Legacy printing (lpd)
Printers are assigned to queues, which are managed by lpd, the print daemon. lpd listens for inbound print requests, forking a copy of itself for each active print queue.
lpr submits jobs to print queues.
lpq queries and displays queue status.
lprm allows jobs to be removed from print queues.
lpc allows root to administer queues; it has both interactive and command-line forms.
Filters translate data formats into a printer definition language.
Spool directories hold spooled job data.