When creating iPhone 4, Apple designers and engineers didn’t start with a clean sheet of paper. They started with three years of experience designing and building the phones that redefined what a phone can do. iPhone 4 is the result of everything they’ve learned so far. And it’s all contained in a beautiful enclosure a mere 9.3 millimeters thin, making iPhone 4 the world’s thinnest smartphone. With its easy-to-use interface, amazing features, and rock-solid stability, iOS — Apple’s mobile operating system — is the foundation of iPhone. And even as other phones try to catch up, the technologies and features built into iOS 4 keep it years ahead of the competition.