Cortana is an intelligent personal assistant on Windows Phone 8.1 and the Microsoft Band. In the Technical Preview of Windows 10, also some files leaked showing that Microsoft will port it to their new OS. Its name comes from Cortana, the artificial intelligence character in Microsoft's Halo video game series, with Jen Taylor, the character's voice actress, returning to voice the personal assistant's US-specific version. It is similar in function to Siri, which is found on Apple's iOS devices. Cortana was demonstrated for the first time at the Microsoft BUILD Developer Conference in San Francisco. It has been launched as a key ingredient of Microsoft's planned "makeover" of the future operating systems for Windows Phone, Windows, as well as Xbox One. It is currently available to all users of Windows Phone 8.1 in the United States, China, and the United Kingdom. Users in India, Canada and Australia can also choose to opt-in to the beta for the American English version of Cortana as of August. Microsoft expects Cortana to be available globally by either late 2014 or early 2015.