AND-state:

Currently Q1 is active. Assuming that the environment provides event A, state Q2 is entered and event C is generated. Q2 is a so-called AND-state consisting of the two parallel sub-states R1, R2. When entering Q2 both states R1 and R2 are entered simultaneously, so the states S1 and T1 become active. The fact that S1 (resp. T1) becomes active and not S2 (resp. T2) is implied by the fact that the default connector points to S1 (resp. T1). Note that only OR-state s and basic states occupy space whereas AND-state s are given only by their borderline.