iOS is the abbreviation of iPhone OS. It is a mobile operating system created and developed by the Apple Inc. for their devices. It is the second most popular OS after Android. The iOS user interface is based on the concept of direct manipulation, using multi-touch gestures. Interface control elements consist of sliders, switches, and buttons. Interaction with the OS includes gestures such as swipe, tap, pinch, and reverse pinch, all of which have specific definitions within the context of the iOS operating system and its multi-touch interface.