Finite State Machines
A finite state Machine(FSM) is a series of states, input events, output events, and a state transition function. These characteristincs determine the action of the machine. There are four basic actions:

Entry Action - An action is executed when entering a state.

Exit Action - An action is executed when exiting a state.

Input Action - An action is executed when receiving an input and the macine is in a prticular state.

Transistion Action - An action is executed when the machine is between particular states.

FSMs can be characterized as either "Mealy Model " or "Moore Model ". Choosing between the two models is determined by the use of the machine.

The Moore Model executes actions only when entering a state.

The Mealy Model executes actions when input is received and the machine is in a particular state (input action). The action is tied to the transition.


We can further define a FSM as either deterministic or nondeterministic.

A deterministic FSM relys on a single input event whereas a nondeterministic depends on the initial input plus a number of following inputs that determine the output.

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