Partially. I am old enough to remember computers with one floppy drive (for old software, explaining the A:-position), but too young to have experienced the times when you needed two.
I hope that's a joke. In case it isn't: IBM PC predates all of those except UNIX (and you wouldn't think much of the pre-1980 UNIXen); CP/M, which originated the standard, comes from 1973.