Finite state machines: flip-flop
	Flip-flop can be modeled as a finite-state machine
	D flip-flop					q	D	q+	z
		State: 1 bit (q)				0	0	0	0
		Input: 1 bit (D)				0	1	1	0
		Output: current state (z)				1	0	0	1
						1	1	1	1
	In state 0:						In state 1:
		input 0 gives new state 0 (reset)						input 0 gives new state 0 (reset)
		input 1 gives new state 1 (set)						input 1 gives new state 1 (set)