Linux, how much do you know! __linux

1, Linux overview   

Linux is a free and open source Unix-like operating system. Strictly speaking, the term Linux only represents the operating system kernel itself, but usually uses the Linux kernel to express that meaning. Linux is often used to refer to a full operating system based on the Linux kernel, including GUI components and many other utilities. Since these support user-space system tools and libraries are primarily provided by the GNU program launched by Richard Stallman in 1983, the FSF proposes to name the composite system Gnu/linux, but Linux is not part of the GNU program, so the name is not shared by the community. But we can't forget the GNU campaign's push for Linux. In addition, as long as the GNU General Public License is followed, any individual or organization is free to use all of Linux's underlying source code.

* Professional Terminology

UNIX	a computer operating system with multiple tasks and multi-user characteristics. In 1969, the United States At&t Company's Bell Labs developed by Ken Thompson.
GUI Components	Tools to support graphical desktops
GNU Program	The GNU program (English: GNU Project), also translated as a Slave program, is a free software collective collaboration project designed to achieve open source and collaboration in software
FSF	Its main job is to execute the GNU program and develop more free software
GNU General Public License	Also known as the LGPL protocol, is the standard that people must follow to use open source code.

2. Linux development

To abandon the gorgeous graphical interface, and to pay more attention to the system security and performance of Linux, will be the attention of people. Slowly, non-GNU components developed by individuals and businesses are also starting to provide support for the Linux kernel, including a large number of kernel modules, user applications, and libraries. Linux communities or businesses are also starting to launch some important Linux distributions.

3, Linux working principle

  

Linux at the bottom of the same CPU, memory of a variety of hardware, working on the hardware kernel is the most important part of the entire Linux operating system, its importance, described in detail below. On top of the kernel are a variety of applications, as well as a very important shell interface, where the application uses the shell to implement hardware operations that can be likened to Windows click events.

Here's how important the kernel is throughout the system: to take advantage of the computing power of the underlying hardware, the application must have an application program to drive the hardware, and the top application must be compiled to be converted into binary code that the computer can recognize. means that any application that wants to run requires not only a complete set of drivers, but also a compiler. You know, the early CPUs have their own specific set of instructions, which determines the different libraries that are called by the upper level. Even if you compile a program, the process will need to be restarted when the program is switched to another platform, and the program that originally drives the hardware will lose its meaning and the portability of the program is greatly reduced. So there is the kernel, it through system call (called) isolated different applications to different manufacturers CPU dependencies, not only provide a powerful compiler function, but also drive a variety of hardware drivers are loaded into the kernel, the convenience of the program greatly improved. So how are the top apps written, using the countless 0 and 1. or directly using system call provided by the kernel. Obviously impossible, these original programming interfaces, believe only the Ashes class engineers will call it. At this point, the kernel will come in handy again, which encapsulates the system call again, and becomes the library call, the ABI (the application binary interface, i.e.,. so), with BIF (built-in functions), the API (Application programming interface, such as print (), read (), if, and so on, can be invoked directly by the application. On top of that, a large number of applications have been created, together with the provision of VFS (virtual file system), a complete Linux operating system can work smoothly.

4. Linux status

Today there are a variety of occasions using a variety of Linux distributions, home air-conditioning, smart watches, mobile phones, aviation ... From these embedded devices to supercomputers (Super Computer), Linux also has a considerable place in the server domain (usually the server uses lamp combinations). Although most people still know very little about Linux, but it has already entered our life, I believe that open source Linux will be better tomorrow.