Acer will expand its commitment to Windows 8 tablets this year with the launch of a touch-screen device smaller than 10 inches and priced below the typical $400 price tag for Microsoft devices, executives said, even as they demurred when asked about support for a Windows RT tablet. Acer unveiled a 7.9-inch Android tablet on Friday, and President Jim Wong backed Windows wireless devices saying only a lack of mobile applications would prevent Microsoft from competing more effectively with Google and Apple.