D'ALOISIO BEGAN designing iPhone apps nearly the moment the app store opened in 2008. He was 12 years old, working on a Mac in his bedroom in the London district of Wimbledon. Because he was too young, he signed up for the Apple developer's license using his father's name. He'd taken no formal computer science classes at school, and neither of his parents (Diana and Lou, a lawyer and a business executive, respectively) knew much about tech. Instead, he learned how to program almost entirely by himself, scouring websites and watching instructional videos.