怎样用C语言程序画圆

#include <math.h>
#include <graphics.h> /*预定义库函数*/
void circlePoint(int x,int y) /*八分法画圆程序*/
{
circle(320 x*20,240 y*20,3);
circle(320 y*20,240 x*20,3);
circle(320-y*20,240 x*20,3);
circle(320-x*20,240 y*20,3);
circle(320-x*20,240 y*20,3);
circle(320-x*20,240-y*20,3);
circle(320-y*20,240-x*20,3);
circle(320 y*20,240-x*20,3);
circle(320 x*20,240-y*20,3);
}
void MidBresenhamcircle(int r) /* 中点Bresenham算法画圆的程序 */
{
int x,y,d;
x=0;y=r;d=1-r; /* 计算初始值 */
while(x<y)
{ circlePoint(x,y); /* 绘制点(x,y)及其在八分圆中的另外7个对称点 */
if(d<0) d =2*x 3; /* 根据误差项d的判断,决定非最大位移方向上是走还是不走 */
else
{ d =2*(x-y) 5;
y--;
}
x ;
delay(900000);
} /* while */
}
main()
{
int i,j,r,graphmode,graphdriver;
detectgraph(&graphdriver,&graphmode);
initgraph(&graphdriver,&graphmode," ");
printf("中点Bresenhamcircle算法画圆的程序\n")