What is the reason why linux and unix are similar?

The original intention of Linux is to replace UNIX and optimize its functions and user experience. Therefore, Linux imitates UNIX (but does not plagiarize the source code of UNIX), making Linux better in appearance and user experience. The interaction is very similar to UNIX. Therefore, it can be said that "UNIX is the father of Linux". It is precisely because Linux and UNIX are inextricably linked that people call Linux a "UNIX-like system."

The relationship between UNIX and Linux is a very interesting topic. Among the current mainstream server-side operating systems, UNIX was born in the late 1960s, Windows was born in the mid-1980s, and Linux was born in the early 1990s. It can be said that UNIX is the "big brother" among operating systems. Later Windows and Linux both referenced UNIX.

Modern Windows systems have developed in the direction of "graphical interfaces", which are hugely different from UNIX systems. On the surface, the relationship between the two cannot even be seen.

The Troubled History of UNIX

The UNIX operating system was invented by Ken Thompson and Dennis Ritchie. Part of its technical origins can be traced back to the Multics engineering program started in 1965, which was jointly initiated by Bell Labs, MIT, and General Electric Company. The goal was to develop an interactive, multi-program processing capable time-sharing operating system to replace the widely used batch operating system at the time.

Description: The time-sharing operating system enables one computer to serve multiple users at the same time. The terminal user connected to the computer issues commands interactively, and the operating system uses time slice rotation to process the user's service request. And display the results on the terminal (the operating system divides the CPU time into several segments, called time slices). The operating system provides services to each end user, taking turns in units of time slices, one time slice at a time.

Unfortunately, because the goal pursued by the Multics engineering plan was so huge and complex that its developers didn’t know what to do, it ultimately ended in failure.

Bell Labs researchers headed by Ken Thompson learned from the failure of the Multics project plan and implemented a prototype of a time-sharing operating system in 1969. In 1970, the system was officially named UNIX .

Think carefully about the meaning of the two English prefixes "Multi" and "Uni", and you will be able to understand the implicit meaning of UNIX. Multi means large-scale and complicated; Uni means small-scale and exquisite. This was the original design intention of UNIX developers, and this concept continues to influence today.

What’s interesting is that Ken Thompson’s original intention to develop UNIX was to run a computer game he wrote called Space Travel. This game simulates the movement of celestial bodies in the solar system. Players drive a spacecraft, enjoy the scenery and try to navigate various Landing on planets and moon. He tried experimenting on several systems, but it didn't work well, so he decided to develop his own operating system, which eventually led to UNIX.

Since 1970, UNIX systems have gradually become popular among programmers within Bell Labs. From 1971 to 1972, Ken Thompson's colleague Dennis Ritchie invented the legendary C language, a high-level language suitable for writing system software. Its birth was an important milestone in the development of the UNIX system, and it announced In the development of operating systems, assembly language is no longer the dominant language.

By 1973, most of the source code of the UNIX system was rewritten in C language, which laid the foundation for improving the portability of the UNIX system (previously, the operating system mostly used assembly language, which required a lot of effort on the hardware. strong dependence), also creates conditions for improving the development efficiency of system software. The UNIX system and the C language can be described as a pair of closely linked brothers, and the relationship between them is inseparable.

In the early 1970s, there was another great invention in the computer industry-TCP/IP protocol, which was a network protocol developed by the U.S. Department of Defense after it took over ARPAnet. The U.S. Department of Defense bundled the TCP/IP protocol with the UNIX system and C language, and AT&T issued non-commercial licenses to various universities in the United States. This kicked off the development of the UNIX system, C language, and TCP/IP protocol. They have influenced the three fields of operating systems, programming languages, and network protocols to this day respectively. Ken Thompson and Dennis Ritchie received the Turing Award, the highest award in computer science, in 1983 for their outstanding contributions to the field of computing.

Subsequently, various versions of UNIX systems appeared. Currently, the common ones are Sun Solaris, FreeBSD, IBM AIX, HP-UX, etc.

Solaris and FreeBSD

Focus on Solaris, an important UNIX system branch. In addition to running on SPARC CPU platforms, Solaris also runs on x86 CPU platforms. Sun's hardware platform occupies the position of the dominant UNIX system in the server market, and its high availability and high reliability are commendable.

For users who have difficulty accessing Sun SPARC architecture computers, they can experience the commercial UNIX style of world-renowned manufacturers by using Solaris x86. Of course, Solaris x86 can also be used in servers for actual production applications. Solaris x86 can be used for free for study, research or commercial applications, subject to Sun's relevant licensing terms.

