Microsoft unveiled on Wednesday Windows Phone 8.1, and the new OS for smartphones will include a digital, voice-enabled assistant called Cortana. While Windows Phone 8.1 will not be available until it is expected to be shipped in May, the new operating system and digital assistant were unveiled by Windows Phone chief Joe Belfiore at the firm's Build developers conference in San Francisco. In a major announcement, Microsoft launched Cortana, a digital assistant named after the artificial intelligence system in Microsoft's Halo video game franchise. Cortana has come three years after Siri was launched with the iPhone 4S and the launch of Google Now for Android 4.1 smartphones in 2012. Belfiore said that Cortana is better than Siri, calling it the "first truly personal digital assistant who learns about me and the people that matter to me most." Cortana will appear as a pulsating button on the phone's home screen and will offer its own suggestions for tasks the owner might want to do based on location and past behavior. Like other digital assistants, Cortana can be asked, using voice commands, to find information, make appointments and access emails, text messages and contacts. During the course of interacting with the program a user can change the rules Cortana follows using the Notebook function. This function can also be used to tweak who Cortana deduces are the user's close friends and family or the user's "quiet hours." While the demo showed the flexibility and intelligence of the system, Belfiore did have a few mishaps during the demo. When he asked the program to call the second of two Mexican restaurants, Cortana had searched for him, Cortana instead started to call the first restaurant. For such instances, Belfiore said that the program will improve as it is trained and if the problem persists the command can be typed in. "We're launching Cortana as a beta while we train the service on the back end, with lots of voice utterances to improve speech recognition," Belfiore said, calling it a "minor bug."