And so… Windows 7 is the name for the new version of Windows, the successor of Windows Vista. The thing is… It actually is Windows 6.1 if you check system properties and this has been confirmed by the Windows Team Blog. I don’t think it’s that great an idea honestly. I prefer the marketing version number to coincide with the development version number.
we decided to ship the Windows 7 code as Windows 6.1
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.
We learned a lot about using 5.1 for XP and how that helped developers with version checking for API compatibility. We also had the lesson reinforced when we applied the version number in the Windows Vista code as Windows 6.0– that changing basic version numbers can cause application compatibility issues.
So we decided to ship the Windows 7 code as Windows 6.1 – which is what you will see in the actual version of the product in cmd.exe or computer properties.
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. (Source: Windows Team Blog)
In the case, I think it would be better to just call Windows 6.1 Windows 7. I think it’s clearer for developers who are going to start using the Windows platform.