Apple Inc. Chairman andCEO Steve Jobs speaks at an Apple event at the YerbaBuena Centerfor the Arts Theater in San Francisco,on Wednesday, March 2, 2011. Tablet computers existed long before the iPad, but took Apple to build a device that made it popular. Apple simplified the software, designed a sleek, shiny shell and sold 15 million of the iPads in nine months. The iPad was initially used for checking e-mail, surfing the Web and watching online video. But as the number of apps grew, the tablet made itself at home in offices, shops, restaurants and countless other settings.