#include <GL/freeglut.h>
#include  <math.h>
 
 
 
const float DEG2RAD = 3.14159/180;
 
void drawCircle(float radius)
{
   glBegin(GL_TRIANGLE_FAN);
	glVertex2f(0.5,0.5);
   for (int i=0; i <= 360; i++)
   {
      float degInRad = i*DEG2RAD;
      glVertex2f(cos(degInRad)*radius+0.5,sin(degInRad)*radius+0.5);
   }
    glEnd();
}
 
void display(void)
{
/* clear all pixels */
       glClear (GL_COLOR_BUFFER_BIT);
/*     draw white polygon (rectangle) with corners at
  *    (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0)
  */
     glColor3f (1.0, 1.0, 1.0);
	drawCircle(0.4);
/* don't wait!
  * start processing buffered OpenGL routines
  */
     glFlush ();
}
 
void init (void)
{
/* select clearing (background) color                          */
     glClearColor (0.0, 0.0, 0.0, 0.0);
/*   initialize viewing values */
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}
 
 
int  main(int argc, char** argv)
{
     glutInit(&argc, argv);
     glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
     glutInitWindowSize (250, 250);
     glutInitWindowPosition (100, 100);
     glutCreateWindow ("hello");
     init ();
     glutDisplayFunc(display);
     glutMainLoop();
     return 0;        /* ISO C requires main to return int. */
}