Microsoft is taking on Apple's Siri and Google Now with a speaking smartphone personal assistant dubbed Cortana.
Windows Phone vice-president Joe Belfiore introduced Cortana onstage at the technology titan's annual developers conference.
"Cortana is the first truly personal digital assistant who learns about me, and the things that matter to me most, and knows about the whole Internet," Belfiore said in a presentation to application developers.
Cortana responds to conversationally spoken requests or commands, using insights gleaned from calendars, contact lists, online searches and other smartphone sources to respond in a manner akin to a real-life aide, Belfiore said.
Cortana's voice and character are based on a popular artificial intelligence character in Microsoft's blockbuster Xbox console video game Halo.
It comes as a long-awaited counter to the Siri virtual assistant on Apple mobile devices and Google Now capabilities in Android tablets and smartphones.
Cortana will be in a test, or beta mode when it becomes available in a Windows Phone 8.1 software update, which is to begin rolling out in the United States in coming months.
The new version of Windows Phone 8.1 should be available on new phones beginning in late April or early May, Belfiore said.
Microsoft met real-life personal assistants while designing Cortana, which is powered behind the scenes by search engine Bing, he said.
Like Siri and Google Now, Cortana can remind users of flights, appointments, birthdays, routes, or other information for managing lives.
"Imagine a real personal assistant, and the kinds of things you might ask to be organised," Belfiore said while extolling Cortana's capabilities.
After it is tested in the US, Cortana will expand to Britain and China, and then other countries.
In a sign that Microsoft gave Cortana a playful side, Belfiore asked it to reveal the storyline of the next Halo game, only to be told: "I'm quite certain you don't have the proper security clearance for that information."
Microsoft's insights into updates of Windows software for mobile devices and traditional computers came as the company wooed developers of the fun, hip, or functional applications that strongly influence the public's decisions about which gadgets to buy.
Microsoft is also keen to entice business and consumers to remain faithful to its computer operating system as it phases out support for its much-loved but ageing version Windows XP.
"We have a billion-plus PCs that will all be upgrading," new Microsoft CEO Satya Nadella told the gathering of developers.
"That is a significant opportunity for any application that targets Windows."
Software improvements were aimed at business, where Microsoft products remain strong, as well as at the booming tablet and smartphone markets.
Microsoft also announced that Nokia would release a set of low-priced, Windows-powered Lumia smartphones, starting in developing markets in Asia and India next month before gradually working its way to the United States in July.
The move aims to tap overlooked and underserved markets, instead of trying to slug it out with Apple iPhones and Android-powered Samsung handsets in countries where buyers are more interested in high-end or medium-tier devices, Gartner principal research analyst Tuong Huy Nguyen said.
"They really needed to move the price point of Windows devices down market, and this seems to be a step in that direction," Nguyen said.
"The US is essentially a two-horse market with Apple and Samsung; they have tried to push in with previous Lumia devices but it is hard."