What is UNIX?

Unix is ​​a portable, multitasking and multiuser operating system. It was originally developed in 1969 by a group working at AT&T Bell Laboratories, including Ken Thompson, Dennis Ritchie, and Douglas McIlroy.

What is UNIX?

What is UNIX Operating System?

Until 2009, it was The Open Group, an industry standardization consortium with a UNIX brand. As of March 2010 and after a long legal battle, it once again became the property of Novell Inc.

Only fully compatible systems certified by the Single UNIX Feature can be called UNIX.

The term is often used for an operating system with Unix or UNIX Version 7 or System V features.


In the late 1960s, the Massachusetts Institute of Technology, AT&T Bell Laboratories, and General Electric was working on an experimental operating system called Multics (Multiplexed Information and Computing Service) developed to run on the GE-645 model host.

The aim of the project was to develop a wide interactive operating system that includes many innovations, including improvements in Security Policies.

The project managed to give birth to production versions, but the first versions had poor performance. AT&T Bell Labs has decided to devote itself and dedicate resources to other projects.

Ken Thompson, one of the programmers in the Bell Labs team, continued working on his GE-635 computer and wrote a game called Space Travel. However, he found that the game was slow on the General Electric machine and that it was something like $75 for every game.

So Thompson rewrote the program to run on the DEC PDP-7 computer with the help of Dennis Ritchie in Assembly PD.

This experience began to create a new operating system for Thompson’s DEC PDP-7, with the work it developed for the Multics project.

Thompson and Ritchie led a group of programmers, including Rudd Canaday, in Bellds to develop both the File System and the multitasking operating system.

They added a shell and a small set of programs to the above. The project was named UNICS, Acronym Uniplexed Information and Computing System, as it only serves two users.

The author of this abbreviation is attributed to Brian Kernighan because he is a Multics hack. Given the popularity of a word game that sees UNICS as a castrated MULTICS system, the name has been changed to UNIX and has resulted in legacy to this day.

Until then, there was no financial support from Bell Laboratories, but it changed when the Computer Science Research Group decided to use UNIX on a machine superior to PDP-7.

Thompson and Ritchie succeeded in complying with the request to add tools to allow UNIX word processing on a PDP-11/20 machine, and as a result, received financial support from Bell Labs.

Thus, for the first time, in 1970, the UNIX operating system was officially spoken in a PDP-11/20. It includes a program for editing text and a Text Editor.

Both the operating system and programs are written in the assembly language of PDP-11/20. This first “word processing system”, consisting of both the operating system and the flow system and text editor, was used to process patent applications they received at Bell Labs.

It soon became Troff, the first electronic publishing program to enable streaming strings. On November 3, 1971, Thomson and Ritchie published a programming guide.

It was decided to rewrite UNIX in 1972, but this time it was Programming Language C. This change meant that UNIX could easily be modified to run on other computers, thereby improving other variations by other programmers.

Now the code was more concise and compact, which caused the speed of development to increase. AT&T has offered UNIX to universities and companies, including the US government, under license.

One of these licenses was issued to the UC Berkeley-based IT Department.

In 1975, this agency developed and released its own backup product, known as Berkeley Software Distribution (BSD), which became a strong competition for the AT&T family.

Meanwhile, AT&T has created a division called Unix Systems Laboratories for commercial use of the operating system. Development continued in 1975 with the introduction of versions 4, 5, and 6.

These releases included Pipes, which provided the development with a modular orientation relative to the codebase and was able to further improve its development speed. As early as 1978, about 600 or more machines were running, with one of its various incarnations.

Version 7, the latest version of the originally distributed UNIX, went into circulation in 1979. Versions 8, 9, and 10 were developed in the 1980s, but despite their reports explaining the new job, their circulation was limited to several universities.

The results of this research were the basis for the creation of Plan 9 from Bell Labs, a new portable and distributed operating system designed as the successor of UNIX in research by Bell Labs.

AT&T then began the development of UNIX System III based on version 7 as a commercial paint variant, thus selling the product directly. The first version was released in 1981.

Despite this, the subsidiary Western Electric continued to sell older versions of Unix, based on different versions until the seventh.

To end the confusion with all divergent versions, AT&T decided to combine several versions developed in different universities and companies, leading to Unix System V Version 1 in 1983.

This version included features such as the Vi editor and curses library developed by Berkeley Software Distribution at the University of California, Berkeley. DEC also had compatibility with VAX machines.

In 1993, Novell acquired the Unix Systems Laboratories division of AT&T with its intellectual property.

This happened at a sensitive time when Unix Systems Laboratories sued BSD for copyright infringement, disclosure of secrets, and trademark infringement in courts.

BSD not only won the case but also changed tables by discovering that large portions of the BSD code were illegally copied to UNIX System V.

In fact, Novell’s intellectual property fell into several source files. The corresponding case resulted in an out-of-court solution that remained hidden at Novell’s request.

At the same time, a computer science student named Linus Torvalds developed a kernel for computers with Intel X86 processor architecture that mimics many of UNIX’s functionality and released it in 1991 under the name of Linux under the open-source form.

In 1992, the GNU Project started to use the Linux kernel alongside the programs.

In 1995, Novell sold its commercial division Santa Cruz Operation (SCO) and apparently reserved some intellectual property rights in the software.

SCO continues to market System V on its product, which has been renamed OpenUnix for some time but has returned to UnixWare.


