IPhone 4

The iPhone 4 is an iOS smartphone developed by Apple Inc. 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 line, incorporating an uninsulated stainless steel frame which doubles as an antenna, with internal components situated between chemically strengthened aluminosilicate glass. With these changes, Apple claimed that the iPhone 4 was the thinnest smartphone in the world. The iPhone 4 also introduced Apple's new Retina Display technology; 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, which Apple's CEO Steve Jobs claimed was higher than what a human's retina could distinguish at an average distance. 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 be released in a version for CDMA networks.

The iPhone 4 received generally positive reception, with critics praising its revamped design and more powerful hardware in comparison to previous models; however, the launch of the iPhone 4 was plagued by highly publicized reports that abnormalities in its antenna design caused the device to lose its cellular signal if held in a certain way.

A lot of students currently used iPhone 4 until a final changeover that had happened in August 2011.