/* PROGRAM TO GENERATING A CIRCLE USING MIDPOINT FORMULA */
#include <stdio.h>
#include <graphics.h>
#include <conio.h>
#include <math.h>
main()
{
 int gd=DETECT;
 int gm=DETECT;
 int xc,yc,r;
 initgraph(&gm,&gd,"c:\\turboc\\bgi");
 cleardevice();
 printf("Enter the center x - coordinates : ");
 scanf("%d",&xc);
 printf("\nEnter the center y - coordinates : ");
 scanf("%d",&yc);
 printf("\nEnter the radius of the circle : ");
 scanf("%d",&r);
 cleardevice();
 drawcircle(xc,yc,r);
 getche();
 circle(xc,yc,r);
 getche();
 closegraph();
}

/*FUNCTION TO DRAW CIRCLE*/
drawcircle(int x,int y,int ra)
{
 int d,xc,yc;
 xc=x;
 yc=y;
 x=0;
 y=ra;
 d=1-ra;
 while(x<=y)
 {
  if(d<0)
  {
   x++;
   d=d+2*x+1;
  }
  else
  {
   x++;
   y--;
   d=d+2*x+1-2*y;
  }
  plot(x,y,xc,yc);
 }
}

/*FUNCTION TO TURN ON PIXELS*/
plot(int x,int y,int xc,int yc)
{
 putpixel(x+xc,y+yc,RED);
 putpixel(-x+xc,y+yc,WHITE);
 putpixel(x+xc,-y+yc,MAGENTA);
 putpixel(-x+xc,-y+yc,CYAN);
 putpixel(y+xc,x+yc,YELLOW);
 putpixel(-y+xc,x+yc,YELLOW);
 putpixel(y+xc,-x+yc,WHITE);
 putpixel(-y+xc,-x+yc,RED);
}