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. Although the
meaning and the pronunciation have drifted, we think this glossary
reflects current (1993) usage.
Historical footnote: DDT was developed at MIT for the PDP-1
computer in 1961. At that time DDT stood for "DEC Debugging
Tape". Since then, the idea of an on-line debugging program has
propagated throughout the computer industry. DDT programs are now
available for all DEC computers. Since media other than tape are
now frequently used, the more descriptive name "Dynamic Debugging
Technique" has been adopted, retaining the DDT abbreviation.
Confusion between DDT-10 and another well known pesticide,
dichloro-diphenyl-trichloroethane (C14-H9-Cl5) should be minimal
since each attacks a different, and apparently mutually exclusive,
class of bugs.
(The `tape' referred to was, incidentally, not magnetic but paper.)
Sadly, this quotation was removed from later editions of the
handbook after the suits took over and DEC became much more
`businesslike'.
The history above is known to many old-time hackers. But there's
more: Peter Samson, compiler of the original TMRC lexicon,
reports that he named `DDT' after a similar tool on the TX-0
computer, the direct ancestor of the PDP-1 built at MIT's Lincoln
Lab in 1957. The debugger on that ground-breaking machine (the
first transistorized computer) rejoiced in the name FLIT
(FLexowriter Interrogation Tape).
Perhaps the ultimate death code is on the TI 990 series, where all
registers are actually in RAM, and the instruction "store
immediate 0" has the opcode "0". The PC will immediately wrap
around core as many times as it can until a user hits HALT. Any
empty memory location is death code. Worse, the manufacturer
recommended use of this instruction in startup code (which would be
in ROM and therefore survive).
Demons in sense 1 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.
[Outsiders often observe in the PARC culture an institutional
arrogance which usage of this term exemplifies. The brilliance and
scope of PARC's contributions to computer science have been such
that this superior attitude is not much resented. --- ESR]
wart: n. A small, crocky feature that sticks out of
an array (C has no checks for this). This is relatively
benign and easy to spot if the phrase is bent so as to be
not worth paying attention to the medium in question.
Here is a short example of letter-based Dissociated Press applied
to the same source:
window sysIWYG: n. A bit was named aften /bee't*/ prefer
to use the other guy's re, especially in every cast a
chuckle on neithout getting into useful informash speech
makes removing a featuring a move or usage actual
abstractionsidered interj. Indeed spectace logic or problem!
A hackish idle pastime is to apply letter-based Dissociated Press
to a random body of text and vgrep the output in hopes of finding
an interesting new word. (In the preceding example, `window
sysIWYG' and `informash' show some promise.) Iterated applications
of Dissociated Press usually yield better results. Similar
techniques called `travesty generators' have been employed with
considerable satirical effect to the utterances of USENET flamers;
see pseudo.
[Note: in early 1992, advertising copy from Rainbow Technologies (a
manufacturer of dongles) included a claim that the word derived from
"Don Gall", allegedly the inventor of the device. The company's
receptionist will cheerfully tell you that the story is a myth
invented for the ad copy. Nevertheless, I expect it to haunt my
life as a lexicographer for at least the next ten years. --- ESR]
This term originated on the Stanford extended-ASCII keyboard, and
was later taken up by users of the space-cadet keyboard at
MIT. A typical MIT comment was that the Stanford bucky bits
(control and meta shifting keys) were nice, but there weren't
enough of them; you could type only 512 different characters on a
Stanford keyboard. An obvious way to address this was simply to
add more shifting keys, and this was eventually done; but a
keyboard with that many shifting keys is hard on touch-typists, who
don't like to move their hands away from the home position on the
keyboard. It was half-seriously suggested that the extra shifting
keys be implemented as pedals; typing on such a keyboard would be
very much like playing a full pipe organ. This idea is mentioned
in a parody of a very fine song by Jeffrey Moss called
"Rubber Duckie", which was published in "The Sesame
Street Songbook" (Simon and Schuster 1971, ISBN 0-671-21036-X).
