A state machine is a model used to describe the behavior of a real-world system. State machines are used to solve a large number of problems. They are used to model the behavior of various types of devices, such as electronic control devices, programs that parse communication protocols, and programs that perform text or pattern searches.

State machines may be described using a state diagram and a state table. A state diagram is composed of states, inputs, outputs, and transitions between states. A state table describes a state machine with the present state and input on the left, and the next state and output on the right.

State machines may be implemented using either a hardware architecture or a software architecture. The advantage of a hardware implementation is that it operates very fast, but it is difficult to modify and usually requires more circuit board space. The advantage of a software implementation is that it is easier to design and modify, but can be slower than the hardware equivalent.