I wrote a program in high school for my calculator to balance chemical equations. Ran the idea by my teacher and he said if I could make it myself I could use it. Probably was more work for me in the long run than just studying equation balancing, but I did get it working well and then had access to it for my AP Chem test.<p>Did some others I don't remember as well, definitely some physics, some trigonometry and other convenience functions for math, etc. I didn't have the cable to plug it into a computer and it was pretty annoying typing it all using the calculator keys, but it was my first experience with programming and I did end up making some stuff that was personally useful for my classes.<p>I wonder if my old calculator still has all the programs I did in memory too. Not sure if it still works, since it was over ten years ago, but I'm pretty sure I have it in a closet box and saw it when I moved last.