Replica HP-16C coding calculator

Redditor someyob built a replica 1980s Hewlett-Packard HP-16C calculator around Raspberry Pi Pico.

What’s it made with?

Raspberry Pi Pico powers a tiny little 602 LCD display and three keypads. A level shifter converts the voltage between the Pico and the LCD display. The maker is still working on the code. They built this replica calculator to emulate the code testing experience HP-16C gave coders, except they’re using it to learn CircuitPython. Once they’ve a better grip on the language, they hope this recreation will have all of the original functions of Hewlett-Packard’s bespoke handheld.

Spoiler: Before you get too excited and start scrolling, this is a work in progress so we’ve no further details on the inner workings. But if you’re in the market for a twee look back at how coding calculations were done in the days of yore, continue on.

I am under the age of 40, please explain

The HP-16C Computer Scientist was a programmable pocket calculator produced by Hewlett-Packard which launched in 1982 but was discontinued in 1989. It was like a little debugging side-kick for computer programmers. HP-16C weighed in at 133 grams and measured a cute little 128 × 79 × 15 mm. It was the only programmer’s calculator ever produced by HP, so it’s not surprising that original units are highly sought-after by collectors, and that lots of emulators, like this one, are being created by the community.

hp 16c
The original

Why on earth did we need specialised calculators for programmers? Well, in the late 20th century, which is the trolls’ way of saying: “in the 1980s”, coders wouldn’t necessarily have had access to the massive expensive computers needed to do their complex calculations. Short of a smart phone or tablet to do their working out on, they relied on bespoke kit, and Hewlett-Packard created the HP-16C especially for them.

Calling all old school coders

We’ve already put the bat signal out at Pi Towers, so expect some of our engineers to comment with warm memories of their early coding contraptions. But the HP-16C was most typically used in the US, and we don’t have any American engineers, so over to our transatlantic blog readers to recall the giddy days of this pocket code tester.


Simon Long avatar

Sadly, I was never in the sort of financial bracket required to own an HP-16C back in the day when they were actually available, but a company in Switzerland called SwissMicros make modern copies of them, and I have two of their HP-16C clones, one at home and one at work. They’re incredibly useful for any programming or debugging work, as base conversions are a single keystroke away. For floating-point maths, they are basically hopeless, but if you are in a place where you are just pushing hex around, they are worth their weight in gold!

Liz Upton avatar

The fascinating thing here is that the conversation we had down at this end of the office went like this:

“Do you suppose one of the engineers has one?”
“Probably Simon.”

Simon Long avatar

I have to confess that, while I don’t own a genuine HP-16C, I do own multiple other Hewlett-Packard calculators – an HP-48G, an HP-48GX, an HP Prime and the anniversary re-issue of the HP-15C, which is identical hardware-wise to the 16C, but is an advanced scientific calculator rather than one for programmers.

Having spent quite some time reprogramming my brain to work in reverse Polish notation back in the 90’s, I am now unable to use any calculators which are not made by HP…

Alasdair Allan avatar

Casio did do a really nice line in reverse Polish graphing calculators back in the mid 90’s, but they were insanely hard to get hold off, and I hardly knew anyone that had one. I’m totally blanking on the model number(s) though, I wonder if I still have mine?

Liz Upton avatar

Just leaving this here:

Bruce Richardson avatar

I had a Casio fx-501P which I got for a bargain bin price. I always wanted the cassette interface for it because .. it existed.

Mike T. avatar

You might also like this

Brian Inglis avatar

Never liked RPN so always used TI Programmer calculators (and still own one) which had the same kinds of keyboards, operators, and feature sets. See and

Michael Benzinger avatar

Thanks, Liz, for the link. I ordered one straight away. I was a computer science student in the early eighties and could not afford to buy one of these at the time. This will be a good substitute and on a positive note still very useful in my work.

Ralph Hightower avatar

My HP-16C still works after 40 years.

Dave avatar

Yep. Mine too. I use it almost every day. :-)
I also have an HP-67 floating around in a box somewhere.

Al Martin avatar

My sister got an HP-16C when she decided to take some CS courses in college. She never got very far, but I ended up getting it from her, still have it. (I used an HP-67 as an undergrad.)

Al Martin avatar

I should mention that I’m a practicing logic designer, specializing in floating-point arithmetic units. humblebrag: I can do hexadecimal arithmetic in my head or on paper, and don’t need help from the HP-16C.

Someyob avatar

Hello, project author here. Was kind of surprised and embarrassed this showed up here, so I guess I better get cracking on progressing this project. One comment on the description, pretty accurate, though I wanted to use the 16C as an aid to doing 6502 assembly language programming AND to learn CircuitPython. Thanks for the post.

Liz Upton avatar

Hello! Drop us a line if you want your real name attached to the blog post: we spent ages looking but couldn’t figure out who you are! (My first name [at] And thank you: you got a lot of us very excited.

John avatar

I used to go through every page of the Educalc catalogues. I had the HP-41C and later a CX, the card reader, the barcode wand, the printer, a Zenrom module, and a 16k ram pack. I was into the Synthetic Programming and the Zenrom module + ram pack even let one program in assembly. Along with access to my brother’s Commodore 64 and Vic-20 I had a lot of fun. All this is why I understood the mission behind the pi. I still can’t remeber how I hit on the web site but I’ve said it before and I’ll say it again: Liz Upton’s sense of humor kept bringing me back. And I chuckle when I see any headline that suggests a new SBC is a Raspberry Pi killer. There in no competition. All of the good people working for the foundation are responsible for making computing as accessible now as it was in my youth. I’m my mind the cultivation of the community, the contribution to public software, the educational outreach, the dedication to the User Interface and user experience, partnerships with awesome vendors like Pimoroni and Adafruit all put this product beyond the reach of any other SBC manufacturer. Keep it up. There is a whole new generation of kids that are having the same kind of fun I used to have all because you guys do such a great job!

Simon Long avatar

Ah, Educalc! That takes me back.

HP stuff was really difficult to find in the UK in the 1990s when I could finally afford to buy it, and I remember waiting ages for an Educalc catalogue to be air-mailed to me from the US before I could browse all the goodies within! I bought numerous HP-48 books from them – they had a huge selection – and had funds allowed, I’d have bought even more. I’m pretty sure that one catalogue is still filed away with all my HP-48 manuals in my study – I must go and dig it out – along with a set of the original promotional leaflets for the HP-11, HP-15 and HP-16 that I got hold of back in the 80s when I was looking for a Casio pocket computer…

AndrewS avatar

I’m suddenly reminded of

Martin Nilsson avatar

Oh, RPN… those where the days. Used a HP48GX daily back in the day, still have it.


I own a HP42S since a our 35 years now and am very familiar with RPN. It’s my daily calculator. For special purposes I use the IR Printer.

Sean O'Steen avatar

With regards to the first photo and the number displayed on the LCD screen… I’m genuinely curious if primary school students in the UK played the same game with their calculators as we did here in the US?

Liz Upton avatar

They most certainly do. Or at least, we did 40 years ago.

Ashley Whittaker avatar

*ALL* English school students are mature and sensible and would never write “boobs” on a calculator.

Comments are closed