Source
Naming Windows 7
As major feature work on Windows Vista wound down in early 2006, Blackcomb was renamed Vienna.[6] However, following the release of Windows Vista, it was confirmed by Microsoft on July 20, 2007 that "the internal name for the next version of the Windows Client OS"[7] was Windows 7, a name that had been reported by some sources months before.[6] On October 13, 2008, it was announced that Windows 7 would also be the official name of the operating system.
On October 13, 2008 Mike Nash, Microsoft's vice-president of Windows product management said:
“ The decision to use the name Windows 7 is about simplicity. Simply put, this is the seventh release of Windows, so therefore Windows 7 just makes sense.
Coming up with an all-new 'aspirational' name does not do justice to what we are trying to achieve, which is to stay firmly rooted in our aspirations for Windows Vista, while evolving and refining the substantial investments in platform technology in Windows Vista into the next generation of Windows.”
Numbering this version of Windows as "7" has confused many users, so on October 14, 2008 Nash clarified his earlier remarks, saying:
“ The very first release of Windows was Windows 1.0, the second was Windows 2.0, the third Windows 3.0. Here's where things get a little more complicated. Following Windows 3.0 was Windows NT which was code versioned as Windows 3.1. Then came Windows 95, which was code versioned as Windows 4.0. Then, Windows 98, 98 SE and Windows Millennium each shipped as 4.0.1998, 4.10.2222, and 4.90.3000, respectively. So we're counting all 9x versions as being 4.0. Windows 2000 code was 5.0 and then we shipped Windows XP as 5.1, even though it was a major release we didn't want to change code version numbers to maximize application compatibility. That brings us to Windows Vista, which is 6.0. So we see Windows 7 as our next logical significant release and 7th in the family of Windows releases...There's been some fodder about whether using 6.1 in the code is an indicator of the relevance of Windows 7. It is not. Windows 7 is a significant and evolutionary advancement of the client operating system. It is in every way a major effort in design, engineering and innovation. The only thing to read into the code versioning is that we are absolutely committed to making sure application compatibility is optimized for our customers.
So Windows 95, 98 and 2000 were all counted as 4.0.
