Kernel
Frustrated by the copyright restrictions on Minix, and by the refusal of its owner to considerably extend the functionalities of Minix, a young student at the University of Helsinki, Linus Torvalds, decided to build his own operating system. What began as a hobby project in April 1991, and was released as version 0.01 by Torvalds over the Internet in September 1991, has in the mean time resulted in a huge community project and a widely used operating system. Linux does not contain Unix code; it is a complete rewrite based on published POSIX standards.As Linux was getting more and more users, and was even starting to gain some acceptance in the business community, some changes were necessary to the way in which the Linux kernel evolved. Prior to the release of version 1.0, Torvalds and his fellow developers released a new kernel as often as they saw fit. As a result, upgrading from one version to the next, sometimes resulted in a non-working system.
Starting with version 1, the kernel development was branched into two parts. The first branch, designated by an even minor-release number (e.g. 1.0.x), corresponded with a stable kernel to which only bug fixes were made. The second branch, designated by an odd minor-release number (e.g. 1.1.x), was the kernel where developers would add new features and where no guarantees were made regarding the stability of the system.
The current stable branch is 2.2.x branch and the current development branch is 2.3.x. A code freeze is in effect for the 2.3.99 kernel, which will lead to the new 2.4.0 stable kernel branch. We're now (November 2000) at 2.4.0.test10.
Nowadays, most Linux users run applications, developed by others. Few
users write applications themselves. A very small minority is bold enough
to write device drivers and offer kernel patches to Linus Torvalds, who
still maintains the Linux kernel. He accepts additions and modifications
to the kernel sources from anyone, and merges all the new code into the
kernel himself, exercising strict quality control.