Apple decided to allow outside vendors to write programs, called applications or apps, for the iPhone in June. About 300 million have been downloaded to phones since then, ranging from free to about $10 an application. Apple gets a 30 percent cut from each app sold, and the writer keeps the rest. More than 13 million iPhones have been sold since their introduction in 2007, and Apple now claims to be the world's third largest mobile phone maker after Nokia and Samsung.
