daemon
/day'mn/ or /dee'mn/ [from the mythological meaning,
later rationalized as the acronym `Disk And Execution MONitor'] n.
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 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. 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 (1991) usage.
