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The New Hacker's Dictionary version 4.2.2 by Various editors

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Node:= Y =, Next:[14988]= Z =, Previous:[14989]= X =, Up:[14990]The
Jargon Lexicon

= Y =

* [14991]YA-:
* [14992]YABA:
* [14993]YAFIYGI:
* [14994]YAUN:
* [14995]Yellow Book:
* [14996]yellow card:
* [14997]yellow wire:
* [14998]Yet Another:
* [14999]YHBT:
* [15000]YKYBHTLW:
* [15001]YMMV:
* [15002]You are not expected to understand this:
* [15003]You know you've been hacking too long when:
* [15004]Your mileage may vary:
* [15005]Yow!:
* [15006]yoyo mode:
* [15007]Yu-Shiang Whole Fish:

Node:YA-, Next:[15008]YABA, Previous:[15009]xyzzy, Up:[15010]= Y =

YA- abbrev.

[Yet Another] In hackish acronyms this almost invariably expands to
[15011]Yet Another, following the precedent set by Unix yacc(1) (Yet
Another Compiler-Compiler). See [15012]YABA.

Node:YABA, Next:[15013]YAFIYGI, Previous:[15014]YA-, Up:[15015]= Y =

YABA /ya'b*/ n.

[Cambridge] Yet Another Bloody Acronym. Whenever some program is being
named, someone invariably suggests that it be given a name that is
acronymic. The response from those with a trace of originality is to
remark ironically that the proposed name would then be
`YABA-compatible'. Also used in response to questions like "What is
WYSIWYG?" See also [15016]TLA.

Node:YAFIYGI, Next:[15017]YAUN, Previous:[15018]YABA, Up:[15019]= Y =

YAFIYGI /yaf'ee-y*-gee/ adj.

[coined in response to WYSIWYG] Describes the command-oriented
ed/vi/nroff/TeX style of word processing or other user interface, the
opposite of [15020]WYSIWYG. Stands for "You asked for it, you got it",
because what you actually asked for is often not apparent until long
after it is too late to do anything about it. Used to denote
perversity ("Real Programmers use YAFIYGI tools...and like it!") or,
less often, a necessary tradeoff ("Only a YAFIYGI tool can have full
programmable flexibility in its interface.").

This precise sense of "You asked for it, you got it" seems to have
first appeared in Ed Post's classic parody "Real Programmers don't use
Pascal" (see [15021]Real Programmers); the acronym is a more recent

Node:YAUN, Next:[15022]Yellow Book, Previous:[15023]YAFIYGI,
Up:[15024]= Y =

YAUN /yawn/ n.

[Acronym for `Yet Another Unix Nerd'] Reported from the San Diego
Computer Society (predominantly a microcomputer users' group) as a
good-natured punning insult aimed at Unix zealots.

Node:Yellow Book, Next:[15025]yellow card, Previous:[15026]YAUN,
Up:[15027]= Y =

Yellow Book n.

The print version of this Jargon File; "The New Hacker's Dictionary"
from MIT Press; The book includes essentially all the material the
File, plus a Foreword by Guy L. Steele Jr. and a Preface by Eric S.
Raymond. Most importantly, the book version is nicely typeset and
includes almost all of the infamous Crunchly cartoons by the Great
Quux, each attached to an appropriate entry. The first edition (1991,
ISBN 0-262-68069-6) corresponded to the Jargon File version 2.9.6. The
second edition (1993, ISBN 0-262-68079-3) corresponded to the Jargon
File 3.0.0. The third (1996, ISBN 0-262-68092-0) corresponded to

Node:yellow card, Next:[15028]yellow wire, Previous:[15029]Yellow
Book, Up:[15030]= Y =

yellow card n.

See [15031]green card.

Node:yellow wire, Next:[15032]Yet Another, Previous:[15033]yellow
card, Up:[15034]= Y =

yellow wire n.

[IBM] Repair wires used when connectors (especially ribbon connectors)
got broken due to some schlemiel pinching them, or to reconnect cut
traces after the FE mistakenly cut one. Compare [15035]blue wire,
[15036]purple wire, [15037]red wire.

Node:Yet Another, Next:[15038]YHBT, Previous:[15039]yellow wire,
Up:[15040]= Y =

Yet Another adj.

