Microsoft promises Windows 9 convergence for universal apps on Windows Phone, Xbox and PC

The "Holy Grail" of operating systems could arrive in Windows 9. Microsoft CEO Satya Nadella has promised that Windows 9 will be one OS that works with universal apps across all devices.

Nadella said, on a call to analysts: "We will streamline the next version of Windows from three operating systems into one single converged operating system for screens of all sizes."

This means developers will only have to create one version of an app and that will work across PCs, Windows Phones and Xbox consoles. This should mean more developers want to work with Microsoft meaning more, higher quality apps, becoming available to users.

Apple still has separated ecosystems with its iOS mobile and Mac OS PC approach splitting apps across devices. It has brought them closer together but ultimately they still require separate apps to be built for each platform.

Nadella has promised that this unifying Windows system will appear in the next version of Windows which is due to arrive before the end of this year. The first version will be a cheap OS while the Windows Enterprise and Windows Pro editions will follow later. Presumably that will mean updates for Windows Phone and Xbox arrive alongside that update.

READ: Windows 9 and Windows Phone 9 could arrive as soon as April 2015