Chapter 3 - Standard State Machine Implementations

Abstract

This chapter discusses standard state machine implementation techniques, which one can find in the literature or in the working code. They are mostly applicable to the traditional nonhierarchical extended finite state machines (FSMs) because hardly any standard implementations of hierarchical state machines (HSMs) are intended for manual coding. The standard implementation techniques and their variations discussed in this chapter can be freely mixed and matched to provide a continuum of possible trade-offs. Indeed, most of the implementations of state machines that you can find in the literature seem to be variations or combinations of the three fundamental techniques: the nested switch statement, the state table, and the object-oriented State design pattern. In all techniques, state machines tend to eliminate many conditional statements from your code. By crisply defining the state of the system at any given time, state machines require that you test only one variable (the state variable) instead of many variables to determine the mode of operation.