There is provided a hybrid stepping motor including a rotor including a plurality of rotor small teeth arranged at an equal pitch on an outer circumferential surface thereof, and a stator including a plurality of salient poles, each including a plurality of stator small teeth arranged to face the outer circumferential surface of the rotor via a gap. In one embodiment, the well is operated between an on cycle and an off cycle. The wafer is held in a stepper device, which controllably positions the wafer under the desired image of the mask for exposure of a resist on the wafer. Instruction processors are scheduled from the scheduling queue associated with its assigned cluster whenever tasks remain within the cluster.