DFF as a Finite State Machine
A DFF is a finite state machine with two possible states. Lets call these states S0 and S1. (state enumeration).
Furthermore, lets say when the Q output = ‘0’, then we are in State S0, and that when Q output = ‘1’, we are in State S1. This is called the State Encoding.
Bubble Diagram: States represented by bubbles. State transitions represented by arrows. Labeling on arrows represent input values (in this case, the D-input!). Labeling inside bubbles represent output values.