The assistant, named Cortana, tries to be chatty like Siri on Apple's iPhones and iPads, while anticipating information you might want, like Google Now on Android devices.
Cortana will warn you of conflicts when you add items to your calendar, and it will remind you to ask about the new dog your sister just got the next time you communicate with her, whether that's by phone, chat or email. It will offer to remind you of upcoming travel by scanning your email.
Microsoft Corp. unveiled Cortana on Wednesday. It also announced a new Action Center for the Windows Phone system as a hub for app notifications and information such as remaining battery life.