C Program to implement DDA Circle Drawing Algorithm

#include<stdio.h>

#include<conio.h>

#include<graphics.h>

#include<math.h>

void main()

{

 float x1,x2,y1,y2,startx,starty,epsilon;

 int gd=DETECT,gm,i,val;

 int r;

 initgraph(&gd,&gm,"c:\\tc\\bgi"); //Intialize your graphics path

 printf("\n Enter the radius of the circle:");

 scanf("%d",&r);

 x1=r*cos(0);

 y1=r*sin(0);

 startx=x1;

 starty=y1;

 i=0;

 do

 {

  val=pow(2,i);

  i++;

  }

  while(val<r);

  epsilon=1/pow(2,i-1);

  do

 {

  x2=x1+y1*epsilon;

  y2=y1-epsilon*x2;

  putpixel(200+x2,200+y2,15);

  x1=x2;

  y1=y2;

  delay(10);

  }

  while((y1-starty)<epsilon||(startx-x1)>epsilon);

  getch();

  closegraph();

  }

OUTPUT: