It should be self-explanatory. This only works with natural numbers and bases 2 through 10. It will reject your base if you enter one not between 2 and 10, but it can't yet tell if your starting number is in the correct base. I'm working on getting it for bases up to 36. If you're confused about the lesson, comment and I'll try to help you.
I learned how to do all of this from my math teacher who is amazing!
