iPhone 4

The iPhone 4 is an iOS smartphone developed by Apple Inc. ... The iPhone 4 introduced a new hardware design to the iPhone line, which Apple's CEO Steve Jobs touted as the thinnest smartphone in the world at the time; it consisted of an uninsulated stainless steel frame which doubles as an antenna, with internal components situated between chemically strengthened aluminosilicate glass. The iPhone 4 also introduced Apple's new high-resolution "Retina Display"; while maintaining the same physical size and display resolution as its precursors, its liquid crystal display had a pixel density of 326 pixels per inch. 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, notably ending AT&T's period as the exclusive carrier of iPhone products in the United States. [iPhone 4. Wikipedia]