The cups-driverd helper program lists all available printer drivers, a subset of "matching" printer drivers, or a copy of a specific driver PPD file.
The cups-exec helper program runs backends, filters, and other programs. On macOS these programs are run in a secure sandbox.
/Library/Printers /opt/share/ppd /System/Library/Printers /usr/local/share/ppd /usr/share/cups/drv /usr/share/cups/model /usr/share/ppd
PPD files can be compressed using the gzip(1) program or placed in compressed tar(1) archives to further reduce their size.
Driver information files must conform to the format defined in ppdcfile(5).backend(7), cups(1), cupsd(8), cupsd.conf(5), filter(7), ppdcfile(5), CUPS Online Help (http://localhost:631/help)