What happens when you divide by zero on a mechanical 1950s calculator? In the 1950s, mechanical calculators didn’t have the safety checks of modern machines. So when someone tried to divide a number by zero, the calculator didn’t display an error. Instead, it would enter into a chaotic loop,... spinning its gears uncontrollably. This endless motion happened because the machine was trying to calculate something undefined, and it simply didn’t know when to stop.show more

Computer programs used to do that too: it is just an an infinite loop.

Early computers like EDSAC or the IBM 650 would just go into an infinite loop on divide-by-zero, same as that old Facit calculator. No error message, just spinning forever until someone pulled the plug 😂

Maybe it's doing the "repeated subtraction" method, that's why it can't stop.

That’s because a positive X divided by zero isn’t “undefined”, it’s infinite, so the mechanical calculator is trying to count to infinity.

Is this a perpetual engine?

no

It is calculating infinity! 😯 😝

it is calculating nothing

They would divide by moving a head forward by the divisor and count how many times it can do that. Divide by zero would never move forward, so it kept repeating it endlessly.

correct answer

This also happened on mainframe computers up until about the early 1980’s. If you tried to divide by zero, it would send the mainframe into an infinite loop, and the machine would have to be unplugged and restarted.

Wild to think how far we've come with exceptions and traps

It is. It wasn’t just dividing by zero. We had to analyze our code diligently back then to ensure we didn’t have infinite loops nested anywhere that could result in something like: x=1; while x≠0… x=x+1; Once the process grabbed hold, it never let go and you’d have to crash it. There were a lot of TSO mainframes back then, and doing something like that would typically shut down all kinds of stuff being used by companies, universities, and government agencies.

It’s like when you’re taking your girlfriend to dinner and asking her to pick the restaurant.

Haha so true

There's no "uncontrolled rotation of gears." The machine does long division as expected, but it can't stop at the last digit and keeps spinning. But not uncontrollably and chaotically — The error occurs at a specific location and can be stopped.

They used repeated subtraction for division. So it was not a matter of being undefined; they were in a sense calculating the correct answer -- infinity.

You make it sound more mystical than it is. Mechanical calculators perform division by counting subtractions. The problem is, if you subtract 0 from a number, you're left with the same number, so the process repeats forever.

Did they try unplugging it and plugging it back in?

wait so dividing by zero makes an engine

This calculator saw the Time Knife

Perpetual motion machine, just add dynamo.

Oh a naked CA-13, I have one of those!

cool

So is it still in a loop, or did it find the value of dividing by zero?

Mechanical calculators didn’t crash when you divided by zero. They spun forever. No error message, no fail-safe -just an endless loop trying to solve the unsolvable. That’s the physics of systems: When the input is undefined, the machine can’t exit the loop. Humans do the same. Any problem we refuse to define becomes a thought-loop we can’t escape. Clarity isn’t optional - it’s the stop condition.

I love that machine

is this why all the boomers thought we were doomed when the year turned to 2000 lol

The loop is not chaotic, and that is a very poor description of the behavior and the reason.

When I started work in 1974, I had to work on a monster calculator bigger than that one.

That's a cool personal anecdote, those early machines were absolute beasts! What was the wildest thing you saw it do (or break) on the job back then?

I hated it.

llms hallucinate numbers forever, mechanical calculators just spun their gears, machines always find a way to break beautifully when faced with the impossible

I'm gonna tell my kids this was Y2K🤣

Proves my theory that zero is infinity.

no

The machine is doing exactly what it was programmed to do. Dividing by 0 is nothing so it can never complete without returning to the problem.

Its old. Let the poor machine take its time. It will eventually calculate the infinity ♾️. Be patient. Wait for it.

So glad we have AI today which would never hallucinate an answer that is completely inaccurate

Looks exactly like when you tell someone: "Calm down"

Yeah, we've really advanced. Now Grok will just make up an answer.

what even is that thing

calculating nothing

The folks who wrote for Star Trek TOS were from that era & they couldn't shake the idea that a computer could be freaked out this way. So even though it was set in like the 23rd century, they constantly worked this type of thing into the plots.

“…and it simply didn’t know when to stop.” Today I learned I have something in common with a mechanical 1950’s calculator.

I had an early battery operated calculator (it was huge) and the digital numbers would go into a frenzy when trying to calculate anything more complex than square root of a number.

One time I tried sqrt(-1) on it and the whole display just started rolling 88888888 like it was having a stroke, then it got burning hot and shut off forever. RIP little chaos machine, it died doing what it loved: breaking math.

Sounds about right! Lol

if we make a big real mechanical calculator which won't need any external power source, and try this, maybe we can get free energy