Given the recent PR blitz on the subject, most computer users have heard about the imminent launch of Microsoft’s new operating system Windows 10. However, given that the vast majority of those users are running Windows 7, 8 or 8.1 today, the launch of the new OS is leading many to ask “what happened to Windows 9?”

Of note, Windows 10 is officially scheduled for release on July 29th, 2015.

Windows 10 Microsoft

The history of Microsoft Windows system numbering is inconsistent

Old timers and those with a good memory will remember that between Windows 3 and Windows 7, Microsoft labeled each new version of the OS with a name instead of a number, ie, Windows 95, 98, NT, Me, 2000, Vista, and so forth. Then when the company announced Windows 7, there was a bit of a public uproar, as after several named versions of Windows, it seemed a bit odd to many to switch back to numbers again.

Moreover, the name of each Windows release doesn’t actually match the real version number. For example, Windows 8.1 is actually version 6.3 of Windows, and Windows 10 is version 6.4. The last time the release name actually matched the version number was the enterprise-focused Windows NT 4.0, released 19 years ago. Windows 2000, dubbed NT 5.0 during development, was really version 5.0. In reality, Windows XP was version 5.1. Windows Vista was 6.0, Windows 7 was 6.1, Windows 8 was 6.2, and Windows 8.1 is version 6.3.

Potentials reason for Microsoft skipping Windows 9

Keep in mind that the number 9 is considered unlucky in Japan. Microsoft has a big enough presence in Japan that it may have skipped Windows 9 to avoid any sales problems in that major market. Of interest, other Japanese companies have done this. For example, a few years ago Japan-based Trend Micro skipped version 9 of its antivirus software.

As another possibility, someone claiming to be a Microsoft developer posted on Reddit that some developers had already used “Windows 9” in certain applications such as checking for OS version, and it was skipped as this could potentially lead to problems.

Extreme Tech notes: “…it is actually quite feasible that there are still a lot of legacy Desktop apps that use this method (or something similar) to check for Windows 95 or 98. Bear in mind that this is just an example piece of code — some developers will check for the OS name (“Windows…”), some will check for the version number (as discussed in the previous section of this story), and some may use other methods entirely to find out what OS the app is running on.”

Hints from Microsoft on the naming of Windows 10

The Windows 10 unveil event did provide gives us a few clues about the company’s thought process regarding the naming of the OS. Starting at around the 2:10 mark, Microsoft OS head Terry Myerson says: “We know, based on the product that’s coming, and just how different our approach will be overall, it wouldn’t be right to call it Windows 9.” He goes on to discuss how Windows One would make sense with Xbox One, OneDrive, and OneNote, “but unfortunately Windows 1 has been done by the giants that came before us.” This makes it seem like the only other viable option was Windows 10.

Marketing analysts have noted that 10 is obviously a strong, easily remembered version number, and skipping a number is also an effective method of clearly separating it from the older Windows 8.