When Windows 10 got announced, there was one immediately glaring question: Why Windows 10? Maybe for the extra distance from 8, but a Redditor who claims to be a Microsoft dev has a better—and funnier—answer. The name "Windows 9" could break a whole bunch of lazy code.
Cranbourne describes the issue like this:
If you're not code literate, allow me to explain. An easy (and lazy, and bad) way to check what version of Windows a user is running is to just read in the first little bit of the name the operating system is using to identify itself. There are better ways to do it, but if that first bit reads "Windows 9" it means the operating system has to be either Windows 95 or Windows 98.
Unless of course there's a Windows 9.
It's a y2k sort of problem, where programmers either didn't think the Windows naming scheme could ever generate another "Windows 9x" version, or didn't want to bother future-proofing their code to control for it. And while it's just an unsubstantiated theory that this is why the name is Windows 10, the problem this coder brings up is verifiably a common shortcut. We've reached out to Microsoft for comment, but we may never really know. What's for sure though is that this name just happens to solve one big, obnoxious problem.
Update: A Microsoft spokesperson provided us with the following, mystery-preserving statement:
Windows 10 carries Windows forward into a new way of doing things. It is not an incremental change, but a new Windows that will empower the next billion users.
[Reddit h/t Mikko Hypponen] Thanks, Ryan!