A great and concise history of the run-up to MS-DOS 2.0.
Yet, there was a nagging feeling that a single-tasking CP/M clone was inadequate for the new generation of personal computers. Digital Research released multi-user, multitasking MP/M-86 in September 1981 and announced the single‑user multitasking Concurrent CP/M in early 1982. In response, Microsoft came up with a plan for tiered approach to its operating systems: single-user/single-tasking MS-DOS at the bottom; multi-user/multitasking XENIX at the top; and in the middle, something called XEDOS: a single-user version of XENIX. This “pyramid of upward-compatible operating systems” was announced in a Byte Magazine editorial in January 1982.
↫ Nemanja Trifunovic
I’ve always found this tiered approach fascinating, and the world surely would’ve looked quite different had Microsoft been able to make it work. I doubt Windows NT would ever have existed, and most of the world would probably be running a XENIX-based Windows today (all else being equal, which is of course unlikely and silly). Regardless, MS-DOS 2.0 contained a few UNIX-like utilities to deal with its brand new support for directory trees and other new features, and even had a /dev directory.
