# The Jargon File, Version 2.9.10, 01 Jul 1992

## Part 13

Book page: https://www.cyberlibrary.org/en/books/the-jargon-file-version-2-9-10-01-jul-1992-38/index.md

:cyberspace: /si:'ber-spays/ n. 1. Notional `information-space' loaded with visual cues and navigable with brain-computer interfaces called `cyberspace decks'; a characteristic prop of {cyberpunk} SF. At the time of this writing (mid-1991), serious efforts to construct {virtual reality} interfaces modeled explicitly on Gibsonian cyberspace are already under way, using more conventional devices such as glove sensors and binocular TV headsets. Few hackers are prepared to deny outright the possibility of a cyberspace someday evolving out of the network (see {network, the}). 2. Occasionally, the metaphoric location of the mind of a person in {hack mode}. Some hackers report experiencing strong eidetic imagery when in hack mode; interestingly, independent reports from multiple sources suggest that there are common features to the experience. In particular, the dominant colors of this subjective `cyberspace' are often gray and silver, and the imagery often involves constellations of marching dots, elaborate shifting patterns of lines and angles, or moire patterns.

:cycle: 1. n. The basic unit of computation. What every hacker wants more of (noted hacker Bill Gosper describes himself as a "cycle junkie"). One can describe an instruction as taking so many `clock cycles'. Often the computer can access its memory once on every clock cycle, and so one speaks also of `memory cycles'. These are technical meanings of {cycle}. The jargon meaning comes from the observation that there are only so many cycles per second, and when you are sharing a computer the cycles get divided up among the users. The more cycles the computer spends working on your program rather than someone else's, the faster your program will run. That's why every hacker wants more cycles: so he can spend less time waiting for the computer to respond. 2. By extension, a notional unit of *human* thought power, emphasizing that lots of things compete for the typical hacker's think time. "I refused to get involved with the Rubik's Cube back when it was big. Knew I'd burn too many cycles on it if I let myself." 3. vt. Syn. {bounce}, {120 reset}; from the phrase `cycle power'. "Cycle the machine again, that serial port's still hung."

:cycle crunch: n. A situation where the number of people trying to use the computer simultaneously has reached the point where no one can get enough cycles because they are spread too thin and the system has probably begun to {thrash}. This is an inevitable result of Parkinson's Law applied to timesharing. Usually the only solution is to buy more computer. Happily, this has rapidly become easier in recent years, so much so that the very term `cycle crunch' now has a faintly archaic flavor; most hackers now use workstations or personal computers as opposed to traditional timesharing systems.

:cycle drought: n. A scarcity of cycles. It may be due to a {cycle crunch}, but it could also occur because part of the computer is temporarily not working, leaving fewer cycles to go around. "The {high moby} is {down}, so we're running with only half the usual amount of memory. There will be a cycle drought until it's fixed."

:cycle of reincarnation: [coined by Ivan Sutherland ca. 1970] n. Term used to refer to a well-known effect whereby function in a computing system family is migrated out to special-purpose peripheral hardware for speed, then the peripheral evolves toward more computing power as it does its job, then somebody notices that it is inefficient to support two asymmetrical processors in the architecture and folds the function back into the main CPU, at which point the cycle begins again. Several iterations of this cycle have been observed in graphics-processor design, and at least one or two in communications and floating-point processors. Also known as `the Wheel of Life', `the Wheel of Samsara', and other variations of the basic Hindu/Buddhist theological idea.

:cycle server: n. A powerful machine that exists primarily for running large {batch} jobs. Implies that interactive tasks such as editing are done on other machines on the network, such as workstations.

= D = =====

:D. C. Power Lab: n. The former site of {{SAIL}}. Hackers thought this was very funny because the obvious connection to electrical engineering was nonexistent --- the lab was named for a Donald C. Power. Compare {Marginal Hacks}.

:daemon: /day'mn/ or /dee'mn/ [from the mythological meaning, later rationalized as the acronym `Disk And Execution MONitor'] n. 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 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. 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 (1991) usage.

:dangling pointer: n. 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 is 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.

:dark-side hacker: n. A criminal or malicious hacker; a {cracker}. 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. Oppose {samurai}.

:Datamation: /day`t*-may'sh*n/ n. A magazine that many hackers assume all {suit}s read. Used to question an unbelieved quote, as in "Did you read that in `Datamation?'" It used to publish something hackishly funny every once in a while, like the original paper on {COME FROM} in 1973, but it has since become much more exclusively {suit}-oriented and boring.

:day mode: n. See {phase} (sense 1). Used of people only.

