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D. C. Power Lab
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daemon
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C|N>K
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D. C. Power Labn.
The former site ofSAIL. Hackers thought this was very funny because the obvious connection to electrical engineering was nonexistent -- the lab was named for a Donald C. Power. CompareMarginal Hacks.
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daemon
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daemon book
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D. C. Power Lab
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daemon/day'mn/ or /dee'mn/ n.
[from the mythological meaning, later rationalized as the acronym `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, underITSwriting a file on theLPTspooler'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 theLPT. 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 anddemonare often used interchangeably, but seem to have distinct connotations. The term `daemon' was introduced to computing byCTSSpeople (who pronounced it /dee'mon/) and used it to refer to what ITS called adragon; 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 (2000) usage.
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daemon book
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dahmum
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daemon
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daemon bookn.
"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, SBN 0-201-54979-4) Either of the standard reference books on the internals ofBSDUnix. So called because the covers have a picture depicting a little devil (a visual play ondaemon) in sneakers, holding a pitchfork (referring to one of the characteristic features of Unix, thefork(2)system call). Also known as theDevil Book.
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dahmum
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dancing frog
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daemon book
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dahmum/dah'mum/ n.
[Usenet] The material of which protractedflame wars, especially those about operating systems, is composed. Homeomorphic tospam. The term `dahmum' is derived from the name of a militantOS/2advocate, and originated when an extensively crossposted OS/2-versus-Linuxdebate was fed throughDissociated Press.
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dancing frog
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dangling pointer
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dahmum
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dancing frogn.
[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).
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dangling pointer
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dark-side hacker
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dancing frog
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dangling pointern.
[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. Comparedead link.
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dark-side hacker
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Datamation
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dangling pointer
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dark-side hackern.
A criminal or malicious hacker; acracker. From George Lucas's Darth Vader, "seduced by the dark side of the Force". The implication that hackers form a sort of elite of technological Jedi Knights is intended. Opposesamurai.
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Datamation
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DAU
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dark-side hacker
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Datamation/day`t*-may'sh*n/ n.
A magazine that many hackers assume allsuits read. Used to question an unbelieved quote, as in "Did you read that in `Datamation?'" (But see below; this slur may be dated by the time you read this.) It used to publish something hackishly funny every once in a while, like the original paper onCOME FROMin 1973, and Ed Post's "Real Programmers Don't Use Pascal" ten years later, but for a long time after that it was much more exclusivelysuit-oriented and boring. Following a change of editorship in 1994, Datamation is trying for more of the technical content and irreverent humor that marked its early days.
Datamation now has a WWW page at http://www.datamation.com worth visiting for its selection of computer humor, including "Real Programmers Don't Use Pascal" and the `Bastard Operator From Hell' stories by Simon Travaglia (seeBOFH).
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DAU
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Dave the Resurrector
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Datamation
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DAU/dow/ n.
[German FidoNet] German acronym for Dümmster Anzunehmender User (stupidest imaginable user). From the engineering-slang GAU for Grösster Anzunehmender Unfall, worst assumable accident, esp. of a LNG tank farm plant or something with similarly disastrous consequences. In popular German, GAU is used only to refer to worst-case nuclear acidents such as a core meltdown. Seecretin,fool,loserandweasel.
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Dave the Resurrector
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day mode
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DAU
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Dave the Resurrectorn.
[Usenet; also abbreviated DtR] Acancelbotthat cancels cancels. Dave the Resurrector originated when somespam-spewers decided to try to impede spam-fighting by wholesale cancellation of anti-spam coordination messages in thenews.admin.net-abuse.usenetnewsgroup.
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day mode
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dd
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Dave the Resurrector
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day moden.
Seephase(sense 1). Used of people only.
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dd
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DDT
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day mode
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dd/dee-dee/ vt.
[Unix: from IBMJCL] Equivalent tocatorBLT. Originally the name of a Unix copy command with special options suitable for block-oriented devices; it was often used in heavy-handed system maintenance, as in "Let'sddthe root partition onto a tape, then use the boot PROM to load it back on to a new disk". The Unixdd(1)was designed with a weird, distinctly non-Unixy keyword option syntax reminiscent of IBM System/360 JCL (which had an elaborate DD `Dataset Definition' specification for I/O devices); though the command filled a need, the interface design was clearly a prank. The jargon usage is now very rare outside Unix sites and now nearly obsolete even there, asdd(1)has beendeprecatedfor a long time (though it has no exact replacement). The term has been displaced byBLTor simple English `copy'.
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DDT
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de-rezz
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DDT/D-D-T/ n.
[from the insecticide para-dichloro-diphenyl-trichloroethene] 1. Generic term for a program that assists in debugging other programs by showing individual machine instructions in a readable symbolic form and letting the user change them. In this sense the term DDT is now archaic, having been widely displaced by `debugger' or names of individual programs likeadb,sdb,dbx, orgdb. 2. [ITS] Under MIT's fabledITSoperating system, DDT (running under the alias HACTRN, a six-letterism for `Hack Translator') was also used as theshellor top level command language used to execute other programs. 3. Any one of several specific DDTs (sense 1) supported on earlyDEChardware and CP/M. The PDP-10 Reference Handbook (1969) contained a footnote on the first page of the documentation for DDT that illuminates the origin of the term:
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 thesuits took over andDECbecame much more `businesslike'.
The history above is known to many old-time hackers. But there's more: Peter Samson, compiler of the originalTMRClexicon, 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).
