#include <windows.h>
#include <GL/glut.h>
#define SIZE 50.0
int i;

void init(void)
{
  glEnable(GL_DEPTH_TEST);
  glClearColor(0.0, 0.0, 0.0, 0.0);
}
void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glPushMatrix();
    glRectf(-20,-20,20,20);
  glPopMatrix();
  glutSwapBuffers();
}
void reshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  if(w<=h && w>0)
    glOrtho(-SIZE,SIZE,(GLdouble)-h/w*SIZE,
    (GLdouble)h/w*SIZE,0.0,2*SIZE);
  else if(h>0)
    glOrtho((GLdouble)-w/h*SIZE,(GLdouble)w/h*SIZE,
    -SIZE,SIZE,0.0,2*SIZE);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0.0,0.0,-SIZE);
}
void keyboard(unsigned char key, int x, int y)
{
  switch(key){
    case 27:
      exit(0);
      break;
    case 'f':
      glutFullScreen();
      break;
    case 'w':
      glutReshapeWindow(250, 250);
      break;
   }
}
void main (int argc, char** argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
  glutInitWindowSize(250, 250);
  glutCreateWindow(argv[0]);
  init();
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  glutDisplayFunc(display);
  glutIdleFunc(display);
  glutMainLoop();
}