Linux is an operating system that is Unix-like in its configuration. It is named after its designer, Linus Torvalds, who created Linux at the age of 22 as a project while a student at the University of Helsinki, Finland. His motivation was to emulate the UNIX operating system on a personal computer. At that time, UNIX software cost upwards of $5,000.

In contrast to other operating systems, like Microsoft Windows, which must be purchased, Torvalds made the first version of Linux, in 1991, available for free over the Internet. Even today, Linux can be obtained from the Internet without cost. Linux also differs fundamentally from other operating systems in that users can modify the program. Anyone can have access to the Linux kernal--the heart of the operating system--and make changes. For these reasons, Linux is known as open source, or free software.

As the operating system is changed by users, their...