#include<graphics.h>/*加入c圖形庫*/
#include<math.h>/*數學庫*/
#include<conio.h>/*鍵盤控制*/
void MidpointCircle( int r,int value)
{
	float x,y,d,deltaE,deltaSE;
	x=0; y=r; d=1-r;deltaE=3;deltaSE=2.5-r;
	putpixel(x,y,value);
	while(x<y)
	{
		if(getch()==17)exit();/*讀入鍵盤按鍵*/
		if(d<0)
		{
			d+=deltaE;
			deltaE+=2;deltaSE++;
			x++;
		}
		else
		{
			d+=deltaSE+deltaSE;
			deltaE+=2; deltaSE+=2;
			x++;
			y--;
		}
		putpixel(x,y,value);
	}
}

void main()
{
int i,driver,mode;
driver=DETECT;/*初始化顯示模式參數*/
initgraph(&driver,&mode,"..\\bgi");/*初始化顯示為默認驅動的640*480、16色模式*/
printf("Press any key to continue except 'Ctrl+Q' to quit.\n");
MidpointCircle( 400,15);/*設置半徑為400，顏色為15*/
closegraph();/*關閉圖形模式*/
}