UBASIC
Yuji Kida <kida@rkmath.rikkyo.ac.jp>.
An extension of BASIC for symbolic mathematics and number theory.
UBASIC supports bignums, fractions, complex numbers, polynomials and integer factorisation. It runs under MS-DOS and is written in assembly language.
ftp://ftp.simtel.com/math/utk/software/msdos/number.theory/ubasic/.
[Review, W.D. Neumann, Notices of AMS 36 (May/June 1989)]
["A math-oriented high-precision BASIC", Notices of the A.M.S, 38 (Mar 1991)].