IPhone 4S announced iPhone 5s and iPhone 5c. This was unusual for Apple as an upper case 'S' had been used since the introduction of the iPhone 3GS in 2009. On September 9, 2014, the iPhone 4S was officially discontinued following the reveal of the iPhone 6 and the iPhone 6 Plus. However, 4S production did continue for developing markets until February 17, 2016. On June 13, 2016, following the release of iOS 10, Apple dropped support on the iPhone 4S, making iOS 9.3.5 the last version available for the device. The runs iOS, Apple's mobile operating system. The user interface of
IPhone send and receive text messages, follow GPS navigation, record notes, perform mathematical calculations, and receive visual voicemail. Other functionality, such as video games, reference works, and social networking, can be enabled by downloading mobile apps. , Apple's App Store contained more than 2.2 million applications available for the iPhone. Apple has released eleven generations of iPhone models, each accompanied by one of the eleven major releases of the iOS operating system. The original first-generation iPhone was a GSM phone and established design precedents, such as a button placement that has persisted throughout all releases and a screen size maintained for