Ellipse using Bresenham

AIM:- Draw ellipse using Bresenham Algorithm

CODE:-
#include <GL/glut.h>
#include <math.h>
#include <GL/gl.h>
#include<stdio.h>
void display()
{
	float a,rx,b,ry,d1,d2,x,y;
	printf("Enter the major axis and  minor axis\n");
	scanf("%f%f",&rx,&ry);
	a=rx;    
	b=ry;
	x=0;    
	y=b;    
	d1=(b*b)+(a*a)*(0.25-b);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glColor3f(0,0,0);
	glPointSize(5);
	glBegin(GL_POINTS);
	while((x*b*b)<=(y*a*a))
	{
			if(d1<0)
				d1= d1+ (b*b) * (2*x+3);
			else
			{
				d1= d1+ (b*b) * (2*x+3) - (a*a) * (2*y-2);
				y=y-1;
			}
			x = x + 1;  
			glVertex2f(x, y);  glVertex2f(x,-y);
            glVertex2f(-x, -y); glVertex2f(-x, y);
	}
	d2=(b*b)((x+0.5)(x+0.5)) + (a*a) * ((y-1)*(y-1)) - (a*a*b*b);
	while(y!=0)
	{
		if(d2<0)
		{
			d2=d2+ 2* (b*b) * (x+1) - (a*a) *  (2*y-3);
            x=x+1;
		}
		else
			d2=d2+ (a*a) * (3-2*y);
		y=y-1;
		glVertex2f(x, y);  glVertex2f(x,-y);
        glVertex2f(-x, -y); glVertex2f(-x, y);
	}
	glEnd();
	glFlush();
}

int main(int argc,char** argv)
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(0,0);
	glutCreateWindow("Ellipse Mid-Point");
	glClearColor(1,1,0,0);
	gluOrtho2D(-200.0,200.0,-200.0,200.0);
	glutDisplayFunc(display);
	glutMainLoop();
	return 0;
}