Arguably, the HP-41 is the best calculator Hewlett-Packard has ever released. I should write the best calculator platform, by the way. Indeed, the 40 family counts three models. The first one, 41C released in 1979, the last one, 41CX, was released in 1983. Along with the calculators and their various peripherals, a vibrant third-party ecosystem developed a plethora of software and expansion hardware. Technically, the 41 introduced several advanced features for the time. It used an alphanumerical LCD – compared to the energy-hungry red LED common in the ’70s –, four expansion slots to host application-specific ROMs, a vast memory to store programs and data, and an OK keystroke programming language. Last, the 41’s card reader can read and run HP-65-67 programs thanks to its own embedded ROM.

For sure, the 41 was a commercial success. As I mentioned in a previous post (here), the best proof of this success is the number of HP-41 emulators and physical copies sold over the years. Hewlett-Packard introduced several of them to ease the migration of the 41 users to the new platforms. They called this an upgrade path. I own two of them: 41-Translator (5061-7269) for the HP-71B pocket computer and 41CV emulator (82210A) for the HP-48 platform (this one was co-developed with Zengrange). The second proof, if one were needed, is the physical copies released over the years. They are, after all, the best homage one can make to the original. I won’t write extensively today about all the available options. But instead, focus on the few I own and would recommend to someone willing to discover the 41 without using one. More niche, you die😊.

Let’s begin with the emulators by HP. The ones I own allows running 41 programs on an HP-71B or an HP-48, respectively. I will not detail the first one (5061-7269) – my preferred module as it brings RPN to the HP-71 – I described in detail here. I use the second (82210A) with my HP-48SX, the model I favor in the series (and yes, the emulator doesn’t work with the GX). It is an expansion card that takes one slot (out of the two available). After inserting the card and attaching the library, the 48 becomes more or less a 41. I don’t see a significant advantage to use the 48 as a simple 41 calculator (the user experience of the 48 is far superior, to be honest). Assuming your 41 has an infrared module (HP8224A), you can beam your entire 41 software library and data into a 48. The first time you use the emulator, it creates several 48 variables to store the emulator’s state. Interestingly, these states allow the user to keep side by side multiple 41 emulations, each one configured and tweaked for a specific use. Pretty cool!

To my knowledge, the 48 doesn’t support the HP-IL interface, which explains probably why the emulator doesn’t support it either. Yet, 41 programs and data can be transferred into the 48 using the 48 PC Kit. One infuriating aspect of the emulator is how the keyboard overlay attaches to the calculator using six small tabs. So, either you don’t insert all the tabs of the overlay, in which case you may damage it or lose it, or you spend five minutes each time you want to use the 48 features. And that happens every time one exits the HP-41 mode. And it happens pretty often. True, you also could memorize the keyboard layout of one of the calculators. Since the emulator card doesn’t provide additional memory (it’s a ROM-only solution), you can remove the card without losing any 41 program or data stored in the 48. True, you cannot run them until you re-insert the emulator, but it is a cool side-effect. That being said, the emulator can use more memory than the 41 could natively. The last detail of interest about this emulator, like with the HP-71 translator, uses the 48’s precision, which will improve your applications’ precision for sure (two more digits) and may change their behavior.

Inbetween the emulators and the physical copies, we find the other emulators. By these, I mean applications that emulate an HP-41 for smartphones, tablets, or desktop computers. There are plenty and at the end of the day, pick the one that fits your needs the best. In this category, the emulation’s fidelity is quite variable, and some of the liberties taken by the developers may be seen as heresy or a blessing—your pick. I consider these emulations as a necessary evil. Honestly, I was bit several times by such emulators. My biggest disillusion came from Hewlett-Packard itself and its HP-15C emulator for iOS. HP released it along with the Special Edition re-release (and it was not free or cheap, to that matter). As soon as Apple updated its OS, the emulator stopped working and was never updated. Cha-ching, I just lost ~$20! Today, for the 41, I am using i41CX by AL Software.

I will use this as an opportunity to write about the expansion ROM modules. Indeed, what really made the success of the HP-41 platform is its software library, mostly coming in ROM modules. There are a little less than 400 of them, and you can have a peek at a pretty complete database here. You can also download their images here. Whatever your field is, there is undoubtedly a ROM module for it and the 41. These modules will be helpful with the physical copies we will review next, as they use software emulation to load them. Emulators handle the modules more or less well. If they do, the main question is how they run programs using functions exposed by a ROM. Last but not least, you should own an original copy of modules you use with your emulator for copyright reasons.

In my opinion, the following best solutions and the last section of this post are the physical copies. I always had an outstanding experience with the calculators sold by SwissMicros. If you don’t know the company, describing itself as a small manufacturer of RPN calculators based in Switzerland, you must check them out (here). In 2015, I bought their DM41L – unfortunately, I could not find it because of my recent move –, a Voyager-like version of the 41. Really cool to use if, like me, you appreciate the letter format for calculators. In 2018, I bought the DM42 and posted about it here. Finally, for last Xmas, my wife offered me a DM41X! To me, it is the best HP-41 available that you can use day-in, day-out. Some of you may also consider the HP-41CL by Systemyde. Although I never used such modded 41, I may fall for it in the future.

I hope you enjoyed this short survey, and who knows, will fall for one of these homages to the HP-41’s undeniable success. Finally, I added here articles about the HP-41 published in Byte, L’Ordinateur de poche, Measure, and Hewlett-Packard Journal (they own their respective copyright).

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