We will use two forms of a truth table (Table 6.3) and a state diagram
to describe the behavior of each type of flip flop. Although these
are particularly simple for the D flip flop, we will show them here as
well. In the first form of the truth table, the flip flop input(s) and the
present state are in the input columns; in the second, only the flip
flop input(s) are needed. The state diagram for a D flip flop is shown in
Figure 6.9. It has two states (for all types of flip flops). The transition
paths are labeled with the input that causes that transition. The output is
not shown in the circle since it is the same as the state.