:dd: /dee-dee/ [UNIX: from IBM {JCL}] vt. Equivalent to {cat} or {BLT}. This was originally the name of a UNIX copy command with special options suitable for block-oriented devices. Often used in heavy-handed system maintenance, as in "Let's `dd' the root partition onto a tape, then use the boot PROM to load it back on to a new disk". The UNIX `dd(1)' was designed with a weird, distinctly non-UNIXy keyword option syntax reminiscent of IBM System/360 JCL (which had an elaborate DD `Data 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, as `dd(1)' has been {deprecated} for a long time (though it has no exact replacement). Replaced by {BLT} or simple English `copy'.

:DDT: /D-D-T/ n. 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 like `dbx', `adb', `gdb', or `sdb'. 2. [ITS] Under MIT's fabled {{ITS}} operating system, DDT (running under the alias HACTRN) was also used as the {shell} or top level command language used to execute other programs. 3. Any one of several specific DDTs (sense 1) supported on early DEC hardware. The DEC PDP-10 Reference Handbook (1969) contained a footnote on the first page of the documentation for DDT which 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.

Sadly, this quotation was removed from later editions of the handbook after the {suit}s took over and DEC became much more `businesslike'.

The history above is known to many old-time hackers. But there's more: Peter Samson, author of the {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).

: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 as *fictional* hacker jargon, and adopted in a spirit of irony by real hackers years after the fact. 2. vt. On a Macintosh, many program structures (including the code itself) are managed in small segments of the program file known as `resources'. The standard resource compiler is Rez. The standard resource decompiler is DeRez. Thus, decompiling a resource is `derezzing'. Usage: very common.

:dead: adj. 1. Non-functional; {down}; {crash}ed. Especially used of hardware. 2. At XEROX PARC, software that is working but not undergoing continued development and support.

:dead code: n. 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 also {software rot}); a good compiler should report dead code so a maintainer can think about what it means. Syn. {grunge}.

: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. 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.

:deadlock: n. 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', where each process is trying to send stuff to the other but all buffers are full because nobody is reading anything.) See {deadly 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 both move the same way at the same time.

:deadly embrace: n. Same as {deadlock}, though usually used only when exactly 2 processes are involved. This is the more popular term in Europe, while {deadlock} predominates in the United States.

:death code: n. 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). Death code is much less common, and more anti-social, on modern multi-user machines. It was very impressive on earlier hardware that provided front panel switches and displays to show register and memory contents, esp. when these were used to prod the corpse to see why it died.

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).

:Death Star: [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 of {BSD} UNIX, 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' for 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.

:DEC Wars: n. A 1983 {USENET} posting by Alan Hastings and Steve Tarr spoofing the "Star Wars" movies in hackish terms. Some years later, ESR (disappointed by Hastings and Tarr's failure to exploit a great premise more thoroughly) posted a 3-times-longer complete rewrite called "UNIX WARS"; the two are often confused.

:DEChead: /dek'hed/ n. 1. A DEC {field servoid}. Not flattering. 2. [from `deadhead'] A Grateful Dead fan working at DEC.

:deckle: /dek'l/ [from dec- and {nybble}; the original spelling seems to have been `decle'] n. Two {nickle}s; 10 bits. Reported among developers for Mattel's GI 1600 (the Intellivision games processor), a chip with 16-bit-wide RAM but 10-bit-wide ROM.

:deep hack mode: n. See {hack mode}.

:deep magic: [poss. from C. S. Lewis's "Narnia" books] n. An awesomely arcane technique central to a program or system, esp. one not generally published and available to hackers at large (compare {black art}); one that could only have been composed by a true {wizard}. Compiler optimization techniques and many aspects of {OS} design used to be {deep magic}; many techniques in cryptography, signal processing, graphics, and AI still are. Compare {heavy wizardry}. Esp. found in comments of the form "Deep magic begins here...". Compare {voodoo programming}.

:deep space: n. 1. Describes the notional location of any program that has gone {off the trolley}. Esp. used of programs that just sit there silently grinding long after either failure or some output is expected. "Uh oh. I should have gotten a prompt ten seconds ago. The program's in deep space somewhere." Compare {buzz}, {catatonic}, {hyperspace}. 2. The metaphorical location of a human so dazed and/or confused or caught up in some esoteric form of {bogosity} that he or she no longer responds coherently to normal communication. Compare {page out}.

