Microsoft shows off their newest version of its phone OS - Windows Phone 8.1 at today's Build Developer Conference. They are also showcasing Cortana, its own personal assistant. It is your Google Now and Siri combined!

Here she is in action:

Cortana is powered by Bing and mixes Google-Now like prediction powers with some Siri-like attitude. Also, she's got a lovely voice. Not Scarlett Johansson "Samantha" lovely, but lovely enough.

You can pull up Cortana by a Live Tile on the home screen or via the phone's built-in search button.

Cortana will be able to add items to calendars, set alarms, find nearby restaurants, and do all the stuff Google Now or Siri can do. For now, she's launching as a beta. She's also hiding a few tricks up her sleeve, including contextual reminders that remind you of a specific thing when you're talking to a specific person.

Cortana will learn about you, which makes her very personal indeed. You can use her "Notebook" to set up things like specific contacts you only want calling you at a specific hours, and more of course.

Windows 8.1 will start rolling out to consumers sometime "in the next few months" and will start shipping on new phones sometime in late April or early May.