Software Engineers Handbook/Life Cycle/Development Methodologies/Traditional Waterfall

When it was first created, the Waterfall Model of Software Development presumed that writing software is a linear process, with clearly defined phases. Many experts have come to realize that this is not true in all cases. However, Waterfall is always useful as a checklist, even if it is not followed in a linear, rigorous fashion. A summary follows.

Phases:

1. Requirements Allocation
2. Preliminary Design (AKA Top Level Design or Architecture)
3. Detailed design
4. Code and Unit Test
5. Integration and Integration test

Scope:

1. Requirements
   • Capabilities – what the software does
   • Human interface – all screens and messages defined
   • All interfaces to external hardware and software identified
   • Size and timing requirements
2. Preliminary Design
   • Structure diagram
   • Functional flow diagrams
   • All major function prototypes defined and comments for functions written
   • All major data structures and data bases defined
   • Header files defined
   • Sizing and timing estimates (may be deferred to detailed design)
3. Detailed Design
   • PDL C Program design language (or pseudo code) written. Rule of thumb: 1 line of pseudo code = 3 to 10 lines of “C” code (approximately).
   • Better sizing and timing estimates
4. Code And Unit Test
   • Convert PDL to code
   • Design unit test plan and test code. Test Drivers, test stubs, and any special requirements defined (e.g., special test hardware configurations, test software, lab equipment, etc.).
   • Better sizing and timing estimates
   • Metrics, test coverage tool results, etc.
5. Integration and Integration Test
   • Design integration test plan and test code
   • Run code on target system and debug
   • Take sizing and timing measurements and ensure that you are meeting requirements.
   • Line count - Total lines of text, and lines of code.