State machine

An abstract model of computation defined by a set of distinct states, one active at a time, and a set of rules describing which state comes next given the current state and an input. A state machine formalizes a system whose behavior depends not just on its present input but on where it already is in some prior sequence — the model underlying everything from a vending machine’s logic to a synthesizer’s envelope stages, and a restricted special case of the more general Turing machine.