Yes CP/M was an earlier or pre-DOS AFAIK used I think mostly on mainframes. You can correct me there of course lol I am aware of Xenix, I think a variation of Unix I think designed for mini computers, some commands were different.

Well 2 C would be freezing for us. Goes to show what people get used to in their local climate. Not sure you'd cope well with 40-45 C like our summers tend to have on the hottest days.