The move marks a major change for Microsoft, which used the Windows CE core as the basis for its current Windows Phone 7 OS.

"As phones get more powerful, we have been feeling more and more that phones could benefit from an upgrade at the core," said Joe Belfiore, corporate vice president of Microsoft, speaking at a developer presentation in San Francisco.

"For consumers, this new shared core is going to mean a much greater choice in hardware and some new experience that cross over between phone and PC," said Belfiore.

Microsoft said the switch would mean several changes, including greater support for NFC (near field communications) wireless technology for mobile wallet applications and the ability to easily support ports of Windows games to Windows Phone 8.

The latter feature, Belfiore said, will mean, "we're going to see some freaking killer games."