The following figure shows what happens when a user submits a request to print a PostScript file on a local printer, which is a printer connected to the user's system. The lpsched daemon on the local system does all processing.
This processing might include the following:
Matching the printer and content type
Identifying the default printer, filtering the request
Starting the specified printer interface program
The printer interface program does the following:
Prints the banner page.
Catches printer faults.
Determines the printer fault policy to either reset, continue, or begin the print job over again.
Finally, the interface program uses the lpcat program to download the print request to the local printer's serial port.