Specifications

6-2
Guide to Printers and Printing
Understanding the Print Service
The System V print service is a collection of utilities that help you, as system administrator
(or printer administrator), to configure, monitor, and control the printers on your system.
The print service:
• Receives files users want to print
• Filters the files (if needed) so they can print correctly
• Schedules the work of one or more printers
• Starts programs that interface with the printers
• Keeps track of the status of jobs
• Alerts you to printer problems
• Keeps track of mounting forms and filters
• Issues error messages when problems arise
When a user sends a file to a printer, the print service assigns to the request (print job) a
unique name, the request ID.
The request ID consists of the name of the printer on which the file is to be printed and a
unique number identifying the file. Use this request ID to find out the status of the print job
or to cancel the print job. The print service keeps track of all the print requests in the request
log.
The print job is spooled, or lined up, with other print jobs to be sent to a printer. Each print
job is processed and waits its turn in line to be printed. This line of pending print jobs is
called a print queue.
Each printer has its own queue; you can hold jobs in the queue, move jobs up in a queue, or
transfer jobs to another queue.
Overview of Print Request Processing
As the following figure illustrates, each print request is sent to a spooling daemon
(background program) that keeps track of all the jobs. (This information is archived in the
request log.) The daemon is created when you start the print service. The spooling daemon
is also responsible for keeping track of the status of the printers and slow filters; when a
printer finishes printing a job, the daemon initiates printing another job if one is queued.
Figure 4. Overview of Print Request Processing