| #include <GL/glut.h>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).
 glBegin(GL_POLYGON).
 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().
 /* don t wait!
 * start processing buffered OpenGL routines
 */
 glFlush ().
 }
 void init (void)
 {
 /* 0select clearing 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).
 }
 /*
 * 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. */
 }
 
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