Overview and Introduction to Linux Operating System

Introduction: In these years, before I learned knowledge in the computer field, I was accustomed to thinking about several basic elements of knowledge itself: **1. What is it; 2. Where does it come from; 3. What can it do. **I also increasingly feel that before learning any technology, it is necessary to think about these questions and start learning with these questions in mind. Otherwise, it is easy to fall into misconceptions, have no goals, feel confused, and forget what you have learned over time, from getting started to giving up.
Therefore, before learning Linux, it is necessary to first understand what Linux is, its origin and characteristics (some friends may not understand this and think that it is enough to just learn it, why do you have to know where it came from. In fact, I had this idea at first, but I found that any thing has its background, and it is born under this background out of some need or under some kind of impetus. Then think about why it was not other technologies that were born, but this one?), and what is the role of Linux.

1. What is an Operating System

Linux is a computer operating system, similar to Windows, and is a system software. Among the operating systems that everyone is familiar with, computer operating systems include Windows, Linux, and Mac OS. The more famous mobile device operating systems include Android, IOS, and Hongmeng, which was just launched by Huawei.

How to understand the concept of operating system? We understand the hierarchical structure of computer systems from life experience:

Scenario: If we want to chat with friends using QQ on a computer, an experienced programmer will buy hardware and configure a bare metal machine, then install the Linux operating system on the bare metal machine, then install the QQ application, and finally log in to QQ to chat with friends.

The installation process in the above scenario describes the bottom-up hierarchical structure of the computer system, including the underlying hardware, operating system, and application software. The operating system is a link between the upper and lower levels. It is responsible for managing and coordinating computer resources such as hardware and software resources, and providing advisory services to upper-level application software and users. Therefore, the operating system is system software and is the software closest to the underlying hardware. The earliest operating systems were written in assembly language or C language.

Note: The interface for direct interaction between users and the operating system is the shell command. This batch command interface allows users to use it directly.

Based on the above description, the definition of operating system is given here: Operating System (OS) controls and manages the hardware and software resources of the entire computer system, and rationally organizes and schedules the computer's work and resource allocation to provide users and other software with a convenient interface and environment. It is the most basic system software in the computer system.

2. The Origin of Linux

A long time ago (in the 1960s), computers were not yet popular and only a few people could use them. Computer systems at that time were all batch processing operating systems. Batch processing is a process in which a group of tasks are submitted to a computer at one time, and the computer cannot be interacted with during the process while waiting for the calculation results. Only one user can use it at a time, and preparing the I/O input for the job takes a long time, resulting in a huge waste of computer resources.

Later, in 1965, the Multics project was jointly initiated by Bell Labs, Massachusetts Institute of Technology and General Electric to design and develop an interactive, time-sharing operating system with multiprogramming capabilities to replace the batch processing operating system that was widely used at the time.

A time-sharing operating system enables a computer to serve multiple users at the same time. Terminal users connected to the computer interactively issue commands, and the operating system processes user service requests in a time-slice rotation manner and displays the results on the terminal (the operating system divides the CPU time into several segments, called time slices). The operating system uses time slices as units and serves each terminal user in turn, one time slice at a time.

The project failed because its goals were so large and complex that its developers didn't know what to do. Based on this experience, Ken Thompson and Dennis Ritchie implemented a prototype of a time-sharing operating system in 1969. In 1970, the system was officially named UNIX, which means small and streamlined.

Who is Dennis Ritchie? Students who are familiar with C language should know that he invented C language because he liked to play the computer game "Around the World" in the laboratory and was hailed as the father of C language. This is a high-level language suitable for writing system software. Its birth is an important milestone in the development of the UNIX system. It declares that assembly language is no longer the dominant language in the development of operating systems. In 1973, most of the source code of the Unix system was rewritten in C language, which improved the portability of the Unix system.

It is clear from the early UNIX system documents and content that the development of UNIX is a free, open source process that is fully dedicated to making UNIX better. This process led to the sharing of code (both within and outside Bell Labs) and enabled the rapid development of high-quality UNIX operating systems.

Because the US government was worried that AT&T, which had already monopolized the telephone industry, would once again monopolize the computer industry, AT&T was banned from selling computer systems. Because AT&T was strictly restricted from selling computers directly to consumers before its asset breakup, the UNIX source code was licensed to universities for teaching and research use, charging a nominal fee.