[From Unix's yacc(1), `Yet Another Compiler-Compiler', a LALR parser
generator] 1. Of your own work: A humorous allusion often used in
titles to acknowledge that the topic is not original, though the
content is. As in `Yet Another AI Group' or `Yet Another Simulated
Annealing Algorithm'. 2. Of others' work: Describes something of which
there are already far too many. See also [15041]YA-, [15042]YABA,

Node:YHBT, Next:[15044]YKYBHTLW, Previous:[15045]Yet Another,
Up:[15046]= Y =


[Usenet: very common] Abbreviation: You Have Been Trolled (see
[15047]troll, sense 1). Especially used in "YHBT. YHL. HAND.", which
is widely understood to expand to "You Have Been Trolled. You Have
Lost. Have A Nice Day". You are quite likely to see this if you
respond incautiously to a flame-provoking post that was obviously
floated as sucker bait.

Node:YKYBHTLW, Next:[15048]YMMV, Previous:[15049]YHBT, Up:[15050]= Y =

YKYBHTLW // abbrev.

Abbreviation of `You know you've been hacking too long when...', which
became established on the Usenet group alt.folklore.computers during
extended discussion of the indicated entry in the Jargon File.

Node:YMMV, Next:[15051]You are not expected to understand this,
Previous:[15052]YKYBHTLW, Up:[15053]= Y =

YMMV // cav.

Abbreviation for [15054]Your mileage may vary common on Usenet.

Node:You are not expected to understand this, Next:[15055]You know
you've been hacking too long when, Previous:[15056]YMMV, Up:[15057]= Y

You are not expected to understand this [Unix] cav.

The canonical comment describing something [15058]magic or too
complicated to bother explaining properly. From an infamous comment in
the context-switching code of the V6 Unix kernel. Dennis Ritchie has
[15059]explained this in detail.

Node:You know you've been hacking too long when, Next:[15060]Your
mileage may vary, Previous:[15061]You are not expected to understand
this, Up:[15062]= Y =

You know you've been hacking too long when

The set-up line for a genre of one-liners told by hackers about
themselves. These include the following:

* not only do you check your email more often than your paper mail,
but you remember your [15063]network address faster than your
postal one.
* your [15064]SO kisses you on the neck and the first thing you
think is "Uh, oh, [15065]priority interrupt."
* you go to balance your checkbook and discover that you're doing it
in octal.
* your computers have a higher street value than your car.
* in your universe, `round numbers' are powers of 2, not 10.
* more than once, you have woken up recalling a dream in some
programming language.
* you realize you have never seen half of your best friends.

A [15066]list list of these can be found by searching for this phrase
on the web.

[An early version of this entry said "All but one of these have been
reliably reported as hacker traits (some of them quite often). Even
hackers may have trouble spotting the ringer." The ringer was
balancing one's checkbook in octal, which I made up out of whole
cloth. Although more respondents picked that one out as fiction than
any of the others, I also received multiple independent reports of its
actually happening, most famously to Grace Hopper while she was
working with BINAC in 1949. --ESR]

Node:Your mileage may vary, Next:[15067]Yow!, Previous:[15068]You know
you've been hacking too long when, Up:[15069]= Y =

Your mileage may vary cav.

[from the standard disclaimer attached to EPA mileage ratings by
American car manufacturers] 1. A ritual warning often found in Unix
freeware distributions. Translates roughly as "Hey, I tried to write
this portably, but who knows what'll happen on your system?" 2. More
generally, a qualifier attached to advice. "I find that sending
flowers works well, but your mileage may vary."

Node:Yow!, Next:[15070]yoyo mode, Previous:[15071]Your mileage may
vary, Up:[15072]= Y =

Yow! /yow/ interj.

[from "Zippy the Pinhead" comix] A favored hacker expression of
humorous surprise or emphasis. "Yow! Check out what happens when you
twiddle the foo option on this display hack!" Compare [15073]gurfle.

Node:yoyo mode, Next:[15074]Yu-Shiang Whole Fish,
Previous:[15075]Yow!, Up:[15076]= Y =

yoyo mode n.

The state in which the system is said to be when it rapidly alternates
several times between being up and being down. Interestingly (and
perhaps not by coincidence), many hardware vendors give out free yoyos
at Usenix exhibits.

Sun Microsystems gave out logoized yoyos at SIGPLAN '88. Tourists
staying at one of Atlanta's most respectable hotels were subsequently
treated to the sight of 200 of the country's top computer scientists
testing yo-yo algorithms in the lobby.

Node:Yu-Shiang Whole Fish, Next:[15077]zap, Previous:[15078]yoyo mode,
Up:[15079]= Y =

Yu-Shiang Whole Fish /yoo-shyang hohl fish/ n. obs.

