2.3 software engineering.ppt

1、Ch2 software knowledge,2.3 Software Engineering,第1次课,review,指令 汇编语言 符号 编译器 解释器 源代码 目标代码,Main contents,Key words Text Software engineering The software life cycle Requirements definition exercises,key words,software engineering sftw .endiniri 软件工程 Software engineering is the app-lication of tools, me

2、thods, and dis-ciplines to produce and maintain an automated solution to a real-world problem.,key words,maintain mentein 维护，维修 keep in safety and protect from harm, decay, loss, or destruction Mankind have been trying every means to maintain the balance of nature.,key words,emerge Im:d 出现，形成 The su

3、n emerged from behind the clouds. juxtaposition.dkstpzin 并置，并列，并排 provocative prvktiv 引起争论的，煽动的 budget bdit 预算,key words,aspiration .sprein 热望，渴望 She was filled with the aspiration to succeed in life. boundary baundri 边界，分界线 They marked the boundaries of the football fields. overrun .uvrn 超出限度，超过 Th

4、e lecturer overran by ten minutes.,key words,barrier bri 界线,屏障,障碍物 Heavy duties on imports and exports are a barrier to international trade. 进出口的高关税是国际贸易的障碍。 span spn 跨度，跨距，范围，一段时间 Modern medicine has increased mans life span. terminology .t:minldi 术语，术语学,key words,implementation .implimentein 实现 pr

5、oject implementation 项目实现 install inst:l 安装 error er 错误，过失，误差 feedforward .fi:df:wd 前馈 feedback fi:dbk 反馈 reveal rivi:l 显示，揭露 I promise never to reveal his secret.,key words,flaw fl: 缺点，缺陷 constraint knstreint 约束，限制 precede pri(:)si:d 领先于，先于，在之前 He preceded his speech with a few words of welcome the

6、 special guests.,key words,prototype pruttaip 原型 An original type, form, or instance that serves as a model on which later stages are based or judged. 一种原初的类型、形式或例证，是作为其后期阶段的基础的模型 debug di:bg 调试 debug a computer program faulty f:lti 有错误的，有缺点的 substantial sbstnl 丰富的，大量的,Acronym,NATO-North Atlantic Tr

7、eaty Organization 北大西洋公约组织,Software Engineering,Software engineering is the application of tools, methods, and disciplines to produce and maintain an automated solution to a real-world problem.,Software Engineering,A large-scale software projects spans a considerable period of time. A number of dist

8、inct phases can be identified over this period of time. Together, these make up what is known as the “software life cycle”.,The software life cycle,1. Requirements definition: The requirements of the software are established and specified. 2. Design: A design is developed from an analysis of the req

9、uire-ments.,The software life cycle,3. Implementation: The design is coded in a particular program-ming language on a particular machine. 4. Testing: The implemented sys-tem is tested to see if it meets the specified requirements.,The software life cycle,5. Operation and maintenance: The system is i

10、nstalled and used. Errors found must be repaired.,Requirements definition,The first phase, requirements defini-tion, refers to the period during whi-ch the requirements of the system desired, that is, its functional chara-cteristics and operational details, are specified. The input to this phase is

11、the stated (often rather loosely stated) needs for the software.,Requirements definition,Typically, a “requirements document” is the output of this phase, a set of pre-cisely stated properties or constraints that the final product must satisfy. As with any of the phases, it is import-ant that errors

12、 not be allowed to move into subsequent phases.,Exercises,软件工程 维护，维修 安装 错误，过失，误差 原型 调试,第2次课,Review,软件工程 维护，维修 安装 错误，过失，误差 原型 调试,Main contents,Key words Text Design Implementation Testing Program maintenance Exercises,Key Words,predominantly pridminntli 主要地，支配地，占统治地位地 inherent inhirnt 内在的，固有的，与生俱来的 T

13、here is an inherent weakness in the design. 这设计本身存在弱点。 pseudo psju:du 假的，冒充的,Key Words,pseudo-code 伪代码 Pseudo-code is a detailed yet readable description of what a computer program or algorithm must do, expressed in a formally-styled natural language rather than in a programming language.,Key Words,

14、pseudo-code example： while(已跑的圈数 3 ,Key Words,validation vlidein 确认 the act of validating; finding or testing the truth of something fragment frgmnt 片段，碎片 She dropped the vase on the floor and it broke into fragments. verification .verifikein 确认，验证 lure lju 吸引力，诱惑力，魅力 He left home because of the lur

15、es of the life in the city.,Key Words,foolhardy fu:lh:di 有勇无谋的，鲁莽的 It was foolhardy of him to go swimming alone. simulate simjuleit 模拟，模仿，假装 He shook a sheet of metal to simulate the noise of thunder. exhaustive igz:stiv 无遗漏的，详尽的，彻底的 exhaustive test 无遗漏测试,Key Words,deteriorate ditirireit 损坏，恶化 defec

16、t difekt 缺点，缺陷 apportion p:n 分配 judiciously du:disli 明智地，头脑精明地，判断正确地,Design,The second phase, design, is pre-dominantly creative, while some would argue that creativity is in-herent and cannot be trained or improved, it can certainly be enh-anced by the use of good proce-dures and tools.,Design,The

17、input to this phase is a (deb-ugged and validated) requireme-nts document: the output is a de-sign expressed in some approp-riate form (for example, pseudo-code).,Design,Each requirement in the require-ments document must have a cor-responding design fragment to meet it.,Implementation,The third pha

18、se, implementation, is the actual coding of the design developed in the second phase. The lure of this phase is strong, and many a foolhardy program-mer has been drawn to it before adequately laying the groundwork in the first two phases.,Implementation,As a result, requirements are incompletely und

19、erstood and the design is flawed. The implementation proceeds blindly, and many problems arise as a result.,Testing,The fourth phase, testing, is co-ncerned with demonstrating the correctness of the implemented program. Inevitably some test-ing is performed as part of the previous two phases as well

20、.,Testing,Any experienced programmer mentally tests each line as it is produced and mentally simula-tes the execution of any module prior to any formal testing stage.,Testing,A “successful” test run means only that no errors were uncovered with the particular circumstances test-ed; it says nothing about other cir-cumstances.,Testing,In theory, the only way that tes-ting can show that a program is correct is if all possible cases are tried (known as an exhau-stive test), a situation techni-cally imp