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 6S countries and a lack of iPhone purchases in developing countries. Before the official unveiling, several aspects of the iPhone 6S were rumored, including the base model having 16 gigabytes of storage, the pressure-sensitive display technology known as 3D Touch, and a new rose gold color option. iPhone 6S and iPhone 6S Plus were officially unveiled on September 9, 2015, during a press event at the Bill Graham Civic Auditorium in San Francisco. Pre-orders began September 12, with the official release on September 25. On September 7, 2016, Apple announced the iPhone 7 and iPhone 7 Plus as successors to the