>>824377
If it lets you operate the computer, edit/run programs, read/write files to a storage device, interface with other hardware via serial/parallel ports, and so on, then it qualifies as an OS. That's basically all MS-DOS did, and CP/M too. The Amiga was really advanced for its time, and so had a more powerful OS.
The tragedy of modern computing is that OS's (and software in general) have become so complicated that they're always in flux - to fix bugs, add stupid "features" (that half the people didn't want), and other wastes of time. In the old days, you could just sit down at the computer and have fun, not worry about the OS crap constantly. I really miss that. Back then it was even common to make your own tools, like this guy explains:
https://youtube.com/watch?v=lJJfuQTjSQ8
These days the only way to have fun is with experimental stuff like TempleOS, or cobbling together old chips and/or microcontrollers into custom board, and then write your own simple OS. Modern stuff is a snozze fest and endless grind.
Btw, the OP was supposed to be attached to the thread "What's the longest you've ever gone between OS upgrades?" I probably got distracted by multitasking or cianiggers or someshit.