I’d tried several of the other RPN calculators on the iPhone (including a very nice 41C emulator), but they never felt right and I had to hunt-and-peck too much to figure out the keys. When I saw the 15C emulator, I spent $20 for it (the most money I’ve spent on a single app).

Here’s the weird psychological thing. I haven’t touched a real 15C in a bit over 20 years, but my fingers still remembered where most of the keys were and I can tap out problems pretty quickly on the iPhone. Even without tactile feedback, it “feels” like a 15C. As geeky as this sounds, I’ve actually dug out some math problems to solve just because I’m so happy to have a 15C again…

Once I found a scan of the 15C manual, I was all set. They really don’t write calculator manuals like that anymore, either.

The days of smiling quietly to myself when people asked to borrow it and ignored my warnings of “if you haven’t used one before you probably won’t be able to add 2 and 2″ are long gone, but this is easily the object I would miss most if it were to disappear off my desk.

HP calculators have only gone down hill since the late 90s. Sadly at the turn of the millennium HP decided it wasn’t worth the effort to do much product R&D anymore. To quote their director of supply chains in 1999: “We’ll let Intel do our hardware R&D, Microsoft will do our software R&D and we’ll own the supply chain”. HP Corvallis calculator operations had already been moved to Australia and not long after in 2001 the Australian operation was shutdown and the calculator division was moved to Singapore. At that point calculator design and manufacture was largely outsourced.

The result was the “return to the market mediocre” loss of RPN. Only market demand seems to have resulted in a grudging implementation in the latest versions. At this point you’d have to hold a gun to my head AND pay me to even accept possession of a new HP calculator, which is quite a reversal for someone who was an early and long-standing PPC member, 30-year user of HP calculators and 10-year veteran of HP itself! They are *so* bad. The sad part is they’ve lost the very thing that allowed the higher product margins which funded the features which locked-in engineering students and elite users who could afford the prices. Break the cycle and you have to compete with the dogs!

The best hope for having a revived 10-series is to look to non-HP sources – i.e. the enthusiasts and hackers. This community has historically been amazingly technical. Back in the day these folks “discovered” synthetic programming which is a back door into the HP41′s firmware. I was a hardcore synthetic programmer back in college. Several calculator enthusiast groups on the web have voiced a desire (and sort of started) attempts to create from scratch RPN/RPL calculators in the original HP spirit.

I think the biggest problem is they are probably biting off too much to both create the hardware and extend it. Reproducing an HP 15C with modern components without trying to go too far beyond is quite doable and probably with some impressive speed/power performance. A single current FPGAs could trivially implement the entire hardware of a 10-series which originally had several ICs (the original 10-series used an early form of surface mount).

It’s always about time however. For example I’ve completely reverse engineered and built HP-IL (calculator networking for the HP41, HP71, HP75) from the ground up with modern off-the-shelf components but I haven’t had time to do much with it let alone document and publish how to do it.

Thin. Elegant. Well built. RPN. Wonderful. When HP was still an electrical engineering company. The real HP is now Agilent.

My iMac has an RPN calculator.