FreeBSD originated from the UNIX version developed by the University of California, Berkeley. It is developed and maintained by volunteers from all over the world, providing varying degrees of support for computer systems of different architectures. FreeBSD is released under the BSD license agreement, which allows anyone to use and distribute it freely while retaining the copyright and license agreement information. It does not restrict the release of FreeBSD code under another agreement, so commercial companies can freely integrate FreeBSD code into in their products. OS X, the operating system used by Apple Inc., is built upon the FreeBSD operating system.

The user groups of FreeBSD and Linux overlap considerably, the hardware environments they support are relatively consistent, and the software they use is also relatively similar. The biggest feature of FreeBSD is its stability and efficiency, making it a good choice as a server operating system; however, its hardware support is not as complete as Linux, so it is not suitable as a desktop system.

Other UNIX versions will not be introduced too much here due to their relatively limited scope of application.

Those past events of Linux

The Linux kernel was originally written by Linus Torvalds as a personal hobby when he was studying at the University of Helsinki. At that time, he felt that Minix, the mini version of the UNIX operating system used for teaching, was too difficult to use, so he decided to develop an operating system by himself. When the first version was released in September 1991, there were only 10,000 lines of code.

After Linas Torvalds disclosed the Linux source code, he did not retain the copyright and invited others to participate in the improvement. Unlike Windows and other proprietary operating systems, Linux uses open source code, which means anyone can use it for free.

It is estimated that only 2% of the Linux core code is now written by Linus Torvalds himself, although he still owns the Linux kernel (the core part of the operating system) and retains the option of new code and final authority for new methods that require incorporation. The Linux that everyone is using now, I prefer to say that it was jointly developed by Linus Torvalds and many Linux enthusiasts who joined later.

Linus Torvalds is undoubtedly one of the greatest programmers in the world. What's more, he also created the world's largest programmer dating community GitHub (open source code base and version control system ).

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

Why choose penguins instead of lions, tigers or little white rabbits? Some people say that Linus Torvalds chose penguins because he is Finnish. Some people say that because all other animal patterns were used up, Linus Torvalds had to choose penguins.

I prefer to believe the following statement. 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. However, no country has the right to include Antarctica in its territory. . Linux chose the penguin pattern as its logo, which means: open source Linux is owned by all mankind, but the company has no right to keep it private.

The close relationship between UNIX and Linux

A more appropriate statement is that the relationship between UNIX and Linux is not that of brothers or elders, but that "UNIX is Ancestor of Linux”. The reason why I want to introduce their relationship is to tell readers that Linux and UNIX actually have a lot in common when learning. Simply put, if you have mastered Linux, it will be very easy to start using UNIX. .

There are also two big differences between the two:

• UNIX systems are mostly matched with hardware, that is to say, most UNIX systems For example, AIX, HP-UX, etc. cannot be installed on x86 servers and personal computers, while Linux can run on a variety of hardware platforms;

• UNIX is commercial software, and Linux It is open source software, free and open source code.

Linux is loved by most computer enthusiasts for two main reasons:

• It is open source Software, users can obtain it and its source code without paying any fees, and can make necessary modifications to it according to their own needs, use it free of charge, and continue to spread it without restriction;

• It has all the functions of UNIX. Anyone who uses the UNIX operating system or wants to learn the UNIX operating system can benefit from Linux.

Open source software is a model different from commercial software. Literally, it means open source code. You don’t have to worry about any tricks in it. This will bring about software innovation. and safety.

In addition, open source does not actually mean free, but a new software profit model. Currently, many software are open source software, which has a profound impact on the computer industry and the Internet.

Summarize the relationship/difference between Linux and UNIX

Linux is an operating system similar to Unix. Unix is ​​earlier than Linux. The original intention of Linux is to replace UNIX and optimize functions and user experience, so Linux imitates UNIX (but does not plagiarize UNIX source code) , making Linux very similar to UNIX in appearance and interaction.

If you say imitation, you may get criticized. You can also say micro-innovation or improvement.

Compared with UNIX, the biggest innovation of Linux is that it is open source and free, which is the most important reason for its vigorous development; while most of the current UNIX is paid, which is difficult for small companies and individuals to use bear.

It is precisely because Linux and UNIX are inextricably linked that people call Linux a "UNIX-like system".

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