Overview
State diagrams are used to give an abstract description of the behavior of a system. This behavior is analyzed and represented in series of events, that could occur in one or more possible states. Hereby "each diagram usually represents objects of a single class and track the different states of its objects through the system".
State diagrams can be used to graphically represent finite state machines. This was introduced by C.E. Shannon and W. Weaver in their 1949 book "The Mathematical Theory of Communication". Another source is Taylor Booth in his 1967 book "Sequential Machines and Automata Theory". Another possible representation is the State transition table.
Read more about this topic: State Diagram