Cortana

Microsoft unveiled Windows Phone 8.1 on Wednesday, and confirmed reports that the new OS includes Microsoft's first voice-activated digital assistant, called Cortana.

Windows Phone 8.1 won't be generally available for several months -- it's slated to run new phones shipping in late April or early May, according to Joe Belfiore, corporate vice president of Microsoft's operating systems group.                                                    

Belfiore spoke at the opening of Microsoft's Build 2014 developer conference, which was webcast.

Another major new feature in WP 8.1 is a shape writing capability now commonly available in some other smartphones and via add-on apps. Belfiore demonstrated the shape writing by swiping his finger through a keyboard without lifting it between letters.

Cortana will first appear in beta.