These lyrics were written on May 27, 1978, in celebration of the
Stanford keyboard:
Double Bucky
Double bucky, you're the one!
You make my keyboard lots of fun.
Double bucky, an additional bit or two:
(Vo-vo-de-o!)
Control and meta, side by side,
Augmented ASCII, nine bits wide!
Double bucky! Half a thousand glyphs, plus a few!
Oh,
I sure wish that I
Had a couple of
Bits more!
Perhaps a
Set of pedals to
Make the number of
Bits four:
Double double bucky!
Double bucky, left and right
OR'd together, outta sight!
Double bucky, I'd like a whole word of
Double bucky, I'm happy I heard of
Double bucky, I'd like a whole word of you!
--- The Great Quux (with apologies to Jeffrey Moss)
[This, by the way, is an excellent example of computer filk
--- ESR] See also meta bit, cokebottle, and [quadruple
bucky}.
However, note that ground-to-space communications has its own usage
rule for this term. Space-to-earth transmission is always `down'
and the reverse `up' regardless of the relative size of the
computers involved. So far the in-space machines have invariably
been smaller; thus the upload/download distinction has been
reversed from its usual sense.
Typical droid positions include supermarket checkout assistant and
bank clerk; the syndrome is also endemic in low-level government
employees. The implication is that the rules and official
procedures constitute software that the droid is executing;
problems arise when the software has not been properly debugged.
The term `droid mentality' is also used to describe the mindset
behind this behavior. Compare suit, marketroid; see
-oid.
At Xerox PARC in the 1970s, most people kept a can of copier
cleaner (isopropyl alcohol) at their desks. When the steel ball on
the mouse had picked up enough cruft to be unreliable, the
mouse was doused in cleaner, which restored it for a while.
However, this operation left a fine residue that accelerated the
accumulation of cruft, so the dousings became more and more
frequent. Finally, the mouse was declared `alcoholic' and sent
to the clinic to be dried out in a CFC ultrasonic bath.
register n = (count + 7) / 8; /* count > 0 assumed */
switch (count % 8)
[
case 0: do [ *to = *from++;
case 7: *to = *from++;
case 6: *to = *from++;
case 5: *to = *from++;
case 4: *to = *from++;
case 3: *to = *from++;
case 2: *to = *from++;
case 1: *to = *from++;
} while (--n > 0);
}
Shocking though it appears to all who encounter it for the first
time, the device is actually perfectly valid, legal C. C's default
fall through in case statements has long been its most
controversial single feature; Duff observed that "This code forms
some sort of argument in that debate, but I'm not sure whether it's
for or against."
[For maximal obscurity, the outermost pair of braces above could be
actually be removed --- GLS]
Warren Teitelman originally wrote DWIM to fix his typos and
spelling errors, so it was somewhat idiosyncratic to his style, and
would often make hash of anyone else's typos if they were
stylistically different. Some victims of DWIM thus claimed that
the acronym stood for `Damn Warren's Infernal Machine!'.
In one notorious incident, Warren added a DWIM feature to the
command interpreter used at Xerox PARC. One day another hacker
there typed `delete *$' to free up some disk space. (The
editor there named backup files by appending `$' to the
original file name, so he was trying to delete any backup files
left over from old editing sessions.) It happened that there
weren't any editor backup files, so DWIM helpfully reported
`*$ not found, assuming you meant 'delete *'.' It then started
to delete all the files on the disk! The hacker managed to stop it
with a Vulcan nerve pinch after only a half dozen or so files
were lost.
The disgruntled victim later said he had been sorely tempted to go
to Warren's office, tie Warren down in his chair in front of his
workstation, and then type `delete *$' twice.
DWIM is often suggested in jest as a desired feature for a complex
program; it is also occasionally described as the single
instruction the ideal computer would have. Back when proofs of
program correctness were in vogue, there were also jokes about
`DWIMC' (Do What I Mean, Correctly). A related term, more often
seen as a verb, is DTRT (Do The Right Thing); see [Right
Thing}.