Daemon

 DAEMON (day'mun, dee'mun) [archaic form of "demon", which
       has slightly different connotations (q.v.)] n. A program which is not
       invoked explicitly, but which lays 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, writing a file on the lpt
       spooler's directory will invoke the spooling daemon, which prints the
       file. The advantage is that programs which want (in this example)
       files printed need not compete for access to 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. Usage:
       DAEMON and DEMON (q.v.) are often used interchangeably, but seem to
       have distinct connotations. DAEMON was introduced to computing by CTSS
       people (who pronounced it dee'mon) and used it to refer to what is now
       called a DRAGON or PHANTOM (q.v.). The meaning and pronunciation have
       drifted, and we think this glossary reflects current usage.