How many layers is the architecture of android operating system?

Android system architecture is a four-layer structure, from the upper layer to the lower layer are application layer, application framework layer, system running layer and Linux kernel layer, which are introduced as follows:

1. Application layer (application)

Android platform is not only an operating system, but also contains many applications, such as SMS client program, telephone dialing program, picture browser, web browser and so on. These applications are written in Java language, and can be replaced by other applications developed by developers, which is more flexible and personalized than the solidified system software in other mobile phone operating systems.

2. Application framework layer (application framework)

The application framework layer is the foundation of our Android development, and many core applications also realize their core functions through this layer. This layer simplifies the reuse of components, so that developers can directly use the components provided by them for rapid application development, and can also realize personalized expansion through inheritance.

3. System runtime layer (library)

The system runtime layer can be divided into two parts, namely the system library and the Android runtime, which are introduced as follows:

A. System database

System library is the support of application framework and an important link between application framework layer and Linux kernel layer. that

B.Android runtime

Android applications are written in Java language, and programs are executed in Androidruntime. Its runtime is divided into two parts: core library and Dalvik virtual machine.

4.Linux kernel layer (Linux kernel)

Android is based on Linux2.6 kernel, and its core system services such as security, memory management, process management, network protocol and driver model all depend on Linux kernel.