计算机专业英语课件.ppt

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1、第10章Network本章要点WhatisaNetwork?WordsandExpressionsHowToDo:ASearchToolHowToWork：SecuritysuitesGrammarFocus：倒装句及句子种类TextinChinese：网络ReadingSelection:AHome(Page)ofYourOwn科技英语翻译方法与技巧（Ⅲ）PracticalWriting：标点符号WhatisaNetwork?Throughouttheworld,yourmicrocomputercanconnecttoothermicrocomputers,totheInternet

2、,andtolargercomputersthroughtheelectroniccommunicationsystems.Theelectroniccommunicationsystemstransmitinformationovercommunicationlinesofcableandairfromonelocationtoanother.Suchelectroniccommunicationlinesareknownasnetworks(Figure10-1).Anetworkcanbearrangedinseveraldifferentwaystomeetdifferentus

3、ers′needs.Thenetworkarrangementiscalledthenetwork′stopology.Thefourprincipaltopologiesarestar,bus,ring,andhierarchical.Inastarnetwork,anumberofsmallcomputersorperipheraldevicesarelinkedtoacentralunit—maybeahostcomputerorafileserver.Thehostcomputermaintainsitscontrolbyaskingwhethereachconnecteddev

4、icehasmessagestosend.Oneadvantageofthestarnetworkisthatseveraluserscanshareresourcesonacentralhostcomputer(Figure10-2).Inabusnetwork,thereisnohostcomputer,andinsteadeachdeviceinthenetworkhandlesitsowncommunicationcontrol.Allcommunicationstravelalongacommonconnectingcablecalledabusandastheinformat

5、ionpassesalongthebus,eachdeviceexaminestoseeiftheinformationisintended.*WhatisaNetwork?Thisarrangementiscommonforsharingdatastoredondifferentmicrocomputersbutnotasefficientasthestarnetworkforsharingcommonresources(SeeFigure10-3).Figure10-1Figure10-2Figure10-3WhatisaNetwork?Inaringnetwork,eachdevi

6、ceisconnectedtotwootherdevices,formingaring.Thereisnocentralcomputerorfileserver.Messagesarepassedaroundtheringuntiltheyreachthecorrectdestination.Withmicrocomputers,theringarrangementistheleastfrequentlyusedofthefournetworks.Itisoftenusedtolinkmainframecomputers,especiallyoverwidegeographicalare

7、as(SeeFigure10-4).*Thehierarchicalnetworkconsistsofseveralcomputerslinkedtoacentralhostcomputer,justlikeastarnetwork,buttheseothercomputersarealsohoststoothersmallercom-puters.Ahierarchicalnetworkisusefulincentralizedo