History of UNIX - Origin & versions of the Operating System

The origins of UNIX

The origin of the UNIX system is linked to the development of a project started in 1968.

At that time A group of researchers from General Electric, AT & T Bell and MIT (Massachusets Institute of Technology, Massachusetts Institute of Technology) undertook the development of an operating system that took into account new concepts such as multimedia, file management or the interaction with the user.

The result of these investigations was baptized as MULTICS (Multiplexed Information and Computing System, Multiplexed Information and Computing System). The project turned out to be too ambitious, so it did not come to a good end and ended up leaving after suffering several setbacks and delays.

However, they were not useless. Subsequently the idea of this project is retaken and leads to the development in 1969 of the UNIX operating system by Ken Thomson, Dennis Ritchie and other researchers, some of them members of the group of programmers who carried out the project MULTICS.

The computer on which this new operating system was implemented, which was called UNICS, was a DEC PDP-7.

The name that was given to the operating system is actually a game of words that is formed with the initials of Uniplexed Information and Computing System (multiplexed system of information and computation), making reference to its predecessor, MULTICS and taking into account Note that on this occasion the operating system could only support two users simultaneously.

Later, in 1970, the name undergoes a small variation and is now called UNIX, with which it is currently known.

The UNIX code was initially written in assembly language, this issue had a negative impact on its portability and was soon solved.

It was later in 1973, when Dennis Ritchie, one of the mythical creators of the C language, carried out a project in collaboration with Ken Thompson with the intention of rewriting the UNIX code in C language.

UNIX thus became the first operating system written in high level language.

This step was undoubtedly fundamental for its further development, because until then the code of the operating system was very dependent on the type of machine.

With this new approach it was possible to port the operating system to other machines with very few changes, simply by making a new compilation on the target machine.

Thanks to this step, the popularity of UNIX grew and allowed to settle the main aspects of what is called the "UNIX philosophy".

Although initially UNIX was considered as a research project, to the point of being distributed free of charge among the IT departments of some universities, soon the demand for the product caused the Bell laboratories to begin their official distribution by granting licenses to different users.

It was around 1974 when UNIX, already in its fourth edition, began to be used massively in the Bell laboratories.

The two fundamental variants: System V and BSD

The University of California at Berkeley, akin to the UNIX project, then began its developments in this field, adding new features to the system and making it a standard.

Thus, in 1975 Ken Thompson promoted the development and brought to light his own version BSD went on to become the main competitor of the Bell laboratories.

In this version the works were carried out in large part by two graduate students, Bill Joy and Chuck Haley. His contributions are numerous and among them is a compiler of Pascal, the former editor, Shell C and editor vi.

Meanwhile, the Bell laboratories continued with the developments, presenting different research versions until 1982 when the launch of System III, the first commercial version of the UNIX operating system, took place. In 1983 AT & T introduced the UNIX System version 1.

For the first time, AT & T promised upward compatibility in the next versions of its UNIX systems. This meant that the programs developed on UNIX System version 1 would work correctly in the following versions.

For its part, the BSD version followed a similar path until the late 1970s, when it became the basis of a research project of the Advanced Research Projects Agency of the Department of Defense (DARPA).

In 1983 Berkeley released a powerful version of UNIX known as BSD version 4.2. Among its main features are a very sophisticated file management, as well as the possibility of working in networks based on TCP / IP protocols (the same that are now used on the Internet).

This version had a great impact and was adopted by several computer manufacturers for their equipment; among them stands out Sun Microsystems, a company founded by Bill Joy, which gave rise to the well-known SunOS system.

Microsoft also launched the UNIX project developing its own PC version known as XENIX that was released in 1980.

The main contribution of XENIX lies in the approach of the UNIX system to PC platforms, previously only relegated to large machines.

There are also versions for the Motorola 68000 processors.

Later, Microsoft and AT & T carried out the fusion of XENIX with UNIX System V in 1987, thus presenting version 3.2 of UNIX System V, and achieving a unification that allowed to have a UNIX system in a wide variety of computers, from a PC until a great station.

At that time the differences between the different versions of UNIX were very large, and were the cause of many headaches for programmers, who were forced to develop different versions of their programs for each variant of UNIX.

The standards and the attempt of unification POSIX

During the eighties Bell laboratories decided to make a unification attempt, in order to increase the portability of applications between different UNIX systems.

It was about combining the best versions of the era, resulting in a single operating system capable of bringing together all developments: UNIX System V version 4.

This version compiles the best of UNIX System V of AT & T, Microsoft's XENIX and SunOS from Sun Microsystems. With this, the fundamental variants of UNIX are reduced to System V and BSD.

In 1985 / usr / group, an independent organization formed by users of the UNIX system, whose main objective was to ensure the portability of applications, decides to publish a standard known as POSIX (Portable Operating System Interface for Computer Environment, operating system interface portable for computer environments). The standard covers different areas, from system calls to interfaces or security.

Another standard known as X / OPEN sees the light in 1984 promoted by an international consortium of computer vendors.

These companies include AT&T, DEC, Hewlett Packard, IBM, Sun, Unisys, Olivetti and Philips. In this case, the standard aims to unify the software interfaces and contains the POSIX standards.