The character gamma (extended SAIL ASCII 0001001), which with a loop
in its tail looks like a little fish swimming down the page. The term
is actually the name of a Chinese dish in which a fish is cooked whole
(not [15080]parsed) and covered with Yu-Shiang (or Yu-Hsiang) sauce.
Usage: primarily by people on the MIT LISP Machine, which could
display this character on the screen. Tends to elicit incredulity from
people who hear about it second-hand.

Node:= Z =, Previous:[15081]= Y =, Up:[15082]The Jargon Lexicon

= Z =

* [15083]zap:
* [15084]zapped:
* [15085]Zawinski's Law:
* [15086]zbeba:
* [15087]zen:
* [15088]zero:
* [15089]zero-content:
* [15090]Zero-One-Infinity Rule:
* [15091]zeroth:
* [15092]zigamorph:
* [15093]zip:
* [15094]zipperhead:
* [15095]zombie:
* [15096]zorch:
* [15097]Zork:
* [15098]zorkmid:

Node:zap, Next:[15099]zapped, Previous:[15100]Yu-Shiang Whole Fish,
Up:[15101]= Z =


1. n. Spiciness. 2. vt. To make food spicy. 3. vt. To make someone
`suffer' by making his food spicy. (Most hackers love spicy food.
Hot-and-sour soup is considered wimpy unless it makes you wipe your
nose for the rest of the meal.) See [15102]zapped. 4. vt. To modify,
usually to correct; esp. used when the action is performed with a
debugger or binary patching tool. Also implies surgical precision.
"Zap the debug level to 6 and run it again." In the IBM mainframe
world, binary patches are applied to programs or to the OS with a
program called `superzap', whose file name is `IMASPZAP' (possibly
contrived from I M A SuPerZAP). 5. vt. To erase or reset. 6. To
[15103]fry a chip with static electricity. "Uh oh -- I think that
lightning strike may have zapped the disk controller."

Node:zapped, Next:[15104]Zawinski's Law, Previous:[15105]zap,
Up:[15106]= Z =

zapped adj.

Spicy. This term is used to distinguish between food that is hot (in
temperature) and food that is spicy-hot. For example, the Chinese
appetizer Bon Bon Chicken is a kind of chicken salad that is cold but
zapped; by contrast, [15107]vanilla wonton soup is hot but not zapped.
See also [15108]oriental food, [15109]laser chicken. See [15110]zap,
senses 1 and 2.

Node:Zawinski's Law, Next:[15111]zbeba, Previous:[15112]zapped,
Up:[15113]= Z =

Zawinski's Law

"Every program attempts to expand until it can read mail. Those
programs which cannot so expand are replaced by ones which can."
Coined by Jamie Zawinski (who called it the "Law of Software
Envelopment") to express his belief that all truly useful programs
experience pressure to evolve into toolkits and application platforms
(the mailer thing, he says, is just a side effect of that). It is
commonly cited, though with widely varying degrees of accuracy.

Node:zbeba, Next:[15114]zen, Previous:[15115]Zawinski's Law,
Up:[15116]= Z =

zbeba n.

[USENET] The word `moron' in [15117]rot13. Used to describe newbies
who are behaving with especial cluelessness.

Node:zen, Next:[15118]zero, Previous:[15119]zbeba, Up:[15120]= Z =

zen vt.

To figure out something by meditation or by a sudden flash of
enlightenment. Originally applied to bugs, but occasionally applied to
problems of life in general. "How'd you figure out the buffer
allocation problem?" "Oh, I zenned it." Contrast [15121]grok, which
connotes a time-extended version of zenning a system. Compare
[15122]hack mode. See also [15123]guru.

Node:zero, Next:[15124]zero-content, Previous:[15125]zen, Up:[15126]=
Z =

zero vt.

1. To set to 0. Usually said of small pieces of data, such as bits or
words (esp. in the construction `zero out'). 2. To erase; to discard
all data from. Said of disks and directories, where `zeroing' need not
involve actually writing zeroes throughout the area being zeroed. One
may speak of something being `logically zeroed' rather than being
`physically zeroed'. See [15127]scribble.

Node:zero-content, Next:[15128]Zero-One-Infinity Rule,
Previous:[15129]zero, Up:[15130]= Z =

zero-content adj.

Syn. [15131]content-free.

Node:Zero-One-Infinity Rule, Next:[15132]zeroth,
Previous:[15133]zero-content, Up:[15134]= Z =

Zero-One-Infinity Rule prov.

