1. UNIX  Portable (common to many computer architectures), multitasking, multi-user operating system  Introduced by Bell labs in mid-1960’s  Thus, much longer history of serious computing than Windows or Apple OS (Apple OS is practically UNIX)  Stable, secure, high performance  Practically never needs rebooting  Implementations on PC are called Linux  Linux is only the kernel, and numerous packages with graphical interfaces are available  See http://www.linux.com/directory/Distributionshttp://www.linux.com/directory/Distributions  All distributions come with hundreds of free programs  Note LibreOffice, Octave  We use Red Hat Enterprise (this one is not free, but there exists a free equivalent) – good for development, parallel computing  I use Fedora at home  Many people love Ubuntu (user- and media-oriented)

2. UNIX shell  Seismic Un*x and GMT rely on the ability of the shell to combine many programs for achieving a common task  Every processing flow in Seismic Un*x and every image in GMT should be described by a shell script

3. UNIX pipelines

4. Useful shell commands