The state-machine pattern

Abstract

A design pattern is a grouping of a small number of objects that is likely to be useful again and again. In the context of concurrent software design in Ada 95, it is a group of tasks and protected units that is useful in many applications. State machines are common in realtime software. Their use is fairly straight-forward but non-trivial. The State-Machine pattern is intended to capture the various constellations of tasks and protected units that can be used to represent a state machine and associated activities. A number of small examples are used to illustrate different implementations.