Summary of the comments in here:

* I used the programming functionality of the calculator to get around the rules

* I didn't care much for the math, but my TI calculator was my first programming experience and it's what got me to love programming

My experience is similar. We were allowed to use our TI-85s in class, but we had to go up to the teacher before the test and show him that we were running a factory reset, to prove we had nothing programmed in it to cheat.

My buddy and I had made a two player blackjack game and didn't want to have to retype it after every test. So instead we made a program that mimicked the factory reset process. You would run the program before walking up tot he front.

The only indication something was different was the three little dots in the corner indicating a programming was running, but we just covered that with our thumbs.

Ironically we never used it to cheat, only to not erase our game that we programmed!