Cocoa Touch: It is at the highest level of iOS layers. It consists of StoryBoards, Documents, Gesturing, MultiTasking, Notifications, UIKit Framework. It provides an abstraction layer of iOS.
Media Layer: It defines the entire multimedia architecture within Apple powered mobile devices and frameworks. It includes Graphic Technologies, Audio Technologies, Video Technologies, AirPlay.
Core Services Layer: It provides important services to apps but have no direct bearing on application's user interface. It consists if iCloud, In-App purchases, SQLite, Core Data, Core Location.
Core OS Layer: It provides low level services related to hardwares and networks. It includes BlueTooth, External Accesories, Accelerator Framework. The services are mostly based on Kernel and Device Driver's layer.
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