Program to implement Ellipse Generating algorithm in C

/*

   Ellipse Generating Algorithm

   Created By: Pirate

*/

#include<stdio.h>

#include<conio.h>

#include<graphics.h>

#include<math.h>

void disp();

float x,y;

int xc,yc;

void main()

{

                int gd=DETECT,gm,a,b;

                float p1,p2;

                clrscr();

                initgraph(&gd,&gm,"c:\\turboc3\\bgi");

                printf("*** Ellipse Generating Algorithm ***\n");

                printf("Enter the value of Xc\t");

                scanf("%d",&xc);

                printf("Enter the value of yc\t");

                scanf("%d",&yc);

                printf("Enter X axis length\t");

                scanf("%d",&a);

                printf("Enter Y axis length\t");

                scanf("%d",&b);

                x=0;y=b;

                disp();

                p1=(b*b)-(a*a*b)+(a*a)/4;

                while((2.0*b*b*x)<=(2.0*a*a*y))

                {

                                x++;

                                if(p1<=0)

                                p1=p1+(2.0*b*b*x)+(b*b);

                                else

                                {

                                                y--;

                                                p1=p1+(2.0*b*b*x)+(b*b)-(2.0*a*a*y);

                                }

                                disp();

                                x=-x;

                                disp();

                                x=-x;

                                delay(50);

                }

                x=a;

                y=0;

                disp();

                p2=(a*a)+2.0*(b*b*a)+(b*b)/4;

                while((2.0*b*b*x)>(2.0*a*a*y))

                {

                                y++;

                                if(p2>0)

                                p2=p2+(a*a)-(2.0*a*a*y);

                                else

                                {

                                                x--;

                                                p2=p2+(2.0*b*b*x)-(2.0*a*a*y)+(a*a);

                                }

                                disp();

                                y=-y;

                                disp();

                                y=-y;

                                delay(50);

                }

                getch();

                closegraph();

}

void disp()

{

                putpixel(xc+x,yc+y,7);

                putpixel(xc-x,yc+y,7);

                putpixel(xc+x,yc-y,7);

                putpixel(xc+x,yc-y,7);

}




Output