The Origins of Unix

have to say the Unix

"Content Summary" Unix was born in 1969 and has been widely used since then; Unix started out as open source, and later at&t the copyright and unfairly open-source code; UNIX's code is made up of 90% of the C language and 10% of the Assembly; Unix later two major branches:at& T's System V and BSD.

Since early computers were not as prevalent as the current PCs, only a handful of people had access to them, and the computer architecture at the time was difficult to use and the interface cumbersome to operate. So around 1965, Multics's project was launched by Bell Labs, MIT and General Electric (GE), Multics (full name: multiplexed information and Computing System) is a comprehensive, general-purpose time-sharing operating system, the purpose of the Multics project is to enable large hosts to simultaneously provide more than 300 terminals for the use of the target.
However, by 1969, the project was behind schedule and funding was scarce, and Bell Labs withdrew from the project after thinking that the Multics project was unlikely to succeed. The final Multics project has successfully developed their systems, although the Multics system has not received much attention, but the project has trained a lot of talented people, including Ken Thompson, Dennis Ritchie, Joe Ossanna, Douglas McIlroy, Peter Neumann, Stan Dunten, Rudd canaday and so on.

Figure 1. The history of Multics time-sharing operating system

The engineers who participated in the Multics project returned to Bell Labs, and they missed multics very much in the face of the laboratory's outdated computer environment, which was still in batch work. One of the engineers, Ken Thompson, wants to develop a small operating system for use, because he wants to transplant a game called space travel. In August 1969, helpless's Thompson found an idle PDP-7 in the storeroom, just at the time of his vacation and his wife and son visiting the family, and Thompson had an extra one months to implement his plan. After 4 weeks of struggle, a set of kernel programs was written in assembly language, including some kernel tools, and a small file system. He spent a week on the operating system, shell programs, editors, and assembler.
As Thompson obtained ideas from the Multics project, simplifying Multics's large and complex system, the lab friends joked that the system was UNICs (the system was the prototype of Unix).
Thompson's file system has two important concepts, namely, that all programs or system devices are files. Whether you build an editor or a satellite file, the program you write has only one purpose, which is to effectively accomplish the goal.

These concepts later have a significant impact on the development of Linux. This is also known as the Kiss (keep it simple, stupid) principle, the "simplicity principle"-try to solve the problem in a simple way, which is the fundamental principle of "Unix philosophy".

Figure 2. The Dec PDP-7 that originally ran the UNIX system

Thanks to Thompson's UNICs, it was widely circulated inside Bell Labs and has been revised many times. But because UNICs is written in assembly language and relies heavily on hardware, it is necessary to rewrite assembly language every time you install it on a different machine. So Thompson worked with Ritchie to improve portability by switching UNICs to more advanced programming languages. They first selected bcpl (b language), and then tried Pascal, and found that the compiled kernel performance is not very good, because these languages are not very close to the hardware operation. As a result, the two (mainly Dennis Ritchie) decided to develop a new language of their own: This is the famous C language.

Figure 3. Ken Thompson (Sat) and Dennis Ritchie to work before PDP-11.

In the 1973, Dennis Ritchie rewritten and compiled the UNICs kernel in C and finally released the official version of UNIX. "Rewriting" is simply not a simple compilation to C language translation, which contains a lot of inventions and creations. The "pipe" (piping) feature introduced during this period has become a major advantage of UNIX, which makes it easy to deliver results between programs. The concept of piping was invented by Bell Labs ' Douglas McIlroy, which was heavily copied by many operating systems, including all variants of UNIX, Linux, DOS, and Windows.
The rewritten Unix quickly became popular and has since been applied to the production field. More than 40 years on, there are a lot of Unix-like systems (such as Linux), but they all inherit the basic ideas of Unix and flourish. The famous Unix-like systems include Berkeley Unix, Minix, Linux, AIX, A/ux, HP-UX, and Solaris, and Apple's Mac OS X is based on Berkeley Software Distribution (BSD) Unix.

Figure 4. 1998 awarded the National Medal of Science and Technology (left-Thompson, Ritchie and Clinton, respectively)

UNIX, written in C, is theoretically portable, and can be ported to a different host as long as it has the source code of UNIX and modifies the characteristics of a large host.
After 1973, Unix began working with academia, the most important of which was collaboration with the University of California, Berkeley (Berkeley). Bill Joy of the University of Berkeley added many tools and compilers to the process of porting Unix, eventually naming it Berkeley Software Distribution (BSD). BSD is a very important branch of UNIX. Meanwhile, Bill Joy was the founder of Sun's company. Sun is developing its own commercial UNIX version with the BSD-developed kernel. (later, it can be installed on the x86 hardware architecture FreeBSD is the BSD version.) ）
Because of the high portability and strong performance of UNIX, coupled with the lack of copyright disputes at the time, many commercial companies started the development of UNIX operating systems. But each company's own UNIX, although architecturally similar, only supports its own hardware, so earlier UNIX can only be equated to servers (server) or large workstations (Workstation). It was not until 1979 that At&t launched System v Seventh Edition UNIX to support the x86 architecture of personal computer systems. Later, because At&t wanted to reclaim Unix's copyrights for commercial reasons, the strict restrictions on "not providing students with source code" were specifically mentioned in version seventh System V.
Currently known as purebred Unix, the System V and BSD are the two sets.

Figure 5. Unix-like system genealogy

From the day of the birth of Unix, a variety of promises accompanied along with it, saying that UNIX will decay, or be squeezed out of the market by other operating systems. Today, however, it has become as powerful as Linux, BSD, Solaris, MacOS X and several other variants of UNIX.

The story tells us how important it is to be properly given to a creative engineer to take a vacation.