The iPad event in San Francisco.

Tim Cook, Apple’s chief executive, exits the stage after unveiling the new iPad at the Yerba Buena Center for Arts in San Francisco, March, 7, 2012. Nearly two years since the first iPad was shown, Apple is now on its third iteration of the tablet, which has exceeded expectations and become a considerable part of not only Apple?s product lineup but also the company’s revenue. (Jim Wilson/The New York Times)