©Brooks/Cole, 2003 Chapter 10 Software Engineering

©Brooks/Cole, 2003 Understand the software life cycle. Describe the development process models. Understand the concept of modularity in software engineering. Understand the importance of quality in software engineering. After reading this chapter, the reader should be able to: O BJECTIVES Understand the role of documentation in software engineering.

©Brooks/Cole, 2003 SOFTWARELIFECYCLESOFTWARELIFECYCLE 10.1

Figure 10-1 System life cycle

©Brooks/Cole, 2003 Figure 10-2 System development phases

©Brooks/Cole, 2003 Analysis phase ► Four steps in the analysis phase:  Define the user  Define the needs  Define the requirement  Define the methods

©Brooks/Cole, 2003 Design phase ► The design phase defines how the system will accomplish what was defined in the analysis phase.  Modularity ( 模組化 ):  Tools : example -- a structure chart ► A structure chart shows how to break your package into logical steps; each step is a separate module.

©Brooks/Cole, 2003 Implementation phase ► In the implementation phase, you create the actual programs. ► Tools:  Flowchart  Pseudocode ► Coding:  The choice of the language is based on the efficiency of the language for that particular application.

©Brooks/Cole, 2003 Testing phase ► The testing phase can be a time-consuming part of program development.  Black box testing ► Black box testing is done by the system test engineer and the user.  White box testing ► White box testing is the responsibility of the programmer.

©Brooks/Cole, 2003 DEVELOPMENTPROCESSMODELSDEVELOPMENTPROCESSMODELS 10.2

Figure 10-3 Waterfall model

©Brooks/Cole, 2003 Waterfall model ► Figure 10.3 ► The development process flows in only one direction. ► A phase cannot be started until the previous phase is completed. ► Advantage: each phase is completed before the next phase starts ► Disadvantage: the difficulty in locating a problem

©Brooks/Cole, 2003 Figure 10-4 Incremental model ► The process is developed in a series of steps.

©Brooks/Cole, 2003 MODULARITYMODULARITY 10.3

Modularity ► Modularity  To break a large project into smaller parts that can be understood and handled easily  To divide a large program into small programs that can communicate with each other ► Tools : a structure chart and a class diagram  A structure chart shows how to break your package into logical steps; each step is a separate module.  A class diagram is used in object-oriented programming to show the relationships between classes.

©Brooks/Cole, 2003 Modularity ► Modularity  Coupling ( 結合 ) : ► Coupling is a measure of how tightly two modules are bound to each other.  Cohesion ( 結合力 ) : ► Cohesion is a measure of how closely the processes in a program are related.

©Brooks/Cole, 2003 QUALITYQUALITY 10.4

Quality ► Definition: Quality software  Software that satisfies the user ’ s explicit ( 明示的 ) and implicit ( 暗示的 ) requirements, is well documented, meets the operating standards of the organization, and runs efficiently on the hardware for which it was developed.

©Brooks/Cole, 2003 Figure 10-5 Quality factors

©Brooks/Cole, 2003 Figure 10-6 Quality circle

©Brooks/Cole, 2003 DOCUMENTATIONDOCUMENTATION 10.5

Documentation ► User documentation ► System documentation  Documentation in the analysis phase  Documentation in the design phase  Documentation in the implementation phase  Documentation in the testing phase ► Documentation as an ongoing process  If the package is modified, all modifications and their relationships with the original package must also be documented.

©Brooks/Cole, 2003 Key terms ► Analysis phase ► Black box testing ► Design phase ► Efficiency ► Flexibility ► Flowchart ► Implementation phase ► Incremental model ► Modularity ► Modules ► Pseudocode ► Quality circle ► Quality software ► Reliability ► Reusability ► Security ► Software engineering ► Software life cycle ► Structure chart ► System documentation ► Testing phase ► Waterfall model ► White box testing