The D type flip-flop has only one input (D for Data) apart from the clock.
The INDETERMINATE state is avoided with this flip-flop.
When the clock goes high, D (a 0 or a 1) is transferred to Q.
When the clock goes low, Q remains unchanged.
Q stores the data until the clock goes high again, when new data may be
At A, clock and data are high.
Q goes high and stays high until B.
At B, clock is high and data is low.
Q goes low and stays low until C.
At C, clock and data are both high.
Q goes high and stays high until E.
Q does not change during clock pulse D, because clock and data are still both high.
At E, data is low, so Q goes low.
At F, data is high so Q goes high.