: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).
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 Square: /n./ 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 with {Death Star}, because many people believed Novell was bungling the lead in Unix systems exactly as AT&T did for many years.
:Death Star: /n./ [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' 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.
:DEC:: /dek/ /n./ Commonly used abbreviation for Digital Equipment Corporation, now deprecated by DEC itself in favor of "Digital". Before the {killer micro} revolution of the late 1980s, hackerdom was closely symbiotic with DEC's pioneering timesharing machines. The first of the group of cultures described by this lexicon nucleated around the PDP-1 (see {TMRC}). Subsequently, the PDP-6, {PDP-10}, {PDP-20}, PDP-11 and {VAX} were all foci of large and important hackerdoms, and DEC machines long dominated the ARPANET and Internet machine population. DEC was the technological leader of the minicomputer era (roughly 1967 to 1987), but its failure to embrace microcomputers and Unix early cost it heavily in profits and prestige after {silicon} got cheap. Nevertheless, the microprocessor design tradition owes a heavy debt to the PDP-11 instruction set, and every one of the major general-purpose microcomputer OSs so far (CP/M, MS-DOS, Unix, OS/2, Windows NT) was either genetically descended from a DEC OS, or incubated on DEC hardware, or both. Accordingly, DEC is still regarded with a certain wry affection even among many hackers too young to have grown up on DEC machines. The contrast with {IBM} is instructive.
[1996 update: DEC has gradually been reclaiming some of its old reputation among techies in the last five years. The success of the Alpha, an innovatively-designed and very high-performance {killer micro}, has helped a lot. So has DEC's newfound receptiveness to Unix and open systems in general. —ESR]
:dec: /dek/ /v./ Verbal (and only rarely written) shorthand for decrement, i.e. `decrease by one'. Especially used by assembly programmers, as many assembly languages have a `dec' mnemonic. Antonym: {inc}.
: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.
:decay: /n.,vi/ [from nuclear physics] An automatic conversion which is applied to most array-valued expressions in {C}; they `decay into' pointer-valued expressions pointing to the array's first element. This term is borderline techspeak, but is not used in the official standard for the language.
:DEChead: /dek'hed/ /n./ 1. A {DEC} {field servoid}. Not flattering. 2. [from `deadhead'] A Grateful Dead fan working at DEC.