IOS architecture consists of four layers. It has an intermediate layer between the applications and the hardware so they do not communicate directly. The higher layers of iOS provide the user interface and sophisticated graphics and the lower layers of iOS provide the basic services.
The layered architecture of iOS is given as below:
Core OS Layer:
The Core OS is the lower layer of iOS architecture levels and the one closest to the device hardware, being perched right on top of it. This layer provides many of the low-level features necessary that some of the services in the higher levels need to work.
Core Services Layer:
This Core Services layer provides an abstraction over the services provided in the Core OS layer. This layer provides fundamental access to iPhone OS services. Some of the Important Frameworks available in the core services layers are as below:
The Media layer makes the picture on your iOS device crisp and the song you’re listening to sound clear. This layer handled all of the audio, video and graphic frameworks that help deliver a dynamic multimedia experience for the mobile user.
Cocoa Touch Layer:
The Cocoa Touch layer is the upper layer of the iOS architecture. This layer defines the basic application infrastructure and provides several vital technologies, such as multitasking and touch-based input. It provides the following framework: