I’ve loved Chris Staecker’s videos about calculating devices and machinery for years now, and I finally have a reason to link to one here. This is a fascinating 12-minute review of The Kensington Adding Machine from 1993:

It’s a fun (as always) watch, but as a UX designer, it’s also interesting to try to figure out what are the underpinnings of the things Staecker lists as strange from today’s perspective.

I believe that “CE/T” (clearing and totaling) coexisting on one key is a nod to professional accounting use of adding machines where you wouldn’t want to accidentally enter something into the record twice – so totaling also automatically resets the value and prevents you from making a mistake.

I also believe the strange [+=] rule is only because the keypad has to look forward at the same time it is looking back: it needs to serve as a universal computer keypad where [+] and [=] are separate key, but it also needs to pretend to be an adding machine where one key served both purposes.

(You can spot that the back of the box just allows you to swap the [+] key to be something else.)

Overall, the video is a fascinating tale of an “in-betweener” product that was stuck not just in the middle of a transition from physical devices into apps, but also at the intersection of calculators and adding machines (once two very different lines of products), themselves trying to learn from each other. It also serves as a great reminder that skeuomorphism is not just about visuals and sounds, but also behaviours: tearing off the tape, details of specific keys, nuances of rounding.

It’s not a thing of the past, either. In my post about determinism I linked to Apple’s recent travails with the deterministic Clear button (part one, two, and three). A few years ago, Apple also changed the built-in iPhone calculator from its “desktop calculator” roots to a more modern model where you get to input the entire equation before you see the result. But that change had bigger consequences; for example the [=] key could no longer repeat an addition. People complained, and Apple added it back – but the change feels incompatible with the new system and potentially confusing:

Elsewhere, the entire iPhone is an in-betweener, as the keypad coming from calculators is incompatible with the keypad coming from phones.

At this point it seems the calculator keypad will win, but transition has been over a century in the making. Staecker’s video is a good reminder how important, but also hard it is when you try to make these transitions happen faster.