UBASIC is a BASIC-like environment which is suitable
for number theoretic investigations. Version 8 of UBASIC has the
high precision real and complex arithmetic (up to 2600 digits)
of previous versions, but adds exact rational arithmetic and arithmetic
of polynomials with complex, rational, or modulo p coefficients,
as well as string handling and limited list handling capabilities.
In addition UBASIC has context-sensitive on-line documentation
(read ubhelp.doc for information). The file ubhelp.xxx that this
uses is ASCII and can be printed for hard copy documentation.
(from the documentation)