Linux is a free Unix-type operating system created by Linus Torvalds in 1991. It originated as a personal project by Torvalds while he was a student. The kernel version 1.0 was released in 1994 and the latest stable version is 2.6.9. The source code for Linux is freely available under the GNU General Public License. The Unix file system is structured like an inverted tree with the root directory at the top containing sub-directories, which can also contain files and directories. Files and directories are specified with either an absolute or relative path starting from the root directory and separating each level with a slash.