"Allow none of [15135]foo, one of [15136]foo, or any number of
[15137]foo." A rule of thumb for software design, which instructs one
to not place [15138]random limits on the number of instances of a
given entity (such as: windows in a window system, letters in an OS's
filenames, etc.). Specifically, one should either disallow the entity
entirely, allow exactly one instance (an "exception"), or allow as
many as the user wants - address space and memory permitting.

The logic behind this rule is that there are often situations where it
makes clear sense to allow one of something instead of none. However,
if one decides to go further and allow N (for N > 1), then why not
N+1? And if N+1, then why not N+2, and so on? Once above 1, there's no
excuse not to allow any N; hence, [15139]infinity.

Many hackers recall in this connection Isaac Asimov's SF novel "The
Gods Themselves" in which a character announces that the number 2 is
impossible - if you're going to believe in more than one universe, you
might as well believe in an infinite number of them.

Node:zeroth, Next:[15140]zigamorph, Previous:[15141]Zero-One-Infinity
Rule, Up:[15142]= Z =

zeroth /zee'rohth/ adj.

First. Among software designers, comes from C's and LISP's 0-based
indexing of arrays. Hardware people also tend to start counting at 0
instead of 1; this is natural since, e.g., the 256 states of 8 bits
correspond to the binary numbers 0, 1, ..., 255 and the digital
devices known as `counters' count in this way.

Hackers and computer scientists often like to call the first chapter
of a publication `Chapter 0', especially if it is of an introductory
nature (one of the classic instances was in the First Edition of
[15143]K&R). In recent years this trait has also been observed among
many pure mathematicians (who have an independent tradition of
numbering from 0). Zero-based numbering tends to reduce
[15144]fencepost errors, though it cannot eliminate them entirely.

Node:zigamorph, Next:[15145]zip, Previous:[15146]zeroth, Up:[15147]= Z

zigamorph /zig'*-morf/ n.

1. Hex FF (11111111) when used as a delimiter or [15148]fence
character. Usage: primarily at IBM shops. 2. [proposed] n. The Unicode
non-character U+FFFF (1111111111111111), a character code which is not
assigned to any character, and so is usable as end-of-string. (Unicode
is a 16-bit character code intended to cover all of the world's
writing systems, including Latin, Greek, Cyrillic, Chinese, hiragana,
katakana, Devanagari, Thai, Laotian and many other scripts - support
for [15149]elvish is planned for a future release).

Node:zip, Next:[15150]zipperhead, Previous:[15151]zigamorph,
Up:[15152]= Z =

zip vt.

[primarily MS-DOS] To create a compressed archive from a group of
files using PKWare's PKZIP or a compatible archiver. Its use is
spreading now that portable implementations of the algorithm have been
written. Commonly used as follows: "I'll zip it up and send it to
you." See [15153]tar and feather.

Node:zipperhead, Next:[15154]zombie, Previous:[15155]zip, Up:[15156]=
Z =

zipperhead n.

[IBM] A person with a closed mind.

Node:zombie, Next:[15157]zorch, Previous:[15158]zipperhead,
Up:[15159]= Z =

zombie n.

[Unix] A process that has died but has not yet relinquished its
process table slot (because the parent process hasn't executed a
wait(2) for it yet). These can be seen in ps(1) listings occasionally.
Compare [15160]orphan.

Node:zorch, Next:[15161]Zork, Previous:[15162]zombie, Up:[15163]= Z =

zorch /zorch/

1. [TMRC] v. To attack with an inverse heat sink. 2. [TMRC] v. To
travel, with v approaching c [that is, with velocity approaching
lightspeed --ESR]. 3. [MIT] v. To propel something very quickly. "The
new comm software is very fast; it really zorches files through the
network." 4. [MIT] n. Influence. Brownie points. Good karma. The
intangible and fuzzy currency in which favors are measured. "I'd
rather not ask him for that just yet; I think I've used up my quota of
zorch with him for the week." 5. [MIT] n. Energy, drive, or ability.
"I think I'll [15164]punt that change for now; I've been up for 30
hours and I've run out of zorch." 6. [MIT] v. To flunk an exam or

Node:Zork, Next:[15165]zorkmid, Previous:[15166]zorch, Up:[15167]= Z =

Zork /zork/ n.