This project was originally baptized as UNICS, short for Uniplexed Information and Computing System because it only served two users. The author of this abbreviation is attributed to Brian Kernighan because he is a Multics hack.

Given the popularity of a word game that sees UNICS as a castrated MULTICS system, the name has been changed to UNIX and has resulted in legacy to this day.

This marking is applicable only to operating systems that comply with this organization’s “Single Unix Specification” and pay built-in copyrights.

It also applies to POSIX-based multi-user systems such as GNU/Linux, Mac OS X, FreeBSD, NetBSD, OpenBSD, which are expensive for the end consumer or do not require certification for freely distributed products.


As can be deduced from this brief historical review, the operating system has several families that have evolved independently over the years.

Not every family is distinguished by its technical differences as well as its differences in intellectual property. It is observed that all families are directly or indirectly contaminated by other families.

   The most important UNIX families

AT&T: It was considered pure and original. The most important operating systems are UNIX System III and System V.

BSD: This was due to UNIX licensing to Berkely. BSD has been rewritten in version 4 to include IP from AT&T. The first implementation of TCP/IP protocols leading to the Internet is the TCP/IP BSD stack.

AIX: This family is due to the license of UNIX System III to IBM.

Xenix: The family derives from Microsoft’s original AT&T rights acquisition and was sold to Microsoft by SCO.

GNU: In 1983, Richard Stallman announced the GNU Project, an ambitious effort to create a Unix-like system that can be freely deployed. The software developed by this project, GNU Emacs and GCC has also been an essential part of other systems.

Linux: When Linus Torvalds started recommending the Linux kernel and collecting collaborators, GNU tools were a great choice. Combining both elements, they formed the basis of the operating system (POSIX-based), known today as GNU/Linux.

Core-based distributions, GNU software, and other add-ons such as Slackware Linux, Red Hat Linux, and Debian GNU/Linux have become popular both in computer fans and in the business world. Note that Linux has an independent origin, so it is historically considered a ‘clone’ of UNIX, not UNIX.

   The relationships between these families are as follows in approximate chronological order:

The BSD family is due to the license of the original AT&T UNIX.

Although Xenix does not yet belong to SCO, it is also due to the license of the original AT&T UNIX.

AIX is caused by UNIX System III licensing but includes BSD intellectual property.

The original AT&T family illegally incorporates BSD intellectual property in UNIX System III r3.

This time the AIX family is reproducing the intellectual property of the AT&T family from Sistem V this time.

Linux also includes the intellectual property of BSD, where it was released with an open-source license called Open-Source BSD.

According to the SCO Group, Linux contains the intellectual property of AIX, thanks to the cooperation in IBM’s 2.4 version, no more has been proven, there is a judicial process: SCO disputes about Linux.


It is a registered trademark of The Open Group in the USA and other countries. This mark may only be applied to operating systems that comply with the Single Unix Specification of this organization and pay built-in copyrights.

In practice, the term UNIX is used in the sense of family. It also applies to POSIX-based multi-user systems that do not receive certificates because they are expensive for end-consumer products or freely distributed on the Internet.

Major Applications

Numerous commercial applications have emerged throughout history. A small set of products, however, reinforced and reigned the market, thanks to the manufacturers’ continuous development effort. Most important ones:

  1. Solaris from Sun Microsystems: One of the most common operating systems in the business environment and known for its stability. Some of the Solaris source codes have been released under an open-source license (OpenSolaris).
  2. IBM AIX: IBM “proprietary” UNIX turned 20 in 2006 and is still fully evolving with a prominent host heritage in areas such as Virtualization or RAS for services taken over from its older siblings.
  3. Hewlett-Packard HP-UX: This operating system was also born depending on the department computers of this manufacturer. It is also a stable operating system that is still being developed.
  4. Mac OS X: Its users are generally unaware that it is a complete system approved by The Open Group. The obvious difference is that it has a proprietary graphical interface called Aqua and is mainly developed in Objective-C instead of C or C++.

There are operating systems based on the Linux kernel. The most common are:

  1. Red Hat Enterprise Linux: Red Hat is known for its comprehensive solutions and contributions to the development of Free Software. It supports the Fedora project it uses, and compatible distributions such as Oracle Enterprise Linux and CentOS are derived from it, as well as distributions like Mandriva Linux are based on one of the first versions.
  2. SUSE Linux from Novell: Originally launched by the German company SuSE. It is popular with its central management tools. Similar to RedHat and Fedora, it supports the OpenSUSE project.
  3. Debian GNU/Linux: One of the largest and oldest communities in the Free Software movement, Xandros is the basis for deployments such as Mepis, Linspire, and Ubuntu.

Operating systems from 4.4BSD are also popular:

  1. FreeBSD: Perhaps the most popular multipurpose operating system in the family. It is the operating system used by Yahoo servers, with a very detailed SMP application. And it’s the base of many operating systems, including Apple’s Mac OS X.
  2. OpenBSD: It is widely recognized for its proactive security and permanent control of source code. It is used in environments where security is dominant, it is normal to have it installed on servers acting as Firewall, VPN, or Proxy.
  3. NetBSD: As of October 2008, it is known for the portability of 53 supported architecture. NASA used it to research satellite IP networks and to recycle older computers with modern software.

The following apps are historically important, but are currently deprecated:

  1. Tru64
  2. UnixWare ve SCO OpenServer
  3. NEC UX/4800
  4. IRIX

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