All these stories are reminding me of m first encounter with programming. My Grandpa gave me his $600 Visual Basic (5?) book + software when I was 13 (~15 years ago). He didn't have the registration key, but I naively thought I could get lucky with a 16+ digit code. The first code I tried failed, but I tried changing the last digit and after a couple of tries got it. I didn't know what it was called at the time, but I instinctively guessed it could be a checksum, and somehow, that's how Microsoft protected their $600 product in 2002. Anyway, my Grandpa passed before I went to college but I think we would have had a lot of fun talking programming, because I was much more interested in pure math in HS when he died. That first programming book was definitely what got me interested though.