When I was fourteen, my old mentor John, gave me two things at the start of my instruction in the ways of being a programmer. The first was the book Digital Fundamentals (the 2nd Edition from 1982 which I still haven’t read). The second was an HP-42S RPN calculator from 1987 that he raved about. He really wanted me to be converted to the church of RPN, but at school we were using the TI-82 and TI-85 and the teenager in me viewed RPN as a relic. John told me TI calculators were garbage and HPs were the only way to go. I, predictably, did not listen.

John had always been close to the hardware end of things. His labs had breadboards, oscilloscopes, soldering irons, and a number of other similar items. In my early days as a quasi-apprentice, he was trying to get me to dive into these aspects of technology. About this time, I attempted to learn C and realized each and every time that I absolutely hated it. I sense my initial exposure to Logo in grade school had me far more connected with higher level languages and more abstract outputs. Being “close to the metal” has never really interested me1.

Both the book and the calculator have mostly collected dust for the past three decades and have always had far more sentimental value than practical value. I figured it would just stay that way.

My older son recently started learning Algebra and while helping him with a recent assignment I watched as he was doing long multiplication and division by hand. “Bud, you know you can use a calculator now, right? There is no reason to ever do this by hand again unless you have no other choice.” This was certainly a relief to him.

I don’t know if it’s a strange quirk of my household or perhaps my children’s generation, but they love “retro” things. My daughter has a turntable and some old vinyl. My older son has a collection of pocket watches—some of them date back to the late 19th century. My youngest son likes old cameras, film and digital alike, and loves wooden hand planes—so much so that he includes them anthropomorphically in most of his drawings. Apparently, the convenience of our age is just too much.

This fascination extends to all sorts of things. Something that looks decades old seems especially interesting to them. My sons both have a fondness for older Nerf blasters. I don’t get it, but I get it. They often ask me to comment on how “cool” some old thing is and I remind them how much I prefer convenience and how my phone can probably do whatever some other device does better and faster. They do not care—not at all.

So, when I showed him how to pull up a calculator on any of the laptops, iPads, or phones in the house he had one thing on his mind. “Don’t you have that old calculator somewhere?”

“What, you mean that one in my room? The one John gave me.”

“Yeah. Can I use that one?”

I explained that it was “weird” and, of course, this did nothing to dissuade him—quite the opposite of course, which seems obvious as I write this. We went upstairs and I dug the calculator out of keepsake bin. I tried to turn it on but I imagine its batteries had been very dead for some time. No problem though. We popped out the little watch batteries, found the model, ordered new ones, and waited. (Less than 24 hours no less, a point of convenience they actually enjoy.)

As soon as the batteries arrived we put them in, pressed the ON button, and… were disappointed. The calculator failed to power up. I was rather dejected. The idea that it would see use again was something I really liked poetically, almost like John’s spirit or essence was helping another generation learn math. When the screen showed nothing, I felt a very sharp pang in my chest and tried to immediately defuse it.

“That really sucks, but it’s okay. I mean, this thing is really old and hasn’t been used in years. You’ll just have to use something else.” I put it back in the keepsake bin and tried not to think about it. It ate at me nonetheless. John was gone and so was his calculator.

The seed, however, was planted. Both of my sons spent the day looking on eBay for RPN calculators and even discovered that SwissMicros makes a successor to said calculator in the DM42n. They were not letting this go. They kept updating me on new finds. My older son had become fixated on using an RPN calculator.

A funny side note—which I’ll get back to—they realized a calculator they had seen on my father-in-law’s desk was an HP-15C. He had used it back in his days at IBM and still uses to this day. RPN was apparently in their blood.

Like many things with cult-like devotion which are no longer produced, buying one is expensive. In no universe was I dropping $200+ for a 30-year-old calculator that, while kinda neat, is something my phone can do. The fancy SwissMicros can be had for a cool $429. Ugh. Just no.

I don’t know why it hadn’t occurred to me in the first place, but as my sons were talking about saving up money to get one of these things, I knew they were serious and it jolted me to action.

“You know, this is something we can probably fix.”

It didn’t take long either. About five minutes of searching the web lead me to a 21-year-old forum post2. I followed the instructions, got a little piece of copper wire I had on hand from installing a new light switch, discharged the memory, replaced the batteries, and voila, it powered right up.

I was both exhilarated and felt a great sense of relief. I wanted this thing to work and it worked. My son immediately wanted to start using it and began asking questions that I didn’t really have answers for. John had instructed me on using an RPN calculator 32 years ago. About the only thing I remembered was that the operator was entered after the operands, but very little else.

With some fumbling, I remembered how to do mostly basic arithmetic which was good enough for now. While there is no shortage of online literature and videos on the matter3, his grandfather had and RPN calculator as well. I thought this would be a much better and meaningful form of information exchange. My son did some tinkering and, on the weekend when we visited his grandparents for dinner, he sat down with his grandfather to get a tour on using an RPN calculator. He’s already better at it than I ever was!

A few days later, I find myself sitting at the dinner table with my son helping him with ratio equations. As we converted various volumes and weights, and I watched him hammer the numbers in, the elegance of RPN was readily apparent. The impatient teenager in me had dismissed it years ago, but it seems John still has some posthumous lessons for me and, more importantly, for my children.

Maybe I should finally read Digital Fundamentals.

  1. I like the idea of understanding computers better. I really do. Every few years I’ll forget that I like the idea far more than the reality, burn a couple weeks reading up and toying with some lower level language, and then remember, “Oh yeah… I hate this and it’s about as fun as eating glass.” The same thing has happened to me with cars. Every now and then I fantasize about restoring some classic car and then I work on a car and remember that I hate it. I’m concerned Zig will end up being the next incarnation of this cycle. ↩

  2. While the internet in general continues to rot away, it’s nice to find reminders of what is so amazing about living in the Information Age. This relatively niche bit of knowledge was at my fingertips in minutes. ↩

  3. Again, this is what is so amazing about living in the Information Age. ↩