window - create window - glfw

// play the game
int main(int argc, char* argv[])
{
  // on error, print errors to console
  glfwSetErrorCallback(error_callback);

  // initialize glfw. if it fails, exit the program.
  if(!glfwInit())
  {
    return -1;
  }

  // create a 640x480 window titled "Space Invaders"
  GLFWwindow* window = glfwCreateWindow(640, 480, "Space Invaders", NULL, NULL);
  // window doesn't render => close the program
  if(!window)
  {
    glfwTerminate();
    return -1;
  }
  // bind OpenGL calls to this window (allows us to draw on this window)
  glfwMakeContextCurrent(window);

//...