As its annual BUILD developers conference today Microsoft revealed Universal Windows Apps to streamline the process of creating applications that can run on the Windows desktop, tablet and phone platforms. A blog post discusses the tools and intentions in greater detail:

Windows Phone 8 brought the same core set of operating system components used by Windows 8 to the modern UI of Windows Phone. Today we’re taking an even bigger step with Windows Phone 8.1 and Windows 8.1 Update by empowering developers to create universal Windows apps for a common Windows runtime.

Since universal Windows apps run on the same Windows runtime, developers have a common way of building and architecting apps for phones, tablets and PCs; from how they handle suspend and resume and do background processing, to the way they manage in-app security.

Developers of universal Windows apps will be able to choose whether they want to charge per-app or per-device for apps across the various platforms.

Perhaps most interesting is that Microsoft has expressed plans to extend the universal windows app concept onto the Xbox One console, which would surely open to door to many more non-gaming applications on that device than are available today.

We’re enabling universal Windows apps for a common Windows runtime today, and we know we have more work to do, including expanding the range of devices running universal Windows apps so developers can reach more customers in more places, from Xbox One and the Internet of Things scenarios, to millions more desktop Windows users. We also continue to strive to make the app development, submission, and management process faster and easier.

Even more details on the universal windows app functionality can be found in this second detailed blog post.