Linux is a free, open-source version of UNIX that can run on Intel and PowerPC computers. Popular Linux distributions mentioned in the document include Red Hat Linux, SUSE Linux, Turbolinux, and Mac OS X. Red Hat Linux was assembled by Red Hat and was popular until being discontinued in 2004. SUSE Linux was originally based on SLS and Slackware Linux and is pronounced "zoo-zah" in German. Turbolinux included licensed copies of media codecs. Mac OS X is Apple's Unix-based graphical operating system that runs exclusively on Macintosh computers.