OpenGL handles the drawing of models in a window but it does not provide the window, or handle events; that is why SDL is required. The prime purpose of this tutorial is to set up the SDL window and events mechanism. It also sets up the OpenGL environment that uses the window, the game loop, and a rotating cube.
Your program is being a CPU hog! In some cases, this situation can actually make your program run slowly! Your code needs to give some time back to the OS (i.e. delay or sleep).
