When I arrived at MIT, it was still... everyone was still using slide rules. By the time I left, of course, everyone was using calculators. There was a nice intermediate time in between when people were starting to... the rich kids had calculators.

[Q] The HP-45s and...

Yes. But we all actually did learn how to use slide rules. I got to use my grandfather's slide rule at MIT, so that was fun. But that went away pretty quickly... that was a pretty fast transition once it started to happen. But one of the interesting things is we discovered all these universal principles and had fun with them. And so, for example, we kind of... once we realised about universal machines we realised we could make a computer out of anything and so my friend Brian Silverman and I decided to make a computer out of Tinkertoys. So we got 50 giant engineer sets and built a giant machine that played tic-tac-toe and it was... Then some museum in Arkansas wanted it and we did a cross-country trip taking this machine out and we installed it. But it didn't really hold up that well to the shipment, and so we decided to make a stronger one with a different design. And so we got another 50 giant engineer sets and we decided to put them together with these little high-precision nails called 'escutcheon pins', which you normally buy three of or something, and I went down to the hardware store in Boston and I said, you know, 'I'd like 4,000 escutcheon pins.' And the guy said, 'That's a hell of a lot of escutcheon pins.' And I said, 'I've got a hell of a lot of escutcheons.' And took it back and so that was the construction method for holding the Tinkertoys together for the second version, which then went back in the museum. The first version came back here and it went to the Computer Museum and I think it ended up at the Science Museum and I still hear kids talk about it. So it's some place that kids see.