I remember seeing the following a lot when I was younger, and recently saw it again in a DOSbox setting:
For those that haven't seen it, the squiggly red lines shift and undulate quite a bit, and it actually looks like it's doing something fairly complicated. What is the program actually doing here? I don't actually know anything about graphics processing, so I assuming that it's performing some kind of stress test on the system, but I have no clue as to what it might be doing behind the scenes. And: If the software is trying to tune itself, how would it know what to change, especially on an older system?