I remember I was in elementary school when my dad first let me behind the counter at the family hardware store and lumber yard. It was in the mid 1970s and while cash transactions were recorded on a very early 20th century cash drawer that required hand written receipts as well as recording transactions by hand, the adding machine on the counter was quite nifty.

It was identical to the one pictured above: a Sharp Micro Compet.

The display was groovy. Though not shown in the photo, the zero was represented by the bottom portion of the “6” or the “8”, resulting in this half-height number. Unused digits to the left of the number being displayed were filled in with this zero, all eight digits were populated at all times.

It was an adding machine and not a calculator in that the addition and subtraction functions worked as an accumulator instead of doing arithmetic. It’s the accounting way of doing things and if you’re unfamiliar, think of it this way. You have a bucket. You add things to the bucket by pressing whatever number and pressing plus or minus. If you wanted to add two things twice (2+2), you’d hit 2 += 2+=. If you then wanted to subtract one, you’d then hit 1 -=. The display would read, in sequence, 2, 4, 3, as you completed each operation.

You’ll also notice the combination of multiplication and division on one key. The result was dependent on which equals key you hit: 2x÷2+= would result in 4, 2x÷2-= would result in 1. Even at a young age this made a lot of sense to me.

Per the Wikipedia page, this calculator was the first mass produced calculator using integrated circuits. It sold for $395 in 1970 and came with a leather cover.

My grandfather invested in good technology from time to time.

I remember checking my math homework from 2nd or 3rd grade with my father’s assistance. He cautiously watched me work the keys on this technological marvel; probably because it was so expensive. I can still remember the first time I entered a number on that adding machine and being so entranced with how it worked.

It’s no wonder I became such a dork.