedamongusersonthenetworkandhowusersaccessmastercopiesofdataandapplicationsoftwareonthecentralizedharddisk.Itisthefileserver'sjobtomakesurethatusersdon'taccidentallytrytoupdateafileatthesametimeandscramblethedata.Thefileservermayalsomanagetheaccesstoanexpensivepieceofhardwaresuchasalaserprinter.
WhenafileserverisusedonaLAN,largedatabasesarestoredontheserverandusersmaystorealloftheirworkfliesthereaswell.Thisoperationisanalogoustosomeone'smanuallycollectingallthedataeachdayplacingtheminafiledrawer,andthenredistributingthesedatatotheworkersasneeded.
TheLANOperatingSystem--NetWare
Novell'sNetwarehasbecomethestrongestcompetitortoIBM'sownnetworkoperatingenvironmentandpredatesIBMinitssupportforLANs.Infact,IBMnowmarketsNetwareforboththePCNetworkandforTokenRinginadditiontoitsownsoftware.ThekeytoNetwareisthefileserversoftwareanddirectoriesontheserveraremappedtonetworkdrives,thusoperatinglikevirtualdiskettesfromauser'sperspective.TheserversoftwareisamultitaskingoperatingsystemwithafilestructureconsistentwithDOS2.xandDOS3.x.TheNetwareshellineachworkstationintercepts21HDOScallsandredirectsappropriatecallstotheserver.
PerhapstheprimaryadvantageofNetwareisthatitrunsonawidevarietyofnetworkinghardware.RegardlessofwhetheryouchooseanIBMnetwork,CorvusOMNINET,AT&TStarLAN,etc.,youcanobtainNetwareastheoperatingenvironment.Infact,ifyouhaveoneofeachtheuserwillnotbeabletotellthedifference(unlesstherearesomedistinctperformancedifferentials),andtheycanbeinterconnectedthroughNov