The second of the great early experiments in computer fantasy gaming;
see [15168]ADVENT. Originally written on MIT-DM during 1977-1979,
later distributed with BSD Unix (as a patched, sourceless RT-11
FORTRAN binary; see [15169]retrocomputing) and commercialized as `The
Zork Trilogy' by [15170]Infocom. The FORTRAN source was later
rewritten for portability and released to Usenet under the name
"Dungeon". Both FORTRAN "Dungeon" and translated C versions are
available at many FTP sites. See also [15171]grue.

Node:zorkmid, Previous:[15172]Zork, Up:[15173]= Z =

zorkmid /zork'mid/ n.

The canonical unit of currency in hacker-written games. This
originated in [15174]Zork but has spread to [15175]nethack and is
referred to in several other games.

(Lexicon Entries End Here)

Node:Appendix A, Next:[15176]Appendix B, Previous:[15177]The Jargon
Lexicon, Up:[15178]Top

Hacker Folklore

This appendix contains several legends and fables that illuminate the
meaning of various entries in the lexicon.
* [15179]The Meaning of Hack: ...and three famous ones
* [15180]TV Typewriters: A Tale of Hackish Ingenuity
* [15181]A Story About Magic: By Guy Steele
* [15182]Some AI Koans: Wit and Wisdom of the Masters
* [15183]OS and JEDGAR: Intrigue and mayhem under ITS
* [15184]The Story of Mel: One of hackerdom's great myths

Node:The Meaning of Hack, Next:[15185]TV Typewriters,
Previous:[15186]Appendix A, Up:[15187]Appendix A

The Meaning of `Hack'

"The word [15188]hack doesn't really have 69 different meanings",
according to MIT hacker Phil Agre. "In fact, [15189]hack has only one
meaning, an extremely subtle and profound one which defies
articulation. Which connotation is implied by a given use of the word
depends in similarly profound ways on the context. Similar remarks
apply to a couple of other hacker words, most notably [15190]random."

Hacking might be characterized as `an appropriate application of
ingenuity'. Whether the result is a quick-and-dirty patchwork job or a
carefully crafted work of art, you have to admire the cleverness that
went into it.

An important secondary meaning of [15191]hack is `a creative practical
joke'. This kind of hack is easier to explain to non-hackers than the
programming kind. Of course, some hacks have both natures; see the
lexicon entries for [15192]pseudo and [15193]kgbvax. But here are some
examples of pure practical jokes that illustrate the hacking spirit:

In 1961, students from Caltech (California Institute of Technology,
in Pasadena) hacked the Rose Bowl football game. One student posed
as a reporter and `interviewed' the director of the University of
Washington card stunts (such stunts involve people in the stands
who hold up colored cards to make pictures). The reporter learned
exactly how the stunts were operated, and also that the director
would be out to dinner later.

While the director was eating, the students (who called themselves
the `Fiendish Fourteen') picked a lock and stole a blank direction
sheet for the card stunts. They then had a printer run off 2300
copies of the blank. The next day they picked the lock again and
stole the master plans for the stunts -- large sheets of graph
paper colored in with the stunt pictures. Using these as a guide,
they made new instructions for three of the stunts on the
duplicated blanks. Finally, they broke in once more, replacing the
stolen master plans and substituting the stack of diddled
instruction sheets for the original set.

The result was that three of the pictures were totally different.
Instead of `WASHINGTON', the word ``CALTECH' was flashed. Another
stunt showed the word `HUSKIES', the Washington nickname, but
spelled it backwards. And what was supposed to have been a picture
of a husky instead showed a beaver. (Both Caltech and MIT use the
beaver -- nature's engineer -- as a mascot.)

After the game, the Washington faculty athletic representative
said: "Some thought it ingenious; others were indignant." The
Washington student body president remarked: "No hard feelings, but
at the time it was unbelievable. We were amazed."

This is now considered a classic hack, particularly because revising
the direction sheets constituted a form of programming.

Here is another classic hack:

On November 20, 1982, MIT hacked the Harvard-Yale football game.
Just after Harvard's second touchdown against Yale, in the first
quarter, a small black ball popped up out of the ground at the
40-yard line, and grew bigger, and bigger, and bigger. The letters
`MIT' appeared all over the ball. As the players and officials
stood around gawking, the ball grew to six feet in diameter and
then burst with a bang and a cloud of white smoke.

The "Boston Globe" later reported: "If you want to know the truth,
MIT won The Game."

