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daemon /day´mn/, /dee´mn/, n. [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.
daemon book n. The Design and Implementation of the 4.3BSD UNIX Operating System, by Samuel J. Leffler, Marshall Kirk McKusick, Michael J. Karels, and John S. Quarterman (Addison-Wesley Publishers, 1989, ISBN 0-201-06196-1); or The Design and Implementation of the 4.4 BSD Operating System by Marshall Kirk McKusick, Keith Bostic, Michael J. Karels and John S. Quarterman (Addison-Wesley Longman, 1996, ISBN 0-201-54979-4) Either of the standard reference books on the internals of {BSD} Unix. So called because the covers have a picture depicting a little demon (a visual play on {daemon}) in sneakers, holding a pitchfork (referring to one of the characteristic features of Unix, the fork(2) system call).
dahmum /dah´mum/, n. [Usenet] The material of which protracted {flame war}s, especially those about operating systems, is composed. Homeomorphic to {spam}. The term dahmum is derived from the name of a militant {OS/2} advocate, and originated when an extensively cross-posted OS/2-versus-{Linux} debate was fed through {Dissociated Press}.
dancing frog n. [Vancouver area] A problem that occurs on a computer that will not reappear while anyone else is watching. From the classic Warner Brothers cartoon One Froggy Evening, featuring a dancing and singing Michigan J. Frog that just croaks when anyone else is around (now the WB network mascot).
dangling pointer n. [common] A reference that doesn't actually lead anywhere (in C and some other languages, a pointer that doesn't actually point at anything valid). Usually this happens because it formerly pointed to something that has moved or disappeared. Used as jargon in a generalization of its techspeak meaning; for example, a local phone number for a person who has since moved to the other coast is a dangling pointer.
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