The directory which is the value of
*ppd-directory* should contain PPD files (files with extension ppd) either directly, or under subdirectories. The PPD files under each subdirectory are grouped together, with the name of the directory as the group name. PPD files in
*ppd-directory* itself are grouped under the "Other" group.
CAPI User Guide and Reference Manual (Macintosh version) - 3 Aug 2017