Most stepping motor applications involve accurate positioning of a mechanical load. For example, the position of a print head is defined very precisely by the number of switched excitation changes that have taken place in the controlling motor. External load torques, perhaps caused by friction, give rise to a small error in position when the motor is stationary. The motor must develop enough torque to balance the load torque and the rotor is therefore displaced by a small angle from the expected step position. The resultant 'static position error' depends on the external torque, but is independent of the number of steps previously executed; the position error is noncumulative.