When SAS is installed, its entire directory structure is placed on a node in your file system. This node, which forms the root of SAS, is called the !SASROOT directory. Although !SASROOT can be located anywhere in your file system, the system administrator typically installs it in /usr/local/sas91 . The SET system option is used to specify the name of the !SASROOT directory. (See "SET System Option" on page 363.)