One of the first c programs I ever wrote was an infinite loop that wrote a random value to a random address. Sadly DOS 6.xx did not have address spaces as such, and while I did not know what it meant at the time, upon rebooting I found it had a write through cache... Most of the file system was littered with extended ASCII characters. Time to pull out all the floppies again for a reimage

I was going to respond that DOS didn't have any such fanciness, but then I remembered SmartDrive. And indeed, it turns out it had a write-behind cache [1] that may well have ruined your day if abused in such fashion.

[1] https://www.computerhope.com/smartdrv.htm

I remember itade me learn how fat worked, then I would use debug to make recursive directory trees with large files in them so a dir /s would terminate at max depth with a huge aize reported. I used it to make people in my HS cs class think I had found really good floppy disks.

I lost tons of work when playing with toy assembly language programs in DOS, when I would save and compile and run it and it did something to crash necessitating a reboot, faster than SmartDrive would write the cache to disk. Particularly for anything crash-prone like messing with hooking interrupt vectors.

There is russian kmem-roulette[1] - dd if=/dev/urandom of=/dev/kmem bs=1 count=1 seek=$RANDOM

1: http://bash.org/?926695