daemon

1. Chiefly British. Variant of demon.
2. Variant of daimon.
3. Computer Science. A program or process that sits idly in the background until it is invoked to perform its task.

[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.

The noun has 2 meanings:

Meaning #1: one of the evil spirits of traditional Jewish and Christian belief
  Synonyms: devil, fiend, demon, daimon

Meaning #2: a person who is part mortal and part god
  Synonym: demigod

Look up daemon in Wiktionary, the free dictionary.

The term Daemon, dæmon, or demon has several meanings:

For more possible meanings see Demon (disambiguation) and Daimon (alternate spelling)

• Daemon (mythology) - See also: Agathodaemon, Cacodemon, Demon
• Daemons in astrophysics

In literature:

• Daemon (novel), a novel by Daniel Suarez
• Dæmon (His Dark Materials) in the Philip Pullman trilogy of novels His Dark Materials

In computers and software:

• Daemon (computer software), a background process
• Daemon Tools, a popular disk image emulator
• The BSD Daemon is the BSD operating system's mascot.
• Mailer-Daemon, email server software responsible for message delivery.

In gaming:

• Daemon (Dungeons & Dragons) is the original name for creatures now called "Yugoloths" in the game Dungeons & Dragons
• Daemon (Warhammer)
• ZDaemon, a modern version of the game Doom

In film, music and media:

• The Dæmons is a serial in the British science fiction television series Doctor Who
• Daemon (Digimon) an evil character from Digimon
• Daemon is a character in the TV series ReBoot.
• Daemon Records, a record label

In military technology:

• The McDonnell F3H Demon, a Cold-war era carrier based fighter jet used by the US Navy.

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