I recently sold three calculators on eBay: an HP15C, an HP16C, and a TI59. Got slightly over $300 for them, which was less than I paid 30-plus years ago (especially adjusted for inflation), but they had no value sitting on a shelf in my office. Along the way, I realized two things.

First, I was, and may still be, a calculator geek.

I was never one of those people that walked around with his calculator on his belt (indeed, only one of the three even had a case with a belt loop). But, let's be honest, owning a dozen calculators just ain't normal (no, I didn't sell all of my old calculators; sue me). Nor is it normal for a 15-year-old to save his allowance and odd-job money so that he could buy a programmable calculator (a TI-55, which I still have; again, sue me).

The second thing I realized is just how irrelevant calculators are today.

These three calculators were the pinnacle of late-70s/early-80s calculator design. All three were programmable. The HP15 was designed for engineers: it could work with complex numbers, and could compute integrals and roots based on your programmed function. The TI-59, with nearly 1 KB (!) of memory and a magnetic card reader, was a viable competitor for then-current home computers, at 1/10th the price (and was touted as such in contemporary reviews). Certainly I used it as such: looking over my personal program card library, I saw one card that I used to balance my checkbook, tracking credits and debits.

But as desktop computers became more prevalent, nobody needed programmable calculators. In the early 90s I bought what I still consider to be HP's best calculator, the HP27S. It wasn't programmable, but you could still find the root of a function: you simply entered it as a formula and the calculator was smart enough to either solve it algebraically or numerically. It also combined functionality from the financial and computing domains with the basic scientific functions. And it used algebraic notation, which I'm sure upset a lot of HP purists.

I first got a hint of how irrelevant the physical devices had become a few years ago, when I was doing some bit manipulation operations and took out my 16C. When I learned that a new set of batteries would cost $15, I looked for something similar that I could run on my phone. And found apps that were based on the actual HP ROMs (they weren't copyrighted), running on an emulator. For less than the cost of batteries.

So the actual calculator remained on a shelf, unused. And really, I don't use the apps that much either (I also downloaded an HP11 emulation, so plural). When sitting at the computer it's easier to start up a Python shell or a spreadsheet. Really, the only place that I use the calculator is when I'm at Home Depot trying to figure out how many bags of fertilizer I need.

Perhaps high school and college students still use calculators, but I suspect not. Laptops are pervasive and inexpensive; why carry two devices. Which makes me wonder: will the calculators I sold sit unused on the shelf of someone who's more of a calculator geek than me?