OpenGL

#include < gl/glut.h ><="">  [LEFT]void display(void)
{
/* clear all pixels  */
   glClear (GL_COLOR_BUFFER_BIT);[/LEFT] [LEFT]/* 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);
   glBegin(GL_LINES);
      glVertex3f (0.25, 0.25, 0.0);
      glVertex3f (0.75, 0.25, 0.0);
      glVertex3f (0.75, 0.75, 0.0);
      glVertex3f (0.25, 0.75, 0.0);
   glEnd();[/LEFT] [LEFT]/* don't wait! start processing buffered OpenGL routines */
   glFlush ();
}[/LEFT] [LEFT]void init (void) 
{
/* select clearing color  */
   glClearColor (0.0, 0.0, 0.0, 0.0);[/LEFT] [LEFT]/* initialize viewing values  */
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}[/LEFT] /* 
 * Declare initial window size, position, and display mode
 * (single buffer and RGBA).  Open window with "hello"
 * in its title bar.  Call initialization routines.
 * Register callback function to display graphics.
 * Enter main loop and process events.
 */
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;   /* ANSI C requires main to return int. */
}