The Free On-line Dictionary of Computing (30 December 2018):

Calc

    An extensible, advanced desk calculator
   and mathematical tool written in Emacs Lisp by Dave
   Gillespie .  Calc runs as part of GNU
   Emacs.  You can use Calc as only a simple four-function
   calculator, but it also provides additional features including
   choice of algebraic or RPN (stack-based) entry,
   logarithms, trigonometric and financial functions, arbitrary
   precision, complex numbers, vectors, matrices, dates, times,
   infinities, sets, algebraic simplification, differentiation,
   and integration.

   FTP calc-2.02.tar.z from your nearest GNU archive site.

   (2000-10-20)