The latest Windows 10 build number reveals two major features, in a leaked preview.

The latest Windows 10 build number (9901) is scheduled for preview January next year, but a leak preempts some features to expect, including Cortana and an Xbox app.

The biggest, and by far most significant feature of the next Windows 10 consumer preview is Cortana; it's confirmed the Siri-like app will be a major addition to the OS. In a video demo leaked early this month, Cortana is a default on the list of the search interface for the new OS (theverge.com).

Cortana responds to both text and voice commands, and as a port of the Windows Phone version will ensure easy access to notebook, reminders, and interests. The feature is merely a preview and barely functional, but should give users a good idea on how Windows 10 operates upon release.

Microsoft is also integrating the services for its gaming console in the new Windows OS. In the leaked preview, an Xbox app is dedicated as portal to the Microsoft gaming community, with similar functions to Microsoft Store.

There's access to achievement unlocks, friend lists, activity updates, and also to the store. It's a very early demo of the app, with expected updates to new tech, such as SmartGlass.

More tweaks come with the latest Windows 10 build number; new animations for the TaskView switcher, also a revamped Control Panel and settings app. The latter's access button is removed from the Charms Bar.

In an effort to integrate all of the Microsoft Stores into one accessible location, Windows 10 build 9901 also comes with a built-in app, in the beta stage. Instead of separate stores for games, music and TV shows or films, everything is expected to be integrated into the main Windows Store for convenient access.

Check out more details on the video leak here.