BAT-10 is a menu-driven program that performs a lot of interesting mathematical functions. BAT-10 was written in the early 1990's, so any practical utility it may have once had is long since superceded by newer software. BAT-10's real strength lies not in its breadth of functionality, but rather in its prose. Each option in the program has a humorous introductory paragraph which you just have to read to appreciate. (Random trivia: BAT-10 was named in homage to my high school geometry teacher, Mrs. Batten.)

A couple of caveats, in case you ever mistakenly decide to use BAT-10 for serious work:

• Be advised that BAT-10's functionality that supposedly calculates pi to arbitrarily many digits is a complete farce. I wrote it long before I had any clue how to algorithmically calculate pi, so all it does is spew out random numbers. At the time, I thought it was a pretty funny joke. So enjoy the prose, but don't use BAT-10's pi calculator for anything serious. However, the other parts of the program should be mathematically correct insofar as I am aware.
• The calculus module is bogus too.

Enjoy!