=============
State machine
=============
State machine is a model of a system that describes the states of the system and the transitions between those states.
Finite state machine (FSM) is a state machine with a finite number of states.

.. figure:: images/state_machine.jpg
   :alt: State Machine
   :width: 500px

   State Machine

* State - a condition or situation in the life of an object during which it satisfies some condition, performs some activity, or waits for some event (e.g. locked, unlocked)
* Transition represents the change in the system's state in response to an event or condition (e.g. insert coin, push door)
* Event (input) - a trigger that causes a transition from one state to another (e.g.  insert coin, push door)
* Action - an activity that is performed when a transition occurs (e.g. unlock, lock)