The step angle is 360 degrees divided by the total number of poles.
For the four poles, 360 degrees/4 = 90 degrees.
Assuming there is a 36-pole motor, 360 degrees/36 = 10 degrees, and the single-step operating angle of the full-step mode is 10 degrees.
One step angle of the half-step mode is 1/2 of the full-step mode.
One step angle of the micro-step mode can be selected to be 1/4 of the full-step mode and a finer step angle.