A state chart consists of five main elements:
•States that define behavior and may produce actions
•Transitions that are movement from one state to another
•Pseudo-states, like the initial state indicator, that are used to connect transitions to more complex state transition paths
•Behaviors that are associated with transitions and state actions
•Triggers that are either externally or internally generated
Received input events act as triggers that cause an evaluation of the rules that govern the transition from the current state to other states.
State behavior and transition specifications are specified as C expressions. If you are unfamiliar C, we recommend C: A Software Engineering Approach.