The iPhone is a line of smartphones designed and marketed by Apple Inc. It runs Apple’s iOS mobile operating system, known as the “iPhone OS” until June 2010, with the release of iOS 4.
The first generation iPhone was released on June 29, 2007; the most recent iPhone, the sixth-generation iPhone 5, on September 21, 2012. The user interface is built around the device’s multi-touch screen, including a virtual keyboard. The iPhone has Wi-Fi and cellular connectivity (2G, 3G, 4G, and LTE).
There are six generations of iPhone models, each accompanied by one of the six major releases of iOS. The original 1st generation iPhone was a GSM phone, and established design precedents, such as a button placement that has persisted through all models and a screen size maintained until the launch of the iPhone 5 in 2012.
The iPhone 3G added 3G cellular network capabilities and A-GPS location. The iPhone 3GS added a faster processor and a higher-resolution camera that could record video at 480p. The iPhone 4 featured a higher-resolution 960 × 640 “retina display”, a VGA front-facing camera for video calling and other apps, and a 5-megapixel rear-facing camera with 720p video capture.