Windows History: DOS vs NT sourcecode heritage

As a software developer, I’m fascinated by computer and IT history. I grew up with 8 bit home computers like the Sinclair ZX Spectrum, and developed my first applications in Sinclair BASIC which most likely kickstarted my interest in software development.

I find it interesting when developers have very little interest or knowledge in even recent history of the tools and platforms that they work with every day. For example, statements like “I’m glad Windows 10 no longer has any dependence on MS-DOS like Windows 8 did”, or “Microsoft completely developed Windows 10 from scratch, you know”, – neither statements which could be further from the truth.

Up until Windows XP, Windows was developed as two parallel code lines, the MS-DOS based code line, Windows 1.x through 3.x, 95, 98, and ME, (95, 98 and ME aimed at home consumers) and the Windows NT code line for enterprise users. After Windows ME, Windows XP was developed based on the NT kernel from Windows 2000, with some features taken from ME and it’s MS-DOS code line.

There’s a great history of the parallel code lines in this article on the History of Microsoft Windows on Wikipedia, and clearly illustrated in this diagram:

(From https://en.wikipedia.org/wiki/Timeline_of_Microsoft_Windows, shared under Creative Commons Attribution-Share Alike 3.0 Unported license).

Windows ME was the last release of the MS-DOS based Windows code line, and Windows 10 is the next release in the Windows NT code line, which as you can see from the timeline above, shares it’s heritage with 8, 7 and Vista before it.

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