Maintainable software by design

Adequacy of program documentation is the major factor in the maintainability of a product. A maintenance programmer will be faced with learning curves: the `what´ curve-finding out what the program actually does; the `how´ curve-discovering how the program works; the `why´ curve-discovering why the program works in the way that it does. Adequacy of documentation, then, will be reflected in two ways: how well it enables the maintenance programmer to climb each of the three learning curves-and how quickly. The authors look at forms of documentation, particularly diagrammatic design notation and dimensional design notation