the system architecture of iOS is divided into four tiers: the core OS layer, the core service layer, the media layer, and the Cocoa touch layer. The 1.Core OS layer-----contains core parts, file systems, network fundamentals, security features, energy management, and some device drivers, as well as some system-level APIs. The 2.Core service layer----provides core services such as string processing functions, collection management, network management, URL processing tools, contact maintenance, preferences, and more. 3.Media Layer----The layer framework and services rely on the core services layer to provide drawing and multimedia services such as sound, pictures, video, etc. to the cocoa touch layer. 4.Cocoa Touch Layer----This framework is based on the IPhone OS application layer directly calling layer, such as touch events, camera management, etc., which includes the Uikit Framework and foundation framework.
iOS is UNIX-based, so we can trust this operating system, knowing that from the stability of the system it is much better than other operating system products. The bottom layer of the iOS system architecture is the core operating system layer, which includes memory management, file systems, power management, and some other operating system tasks. It can interact directly with the hardware device. The core operating system layer includes these components: OS X Kernel mach 3.0 BSD Sockets & nbsp Power Mgmt file system Keychain certificates security Bon jour The second tier is the core service layer, which we can use to access some of the iOS services. It includes the following components: collections Address book networking File Access &nbs P SQLite core location Net Services threading preferences& nbsp; URL utilities The third layer is the media layer, through which we can use a variety of media files in the application, for audio and video recording, graphic drawing, as well as making the basis of animation effects. It includes the following components: Core Audio OpenGL audio mixing Audio Recording Video Playback jpg,png,tiff PDF Quartz core animation OpenGL es The top layer is the touchable layer, which Layer provides a variety of useful frameworks for our application development, and most of it is related to the user interface, which is essentially responsible for the user's touch interaction on the iOS device. It includes the following components: multi-touch Events core Motion camera View Hierarchy Localization alerts Web views Image picker multi-touch controls   ; Many of the technologies in the cocoa touch layer are based on the Objective-c language. The Objective-c language provides support for iOS like collections, file management, network operations, and more. Like the Uikit framework, it provides a variety of visual components for applications such as window, view, and button components (UIButton). Other frameworks in the Cocoa touch layer are also useful for our development in the application, such as access to the user's correspondence function framework, the framework for obtaining photo information, and the hardware support for the accelerometer and the three-dimensional gyroscope.