FreeBSD is a version of UNIX developed by the University of California, Berkeley in the 1970s. It is developed and maintained by volunteers from all over the world and provides varying degrees of support for computer systems of different architectures. Starting with the BSD system, major commercial companies began to develop Unix systems based on their own hardware architecture and the BSD system, resulting in various versions of the Uinx system, such as: SUN's Solaris, IBM's AIX, HP's HP UNIX, etc., and charged for their services. AT&T must be furious at the thought of this. Isn't this just making wedding dresses for others? If you don't let me make money, you can't make money either.

In the late 1970s, Unix faced another major problem: AT&T suddenly reclaimed its copyright, especially the requirement to prohibit providing Unix system source code to students. AT&T took back the copyright and no longer made it open source. Such problems caused panic in the Unix industry at the time and also led to business disputes. If you want to continue using it, you need to purchase a license, which costs $40,000! ! !

Many users have become accustomed to using Unix, but when they suddenly have to pay for it, many people are very dissatisfied! ! ! One of them is Richard Stallman, who launched the free software movement, blew the clarion call of communism (launched the GUN movement), and published the communist manifesto of the software industry (GPL agreement), and this movement was recognized by many people.

The so-called freedom of free software means: free use, free study and modification, free distribution, and free creation of derivative versions.

In 1985, GNU Richard Stallman founded the Free Software Foundation to provide technical, legal and financial support for the GNU project. As the saying goes, money makes things easier.

By 1990, the software developed by the GNU project included a powerful text editor Emacs, a C language compiler GCC, and most of the program libraries and tools for UNIX systems. The only major component that remains incomplete is the operating system kernel. In fact, history seemed to be waiting for someone to appear, and then he appeared!

In 1991, Linus Torvalds, a student at the University of Helsinki in Finland, wrote it out of personal interest. At that time, he felt that the mini version of UNIX operating system Minix used for teaching was too difficult to use, so he decided to develop an operating system himself. The first version was released in September 1991 and consisted of only 10,000 lines of code. Because Linux has the characteristics of clear structure and simple functions, many college students and researchers in scientific research institutions have chosen it as an object of study and research.

Richard Stallman immediately summoned Linus to join. In March 1994, Linux 1.0 was released with 170,000 lines of code. It was released under a completely free agreement at the time, and then officially adopted the GPL agreement.

The origin of the Linux Logo is a very interesting topic. It is a penguin. Why choose a penguin?

In this regard, the author collected information and found that the following statement is the most reliable. Penguins are the iconic animals of Antarctica. According to international conventions, Antarctica is owned by all mankind and does not belong to any country in the world. No country has the right to include Antarctica in its territory. Linux chose the penguin pattern as its logo, which means that the open source Linux is owned by all mankind and no company has the right to own it privately.

3. Basic Features of Linux

• Programs should be small and focused. Programs should be as small as possible and focus on one thing only. Don't develop features that seem useful but are not used in 90% of cases.
• Linux is a completely free operating system and open source, and anyone can modify its source code at will.
• Linux supports multiple users, and each user has his or her own special rights to his or her own file devices, ensuring that users do not affect each other. Multitasking is one of the most important features of modern computers. Linux allows multiple programs to run simultaneously and independently.
• Linux is safe, reliable and highly stable. The Linux code is open source, so everyone can participate in patching vulnerabilities. Often used for Web server project deployment tasks.
• The primary adaptation platform for most open source software is Linux, so there are many free and open source software tools for you to use in Linux. Supports almost all network protocols and development languages

4. Linux Applications

• 100% of the world's supercomputers run on Linux. Including NASA's cluster.
• SpaceX uses Linux with a special fault-tolerant design on its Merlin rocket engines. Thus, Linux has helped to complete 32 space missions.
• The movie Titanic was the first movie shot on a Linux server.
• Currently, more than 90% of website servers on the Internet use Linux backend servers. With the advent of the big data era, Linux will be the first choice for distributed, parallel computing, embedded and artificial intelligence.

The above is the detailed overview and introduction of the Linux operating system. For more information about the introduction to Linux, please pay attention to other related articles on 123WORDPRESS.COM!