Program development life cycle

Computer Science AS · Software development. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

A development life cycle gives a structured set of stages, so that a project can be planned, managed and checked. The stages are analysis, design, coding, testing and maintenance.

Different programs suit different life cycles. In the waterfall model each stage is completed before the next one starts. It suits requirements that are fixed and well understood. In the iterative model a simple working version is built first and then improved in repeated cycles, using feedback from each version.

In rapid application development (RAD) prototypes are built quickly, often as separate modules by small teams working in parallel, and are refined with frequent user feedback. There is little planning in advance.

Rules to remember

Order of stages: analysis → design → coding → testing → maintenance
Analysis: investigate the problem and the current system; produce the requirements specification
Design: plan the solution with structure charts, pseudocode or flowcharts, and data structures
Coding: write the program. Testing: find and correct errors using test data. Maintenance: correct, adapt and improve the program after release
Waterfall: easy to manage, with clear milestones and full documentation; but users see a working program late, so changes are costly
Iterative: a working version exists early and requirements can change; but the total time and cost are hard to predict
RAD: fast delivery and easy changes; but users must be available often, and it suits smaller projects that split into modules

Common mistake

Choosing a life cycle without looking at the requirements. Ask first whether they are fixed and fully known: if yes, waterfall fits; if they are likely to change, choose iterative or RAD.

Worked example

A shop owner wants a booking program quickly. She is not sure which features she needs and wants to try early versions. Her staff can give feedback every few days. Which life cycle is most suitable?

The requirements are not known at the start, so waterfall is unsuitable: it fixes them before design begins.
The program is needed quickly and the users are available often.
Prototypes can be built fast, shown to the staff and refined from their feedback.

Answer: Rapid application development (RAD)

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