unit 25 internet

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1、Unit25Internet互联网互联网是计算机网络的国际性的集成，这些网络都理解一个标准的地址命令系统，并经中枢链路网络连在一起。互联网可以提供的服务为电子邮件、远程登陆、文件传送、电子新闻和实况对话等。可以说，互联网是你的计算机通向世界其他地方的窗口……TheInternetisagiantnetworkofcomputerslocatedallovertheworldthatcommunicatewitheachother.TheInternetisaninternationalcollectionofcomputernetworksthatallunderstan

2、dastandardsystemofaddressesandcommands,connectedtogetherthroughbackbonesystems.Itwasstartedin1969,whentheU.S.DepartmentofDefence(美国国防部)establishedanationwidenetworktoconnectahandfulofuniversitiesandcontractors.Theoriginalideawastoincreasecomputingcapacitythatcouldbesharedbyusersinmanyloca

3、tionsandtofindoutwhatitwouldtakeforcomputernetworkstosurviveanuclearwarorotherdisasterbyprovidingmultiplepathsbetweenusers.PeopleontheARPNET(阿帕网，因特网的前身)(asthisnationwidenetworkwasoriginallycalled)quicklydiscoveredthattheycouldexchangemessagesandconductelectronic"conferences"withdistantcol

4、leaguesforpurposesthathadnothingtodowiththemilitaryindustrialcomplex.Ifsomebodyelsehadsomethinginterestingstoredontheircomputer,itwasasimplemattertoobtainacopy(assumingtheownerdidnotprotectit).Overtheyears,additionalnetworksjoinedwhichaddedaccesstomoreandmorecomputers.Todaythousandsofnetw

5、orksandmillionsofcomputersareconnectedtotheInternet.Itisgrowingsoquicklythatnobodycansayexactlyhowmanyusers"OntheNet".TheInternetisthelargestrepository(宝库)ofinformationwhichcanprovideveryverylargenetworkresources.Thenetworkresourcescanbedividedintonetworkfacilitiesresourcesandnetworkinfor

6、mationresources.Thenetworkfacilitiesresourcesprovideuswiththeabilityofremotecomputationandcommunication.Thenetworkinformationresourcesprovidesuswithallkindsofinformationservices,suchasscience,education,business,history,law,artandentertainment,etc.ThegoalofyouruseoftheInternetisexchangingm

7、essagesorobtaininginformation.WhatyouneedtoknowisthatyoucanexchangemessagewithothercomputersontheInternetanduseyourcomputerasaremoteterminalondistantcomputers.Buttheinternaldetailsofthelinkarelessimportant,aslongasitworks.Ifyouconnectcomputerstogetheronanetwork,each