Although entire books have been written just about the history of Linux, I will attempt to make this as short as possible. It is not necessary to know this history to be able to use Unix or Linux, but you may find it interesting.
Starting With UNICS
The history of Linux begins with UNICS which was originally written as a gaming platform to run a single game.
Ken Thompson was an employee at Bell Labs in the late 1960’s – before the breakup – working on a complex project called Multics. Multics was an acronym (what isn’t in the computer world) that stood for MULTiplexed Information and Computing System. It was supposed to be a multitasking operating system for the GE (yes, General Electric) 645 mainframe computer. It was a huge, costly, complex project with three very large organizations, GE, Bell Labs, and MIT, working on it.
Although Multics never amounted to much more than a blip on the computing radar scope, it did introduce a good number of then innovative features that had never before been available in an operating system. These features included multitasking and multiuser capabilities.
Ken Thompson wrote a game called Space Travel that ran under Multics. Unfortunately, due at least in part to the committee design of Multics, the game ran very slowly. It was also very expensive to run at about $75 per iteration.
As with many projects developed by committees, Multics died a slow, agonizing death. The platform on which the Space Travel game was run was no longer available.
Thompson then rewrote the game to run on a DEC PDP-7 that was just sitting around gathering dust. In order to make the game run on the DEC, he and some of his buddies, Dennis Ritchie, and Rudd Canaday, first had to write an operating system for the PDP-7. Because it could only handle two simultaneous users – far fewer than Multics was designed for – they called their new operating system UNICS for UNiplexed Information and Computing System.
At some time later the UNICS name was modified slightly to UNIX and that name has stuck ever since.
Eric Raymond, who has been around since the very early days of Unix, has written a very important book, The Art of Unix Programming, which contains a great deal of the history of Unix. For more information take the link: http://www.catb.org/~esr/writings/taoup/html/index.html
Growth and Development
In 1970, finally recognizing its potential, Bell Labs provided some financial support for the new operating system and development began in earnest. In 1972 the entire operating system was rewritten in C to make it more portable and easier to maintain than the assembler it had been written in allowed for. By 1978, Unix was in fairly wide use inside AT&T Bell Labs and many universities.
Due to the high demand, AT&T decided to release a commercial version of Unix in 1982. Unix System III was based on the seventh version of the operating system.
Unix System V
In 1983, AT&T released Unix System V Release 1. For the first time, AT&T promised to maintain upward compatibility for future versions. Thus programs written to run on SVR1 would also run on SVR2 and future releases. Because this was a commercial version, AT&T began charging license fees for the operating system.
Also, in order to promote the spread of Unix and to assist many large universities in their computing programs, AT&T gave away the source code of Unix to many of these institutions of higher learning. This caused one of the best and one of the worst situations for Unix.
The best thing about the fact that AT&T gave the source code to universities was that it promoted rapid development of new features. It also promoted the rapid divergence of Unix into many distributions.
System V was an important milestone in the history of Unix. Many Unix variants are today based on System V. The most current release is SVR4 which is a serious attempt to reconverge the many variants that split off during these early years. SVR4 contains most of the features of both System V and BSD. Hopefully they are the best features.
The Berkeley Software Distribution (BSD)
The University of California at Berkley got into the Unix fray very early. Many of the students who attended the school added their own favorite features to BSD Unix. Eventually only a very tiny portion of BSD was still AT&T code. Because of this it was very different from, though still similar to System V. Ultimately the remaining portion of BSD was totally rewritten as well and folks using it no longer needed to purchase a license from AT&T.
A Brief History of Linux
Linus Torvalds, the creator of Linux, was a student at Helsinki University in 1991. The University was using a very small version of Unix called Minix for school projects. Linus was not very happy with Minix and decided to write his own Unix-like operating system.
Linus wrote the kernel of Linux and selected the then ubiquitous PC with an 80386 processor as the platform for his operating system. He released an early version in 1991, and the first public version in March of 1992.
One of the unique aspects of Linux is that it does not use code from any other versions of Unix. As a result of this there is no need to charge license fees for its use. The fact that it was developed by a student for students and the academic community placed Linux squarely in an environment where free distribution of the software seemed a natural thing to do. So Linux – and perhaps even more importantly, all of its source code – was put up on the Internet where it was – and is – freely available to anyone who wants it. This is called Open Source.
Just because Linux and its source code are freely available does not mean that there are no legal or copyright issues involved. Linux is copyrighted under the GNU General Public License (GPL). The GNU GPL is actually called a copyleft instead of a copyright by most people in the industry because its terms are so significantly different from most commercial licenses. The terms of the GPL allow you to distribute or even to sell Linux (or any other copylefted software), but you must provide the complete source code as well as the compiled binaries.
The original owner – Linus Torvalds in the case of the Linux kernel – retains copyright to the software no matter who or how much it is modified or added to.
GNU is a recursive algorithm that stands for “Gnu’s Not Unix.” It was developed by the Free Software Foundation (FSF) to provide free software to programmers and developers. Most distributions of Linux contain many GNU utilities.
As fellow students and others obtained and used Linux, they began to add more features and components. This was easy to do because of the Open Source nature of Linux which provides anyone who wants it with full access to the source code. This has spurred the tremendous development of Linux in the short time since its development, and has contributed greatly to its popularity.
Open Source has actually become a movement, and many companies are providing the source code for their applications.
Linux is POSIX compliant. POSIX stands for Portable Operating System Interface for Unix. All major versions of Unix are compliant with this standard. In fact, if your version is not POSIX compliant, it is not considered to be Unix.
Linux is derived from BSD, both System V and BSD variants of many commands can be found in some distributions. It is really the best of both of these worlds. In fact a great deal of convergence with BSD and SVR4 is now occurring.