State diagrams emphasize the event-ordered behavior of an object, which is especially useful in modeling reactive systems.
In this case before executing a command the program counter is at some position state before the command is executed.
This ERD notation is used to represent an entity—relationship models.
Statechart diagram describes the flow of control from one state to another state.
Associating State Diagram with a Class You can associate a state machine with a class, which is especially useful when modeling event-driven systems or when modeling the lifetime of a class.
State reduction While designing a sequential circuit, it is very important to remove the redundant states.