The Bourne shell is the obvious shell to examine first for two reasons. First and foremost, it was the first shell written. It was was written at Bell Laboratories, by Stephen Bourne. This makes the Bourne shell the foundation which all other shells are (at least in part) built on. In fact it will be seen that the shells covered in this book fall basically into two categories, or families, the Bourne family and the C shell family. The second reason to start with the Bourne shell is that it comes with all Unix systems, making it a good introductory shell purely on the basis of availability.