Free42

Thomas Okken

About this app

Free42 is a re-implementation of the HP-42S calculator and the HP-82240 printer.
It is a complete rewrite, not using any HP code, and it does not require an HP-42S ROM image.
Free42 is an Open Source project. The executables and source code are released under the terms of the GNU General Public License, version 2.
All third-party code used in Free42 is either in the public domain, or licensed under terms compatible with GPLv2, or used with the authors' permission.

Ratings and reviews

Incredible RPN calculator! If you like HP calculators, this is flat out amazing! It has the same layout as the original HP-42s. It even runs the same programs -- but much faster than the original! There's a "haptic feedback" option which feels something like the actual HP key clicks. There are other layouts if you like a horizontal layout. The settings screen is accessible if you touch the calculator display.

I still have two HP42s, one for my office at work, one for my office at home, both in a drawer. Free42 now resides on my phone and computers. It is a perfect emulation with some significant advantages in stack height and memory. I occasionally miss the HP's programmability, but usually just turn to a spread sheet for highly repetitive calculations or more specialized apps or programs for more challenging work.

This is a great app for all of us RPN nuts out there. I probably have 15 different HP's put out to pasture (in a drawer) that don't get much use as I'm now retired. This has been my everyday, goto calculator since. I plugged in the old Elgin & Knowles astronomic azimuth program which appears to run just fine with current ephemeris data. Send a few bucks in to the developer as this app is worth its weight in gold. I'd rate it higher if possible.

What's new

Fixed crash for certain unrecognized key codes from Bluetooth keyboards.