Android Deep Explore the first chapter

The first chapter introduces Android Drive Development and porting technology

First, Android four-tier system architecture:

Android 's system architecture is divided into 4 tiers, namely:Linux kernel,C + + code base, Android SDK API, application.

Linux kernel: linux kernel includes Linux driver and memory management, process management, power management and other programs.

Linux drivers: Drivers are driving hardware devices to act. Drive is directly with the underlying hardware directly, in accordance with a certain mode of work, read and write device registers, with the completion of the device polling, interrupt processing,DMA Communication, physical memory to virtual memory mapping and other functions, finally let the communication equipment can send and receive data, Allows the display device to display text and images, allowing the storage device to record files and data

Memory management: The basic unit of memory management is the physical page; the function of the memory management unit is to translate the virtual address into a physical address in pages.

Process Management: A process is the basic unit of resource allocation, and a thread is the basic unit of resource scheduling. Among them, the thread only has some necessary resources, this function of the thread makes the thread switching of the same process more convenient and improves the system performance. threads are implemented in 3 ways: User-level threading, kernel-level threading, and hybrid threading models .

Power management by reducing the device voltage, frequency, can reduce the energy consumption, effectively manage the power consumption of the embedded system, to achieve the purpose of saving electricity.

Second, the main work of Android system transplant: Application transplant and system transplant.

An application is a computer program that runs in user mode, interacts with the user, and has a visual user interface for the completion of one or more specific tasks. It has the ability to port the application layer's programs to a specific hardware platform.

System porting: Portability refers to the transfer of software from one environment to another. System porting allows the Android operating system to run on a particular hardware platform.

Third, view the Linux kernel version:thelinux kernel has linux2.4,linux2.6, linux3.x3 versions; there are 2 ways to view them. the Linux version number definition has certain principles.

Four Linux Device drivers: A class of programs that interact directly with hardware, with character devices, network devices, and block devices.

Character Device character device: is a device that is transmitted in character units.

Network devices are network devices and components that are physical entities that are connected to the network. There are many kinds of network devices.

The purpose of a block device is to store information in a fixed-size block.

Android Deep Explore the first chapter