The prank had taken weeks of careful planning by members of MIT's
Delta Kappa Epsilon fraternity. The device consisted of a weather
balloon, a hydraulic ram powered by Freon gas to lift it out of the
ground, and a vacuum-cleaner motor to inflate it. They made eight
separate expeditions to Harvard Stadium between 1 and 5 A.M.,
locating an unused 110-volt circuit in the stadium and running
buried wires from the stadium circuit to the 40-yard line, where
they buried the balloon device. When the time came to activate the
device, two fraternity members had merely to flip a circuit breaker
and push a plug into an outlet.

This stunt had all the earmarks of a perfect hack: surprise,
publicity, the ingenious use of technology, safety, and
harmlessness. The use of manual control allowed the prank to be
timed so as not to disrupt the game (it was set off between plays,
so the outcome of the game would not be unduly affected). The
perpetrators had even thoughtfully attached a note to the balloon
explaining that the device was not dangerous and contained no

Harvard president Derek Bok commented: "They have an awful lot of
clever people down there at MIT, and they did it again." President
Paul E. Gray of MIT said: "There is absolutely no truth to the
rumor that I had anything to do with it, but I wish there were."

The hacks above are verifiable history; they can be proved to have
happened. Many other classic-hack stories from MIT and elsewhere,
though retold as history, have the characteristics of what Jan
Brunvand has called `urban folklore' (see [15194]FOAF). Perhaps the
best known of these is the legend of the infamous trolley-car hack, an
alleged incident in which engineering students are said to have welded
a trolley car to its tracks with thermite. Numerous versions of this
have been recorded from the 1940s to the present, most set at MIT but
at least one very detailed version set at CMU.

Brian Leibowitz has researched MIT hacks both real and mythical
extensively; the interested reader is referred to his delightful
pictorial compendium "The Journal of the Institute for Hacks,
Tomfoolery, and Pranks" (MIT Museum, 1990; ISBN 0-917027-03-5). The
Institute has a World Wide Web page at
[15195]http://hacks.mit.edu/Hacks/Gallery.php. There is rumored to be
a sequel entitled "Is This The Way To Baker Street?". The Caltech
Alumni Association has published two similar books titled "Legends of
Caltech" and "More Legends of Caltech".

Finally, here is a story about one of the classic computer hacks.

Back in the mid-1970s, several of the system support staff at
Motorola discovered a relatively simple way to crack system
security on the Xerox CP-V timesharing system. Through a simple
programming strategy, it was possible for a user program to trick
the system into running a portion of the program in `master mode'
(supervisor state), in which memory protection does not apply. The
program could then poke a large value into its `privilege level'
byte (normally write-protected) and could then proceed to bypass
all levels of security within the file-management system, patch the
system monitor, and do numerous other interesting things. In short,
the barn door was wide open.

Motorola quite properly reported this problem to Xerox via an
official `level 1 SIDR' (a bug report with an intended urgency of
`needs to be fixed yesterday'). Because the text of each SIDR was
entered into a database that could be viewed by quite a number of
people, Motorola followed the approved procedure: they simply
reported the problem as `Security SIDR', and attached all of the
necessary documentation, ways-to-reproduce, etc.

The CP-V people at Xerox sat on their thumbs; they either didn't
realize the severity of the problem, or didn't assign the necessary
operating-system-staff resources to develop and distribute an
official patch.

Months passed. The Motorola guys pestered their Xerox field-support
rep, to no avail. Finally they decided to take direct action, to
demonstrate to Xerox management just how easily the system could be
cracked and just how thoroughly the security safeguards could be

They dug around in the operating-system listings and devised a
thoroughly devilish set of patches. These patches were then
incorporated into a pair of programs called `Robin Hood' and `Friar
Tuck'. Robin Hood and Friar Tuck were designed to run as `ghost
jobs' (daemons, in Unix terminology); they would use the existing
loophole to subvert system security, install the necessary patches,
and then keep an eye on one another's statuses in order to keep the
system operator (in effect, the superuser) from aborting them.

One fine day, the system operator on the main CP-V software
development system in El Segundo was surprised by a number of
unusual phenomena. These included the following:
* Tape drives would rewind and dismount their tapes in the middle of
a job.
* Disk drives would seek back and forth so rapidly that they would
attempt to walk across the floor (see [15196]walking drives).
* The card-punch output device would occasionally start up of itself
and punch a [15197]lace card. These would usually jam in the
* The console would print snide and insulting messages from Robin
Hood to Friar Tuck, or vice versa.
* The Xerox card reader had two output stackers; it could be
instructed to stack into A, stack into B, or stack into A (unless
a card was unreadable, in which case the bad card was placed into
stacker B). One of the patches installed by the ghosts added some
code to the card-reader driver... after reading a card, it would
flip over to the opposite stacker. As a result, card decks would
divide themselves in half when they were read, leaving the
operator to recollate them manually.

