zsbc

zsbc can work with two numeric libraries: libbc (original library of bc) and libgmp.
zsbc is fully compatible with bc language and extends it for a few features like implicit powmod and automatic invmod.

When running with libbc numbers lib, it works with decimal numbers (and it manages the "scale" variable = number of decimals)
When running with libgmp numbers lib, it works with integers only.

zsbc works on Windows and Linux.

zsbc was created just for fun and to work on cryptographic topics.

It can handle an expression like
2^10^100%97 (it'll replace it with powmod(2, 10^100, 97) on-the-fly).

It can also implicitly calculate invmod's as in:
1/4%7 that (if variable autoinvmod is set) will return 2.