Windows 8 will have sole custody of DirectX 11.1, according to a Microsoft engineer.
Responding to a question on an MSDN forum, Daniel Moth, a Microsoft program manager, broke the news that "at this point there is no plan on making DirectX 11.1 to be made available for Windows 7"
That same holds true for versions prior to Windows 7, leaving the new DirectX version exclusive to Windows 8, Windows RT, and Windows Server 2012.
DirectX is a collection of programming interfaces from Microsoft that enable 3D animation and other multimedia effects used mostly in games. Developers tap into DirectX so their applications can take full advantage of the hardware power of the PC.

Read more: Microsoft won't bring DirectX 11.1 to Windows 7 | Windows 8 - CNET Reviews