As with any C++/C program, we must include the header files for resources used in our program. In turn, we include the OpenGL header file gl.h. We also use resources from the OpenGL utilities library GLU and, therefore, we also include its header file glu.h. Last, since we are using GLUT to a create window in which the OpenGL content is displayed, we must include the GLUT header file glut.h.

As usual, what is written with the #include directive is dependent on how we setup our system and, in particular, our Path variable.