This calculator is based in previous programming by
Eiji Kako (1996).
Enhanced by Alvaro Gerardo Suárez (1999)
ENTER is Enter number in X register into Y register (and disable stack lift)
X< >Y is Exchange X and Y registers.
CLST is Clear Stack
CLX is Clear X register (and disable stack lift)
RDN is Roll Down (Roll Stack Down)
This code was tested with Internet Explorer 4.0