圆的计算 含带提示框，含有按钮键，分别可以求得求周长和面积-Calculated with a circle with a prompt box, with buttons keys, respectively, find the perimeter and area can be obtained

直流电机PID调速,simmulink仿真程序, 不错的源码 很好(Dc motor PID control, simmulink simulation program, a good source is very good)