daemon

daemon /day'mn/ or /dee'mn/ n.  [from the mythological
   meaning, later rationalized as the acronym `Disk And Execution
   MONitor'] A program that is not invoked explicitly, but lies
   dormant waiting for some condition(s) to occur.  The idea is that
   the perpetrator of the condition need not be aware that a daemon is
   lurking (though often a program will commit an action only because
   it knows that it will implicitly invoke a daemon).  For example,
   under {{ITS}} writing a file on the {LPT} spooler's directory
   would invoke the spooling daemon, which would then print the file.
   The advantage is that programs wanting (in this example) files
   printed need neither compete for access to nor understand any
   idiosyncrasies of the {LPT}.  They simply enter their implicit
   requests and let the daemon decide what to do with them.  Daemons
   are usually spawned automatically by the system, and may either
   live forever or be regenerated at intervals.

   Daemon and {demon} are often used interchangeably, but seem to
   have distinct connotations.  The term `daemon' was introduced to
   computing by {CTSS} people (who pronounced it /dee'mon/) and
   used it to refer to what ITS called a {dragon}.  Although the
   meaning and the pronunciation have drifted, we think this glossary
   reflects current (1993) usage.



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