牛津译林版高中英语选修七unit 3《the world online》文化背景

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Unit3Theworldonline文化背景HowWorldWideWebworksThetermsInternetandWorldWideWebareoftenusedinevery-dayspeechwithoutmuchdistinction.However,theInternetandtheWorldWideWebarenotoneandthesame.TheInternetisaglobaldatacommunicationssystem.Itisahardwareandsoftwareinfrastructurethatprovidesconnectivitybetweencomputers.Incontrast,theWebisoneoftheservicescommunicatedviatheInternet.Itisacollectionofinterconnecteddocumentsandotherresources,linkedbyhyperlinksandURLs.ViewingaWebpageontheWorldWideWebnormallybeginseitherbytypingtheURLofthepageintoaWebbrowser,orbyfollowingahyperlinktothatpageorresource.TheWebbrowsertheninitiatesaseriesofcommunicationmessages,behindthescenes,inordertofetchanddisplayit.First,theserver-nameportionoftheURLisresolvedintoanIPaddressusingtheglobal,distributedInternetdatabaseknownasthedomainnamesystem,orDNS.ThisIPaddressisnecessarytocontactandsenddatapacketstotheWebserver.ThebrowserthenrequeststheresourcebysendinganHTTPrequesttotheWebserveratthatparticularaddress.InthecaseofatypicalWebpage,theHTMLtextofthepageisrequestedfirstandparsedimmediatelybytheWebbrowser,whichwillthenmakeadditionalrequestsforimagesandanyotherfilesthatformapartofthepage.Statisticsmeasuringawebsite'spopularityareusuallybasedonthenumberof'pageviews'orassociatedserver'hits',orfilerequests,whichtakeplace.HavingreceivedtherequiredfilesfromtheWebserver,thebrowserthenrendersthepageontothescreenasspecifiedbyitsHTML,CSS,andotherWeblanguages.Anyimagesandotherresourcesareincorporatedtoproducetheon-screenWebpagethattheusersees.MostWebpageswillthemselvescontainhyperlinkstootherrelatedpagesandperhapstodownloads,sourcedocuments,definitionsandotherWebresources.Suchacollectionofuseful,relatedresources,interconnectedviahypertextlinks,iswhatwasdubbeda"web"ofinformation.MakingitavailableontheInternetcreatedwhatTimBerners-LeefirstcalledtheWorldWideWeb(initsoriginalCamelCase,whichwassubsequentlydiscarded)inNovember1990.