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 4S announced, it was considered by some media to be a disappointment, due to the expected release of an iPhone 5. There were no external differences between the iPhone 4 CDMA model and the , with the exception of a SIM card slot on the . All changes were internal (slight external differences between the iPhone 4 GSM model and the exist, as said differences existed between the CDMA and GSM models of the iPhone 4). On September 10, 2013, the iPhone 4S name was re-stylised as iPhone 4s, using a lower case 's' to reflect the names of the newly