Help you understand the Linux operating system

1. What is an operating system

Operating System (OS) is a computer program that manages and controls computer hardware and software resources. It is the most basic system software that runs directly on "bare metal". Any other software must be supported by the operating system. to run.

Shangxuetang Knowledge Compilation: Introduction to Linux Operating System

Operating system: kernel, libraries, applications.

Library: Application without execution entry.

Windows system: dll file.

linux：so ：sharded object

2. Operating system in real life

win7

Mac

Android

iOS

3. The development history of operating systems

Unix

Before 1965, computers were not as common as they are now. They were not accessible to ordinary people unless they were military or academic research institutions. At that time, mainframes could provide up to 30 terminals (30 keyboards). , monitor), connect to a computer.

Shangxuetang Knowledge Compilation: Introduction to Linux Operating System

In order to solve the problem of insufficient quantity:

In 1965, Bell Labs, MIT and General Electric jointly launched the Multics project, hoping that the mainframe would support 300 terminals

Around 1969, the project progressed slowly and there was a shortage of funds. Bell Labs withdrew from the research

Ken Thompson, who quit the project in 1969, was bored in the laboratory. In order to run the "Star Trek" parade on an idle computer, he used it around August while his wife was visiting relatives. A prototype of the Unix operating system was written in 1 month

In 1970, Ken Thompson of Bell Labs in the United States, based on the BCPL language, designed the B language (take the first letter of BCPL) which was very simple and close to the hardware, and he wrote the first UNIX in the B language operating system.

Because the cross-platform nature of the B language is poor, in order to be able to run this great Unix operating system on other computers, Dennis Ritchie and Ken Thompson prepared to research a better language based on the B language.

In 1972, Dennis Ritchie of Bell Labs in the United States finally designed a new language based on the B language. He took the second letter of BCPL as the name of this language, which is the C language

In early 1973, the main body of the C language was completed. Thompson and Ritchie couldn't wait to start using it to completely rewrite the now famous Unix operating system

Minix

Due to AT&T (General Electric)'s policy change, after the launch of Version 7 Unix, new terms of use were issued to privatize the UNIX source code, and the UNIX source code can no longer be used in universities. In order to teach students the practical details of operating system operation in class, Professor Andrew S. Tanenbaum decided to develop a UNIX-compatible operating system without using any AT&T source code to avoid copyright infringement. controversy. He called it MINIX, meaning mini-UNIX.

Linux

Because Minix is ​​only for teaching purposes, its functionality is not very strong. Therefore, Torvalds used GNU’s bash as the development environment and gcc as the compilation tool to write the Linux kernel-v0.02. However, at the beginning, Linux was not compatible with Unix, that is, Unix The applications running on Linux cannot run on Linux, that is, the interface between the application and the kernel is inconsistent, because Unix follows the POSIX specification, so Torvalds modified Linux and followed POSIX (Portable Operating System Interface, he standardized the application Interface specification with the kernel); At first, Linux was only applicable to 386. Later, with the help of netizens around the world, it was finally compatible with a variety of hardware;

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