Once upon a time most hackers knew about the infamous IBM "Black Team". In case you don't, I suggest you go read about them first, before you carry on here: The Black Team. (That should open in a new window or tab - just close it when you're done.) So let me tell you a story involving a member of the Black Team. This has come to me 13th hand, so I can't vouch for its veracity, but I can believe it. Oh yes, I can believe it. There was a programmer at IBM who was excited to get the job writing the driver/interface software for a brand spanking new tape-drive. This was one of the fascinating machines - cabinet sized - that you so often see in movies from the 60s, 70s and beyond. Reel to reel tape, running forward, then backwards, stopping, starting, no apparent reason for the direction, speed or duration. Almost hypnotic. Maybe I should write a simulator as a screen-saver. Hmm ... Anyway, our programmer was very excited by the idea of writing the software for this new piece of hardware, but also a little anxious. After all, his work would attract the attention of the Black Team, something no programmer ever really wanted. So he decided to thwart them. There are two ways to write code: write code so simple there are obviously no bugs in it, or write code so complex that there are no obvious bugs in it. - C.A.R. Hoare He decided to write his code perfectly. He decided to prove the code, formally. He decided to write code that was so clean, so neat, so perfect, that nothing wrong could be found with it. He worked really hard at getting this code perfect, and the time came for a member of the Black Team to inspect his code and test his software, they found no bugs. None! And they were annoyed. They came back. At first in twos and threes, but finally the entire team descended on him and his code to find the bugs they simply knew must be there, all to no avail. So our programmer was happy, content, confident, and above all, smug. So the day came when the hardware was to be unveiled and demonstrated to the world. This sort of event was always a big one. "New Hardware" was a big deal, and duly trumpeted. Then, at the last minute before the demonstration began, a member of the Black Team hurried up to the console and began frantically typing in commands. Our programmer was confident - he knew the code was perfect. It was proven and tested. Nothing could go wrong. He wasn't even perturbed when the tape started spinning at full speed and running right to the end. It stopped before the end, as he knew it would. It was safe, it was working, it was perfect. The tape then started to rewind at full speed, but that wasn't a problem either. Again, it stopped just short of the end. No problem. Again and again the tape ran all the way to the end, then all the way to the start. Again and again it stopped within tolerances. Our programmer smirked, knowing the Black Team were beaten. And then he saw it. The cabinet had started to build up a gentle, rocking motion. And it was growing. What could be happening? The Black Team had found the fundamental frequency at which the cabinet would rock, and had programmed the tape to resonate. In mounting horror, matching the mounting amplitude, the programmer watch as the cabinet at first subtly, then clearly, and finally unmistakably began rocking ever more violently, until finally, inevitably, it fell over. In front of the World's press. History doesn't relate what happened to the programmer, or to the product. Despite the tale being utterly believable, I've been able to find no record of it. The greybeard who told me the story has moved on to a place where I can no longer ask questions, and so I'm left with what might just be a tall tale. Surely there would survive some report of this event, some record, somewhere. Do you have a copy?