:defenestration: [from the traditional Czechoslovak method of assassinating prime ministers, via SF fandom] n. 1. Proper karmic retribution for an incorrigible punster. "Oh, ghod, that was *awful*!" "Quick! Defenestrate him!" 2. The act of exiting a window system in order to get better response time from a full-screen program. This comes from the dictionary meaning of `defenestrate', which is to throw something out a window. 3. The act of discarding something under the assumption that it will improve matters. "I don't have any disk space left." "Well, why don't you defenestrate that 100 megs worth of old core dumps?" 4. [proposed] The requirement to support a command-line interface. "It has to run on a VT100." "Curses! I've been defenestrated!"

:defined as: adj. In the role of, usually in an organization-chart sense. "Pete is currently defined as bug prioritizer." Compare {logical}.

:dehose: /dee-hohz/ vt. To clear a {hosed} condition.

:delint: /dee-lint/ v. To modify code to remove problems detected when {lint}ing. Confusingly, this is also referred to as `linting' code.

:delta: n. 1. [techspeak] A quantitative change, especially a small or incremental one (this use is general in physics and engineering). "I just doubled the speed of my program!" "What was the delta on program size?" "About 30 percent." (He doubled the speed of his program, but increased its size by only 30 percent.) 2. [UNIX] A {diff}, especially a {diff} stored under the set of version-control tools called SCCS (Source Code Control System) or RCS (Revision Control System). 3. n. A small quantity, but not as small as {epsilon}. The jargon usage of {delta} and {epsilon} stems from the traditional use of these letters in mathematics for very small numerical quantities, particularly in `epsilon-delta' proofs in limit theory (as in the differential calculus). The term {delta} is often used, once {epsilon} has been mentioned, to mean a quantity that is slightly bigger than {epsilon} but still very small. "The cost isn't epsilon, but it's delta" means that the cost isn't totally negligible, but it is nevertheless very small. Common constructions include `within delta of ---', `within epsilon of ---': that is, close to and even closer to.

:demented: adj. Yet another term of disgust used to describe a program. The connotation in this case is that the program works as designed, but the design is bad. Said, for example, of a program that generates large numbers of meaningless error messages, implying that it is on the brink of imminent collapse. Compare {wonky}, {bozotic}.

:demigod: n. A hacker with years of experience, a national reputation, and a major role in the development of at least one design, tool, or game used by or known to more than half of the hacker community. To qualify as a genuine demigod, the person must recognizably identify with the hacker community and have helped shape it. Major demigods include Ken Thompson and Dennis Ritchie (co-inventors of {{UNIX}} and {C}) and Richard M. Stallman (inventor of {EMACS}). In their hearts of hearts, most hackers dream of someday becoming demigods themselves, and more than one major software project has been driven to completion by the author's veiled hopes of apotheosis. See also {net.god}, {true-hacker}.

:demo: /de'moh/ [short for `demonstration'] 1. v. To demonstrate a product or prototype. A far more effective way of inducing bugs to manifest than any number of {test} runs, especially when important people are watching. 2. n. The act of demoing. 3. n. Esp. as `demo version', can refer to either a special version of a program (frequently with some features crippled) which is distributed at little or no cost to the user for demonstration purposes.

:demo mode: [Sun] n. 1. The state of being {heads down} in order to finish code in time for a {demo}, usually due yesterday. 2. A mode in which video games sit there by themselves running through a portion of the game, also known as `attract mode'. Some serious {app}s have a demo mode they use as a screen saver, or may go through a demo mode on startup (for example, the Microsoft Windows opening screen --- which lets you impress your neighbors without actually having to put up with {Microsloth Windows}).

:demon: n. 1. [MIT] A portion of a program that is not invoked explicitly, but that lies 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. 2. [outside MIT] Often used equivalently to {daemon} --- especially in the {{UNIX}} world, where the latter spelling and pronunciation is considered mildly archaic.

:depeditate: /dee-ped'*-tayt/ [by (faulty) analogy with `decapitate'] vt. Humorously, to cut off the feet of. When one is using some computer-aided typesetting tools, careless placement of text blocks within a page or above a rule can result in chopped-off letter descenders. Such letters are said to have been depeditated.

:deprecated: adj. Said of a program or feature that is considered obsolescent and in the process of being phased out, usually in favor of a specified replacement. Deprecated features can, unfortunately, linger on for many years. This term appears with distressing frequency in standards documents when the committees which write them decide that a sufficient number of users have written code which depends on specific features which are out of favor.

:deserves to lose: adj. Said of someone who willfully does the {Wrong Thing}; humorously, if one uses a feature known to be {marginal}. What is meant is that one deserves the consequences of one's {losing} actions. "Boy, anyone who tries to use {mess-dos} deserves to {lose}!" ({{ITS}} fans used to say this of {{UNIX}}; many still do.) See also {screw}, {chomp}, {bagbiter}.