State machine

A computational model with a finite or otherwise defined set of states and transitions triggered by inputs or events. Its current state determines how it responds to the next trigger.

Finite-state machine: A state machine with a finite set of states and transitions. It is the standard finite form of the model.
Automaton: An abstract machine that processes inputs according to defined rules. State machines are a prominent family of automata.
Protocol state machine: A model of a communication protocol as states and permitted message-driven transitions. It captures which messages are valid at each stage of a conversation.
Petri net: A mathematical model of concurrent systems using places, tokens, and transitions. It represents concurrent activity more naturally than a single global state.
Transition function: A rule mapping a state and input to a next state. It specifies how an input changes the machine's state.
State (computer science): A representation of information retained by a system at a given point in computation. The machine's current state summarizes what matters about its history.
UML state machine: A UML diagram and formalism for modeling event-driven object behavior. It extends basic state diagrams with hierarchy, concurrency, and actions.
Turing machine: An abstract computing device with an unbounded tape, a read-write head, and a finite control. Its unbounded memory gives it computational power beyond finite-state machines.
State transition: A change from one state to another caused by an input or event. Transitions are the model's basic computational steps.
Input (computer science): Data or signals supplied to a computational system. Inputs or events trigger the machine's transitions.

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