包含了DDA方法画线及中点法画圆，在绘图区域任意指定圆心及半径即可实现画圆命令-DDA method of drawing a line and the midpoint method to draw a circle, circle command can be achieved in any specified center and radius of the drawing area

c语言simple法求解二维区域流场的速度与压力分布-c-language with SIMPLE to solve flow problem in 2D area