I've worked on software that controlled servo driven lathes and mills. I still know the e-stop function of that code by heart 30 years later, not because it was such an elegant or beautiful bit of code but mostly because I realized that any kind of fuck-up there would likely mean someone would lose a finger, a limb or even worse, and so I kept on re-reading it and inventing new ways to test it to ensure that it was solid. It definitely raises your level of awareness when you are working on stuff that has real-world consequences.

I should probably do a write-up on how this worked, it was a pretty creative solution to a very hard problem and as far as I know it never failed to work in production. The machines are still in use in some places after all these years, never ceases to amaze me how long lived some of those projects were. Atari ST as the hardware, software in a combination of GFA basic and 68K assembler, just about every port on it used to drive some output or read a sensor.