Windows 10 brings more integration among Microsoft devices than ever before, and to that end the company has announced exactly how Windows Phone fits into the equation.

When the new Windows finally hits shelves, it will be available for one year as a free upgrade to existing Windows devices - including those running Windows Phone 8.1, the company announced.

Microsoft Operating Systems Group Executive Vice President Terry Myerson dropped the news during the company's much-hyped Windows 10 live event.

He said Microsoft is focused largely on a "more personal computing" experience for Windows 10, and a better mobile experience is part of that. To that end, Windows 10 for phones and sub-8-inch tablets is fast and fluid, Belfiore explained. While optimized for smaller devices, the OS can also interact with PCs.

Windows 10 will launch in full later this year. The first build of Windows 10 for phones will arrive later in February.