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Unix Operating System | Part 1

Unix Operating System | Part 1

Unix Operating System

UNIX is a portable computer operating system originally developed by a group of research laboratories of AT & T and Bell Labs, among which were initially Ken Thompson and Dennis Ritchie.

History of UNIX

Unix was designed at Bell Laboratories. The first system that can be defined for all purposes as “Unix System” was developed by Ken Thompson in 1969 to run a program called “Space Travel” that simulated the movements of the sun and planets, as well as the movement of a spaceship that could land in different places.

UNIX Features

The Unix operating system can be summarized into the following characteristics:

  • Multi user: multiple users can interact simultaneously (from different terminals) with the system, which avoids interference between the activities of different users. Within the system each user is uniquely identified by a logical name (the username). In addition, users are divided into groups, each uniquely identified by its name (group name). In every system is called the root, which is the system administrator, and that, in general, has no limitation in access to resources of the system;
  • Multiprogramming (multitasking): its core can support the simultaneous execution of multiple processes run time division;
  • Memory management: virtual memory management system based on Unix paging and segmentation. These features allow any process to address a memory size may exceed those of the main memory that is available;
  • Portable: through the use of C in the implementation of the system, it has high portability, and is now available on a wide range of architectures;
  • Open: especially in more recent versions of Unix features have gradually aligned with the POSIX standard. Also produces some of the most common Unix services and communication protocols of the Internet, enabling easy integration of Unix systems within a network;
  • Development environment for C programs: UNIX still maintains a close link with the C language This relationship is also evident in the availability of system utilities within a fairly rich set of tools for C application development (including the compiler cc).

UNIX and the Bell Laboratories (Sixties)

The development of Unix is partly due to a previous project, Multics, very quickly dismissed by the management at Bell Labs because of its perceived complexity.

Multics was born with conditions very advanced for its time, in particular, was an operating system that supports execution of applications in time-sharing. We chose to develop it internally, given the lack of support that the then computer manufacturer gave to this. His name BESYS the operating system that was installed by default on machines, and this was more like a simple extension of the hardware. BESYS requires massive manual intervention by operators, each sequence of operations should be charged the man with great waste of time.

It was with the intent to automate these operations (timesharing), who was born Multics (Multiplexed Information and Computing Service). The project was however too complex, especially for researchers accustomed to operating systems and classical perfectly linear. Was soon abandoned in favor of another system much simpler, but much more modest: GECOS. Some researchers did not think the correct decision and decided nevertheless to continue the development of the project. They were, especially Ken Thompson and Dennis Ritchie, not to give up: it was through their efforts that, on an old PDP-7 machine, came the final version of UNICS (hereinafter Unix). Name was to emphasize simplicity of design compared to poorly managed complexity of Multics. Following completion of the first kernel, Thompson and others evolved a set of programming:

1.    it makes any program do one thing well;
2.    it is expected that the output of one program becomes the input of another;
3.    software is developed with the idea that it will be tested immediately: do not hesitate to share the program;
4.    using special tools in the planning and do not try to reinvent the wheel.

Invention of C

The invention of the C language is an important step in the history of Unix. C, developed by Thompson and Ritchie during 1969-1973, has now brought the kernel on different platforms from the original PDP-7, constituting in fact the first software in history to be able to operate in totally different environments. Along with the kernel, or core (nucleus) of the operating system, Unix was accompanied by a series of standard applications for file management and users, which are still used in modern operating systems.
First applications in the company (the seventies)

Bell Laboratories were owned by AT & T (telephone communications company operating in the U.S.), which held the rights to Unix. Just at that period in the early seventies, the U.S. telephone system was undergoing a revolution inside: the use of mini-computers for the management of voice and data traffic. These were provided with minimal software type, which allowed maintenance rather limited. Soon it was discovered as Unix, with its modern design and versatility and by allowing mini-computer to do more complex operations. For the first time, maintenance could be handled centrally without sending technicians to investigate the place for any single failure.

UNIX – Development by the university (the eighties and nineties)

AT & T would not have any royalty on the use and modification of Unix. This is not for charity, as one might think wrongly, but for a fact “political”. As a monopolist, AT & T had a range of services to be offered to the market limited by law and not a Unix business directly related to the telecommunications, although in some respects he was. At the center of strong criticism because of its dominant position, which allowed the AT & T Unix source code was freely available for study at universities worldwide.

Obtaining a copy of the operating system was very simple and very inexpensive: Just pay the shipping costs of the support. Quickly formed a worldwide community at the university focused on developing new components and applications for Unix following the lines of Open Source modern. Through this process, during the seventies saw the light of the first seven versions of the operating system.

Unix formed a strong aggregator for the emerging science of information. In fact, you can even say that it was its joint development to create for the first time the idea of computing as a science. Unix has also produced a series of highly desirable consequences in science: the creation of a common environment within which the researchers could monitor and control experiments, the work could be reused and improved products, was the final transition from the laboratory isolated to a workplace community, where everyone could contribute.

To solve the problems of sharing the code was introduced for the first time copying files between systems located in different parts of the world through the telephone line. The system was called UUCP (Unix to Unix Copy) and although he was soon overshadowed by the burgeoning ARPANET (later the Internet), is an example vibrant and productive environment that was built around Unix.



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