Kyle Rankin @kyle@librem.one

Division was possible via repeated subtraction starting from the left and shifting to the right. There were no underflow bells, you'd just have to know when to stop subtracting a row. This is hard to do one-handed so I didn't film a video of that.

Subtraction was weird. You'd subtract w/ addition by the complements method, but would first subtract one from the number, then press down that number using the small digits on each key. You also slide the correct metal tab at the bottom to stop the carry. Here's 9 - 2.

You can perform many calculations surprisingly quickly and w/ one-hand. A well-trained Comptometer user was probably as fast as you'd get until electromechanical calculators. Here I'm calculating 1024 x 768, which just requires pressing 768 a few times and shifting left.

The Comptometer had a superior design. Pressing a key immediately updated the register, no need to pull a lever (the lever here clears the register). This design was so effective it stayed essentially the same (with minor improvements on error prevention) through the `50s.

This is a Comptometer Model E mechanical calculator, made between 1913 and 1914. Comptometers were made starting around 1900 and were a direct competitor to the 1908 Burroughs adding machine I featured earlier.

I didn't realize just how much I blamed Microsoft for the current state of passwords until I sat down to write about their "passwordless future": https://puri.sm/posts/microsoft-ruined-passwords-now-aims-for-a-passwordless-future/

More than 26,000 PG&E customers were without power in the Bay Area today because of fog and mist. Fog. and mist. https://www.nbcbayarea.com/news/local/over-28000-customers-experiencing-power-outages-due-to-fog-mist-pge/2660562/

This is the carry mechanism for the Monroe. The bars form a wave and the last few move, but were completely seized up. A few hours with some oil, pliers, a screwdriver, and ultimately a heat gun, and it finally loosened up. Subtraction finally underflows all the way to the left!

Yesterday I spent a few hours restoring this Monroe Model G calculator. It was only after putting everything back together that I discovered the accumulator is only underflowing half the digits when doing subtraction/division, so I get to take it apart again today and fix that.

To elaborate, this is a disposable VM just for opening random, possibly untrusted links other people send me. I do most of my own browsing in a different VM with ad and javascript blocking in place. It's always jarring to see just how bad the web is without all of that in place.

How do regular folks stand browsing the modern web? I have a VM for opening random links with no javascript or ad blocking. When I open certain news sites my laptop fans spin 100% loading all the ads, and it's almost impossible to read the actual story.

People subtracted on adding machines w/ a neat trick: the complements method. Convert a number to its complement, add it, and discard the extra "1" on the left. Many calculators with subtraction functions use this method under the hood: https://www.mathsisfun.com/numbers/subtraction-by-addition.html

Of course if you can add repeatedly you can multiply, so this machine has a "repeat" button in the bottom right corner. Once pressed, any number you enter stays pressed down after you pull the addition lever, so you can add over and over just by pulling the lever.

The Burroughs is a true adding machine--it can only *add* numbers. Notice the limited buttons on the keyboard. If you ever heard someone refer to a modern calculator as an "adding machine" it derives from the fact that originally that's all they could do back in 1908.

This adding machine has a carriage at the back so you can add a paper spool or even a sheet of typing or ledger paper, with tab stops you can set to speed the process of filling out forms.

This is my Burroughs Class 1, Model 7 Adder/Lister made in 1908. The glass sides and front let you watch the mechanisms as it's adding.

These antique calculators have a funny way of multiplying...