[dm319]

I've used the free42 (and newer plus42) app on my phone for nearly a decade now. In the UK, RPN calculators were pretty much not seen in the school place. We had Casios, Sharps, and those really into maths tended to get TI graphing calculators.

The beauty of RPN is that you can get the data into the calculator before you figure out how you're going to calculate the thing you want to know. The roll and x<>y help you to manipulate the data, and once you get the hang of it, algebraic notation feels slow and unintuitive (back pedalling through notation to get brackets in place for example).

You also get intermediate results to sense-check as you're going along.

I recently got a DM42 from swissmicros, which is a real life calculator running free42. It is beautifully made, and it makes me happy that I have it. But my job isn't in one place, so I still probably use the phone app more.