The Hacker's Dictionary, - [best reads of all time .txt] 📗

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 =

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: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: /dayt*-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 inDatamation?'" 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 UNIXdd(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, asdd(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 likedbx', 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 suddenlyfuzzed 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 isderezzing'. 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 termstarvation' 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