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.
There are two definitions of Linux. The stricter one is just the kernel (i.e., the core of the operating system) itself. The more common one is a coordinated software package, referred to as a distribution, which consists of the kernel together with dozens of free utilities and application programs.
The use of Linux by individuals, corporations, government agencies and other organizations around the world has been growing rapidly as a result of several factors. They include (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 and Linspire (formerly called Lindows). In addition to these mainstream distributions, numerous specialized distributions are 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, e.g., muLinux).
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 licensed under the GNU Public License (GPL) and is completely free. This license allows anyone to download Linux from the Internet, and it makes it completely legal (and even encourages!) anyone to install Linux on any number of computers with absolutely no licensing fees. The GPL also makes it perfectly legal for anybody to make as many copies of Linux as they want and give them away – or even sell them.
Linux is also free in the sense that anyone has the legal right to modify or amend the source code in any way they want. And they may then give away or sell the modified version(s) if they so desire, with the only proviso being that the source code for such modified version(s) likewise be made freely available.
Yet another advantage of Linux is that it can run on a much wider range of hardware than most other Unix-like systems. For example, it can run on cell phones, game machines, notebook computers, desktop computers, workstations, mainframes, supercomputers – and even wristwatches.
Advantages as Compared With Microsoft Windows
Linux also has some very big advantages as compared with the Microsoft Windows family of operating systems. 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 free software (i.e., software that is free in both a monetary sense and with regard to use), just as Linux is, and many are included on the same CDROMs that contain Linux and can be installed automatically during Linux installation.
Additional introductory information about Linux is contained in the handbook.