“Try quickly typing 1+2+3. I bet you won’t get 6.” – Unsung

Earlier this month, I talked about a rotation button in photos that behaved really nicely in iOS, and not so great on the Nothing Phone. Here’s a story of a similar fumble iOS once made that might bring the point home even more.

The calculator app has been preinstalled on iPhones ever since their debut in 2007. For the longest time it hasn’t been anything more than a standard four-function calculator with a decades-old feature set. If you’re not careful, however, you can mess up even that.

Ten years into iPhone’s history, iOS 11 introduced a problem just like the Nothing Phone rotation – quickly tapping on keys would show them as responding, but the actual action wouldn’t be registered. Michael Tsai’s aggregator’s first entry has a video from Stephen Heaps:

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It shows typing 1+2+3+4 where iOS forgets one press of +, resulting in 1+23+4 = 28. Many more people posted about it afterwards, and showed various other examples.

It is oddly enthralling to see a computer fail at basic math. But what’s particularly historically interesting and perhaps even more embarrassing for Apple is the absolutely rich history of solving this kind of a problem.

Calculators evolved alongside typewriters as the earliest devices with button-like (as opposed to piano-like) keyboards. But the stakes were different.

Imagine a badly constructed typewriter and all the ways it can disappoint you: the letter might be faint if you press the key lightly or puncture the paper if you press it too hard, the output might be misaligned, or the typebars will jam in some way, forcing you to go again.

A typewriter has to work hard to divvy up a blank, analog piece of paper into a reliable, pleasant-looking grid via escapements, ratchets, and so on. But a calculator’s work to convince the analog world to be digital was much more important. After all, it’s not likely that the typewriter key you pressed will output the wrong letter – but on a badly constructed calculator, a light press of 5 could absolutely output 4, or 6, or 4.5.

And, while the typewriters only take your words verbatim, the calculator’s job is precisely to create new numbers out of the numbers you type. An imprecise mechanism can mess up that math. A jam could perform a partial or nondeterministic calculation. Adding 1 to 999,999 and the force necessary for the resulting cascading carry could break a device in the middle of work.

On top of all that, languages have a built-in redundancy. Evn if yuo mak many typoes, th sentece can stil be understod. But all numbers basically look alike. A calculator could make a mistake when it comes to a number that is absolutely vital for your payroll, for engineering, or for navigation – and you would never spot it.

Understanding all this, many calculator makers even already in the 19th century spent a wild amount of effort convincing people not just that their devices were helpful, and fast, and easy to use, but also that they could be trusted. Buttons were carefully weighted. Comptometers came with a locking mechanism. If a machine felt something didn’t go right, it would stop working and require a hard reset. The message was: “You can trust me, because I won’t ever show you bad math, and I’ll stop myself before I will ever lie to you.” Charles Babbage was so confident in his Difference Engine that he welcomed people to try to mess with its mechanical wheels in the middle of the calculation, convinced that even a sabotaged machine won’t ever make a mistake.

Just like with the Selectric decades later, those things were solved by people who cared, in the much harsher mechanical conditions.

Of course, I don’t expect everybody at Apple core iOS team to be a calculator UI historian (although it would be nice for at least one person on the team to be one!). It is embarrassing that no one on the team had enough imagination to realize that making a button respond to a quick press during animation, but not register it would cause all sorts of serious trouble. (The bug was fixed in iOS 11.2 by removing the animations, and subsequently the animations were brought back without the original problem in iOS 11.3.)

But maybe the bigger embarrassment is that Apple didn’t have a battery of tests to run on top of the UI at various speeds, mimicking fingers of what must be millions of people using the calculator app. That, too, has been a standard procedure for decades.

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