(Revised 8/1/22) I have been an enthusiastic user of RPN calculators since high school, when Gerry Ford was president. Of course I refer to those made by Hewlett-Packard. My first was the HP-25C. The beauty of the RPN system with its 4 register stack was that it could do fairly elaborate chain calculations without the need for parentheses or an equal key. It is quite intuitive to many of us and was a pleasure to use.
But, alas! The HP RPN calculator has largely gone out of fashion it seems. Only a few models remain on the market and several are financial calculators. The HP-12C financial calculator is a wholly inadequate substitute for a scientific calculator. My 12C now sits in the desk drawer with unused pens and paper clips. All seems lost for the RPN tribe.
Or so I thought. It turns out that there is a manufacturer of Hewlett-Packard RPN clones called SwissMicros. These folks have taken the RPN baton and are running with it. Hero’s, I call them. They knew a good product when they saw it and have saved the day by manufacturing a clone that seems nearly indistinguishable from the corresponding HP unit.
I recently purchased the HP-15C clone called the DM15L. It has the look and heft of the 15C. My use thus far has been cursory, but I look forward to exploring the features. So, here is a shout out to SwissMicros!
Addendum, 8/1/22.. I have twice tried to contact SwissMicros regarding a cord for recharging the calculator. So far I’ve heard nothing. It is disappointing.
Lamentations on Chemistry 
You are definitely older than I am, no offense. I never quite liked these types of calculators after I started using the TI-83 in high school in the 90s. I still use my TI-83 today (multiple times per day) that I bought some 20-22 ish years ago.
No offense taken. I’m glad you have a calculator you like using. I was spoiled early on with HP back in the day when HP was much more progressive than today. I actually transitioned from slide rules to RPN. That transition was happening when I was in high school where I first saw an HP-45. I travelled to another high school to take a morning programming class using a Monroe 1600-series programmable calculator. We were also learning FORTRAN using punch cards. Heady times.
Had the first HP35 on campus. Back then, everyone else was using their slide rules. And we had a Univac 1108 to do the heavy lifting in FORTRAN V.
We got er done. Maybe not quite as quickly….
I still use my HP 15C everyday (bought in the late 70’s). Works like a champ. I’m trying to convince my son to switch to RPN but he looks at me like I have a third eye when I talk about it. I even have a calculator app on my phone that (thank goodness) can be used in RPN.
I am even older; I still have my ancient HP-25c, although the batteries are certainly dead, but my son took over my HP-15c. These days I use emacs calc, by Dave Gillespie (thanks Dave!).
https://www.gnu.org/software/emacs/manual/html_mono/calc.html
Hi Hugh,
I had an HP-25c as well. It was stolen by some mother’s child at CU Boulder. What a wonderful calculator. Sigh. I loved the lunar lander program.
I’m here because I’m looking for a non-programmable RPN calculator I can use on a test. The inefficiency of algebraic would have me all thumbs during a test.
The “Free42” calculator app for smartphone (android and ios devices) is worth checking out.
https://play.google.com/store/apps/details?id=com.thomasokken.free42&hl=en_US&gl=US
https://apps.apple.com/us/app/free42/id337692629
And you can also get versions for Windows, Mac OS, and Linux.
https://thomasokken.com/free42/
I have twice as many HP calculators as you and I have a Swiss Micro too. I also bought the remake Limited Addition HP 15C that HP came out with about 20 years after they stopped making HP 15’s. It is cool and much faster than the original. The Swiss micros are better than the original HP calculators, the batteries last forever and they have accurate clocks and better LCD displays. I still use RPN and it is still better.
Glad to hear that REPN still lives out in the world. Thanks for the note.
thank you for info, I did find a HP41x clone which will replace my two non-working originals
Bite the bullet and buy a used original 15C on eBay instead. I have two, as well as an HP-32II (even better from a usability standpoint) and use them frequently. It’s baffling that 30+ years-old calculators are better than anything that can be bought today.
I agree. I never thought to look on eBay.