计算机专业英语（第二版） -孙建忠 Chapter6.pptVIP

Computer English Chapter 6 Software Engineering 6.2 The Software Life Cycle 6.2.6 Maintenance Software will undoubtedly undergo change after it is delivered to the customer (a possible exception is embedded software). Change will occur because errors have been encountered, because the software must be adapted to accommodate changes in its external environment (e.g. a change required because of a new operating system or peripheral device), or because the customer requires functional or performance enhancements. Software maintenance applies each of the preceding life cycle steps to an existing program rather than a new one. 6.2.6 维护 毫无疑问，软件在递交给用户之后还要进行修改（嵌入式软件例外）。软件一遇到错误就要改变，或是因为软件必须适应它的外在环境的变化（例如，如果换了新的操作系统或外设产生了变化），或是因为用户需求提高功能和性能。软件维护是将前述的各种生命周期步骤应用于现存的程序。 6.2 The Software Life Cycle The classic life cycle is the oldest and the most widely used paradigm for software engineering. However, over the past few years, criticism of the paradigm has caused even active supporters to question its applicability in all situations. Among the problems that are sometimes encountered when the classic life cycle paradigm is applied are: 传统的生存期是软件工程中使用最早的，也是应用最广泛的模型，尽管如此，最近几年出现的对模型法的批评，甚至使那些积极的支持者也质疑它是否适合于所有情况中。下面是传统的生存期模型有时会遇到的问题： 6.2 The Software Life Cycle ·Real projects rarely follow the sequential flow that the model proposes. Iteration always occurs and creates problems in the application on the paradigm. ·It is often difficult in the beginning for the customer to state all requirements explicitly. The classic life cycle requires this and has difficulty accommodating the natural uncertainty that exists at the beginning of many projects. ·The customer must have patience. A working version of the program(s) will not be available until late in the project time span. A major blunder undetected until the working program is reviewed can be disastrous. ·真正的项目很少依照模型所提出的顺序流程来实现，时常会出现迭代，这样会在模型的应用中制造问题。 ·要求用户在开始时明确指出全部要求往往是困难的。传统的生存期却要求如此，这样很难适应许多项目在设计之初就存在的不确定性。 ·这种模型要求用户必需有耐心，