Naturally, the operator called in the operating-system developers.
They found the bandit ghost jobs running, and [15198]gunned them...
and were once again surprised. When Robin Hood was gunned, the
following sequence of events took place:
!X id1

id1: Friar Tuck... I am under attack! Pray save me!
id1: Off (aborted)

id2: Fear not, friend Robin! I shall rout the Sheriff
of Nottingham's men!

id1: Thank you, my good fellow!

Each ghost-job would detect the fact that the other had been
killed, and would start a new copy of the recently slain program
within a few milliseconds. The only way to kill both ghosts was to
kill them simultaneously (very difficult) or to deliberately crash
the system.

Finally, the system programmers did the latter -- only to find that
the bandits appeared once again when the system rebooted! It turned
out that these two programs had patched the boot-time OS image (the
kernel file, in Unix terms) and had added themselves to the list of
programs that were to be started at boot time (this is similar to
the way MS-DOS viruses propagate).

The Robin Hood and Friar Tuck ghosts were finally eradicated when
the system staff rebooted the system from a clean boot-tape and
reinstalled the monitor. Not long thereafter, Xerox released a
patch for this problem.

It is alleged that Xerox filed a complaint with Motorola's
management about the merry-prankster actions of the two employees
in question. It is not recorded that any serious disciplinary
action was taken against either of them.

Node:TV Typewriters, Next:[15199]A Story About Magic,
Previous:[15200]The Meaning of Hack, Up:[15201]Appendix A

TV Typewriters A Tale of Hackish Ingenuity

Here is a true story about a glass tty: One day an MIT hacker was in a
motorcycle accident and broke his leg. He had to stay in the hospital
quite a while, and got restless because he couldn't [15202]hack. Two
of his friends therefore took a terminal and a modem for it to the
hospital, so that he could use the computer by telephone from his
hospital bed.

Now this happened some years before the spread of home computers, and
computer terminals were not a familiar sight to the average person.
When the two friends got to the hospital, a guard stopped them and
asked what they were carrying. They explained that they wanted to take
a computer terminal to their friend who was a patient.

The guard got out his list of things that patients were permitted to
have in their rooms: TV, radio, electric razor, typewriter, tape
player, ... no computer terminals. Computer terminals weren't on the
list, so the guard wouldn't let it in. Rules are rules, you know.
(This guard was clearly a [15203]droid.)

Fair enough, said the two friends, and they left again. They were
frustrated, of course, because they knew that the terminal was as
harmless as a TV or anything else on the list... which gave them an

The next day they returned, and the same thing happened: a guard
stopped them and asked what they were carrying. They said: "This is a
TV typewriter!" The guard was skeptical, so they plugged it in and
demonstrated it. "See? You just type on the keyboard and what you type
shows up on the TV screen." Now the guard didn't stop to think about
how utterly useless a typewriter would be that didn't produce any
paper copies of what you typed; but this was clearly a TV typewriter,
no doubt about it. So he checked his list: "A TV is all right, a
typewriter is all right ... okay, take it on in!"

[Historical note: Many years ago, "Popular Electronics" published
solder-it-yourself plans for a TV typewriter. Despite the essential
uselessness of the device, it was an enormously popular project. Steve
Ciarcia, the man behind "Byte" magazine's "Circuit Cellar" feature,
resurrected this ghost in one of his books of the early 1980s. He
ascribed its popularity (no doubt correctly) to the feeling of power
the builder could achieve by being able to decide himself what would
be shown on the TV. --ESR]

[Antihistorical note: On September 23rd, 1992, the L.A. Times ran the
following bit in Steve Harvey's `Only in L.A.' column:

It must have been borrowed from a museum: Solomon Waters of
Altadena, a 6-year-old first-grader, came home from his first day
of school and excitedly told his mother how he had written on "a
machine that looks like a computer-but without the TV screen."

She asked him if it could have been a "typewriter."

"Yeah! Yeah!" he said. "That's what it was called."

I have since investigated this matter and determined that many of
today's teenagers have never seen a slide rule, either.... - ESR]

Node:A Story About Magic, Next:[15204]Some AI Koans,
Previous:[15205]TV Typewriters, Up:[15206]Appendix A

A Story About `Magic'

Some years ago, I (GLS) was snooping around in the cabinets that
housed the MIT AI Lab's PDP-10, and noticed a little switch glued to
the frame of one cabinet. It was obviously a homebrew job, added by
one of the lab's hardware hackers (no one knows who).

