How ironic that these days there are many millions of computers chock full of nifty devices like that, that are dedicated to individual users, that are all buttoned up so tightly with multi-user protected operating systems that it's virtually impossible for a kid to discover the sense of power you get from banging directly on the metal. Sure, you can still get there, but the road is now very much longer and full of non obvious steps. With good old debug.exe, the curtain was right there for anyone to pull back.