Aqumix.1021
net.general
utcsrgv!utzoo!decvax!ittvax!qumix!msc
Mon Mar 1 13:50:42 1982
DAEMON etymology
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Here are the replies I received to my question about the etymology
of the word DAEMON.
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>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.)
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>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.
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>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.
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>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).
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>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.
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>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
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>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)
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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
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