free42

Free42 is a re-implementation of the HP-42S Scientific Programmable Calculator
and HP-82240 Printer. It is a complete rewrite, not using any HP code. It does
not require an HP-42S ROM image. Even though it contains significant
enhancements compared to the original calculator, Free42 remains fully
compatible with the HP-42S, both in its user interface and in its ability to run
programs written for the HP-42S.