The iPhone 4 is a smartphone that was designed and marketed by Apple Inc. It is the fourth generation iPhone, succeeding the 3GS and preceding the 4S. Following a number of notable leaks, the iPhone 4 was first unveiled on June 7, 2010, at Apple's Worldwide Developers Conference in San Francisco, and was released on June 24, 2010, in the United States, United Kingdom, France, Germany, and Japan. The iPhone 4 introduced a new hardware design to the iPhone family, which Apple's CEO Steve Jobs touted as the thinnest smartphone in the world at the time; it consisted of a stainless steel frame which doubles as an antenna, with internal components situated between aluminosilicate glass. The iPhone 4 also introduced Apple's new high-resolution "Retina Display" with a pixel density of 326 pixels per inch while maintaining the same physical size and aspect ratio as its precursors. The iPhone 4 also introduced Apple's A4 system-on-chip, along with iOS 4—which notably introduced multitasking functionality and Apple's new FaceTime video chat service. The iPhone 4 was also the first iPhone to include a front-facing camera, and the first to be released in a version for CDMA networks, ending AT&T's period as the exclusive carrier of iPhone products in the United States.