掌握直线和圆的生成算法,分别用DDA法和中点画线法在屏幕上画两条直线段-grasp of linear and circular generation algorithm, respectively DDA Act and the dotted lines in the screen painting of two straight

通过程序实现Bresenham画线算法，中点画圆算法以及中点画椭圆的算法-Achieved through the process Bresenham line algorithm, the midpoint circle algorithm, and the dotted ellipse algorithm