finite_state_machine.gv

digraph finite_state_machine {
	rankdir=LR size="8,5"
	node [shape=Mcircle]
	0
	node [shape=ellipse]
	1
	node [shape=ellipse]
	2
	node [shape=doublecircle]
	3
	0 [label=0]
	1 [label=1]
	2 [label=2]
	3 [label=3]
	0 -> 1 [label=a]
	1 -> 2 [label="$"]
	2 -> 3 [label=b]
}