It is possible to incorporate in the SAS software packages that are not part of the official SAS distribution. These we call 'external packages'. All that is needed is to set the environment variable SAS_PATH to point to all directories that contain SAS components, in the form of a colon-separated list. ... He will have to set the SAS_DIR and SAS_PATH environment variable and call the sas-setup script (preferably in a login script), e.g. (csh): setenv SAS_DIR /usr/sas . ...