A long-ish article on the history of Windows and a few behind the scenes look at the technology powering the various generations of Windows. The creation of OneCore explains why Microsoft is able to deploy Windows 10 to such a wide range of platforms, from Raspberry Pi, to XBox, to servers and even Hololens.
Microsoft promised developers that Windows would run anywhere. This summer, it finally will.
Source: OneCore to rule them all: How Windows Everywhere finally happened