A state chart is a representation of an event-driven (reactive) system. In an event-driven system, the system makes a transition from one state or mode to another, if the condition defining the change is true.
For example, you can use a state chart to represent the automatic transmission of a car. The transmission has these operating states: park, reverse, neutral, drive, and low. As the driver shifts from one position to another, the system transitions from one state to another, such as from park to reverse.
State charts are often used to model complex logic including:
Using state charts can provide additional capabilities beyond traditional finite state machines, including: