Fond memories - and hangovers
One of the first computers I used, and on which I learned to do many things, was an RML 380Z, with CP/M 1.4B, and I've played with systems running CP/M86 as well as MP/M later on. Happy days.
And, though the OS itself may be mostly forgotten, it's left us with at least one enduring legacy - those 8.3 file names, and the horrible kludges still found to allow long file names to coexist with them, even in modern kit.
No, it may not have been the first OS to use such a naming convention, but in maintaining compatibility with that that aspect of CP/M in MS-DOS, it's surely endured far longer than it would have done.