The road to MS-DOS 2

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 singleuser 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.