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de-rezz
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dead
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DDT
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de-rezz/dee-rez'/
[from `de-resolve' via the movie "Tron"] (also `derez') 1. vi. To disappear or dissolve; the image that goes with it is of an object breaking up into raster lines and static and then dissolving. Occasionally used of a person who seems to have suddenly `fuzzed out' mentally rather than physically. Usage: extremely silly, also rare. This verb was actually invented asfictionalhacker jargon, and adopted in a spirit of irony by real hackers years after the fact. 2. vt. The Macintosh resource decompiler. On a Macintosh, many program structures (including the code itself) are managed in small segments of the program file known as `resources'; `Rez' and `DeRez' are a pair of utilities for compiling and decompiling resource files. Thus, decompiling a resource is `derezzing'. Usage: very common.
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dead
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dead beef attack
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deadadj.
1. Non-functional;down;crashed. Especially used of hardware. 2. At XEROX PARC, software that is working but not undergoing continued development and support. 3. Useless; inaccessible. Antonym: `live'. Comparedead code.
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dead beef attack
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dead code
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dead
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dead beef attackn.
[cypherpunks list, 1996] An attack on a public-key cryptosystem consisting of publishing a key having the same ID as another key (thus making it possible to spoof a user's identity if recipients aren't careful about verifying keys). In PGP and GPG the key ID is the last eight hex digits of (for RSA keys) the product of two primes. The attack was demonstrated by creating a key whose ID was 0xdeadbeef (seeDEADBEEF).
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dead code
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dead link
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dead beef attack
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dead coden.
Routines that can never be accessed because all calls to them have been removed, or code that cannot be reached because it is guarded by a control structure that provably must always transfer control somewhere else. The presence of dead code may reveal either logical errors due to alterations in the program or significant changes in the assumptions and environment of the program (see alsosoftware rot); a good compiler should report dead code so a maintainer can think about what it means. (Sometimes it simply means that anextremelydefensive programmer has insertedcan't happentests which really can't happen -- yet.) Syn.grunge. See alsodead, andThe Story of Mel.
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dead link
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DEADBEEF
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dead code
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dead linkn.
[very common] A World-Wide-Web URL that no longer points to the information it was written to reach. Usually this happens because the document has been moved or deleted. Lots of dead links make a WWW page frustrating and useless and are the #1 sign of poor page maintainance. Comparedangling pointer,link rot.
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DEADBEEF
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deadlock
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dead link
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DEADBEEF/ded-beef/ n.
The hexadecimal word-fill pattern for freshly allocated memory (decimal -21524111) under a number of IBM environments, including the RS/6000. Some modern debugging tools deliberately fill freed memory with this value as a way of convertingheisenbugs intoBohr bugs. As in "Your program is DEADBEEF" (meaning gone, aborted, flushed from memory); if you start from an odd half-word boundary, of course, you have BEEFDEAD. See also the anecdote underfoolanddead beef attack.
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deadlock
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deadly embrace
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DEADBEEF
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deadlockn.
1. [techspeak] A situation wherein two or more processes are unable to proceed because each is waiting for one of the others to do something. A common example is a program communicating to a server, which may find itself waiting for output from the server before sending anything more to it, while the server is similarly waiting for more input from the controlling program before outputting anything. (It is reported that this particular flavor of deadlock is sometimes called a `starvation deadlock', though the term `starvation' is more properly used for situations where a program can never run simply because it never gets high enough priority. Another common flavor is `constipation', in which each process is trying to send stuff to the other but all buffers are full because nobody is reading anything.) Seedeadly embrace. 2. Also used of deadlock-like interactions between humans, as when two people meet in a narrow corridor, and each tries to be polite by moving aside to let the other pass, but they end up swaying from side to side without making any progress because they always move the same way at the same time.
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deadly embrace
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death code
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deadlock
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deadly embracen.
Same asdeadlock, though usually used only when exactly two processes are involved. This is the more popular term in Europe, whiledeadlockpredominates in the United States.
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death code
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Death Square
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deadly embrace
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death coden.
A routine whose job is to set everything in the computer -- registers, memory, flags, everything -- to zero, including that portion of memory where it is running; its last act is to stomp on its own "store zero" instruction. Death code isn't very useful, but writing it is an interesting hacking challenge on architectures where the instruction set makes it possible, such as the PDP-8 (it has also been done on the DG Nova).
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).
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Death Square
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Death Star
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death code
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Death Squaren.
The corporate logo of Novell, the people who acquired USL after AT&T let go of it (Novell eventually sold the Unix group to SCO). Coined by analogy withDeath Star, because many people believed Novell was bungling the lead in Unix systems exactly as AT&T did for many years.
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Death Star
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DEC
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Death Square
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Death Starn.
[from the movie "Star Wars"] 1. The AT&T corporate logo, which appears on computers sold by AT&T and bears an uncanny resemblance to the Death Star in the movie. This usage is particularly common among partisans ofBSDUnix, who tend to regard the AT&T versions as inferior and AT&T as a bad guy. Copies still circulate of a poster printed by Mt. Xinu showing a starscape with a space fighter labeled 4.2 BSD streaking away from a broken AT&T logo wreathed in flames. 2. AT&T's internal magazine, "Focus", uses `death star' to describe an incorrectly done AT&T logo in which the inner circle in the top left is dark instead of light -- a frequent result of dark-on-light logo images.