The GNU dc arbitrary precision reverse-polish calculator

 GNU dc is a reverse-polish desk calculator which supports unlimited
 precision arithmetic. It also allows you to define and call macros.
 .
 A reverse-polish calculator stores numbers on a stack. Entering a number
 pushes it on the stack. Arithmetic operations pop arguments off the
 stack and push the results.
 Home page: http://directory.fsf.org/GNU/bc.html