iOS small screen, limited input devices, specifically, direct

iOS (previously iPhone OS) is a mobile operating system developed by Apple Inc. and distributed exclusively for Apple hardware 6. It is the operating system that powers iPhone, iPad, iPod Touch, and Apple TV. It is closed source and proprietary and built on open source Darwin core OS. iOS promoted a new style of user interaction for small screen, limited input devices, specifically, direct manipulation. Touch-based gestures like swipe, tap, tap and hold, and pinch are used to control on-screen interface elements, and to perform interface operations. Accelerometers support additional physical gestures like shaking and rotating the orientation of the device 15. iOS is derived from Mac OS X, and shares its basic Darwin foundation, an open source POSIX-compliant UNIX OS. In this sense iOS can be considered a variant of UNIX. iOS is made up of four abstraction layers: Core OS, Core Services, Media, and Cocoa Touch6 15, 20: i.Core OS: The kernel of the operating system, which includes basic low-level features: system support—threads, sockets, IO, DNS, math, memory—general security services—certificates, private/public keys, encryption—external hardware management, bluetooth, and sound and image processing. ii.Core Services: Fundamental system-services, which are subdivided in different frameworks and based on C and Objective C. It includes basic application services, including accounts, contacts, networking, data management, location, calendar events, store purchasing, SQLite, and XML support. iii.Media Layer: Considers the high-level frameworks, which are responsible for using graphic (support for 2d and 3d graphics), audio- and video technologies. iv.Cocoa Touch: The UIKIT, which is an Objective- C based framework and provides a number of functionalities, which are necessary for the development of an iOS Application like the User Interface Management. It also includes APIs for building applications—multitasking, touch input, notifications, interface views, and access to device data. Figure 3 below depicts the ioS architecture