Aqumix.1021 net.general utcsrgv!utzoo!decvax!ittvax!qumix!msc Mon Mar 1 13:50:42 1982 DAEMON etymology =========== LONG ======================= Here are the replies I received to my question about the etymology of the word DAEMON. ==================================================================== >From ittvax!decvax!duke!unc!bch Thu Feb 18 01:43:48 1982 To: duke!decvax!ittvax!qumix!msc Clearly, a DAEMON is a little critter who sits in the bowls of the system and does things without your immediate supervision, i.e. when it wants to. While this may not be precisely accurate, I have always found the visual image useful in understanding the way things fit together. (The AE is of course from the Greek as in AESOP.) ==================================================================== >From ittvax!decvax!ucbvax!ihnss!houxi!houxs!hansen Thu Feb 18 03:43:20 1982 To: houxi!ihnss!ucbvax!decvax!ittvax!qumix!msc Re: demon definition Following are the definitions for daemon, demon, dragon and phantom, all related terms, taken from the hackers-jargon dictionary compiled and maintained at Stanford and MIT. Enjoy! Tony Hansen 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. DEMON (dee'mun) n. A portion of a program which is not invoked explicitly, but which lays dormant waiting for some condition(s) to occur. See DAEMON. The distinction is that demons are usually processes within a program, while daemons are usually programs running on an operating system. Demons are particularly common in AI programs. For example, a knowledge manipulation program might implement inference rules as demons. Whenever a new piece of knowledge was added, various demons would activate (which demons depends on the particular piece of data) and would create additional pieces of knowledge by applying their respective inference rules to the original piece. These new pieces could in turn activate more demons as the inferences filtered down through chains of logic. Meanwhile the main program could continue with whatever its primary task was. DRAGON n. (MIT) A program similar to a "daemon" (q.v.), except that it is not invoked at all, but is instead used by the system to perform various secondary tasks. A typical example would be an accounting program, which keeps track of who is logged in, accumulates load- average statistics, etc. At MIT, all free TV's display a list of people logged in, where they are, what they're running, etc. along with some random picture (such as a unicorn, Snoopy, or the Enterprise) which is generated by the "NAME DRAGON". See PHANTOM. PHANTOM n. (SAIL) The SAIL equivalent of a DRAGON (q.v.). Typical phantoms include the accounting program, the news-wire monitor, and the lpt and xgp spoolers. ======================================================================= >From ittvax!decvax!watmath!atbowler Thu Feb 18 03:43:34 1982 To: decvax!ittvax!qumix!msc Re: DAEMON etymology According to the Concise Oxford (and presumably therefore the Oxford English Dictionary): Supernatural being in Greek mythology; attendant or indwelling spirit. Note that there is no connotation of evil. It may also be spelt 'demon', but that spelling has the alternate meaning of and "evil spirit or devil". It is pronounced as demon. To the best of my knowledge the term was first applied in Multics to the assorted service processes that run continuously in background much like the Unix daemons. ======================================================================= >From ittvax!decvax!duke!unc!lynn Thu Feb 18 10:04:22 1982 To: duke!decvax!ittvax!qumix!msc Re: DAEMON DAEMON is a British variant spelling of DEMON. I first ran across the term in connection with the "daemon file saver" on the PROJECT MAC time-sharing system back in the late 60's. (I didn't use it; I was talking with a friend who did.) The daemons were, then as now, useful programs that ran around automatically doing things in the background, probably by analogy with Maxwell's demons (which, if you will recall, could fight entropy). ======================================================================== >From ittvax!decvax!watmath!djmdavies Thu Feb 18 20:09:45 1982 To: decvax!ittvax!qumix!msc Re: DAEMON etymology The term has certainly been around for a while in DEC software, and more recently got some derived usage in the context of artificial intelligence languages for 'daemon procedures' which get invoked automatically in some context. I don't know the etymology, but suspect that there is an implied association to (I think it was) Maxwell's daemon, who tried to defeat the laws of thermodynamics by looking at individual approaching molecules in a gas and capturing those whose kinetic energy was outside a specified range; thereby supposedly increasing the entropy paradoxically. (The daemon cannot though, because the photons needed to judge the speed of the approaching molecules perturb them too much.) Interesting question anyway. Julian Davies. ======================================================================== >From ittvax!decvax!watmath!watarts!rand Fri Feb 19 00:42:07 1982 The word `daemon' is an archaic spelling of the more common `demon'. The etymology that I have been apprised of in the past is that the daemon is a programme that runs halfway between god (the operating system) and man (the user or user process). This seems to be a fairly accurate description of what a daemon is (and where it fits into the picture of things) Randall Howard ========================================================================= >From ittvax!decvax!pur-ee!purdue!mab Sat Feb 20 00:36:58 1982 Mark, The derivation I've heard (for "daemon") is cute. A daemon passes things on, as in a spooler or mailer. Well, Clark Maxwell (of thermodynamic fame) explained the mixing of hot and cold gases like this: think of a barrier with hot gas on one side and cold gas on the other. A demon sits by the barrier. He lets slow-moving molecules from the cold side which strike the barrier through to the hot side, and fast-moving molecules from the hot side which strike the barrier through to the cold side; he prevents the rest from crossing the barrier. The "a" is because the old way to spell "demon" is "daemon". Matt Bishop (ucbvax!purdue!mab, mab@purdue) ========================================================================== Ahh.. and I thought it stood for something boring like Device Access and Execution MONitor. I like Randall Howard's thought that it is something that lies halfway between God and Man. Incidentally, Randall I deduce that you are a fellow Britain. Thanks for the information everbody. Mark Callow ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.