Page 33 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Unit 2: Software Processes and Models

Usability: Software becomes usable if it does not call for extra efforts to be learned. Usability Notes
increases with good documentation provided along with the software. In software operations
a lot depends on the quality of user manual. If software satisfies all the above characteristics
then it is said to be good software or the software is well engineered.
The first known presentation describing use of similar phases in software
engineering was held by Herbert D. Benington at Symposium on advanced
programming methods for digital computers on 29 June 1956. This presentation
was about the development of software for SAGE.

2.3 Waterfall Model

The Waterfall model is one of the most used models of 70’s. It was proposed as an alternative to
Build and Fix software development method in which code was written and debugged. System
was not formally designed and there was no way to check the quality criteria. Different phases
of Waterfall model are shown in Figure 2.2. Given below are a brief description of different
phases of Waterfall model. Feasibility study explores system requirements to determine project
feasibility. All projects are feasible given unlimited resources and infinite time.

Figure 2.2: The Waterfall Model

Feasibility Study

Requirements Analysis

System Design

Implementation

Testing

Deployment

Operation and Maintenance

Feasibility can be categorized into
• Economic feasibility
• Technical feasibility
• Operational feasibility
• Schedule feasibility
• Legal and contractual feasibility
• Political feasibility
Economic feasibility is also called cost-benefit analysis and focuses on determining.

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