[from Maxwell's Demon, later incorrectly retronymed as `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}; the prototype was a program called DAEMON
that automatically made tape backups of the file system. Although the
meaning and the pronunciation have drifted, we think this glossary
reflects current (2003) usage.
[glossary]
[Reference(s) to this entry by made by: {daemon book}{demon}{dragon}{nastygram}{prowler}{server}]