Plus42

Thomas Okken

About this app

Plus42 is an advanced scientific programmable calculator, based on Free42. Free42, in turn, is a complete re-implementation of the HP-42S scientific programmable RPN calculator, which was made from 1988 until 1995 by Hewlett-Packard. Free42 is a complete rewrite and contains no HP code whatsoever.

Plus42 builds on Free42 and adds: Algebraic expressions modeled after those used on the HP-27S and HP-17B/19B; attached units and unit conversions modeled after those used on the HP-48/49/50 series; directories for more organized storage of programs and variables; a larger display, with 8 rows and 22 columns (131x64 pixels) by default, which the user may resize at will; time value of money and amortization schedules; and two-dimensional plotting of functions, with ability to zoom and pan, and find integrals and roots from points in the plot.

Ratings and reviews

The first program I've always installed on a new phone is Free42. I liked it so much I've donated money to keep the project alive. But I had no idea Plus42 existed. What I nice extension to the HP42s! I bought this within minutes of knowing of it's existence. Thanks Thomas for all your work over the years! (And trust me, it's been years. I remember when Thomas wasn't sure he was going to support Android, he wanted to wait and see if it stayed around long enough to make it worth his while. 🙂)

I liked free42 but needed more than 2 lines, one of which was more often than not used for menu options. This app is better than I could have even hoped, with fully configurable lines up to 99, and adds built in unit conversions, directories, and several other RPL like niceties, while sticking with the simpler programming and functionality of the 42s model. Very happy so far with what is only version 1!

This improves an already excellent calculator. This app has been around in one form or another for maybe 30 years - It was then, and still is, the best calculator I've seen. My OG hp42 still sits next to the mouse pad, but this phone app sees more maths action. For the suggestion box: can we swipe from the shift button to the exit button to turn off (as opposed to tap shift + tap exit). Actually, swipe from shift to any key would be nice. Thanks Thomas

What’s new

Fixed RLN and RRN for negative numbers in BSIGNED mode.