When Windows RT launched in conjunction with Windows 8 in 2012, the operating system ran on ARM-based devices with desktop program support only for software that Microsoft bundled, like a version of Microsoft Office. Because of RT’s inability to user-install Win32 programs, and for a number of other reasons, the operating system failed to catch on. Microsoft's last RT device, the Surface 2, launched in 2013.
Now, new documentation appears to show that Microsoft is working on a “full” version of Windows 10 with Win32 support capable of running on ARM chips. In addition, there’s mention of a Windows 10 version running on x86 mobile devices. First discovered by Twitter user WalkingCat, the documentation is found on a MSDN page describing an Audio Engine Core Test.