Chapter01IntroductiontoSoftwareEngineering

Chapter1.Introdu[e-mail]《SoftwareEngineering》SoftwareCollegeofNankaiUniversity2IntroductiontoSoftwareEngineering1.Software2.SoftwareMyths3.SoftwareCrisis4.SoftwareEngineering5.Professionalandethicalresponsibility《SoftwareEngineering》SoftwareCollegeofNankaiUniversity31.Software1.1Whatissoftware?1.2ThefeaturesofSoftware?1.3SoftwareCategory1.4ThesizeofSoftware1.5LegacySoftware《SoftwareEngineering》SoftwareCollegeofNankaiUniversity41.1WhatisSoftware?-Asetofinstructionsthatcauseacomputertoperformoneormoretasks.-ScienceandTechnologyEncyclopedia-Thevariousprogramsbywhichacomputercontrolsaspectsofitsoperations,suchasthosefortranslatingdatafromoneformtoanother-Wikipedia-Instructionsthattellacomputerwhattodo.-Computerinstructions.-computerprogramthatcontrolsthefunctionsofacomputer.《SoftwareEngineering》SoftwareCollegeofNankaiUniversity5•软件是计算机系统中与硬件相互依存的另一部分，它是包括程序，数据及其相关文档的完整集合。•程序(instructions)是按事先设计的功能和性能要求执行的指令序列•数据(data)是使程序能正常操纵信息的数据结构•文档(documents)是与程序开发，维护和使用有关的图文材料1.1WhatisSoftware?《SoftwareEngineering》SoftwareCollegeofNankaiUniversity61.1Whatissoftware?•Softwareengineersviewsoftwareasbeingmadeupoftheprograms,documents,anddata.•Softwareusersareonlyconcernedwithwhetherornotsoftwareproductsmeettheirexpectationsandmaketheirtaskseasiertocomplete.《SoftwareEngineering》SoftwareCollegeofNankaiUniversity7software=program+data+documentIn1950’s:Software=programIn1960’s:Software=program+documentearly--Veryfewlargesoftwareprojectsweredonebysomeexperts.middletolate--Trulylargesoftwaresystemswereattempted.late—softwarecrisisIn1970’s:Software=program+document+dataProgramdesignProgramsystemSoftwareengineeringTheEvolvingRoleofSoftware《SoftwareEngineering》SoftwareCollegeofNankaiUniversity8Software’sDualRole•Softwareisaproduct–Deliverscomputingpotentialofhardwareandnetworks–Informationtransformer-producing,managing,acquiring,modifying,displaying,ortransmittinginformation•Softwareisavehiclefordeliveringaproduct–Thebasicforthecontrolofthecomputer(operatingsystems)–Thebasicforthecommunicationofinformation(networks)–Thebasicforthecreationandcontrolofotherprograms(softwaretoolsandenvironments)《SoftwareEngineering》SoftwareCollegeofNankaiUniversity9Softwareisdevelopedorengineered,itisnotmanufacturedintheclassicalsense.Softwaredoesn’twearout.Butitdoesdeteriorate!Althoughtheindustryismovingtowardcomponent-basedassembly,mostsoftwarecontinuestobecustombuilt.1.2TheFeaturesofSoftware《SoftwareEngineering》SoftwareCollegeofNankaiUniversity10Manufacturingvs.Development•Onceahardwareproducthasbeenmanufactured,itisdifficultorimpossibletomodify.Incontrast,softwareproductsareroutinelymodifiedandupgraded.•Inhardware,hiringmorepeopleallowsyoutoaccomplishmorework,butthesamedoesnotnecessarilyholdtrueinsoftwareengineering.•Unlikehardware,softwarecostsareconcentratedindesignratherthanproduction《SoftwareEngineering》SoftwareCollegeofNankaiUniversity11Softwaredoesn’twearout.FailurerateTimeInfantmortalityWearoutFailurecurveforhardwareidealizedcurvechangeincreasedfailurerateduetosideeffectsactualcurveButitdoesdeteriorate!“Wearout”vs.Deterioration《SoftwareEngineering》SoftwareCollegeofNankaiUniversity12ComponentBasedvs.CustomBuilt•Hardwareproductstypicallyemploymanystandardizeddesigncomponents.•Mostsoftwarecontinuestobecustombuilt.•Thesoftwareindustrydoesseemtobemoving(slowly)towardcomponent-basedconstruction.《SoftwareEngineering》SoftwareCollegeofNankaiUniversity131.3SoftwareCategories•systemsoftware(系统软件）–服务于其他程序的程序–编译器、编辑器、文件管理程序–操作系统构件、驱动程序、网络软件•applicationsoftware（应用软件）–可以满足特定业务需要的独立应用程序–数据处理、实时控制•engineering/scientificsoftware（工程计算软件）–“数字计算”–计算机辅助设计、系统仿真、Matlab•embeddedsoftware（嵌入式软件）–存在于某个产品或者系统中，可实现和控制面向最终使用者和系统本身的特性和功能。–手持PDA、刹车系统《SoftwareEngineering》SoftwareCollegeofNankaiUniversity141.3SoftwareCategories•product-linesoftware（产品线软件）–为多个不同的用户的使用提供特定功能，关注有限的特定市场或者大众消费市场–Word，excel，多媒体，个人或公司财务应用•WebApps(网络应用)–超文本文件–发展为复杂的计算环境–与企业数据库和商务应用程序相结合•AIsoftware（人工智能软件）–利用非数值算法解决计算和直接分析无法解决的复杂问题–机器人、专家系统、模式识别、神经网络《SoftwareEngineering》SoftwareCollegeofNankaiUniversity151.3Software—NewCategories•Ubiquitouscomputing（普适计算）–开发系统和应用软件，使得小型设备、个人电脑和企业应用可以通过大量的网络设施进行通信。•Opensource（开源软件）–将系统应用程序的源代码开放，并允许用户自行修改•Also…–Datamining–Gridcomputing《SoftwareEngineering》SoftwareCollegeofNankaiUniversity16类别参加人员数开发期限源程序行数微型11～4周0.5k小型11～6月1k～2k中型2～51～2年5k～50k大型5～202～3年50k～100k甚大型100～10004～5年1M(=1000k)极大型2000～50005～10年1M～10M1.4TheSizeofSoftware《SoftwareEngineering》SoftwareCollegeofNankaiUniversity17DramaticimprovementsinhardwareperformanceProfoundchangesincomputingarchitecturesVastincreasesinmemoryandstoragecapacityWidevarietyofexoticinputandoutputoptionsMoresophisticatedandcomplexcomputer-basedsystemsToday:Windows95-1000万行代码Windows2000-5000万行代码Exchange2000Windows2000项目经理25人约250人开发人员140人约1700人测试人员350人约3200人1.4TheSizeofSoftware《SoftwareEngineering》SoftwareCollegeofNankaiUniversity181.5Legacysystems(遗留系统）•遗留系统是以计算机为基础的社会－技术系统（Socio-technicalsystems），是在过去开发出来的，往往采用在今天看来是旧的和不再使用的技术。•Crucialtotheoperationofabusiness（关键