Linux is a high performance, yet completely free, Unix-like operating system that is suitable for use on a wide range of computers and other products. Most distributions (i.e., versions) consist of a kernel (i.e., the core of the operating system) together with hundreds of free utilities and application programs in a coordinated package.
A narrower, and somewhat less common, meaning of the term Linux is just the kernel itself. However, when referring to just the kernel, usually the expression the Linux kernel is used.
Linux was started as a hobby in 1991 by Linus Torvalds while a student at the University of Helsinki (in Finland) because he was unhappy with the MS-DOS operating system that came with his new personal computer. He greatly preferred the much more powerful and stable UNIX that he had been using on the university's computers, but he was not able to afford the high licensing fees for any of the commercial versions then available. Today, Torvalds remains the spiritual leader of the Linux movement, and he still coordinates the development of the Linux kernel.
The use of Linux by individuals, corporations, government agencies and academic institutions around the world has been growing swiftly1, and many computer experts think that it will eventually become the most widely used operating system for many or most types of applications.
This rapid growth is a result of several factors including (1) the major advantages that Linux has over other operating systems (including over the other Unix-like operating systems and the Microsoft Windows family of operating systems), (2) the rapid progress that is being made on further improving the performance and increasing the functions of Linux, (3) the expanding array of high-quality application programs, (4) the growing awareness by individuals, businesses and other organizations throughout the world of the advantages of Linux and (5) an increase in the number of people who are familiar with installing, administering and using Linux.
Well in excess of a hundred (and possibly more than two hundred) Linux distributions have been developed by a diverse range of companies, non-commercial organizations and individuals. Some of the most popular are Red Hat, SuSE, Mandrake, Debian, Slackware, Linspire and Ubuntu. In addition to these mainstream distributions, numerous specialized distributions are also available, including those optimized for specific types of computers or applications (e.g., for use on notebook computers or routers), those for specific languages or countries (e.g., Polish or Chinese) and ultra-miniature distributions (some of which can even fit on just a single floppy disk, such as muLinux).
UNIX was originally developed by Ken Thompson in 1969 at Bell Labs, the highly innovative research arm of AT&T (the former U.S. telecommunications monopoly). Much subsequent work was carried out at the University of California at Berkeley (UCB).
Linux is a clone of UNIX; that is, it was developed to mimic the form and function of UNIX but its source code was written completely independently (i.e., none of it was copied from UNIX source code). Source code is the version of an operating system or other software as it is originally written (i.e., typed into a computer) by a human in a programming language (e.g., the C language in the case of the Linux kernel).
Linux incorporates all of the features that have made Unix-like systems the longest-lived and what many consider to be the best operating systems still in widespread use. That is, it is a multiuser (i.e., allows multiple simultaneous users), multitasking, highly flexible (with regard to configuration), inherently secure (including high resistance to viruses, spyware and other malware) and extraordinarily robust (i.e., resistance to crashing and needing rebooting) operating system. A multitasking operating system is one in which multiple programs or processes (also referred to as tasks) can execute (i.e., run) on a single computer seemingly simultaneously and without interfering with each other.
As is the case with most of the Unix-like operating systems, Linux is a highly mature (and very sophisticated) work of engineering that has been skillfully crafted by the collective efforts of thousands of the best minds in computer science. There is no planned (and little unplanned) obsolescence.
Yet Linux is much more than just a clone of another highly successful operating system. It also represents a philosophy, one which not only incorporates the simple but elegant Unix philosophy but which also has also taken it a big step further and made it a truly free operating system.
Moreover, Linux is a product of the Internet era. In contrast to proprietary (i.e., commercial) operating systems, which have been developed mostly by paid programmers employed at corporations, Linux has been developed virtually since its inception by an informal, world-wide network of unpaid (but highly skilled and motivated) volunteers who communicate via the Internet.
Advantages as Compared With Proprietary Unix-like Systems
Linux has several important advantages over the proprietary Unix-like operating systems (e.g., AIX, HP-UX and Solaris). One is that it is free software. This means that it is free both in a monetary sense and with regard to use. That is, everyone is permitted to download Linux from the Internet (or obtain it from other sources, including from friends) at no cost And everyone is also permitted to use it for any desired purpose, including studying, modifying, extending, installing on as many computers as desired, making copies as many copies as desired and redistributing. This is possible because Torvalds wisely released it under a free software license, the GNU General Public License (GPL).
Yet another advantage of Linux as compared with proprietary Unix-like operating systems is that it can generally run on a much wider range of hardware, including both system types and processor types. For example, it can run on cell phones, game machines, notebook computers, desktop computers, workstations, mainframes, supercomputers -- and even some wristwatches.
Linux is no longer the only Unix-like operating system that available under a free software license. There are several others, most notably the BSD (Berkeley Software Distribution) systems, which descended from work done on UNIX at UCB. Each of these systems, which include FreeBSD, NetBSD, NetBSD and Darwin (which is used by Mac OS X), has its own advantages and disadvantages. However, the number of users of Linux is much greater than that of the BSDs, mainly because it is easier to use, particularly for the less technically proficient.
Advantages as Compared With Microsoft Windows
Linux also has some very big advantages as compared with the Microsoft Windows family of operating systems2. The most obvious is that businesses and other organizations can save vast sums of money because there are no licensing fees nor is their any pressure for costly (and often disruptive) upgrades (so-called forced upgrades).
Linux can also cut administration and maintenance costs as compared with the Microsoft Windows operating systems because it is considerably more stable (it rarely crashes or needs rebooting) and is highly resistant to viruses and other malicious attacks.
In addition, Linux has the advantage that it can operate on older hardware that is unsuitable for newer versions of Microsoft Windows. This is because it is much more compactly written. Whereas upgrading to newer versions of Microsoft Windows generally requires costly outlays for new hardware, it is often possible to upgrade to newer versions of Linux without buying any new equipment.
The availability of the source code for Linux can also offer substantial benefits to users as compared with the closed (i.e., secret) source code for the Microsoft Windows operating systems. For example, corporations, government agencies and other organizations can monitor the code for security holes, including secret backdoors that allow others (e.g., government agencies) to access or change data. Having the source code also allows users to customize Linux to a far greater extent than can be done with closed source operating systems.
Thousands of application programs are available for Linux. Many of them offer performance and functions at least equal to those available for Microsoft Windows and other operating systems. Moreover, most of them are also free software, and many are included on the same CDROMs that contain Linux and can be installed automatically during Linux installation.
2For a more complete list of Linux's advantages as compared with the Microsoft Windows systems, see 25 Reasons to Convert to Linux, The Linux Information Project, January 2006.
Created March 2004. Last updated February 7, 2006.