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1、1.2ComputerGenerations1.2.4Fourth-GenerationComputers:1971～?Softwaredevelopmentduringthefourthcomputergenerationstartedoffwithlittlechangefromthethirdgeneration.Operatingsystemsweregraduallyimproved,andnewlanguagesweredesigned.Databasesoftwarebecamewidelyusedduringthistime.Th
2、emostimportanttrend,however,resultedfromthemicrocomputerrevolution.Packagedsoftwarebecamewidelyavailableformicrocomputerssothattodaymostsoftwareispurchased,notdevelopedfromscratch.在计算机的第四代期间，软件的发展开始与第三代有所不同。操作系统在逐渐地改进，而新的语言被发明。期间数据库软件被广泛使用。然而，最重要的趋势起因于微型计算机革命。用于微型计算机的软件包随处可得，
3、因此今天大多数的软件可以购得,而不需从头开始开发。1.2.5GenerationlessComputersWemayhavedefinedourlastgenerationofcomputersandbeguntheeraofgenerationlesscomputers.Eventhoughcomputermanufacturerstalkof“fifth”and“sixth”-generationcomputers,thistalkismoreamarketingplaythanareflectionofreality.我们可能已经定义了我们
4、最新一代计算机而且开始了计算机的无代时代。即使计算机制造商谈到“第五”和“第六”代计算机,这些说法更多是市场行为，而不是真实的反映。Advocatesoftheconceptofgenerationlesscomputerssaythateventhoughtechnologicalinnovationsarecominginrapidsuccession,nosingleinnovationis,orwillbe,significantenoughtocharacterizeanothergenerationofcomputers.无代计算机的
5、观念提倡者说，即使科技革新接二连三地迅速出现,没有一种革新是,或将是足够重要，作为另一代计算机的特征。1.2ComputerGenerationsNewWords&Expressions:gleanvt.,vi.搜集(情报或事实)MDabbr.Maryland(马里兰)Tflopsabbr.teraflops每秒兆兆(1012)次architecturen.体系机构terabitn.兆兆位factorn.阶乘bandwidthn.带宽Terabyten.兆兆(1012)字节；Petabyten.千兆兆(1015)字节microprocessorn
6、.[计]微处理器contemplatev.凝视,沉思ordern.阶,次turbulencen.扰动；湍流GB=GigaBit,千兆位;=GigaByte,吉字节flopsn.每秒浮点运算次数(floating-pointoperationpersecond)1.3Near-futureSupercomputerDirectionsSomeideaofwhatmightbehappeninginthenearfutureinsupercomputerdesigncanbegleanedfromapressreleaseissuedbytheUSD
7、epartmentofEnergy(DoE).ItcameoutoftheSUPERCOMPUTING2002ConferenceheldlastNovemberinBaltimore,MD.ThepressreleaseannouncedthattheDoEhadawardedIBMa$290(USD)millioncontracttobuildthetwofastestsupercomputersintheworldwithacombinedpeakspeedof460TFlops.Togetanideaofthespeedcomputing
8、throughput460teraflopsrepresents,thepressreleasestatesthat,“Thesetwo
