The Nut CPU (HP Calculator CPU) [pdf]

A long time ago, I worked for the HP Calculator support...made so many people happy by teaching them RPN. Most of the HP calculators had an RPN mode in the last few decades and they’d get stuck in it...a little 1, 2, +, 1,+ would be all the training wheels they’d need to understand RPN. Shame it’s not used more broadly.

https://en.wikipedia.org/wiki/Reverse_Polish_notation

/bin/dc or bc, or M-x calc in Emacs or galculator on the off chance that some HN visitor hasn't experienced RPN.

bc isn't a RPN calculator. dc isn't a very good one ;)

I've been using dc for a while now, is there another one you'd recommend?

For terminals, orpie: https://github.com/pelzlpj/orpie (source) https://opensource.com/article/19/1/orpie (demo)

For Android, RealCalc: https://play.google.com/store/apps/details?id=uk.co.nickfine...

I once bookmarked this modern implementation of an RPN calculator but didn't convince myself to spend CHF 199 on it:

https://www.swissmicros.com/dm42.php

Link is dead, any mirrors?

Interesting, since it works for me (just tried). maybe http://www.systemyde.com/pdf/hhc2006.pdf