void renderScene(void)
{
glClear(GL_COLOR_BUFFER_BIT);

glRectf(-25.0f,25.0f,25.0f,-25.0f);

glFlush();
}

void changeSize(int w, int h)
{
if (h == 0)
    h=1;
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
float ratio = w/h;
if (w<=h)
    glOrtho (-100,100,-100/ratio, 100/ratio, 1,-1);
else
    glOrtho (-100*ratio,100*ratio, -100,100,1,-1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}

int main (void)
{
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
glutInitWindowPosition(100,100);
glutInitWindowSize(500,500);

glutCreateWindow("he");
glutDisplayFunc(renderScene);
glutReshapeFunc(changeSize);
glClearColor(0,0,1,1);

glutMainLoop();

return 0;
}