[rzeznikj at stout]

IIRC, Windows NT was based in large part on Microsoft OS/2 1.3 (OS/2 2 and up were produced solely by IBM).

In fact, WinNT 3.1 was originally designed to be released as OS/2 3.0.

[theBuckwheat]

Dave Cutler was the architect of Digital's VMS, which I think is still the best OS ever written. He was recruited away from DEC by Microsoft to head up the NT project. The first NT architecture book that I was able to purchase states it was a clean sheet design. In looking at the internals, a lot of the excellent features of VMS show through. Indeed, the null task was a signature Cutler feature.

As to the timeline where NT fits with OS/2, I cannot recall. I saw OS/2 and immediately concluded that IBM was not going to take the long view with respect to competing with Microsoft, as much as some people liked it.

As an aside, in the shop I used to work at we kept a running joke going for years: can anyone name any OS feature that Microsoft really invented. The mouse and GUI came from someone else (Xerox PARC), the spreadsheet from Dan Briklin's Visicalc. The only thing that several dozen well-connected techies could ever come up with was BOB, the "feature" that Microsoft included for only a short while in its OS.