Two important developments in modern computing occurred in 1969 at Bell Labs, a part of AT&T. A team developed the UNIX operating system, and the C programming language. The two combined are the foundations of modern operating systems. Unix was designed in a way to be implemented both on servers, as well as computers meant for individual use.
The single most important contribution of UNIX, was to create standards on which independent software and hardware manufacturing companies could work on. This basically meant that a software programmer in one country
knew his program would work on hardware from another country.
UNIX was very influential, and widely used because of the complete documentation provided with the operating system. Another important aspect of UNIX was the way it allowed computers to interface with each other. UNIX allowed tasks to be shared over a network, and thus lay the foundation of the Internet.
Before UNIX, most operating systems were written in assembly level languages. An assembly level language is specific to the hardware for which it is written. If say, a game is written in an assembly language, then the game will run only on the hardware for which it is written, and not run on any other hardware.
This means that any application written in an assembly language is not portable. The same holds true for operating systems as well. UNIX was the first operating system to be written in the C programming language — a high-level programming language — which made UNIX portable. For the first time, a single operating system could run on different hardware, independent of the architecture of the computer system.
Strictly speaking, an operating system written in a higher-level programming language compromises on a lot of benefits of operating systems programmed on assembly level programming languages, particularly noticeable in computing speed. Because of the way computers have grown though, this difference is no longer important, and C itself is considered a low level programming language because of the ease at which it can operate with a wide range of hardware.
UNIX was instantly picked up and widely used, spawning a lot of clone and derivative works. The derivatives include Sun OS, Solaris and BSD (Berkely Software Distribution). All of which are operating systems based on the UNIX code. The Mac OS, and early versions of Windows too, were based on the UNIX code, the edge being in the GUI they provided.
BSD was one of the first operating systems to embrace the concept of open source and free software. BSD’s license is still preferred on some points over the GPL license used by Linux, because it allows third party propriety software to interface with the operating system. BSD allows for derivative works to be used for commercial purposes, something specifically disallowed by the GPL, and thus many consider the BSD license to be more free than the
GPL. BSD was the first operating system to implement IP protocols, which enabled a smoother connection between computers, and is the standard now, as this allowed files to be written and accessed across a network as smoothly as a native hard drive.
One of the mainstays of Linux has been the GPL license. The GPL license, is like the EULA (End User Agreement License) of propriety software and operating systems, only without the restrictive terms and conditions. When you buy a disc with the Windows installation, for example, you don’t buy the operating system at all, but a license to use the operating system on a single computer.
You are not allowed to install the operating system on multiple machines, share it with friends, or modify it for individual use. Restrictions include something as basic as changing the interface and how it looks. The GPL license on Linux does away with many of these restrictions. That does not mean the the GPL itself is without any problems. GPL is highly controversial within the open source community itself, and amongst software developers in general.
Many claim that the GPL has no legal weight whatsoever, and software released under the GPL are essentially ambiguous in license or public domain. The GPL does not protect contributors to a project that is falsely released under the GPL by an unscrupulous programmer. Since anyone is allowed to modify and redistribute software,
GPL makes original developers almost anonymous. Due to the many shortcomings of GPL, Linux is licensed under GPL v. 2.0, whereas a later version of the license is available and used as the license for many a Linux based software. However, the GPL is still a robust, well established and open license for software distribution, and one of the reasons why Linux has risen in popularity.
It allowed adopters of Linux to make changes, and re-release, spawning a horde of Linux distributions.
Linux has found its way to cell-phones, desktops and office computers. The governments of many third world nations like Brazil, Spain, China, Peru, Pakistan and India are actively involved in promoting Linux and associated open source software.
The French parliament works off Linux, and the entire city of Vienna has decided to take the plunge. Using Linux really puts you in better company, if not for ideological and political reasons, there are technological reasons as well. Linux is the most used operating system on supercomputers around the world, and the behemoth of modern technology, the LHC itself is controlled by Linux.