Information Technology Reference
In-Depth Information
The iOS architecture
iOS acts as an intermediary between the underlying hardware components and the applica-
tions that appear on the screen. The applications do not talk to the underlying hardware dir-
ectly. Instead, they communicate through a well-defined system interface that protects the
applications from hardware changes. This abstraction makes it easy to build applications
that work on devices with different hardware capability.
The iOS architecture consists of four layers: the Cocoa Touch layer, Media layer, Core Ser-
vices layer, and Core OS layer, as shown in the following figure. Each layer consists of
several frameworks that would help to build an application.
The iOS layers
The Cocoa Touch layer
The Cocoa Touch layer contains the key frameworks required to develop the visual inter-
face for iOS applications. Frameworks in this layer provide the basic application infrastruc-
ture and support key technologies, such as multitasking and touch-based input, and many
high-level system services.
The Media layer
The Media layer provides the graphics and audio and video frameworks to create the best
multimedia experience available on a mobile device. The technologies in this layer help de-
velopers to build applications that look and sound great.
The Core Services layer
This Core Services layer provides the fundamental system services that are required for the
applications. All these services are not used by the developers though many parts of the
