原创力文档- 1、本文档共25页，可阅读全部内容。
- 2、原创力文档（book118）网站文档一经付费（服务费），不意味着购买了该文档的版权，仅供个人/单位学习、研究之用，不得用于商业用途，未经授权，严禁复制、发行、汇编、翻译或者网络传播等，侵权必究。
- 3、本站所有内容均由合作方或网友上传，本站不对文档的完整性、权威性及其观点立场正确性做任何保证或承诺！文档内容仅供研究参考，付费前请自行鉴别。如您付费，意味着您自己接受本站规则且自行承担风险，本站不退款、不进行额外附加服务；查看《如何避免下载的几个坑》。如果您已付费下载过本站文档，您可以点击 这里二次下载。
- 4、如文档侵犯商业秘密、侵犯著作权、侵犯人身权等，请点击“版权申诉”（推荐），也可以打举报电话：400-050-0827(电话支持时间：9:00-18:30)。
UNIT2TheEvolutionofComputers1Modernelectroniccomputersdidn’tappearuntilthe1940’s.ResearchworkersinAmericaproducedaworkingcomputerin1946.Thefirstmodelswereverybulkybecausetheydependedonvacuumtubessimilartothoseyoumayhaveseeninoldradiosets.Latermachinesusedtransistorsandatpresentweuseintegratedcircuitswhichtakeupverylittlespace.Now,let’sgetaclearerpictureofthedevelopmentofcomputers.1.FirstgenerationcomputersThefirstgenerationofcomputerswereusedfrom1946to1959.TheywerecharacterizedbythemostprominentfeatureoftheENIACvacuumtubes,andwerelarge,costly,expensivetopowerandoftenunreliable.2Moreover,thevacuumtubeswerefairlylarge,andtheygeneratedsomuchheatthatspecialairconditioninghadtobeinstalledtocoolthem.2.SecondgenerationcomputersThesecondgenerationofcomputersspannedtheyearsfrom1959to1964.Themostnotablechangewasthattransistorsreplacedvacuumtubes.3Thetransistorallowedthedevelopmentofmorepowerful,morereliableandlessexpensivecomputersthatwouldoccupylessspaceandgiveofflessheatthandidcomputersusingvacuumtubes.Inaddition,thesecondgenerationcomputersweregivenauxiliarystorage,sometimescalledexternalorsecondarystorage.Datawerestoredoutsidethecomputeroneithermagnetictapesormagneticdisks.Usingmagnetictapesormagneticdisksforinputandoutputoperationsincreasedthespeedofthecomputer.3.Third-generationcomputersThethird-generationcomputerslastedfrom1964to1971.4Thethird-generationismarkedchieflybythedevelopmentofintegratedcircuits,whichreplacedtransistors.Withintegratedcircuits,hundredsofelectricalcomponentscouldbeincludedononesiliconchiplessthanone-eighth-inchsquare.Therefore,thecomputersbecameevensmallerwhiletheirmemorycapacitiesbecamelarger.Thethird-gen
文档评论（0）