/* A Very Simple OpenGL Example! */

/******************************************/

/* this code just creates a window and draws a rectangle in it */

#include <windows.h> /* obviously change this to your native library if you're compiling under unix */

#include <gl\gl.h>

#include <gl\glut.h>

void init(void);

void display(void);

int main (int argc, char **argv) {

 glutInit(&argc, argv);

 glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);

 glutInitWindowSize(250, 250);

 glutInitWindowPosition(100, 100);

 glutCreateWindow("My First OpenGL Application");

 init();

 glutDisplayFunc(display);

 glutMainLoop();

 return 0;

}

void init(void) {

 glClearColor(0.0, 0.0, 0.0, 0.0);

 glColor3f(0.0, 0.0, 1.0);

 glMatrixMode(GL_PROJECTION);

 glLoadIdentity();

 glOrtho(-10.0, 10.0, –10.0, 10.0, –10.0, 10.0);

}

void display(void) {

 glClear(GL_COLOR_BUFFER_BIT);

 glRectf(-5.0, 5.0, 5.0, –5.0);

 glutSwapBuffers();

}

/**********************************************************************/

Lets go through this step by step:

First, I called the glutInit function, which provides general initialization for the GLUT library: