Software giant Microsoft reasserted itself in the mobile smart phone market with the introduction of three handsets on Monday that are powered by the company’s new Windows Phone 7 operating system. Once a leader in smart phone technology before the Apple iPhone revolutionized the industry in 2007, Microsoft has spent two years developing the Windows Phone 7 system, which will compete in a market that is currently dominated by the iPhone, Research-in-Motion’s BlackBerry, and phones operated on the Google Android platform. Statistics supplied by research firm Nielsen indicate that smart phones account for 23% of all mobile phone sales in the U.S. and that Microsoft’s share has fallen to a slim 5% slice of that market. In contrast to the array of small icons found on competitors’ touch-screen handsets, Windows Mobile 7 phones will display applications in large blocks that are updated continuously with personal user content from Facebook and other social network or message sites. Purchasers of Windows Phone 7 devices will also be able to integrate their handsets with other Microsoft products such as Zune, the Bing search engine, Microsoft’s OneNote software, and the Xbox gaming system. Microsoft is also working with various partners that will develop mobile applications and services for Windows Phone 7 devices. On November 8, AT&T will be the first carrier to roll out handsets based on the Windows Phone 7 system, with three models—the Samsung Focus, the HTC Surround, and the Quantum by LG Electronics—to retail at $199.99 with a two-year contract. AT&T will also incorporate U-Verse IPTV functionality with Windows Phone 7 to enable U-Verse customers to watch TV programs on their phones. T-Mobile USA will begin offering the phones to their customers later this year, with Verizon and Sprint to follow early next year. Describing the Windows Phone 7 handset as “a different kind of phone,” Microsoft CEO Steve Ballmer told reporters that his company “focused in on how real people want to use their phones when they are on the go.”