You don't touch an unknown switch on a computer without knowing what
it does, because you might crash the computer. The switch was labeled
in a most unhelpful way. It had two positions, and scrawled in pencil
on the metal switch body were the words `magic' and `more magic'. The
switch was in the `more magic' position.

I called another hacker over to look at it. He had never seen the
switch before either. Closer examination revealed that the switch had
only one wire running to it! The other end of the wire did disappear
into the maze of wires inside the computer, but it's a basic fact of
electricity that a switch can't do anything unless there are two wires
connected to it. This switch had a wire connected on one side and no
wire on its other side.

It was clear that this switch was someone's idea of a silly joke.
Convinced by our reasoning that the switch was inoperative, we flipped
it. The computer instantly crashed.

Imagine our utter astonishment. We wrote it off as coincidence, but
nevertheless restored the switch to the `more magic' position before
reviving the computer.

A year later, I told this story to yet another hacker, David Moon as I
recall. He clearly doubted my sanity, or suspected me of a
supernatural belief in the power of this switch, or perhaps thought I
was fooling him with a bogus saga. To prove it to him, I showed him
the very switch, still glued to the cabinet frame with only one wire
connected to it, still in the `more magic' position. We scrutinized
the switch and its lone connection, and found that the other end of
the wire, though connected to the computer wiring, was connected to a
ground pin. That clearly made the switch doubly useless: not only was
it electrically nonoperative, but it was connected to a place that
couldn't affect anything anyway. So we flipped the switch.

The computer promptly crashed.

This time we ran for Richard Greenblatt, a long-time MIT hacker, who
was close at hand. He had never noticed the switch before, either. He
inspected it, concluded it was useless, got some diagonal cutters and
[15207]diked it out. We then revived the computer and it has run fine
ever since.

We still don't know how the switch crashed the machine. There is a
theory that some circuit near the ground pin was marginal, and
flipping the switch changed the electrical capacitance enough to upset
the circuit as millionth-of-a-second pulses went through it. But we'll
never know for sure; all we can really say is that the switch was

I still have that switch in my basement. Maybe I'm silly, but I
usually keep it set on `more magic'.

1994: Another explanation of this story has since been offered. Note
that the switch body was metal. Suppose that the non-connected side of
the switch was connected to the switch body (usually the body is
connected to a separate earth lug, but there are exceptions). The body
is connected to the computer case, which is, presumably, grounded. Now
the circuit ground within the machine isn't necessarily at the same
potential as the case ground, so flipping the switch connected the
circuit ground to the case ground, causing a voltage drop/jump which
reset the machine. This was probably discovered by someone who found
out the hard way that there was a potential difference between the
two, and who then wired in the switch as a joke.

Node:Some AI Koans, Next:[15209]OS and JEDGAR, Previous:[15210]A Story
About Magic, Up:[15211]Appendix A

Some AI Koans

These are some of the funniest examples of a genre of jokes told at
the MIT AI Lab about various noted hackers. The original koans were
composed by Danny Hillis, who would later found Connection Machines,
Inc. In reading these, it is at least useful to know that Minsky,
Sussman, and Drescher are AI researchers of note, that Tom Knight was
one of the Lisp machine's principal designers, and that David Moon
wrote much of Lisp Machine Lisp.

* * *

A novice was trying to fix a broken Lisp machine by turning the power
off and on.

Knight, seeing what the student was doing, spoke sternly: "You cannot
fix a machine by just power-cycling it with no understanding of what
is going wrong."

Knight turned the machine off and on.

The machine worked.

* * *

One day a student came to Moon and said: "I understand how to make a
better garbage collector. We must keep a reference count of the
pointers to each cons."

Moon patiently told the student the following story:

"One day a student came to Moon and said: `I understand how to make
a better garbage collector...

[Ed. note: Pure reference-count garbage collectors have problems with
circular structures that point to themselves.]

* * *

In the days when Sussman was a novice, Minsky once came to him as he
sat hacking at the PDP-6.

"What are you doing?", asked Minsky.

"I am training a randomly wired neural net to play Tic-Tac-Toe"
Sussman replied.

"Why is the net wired randomly?", asked Minsky.

"I do not want it to have any preconceptions of how to play", Sussman

Minsky then shut his eyes.

"Why do you close your eyes?", Sussman asked his teacher.

"So that the room will be empty."

At that moment, Sussman was enlightened.

* * *

A disciple of another sect once came to Drescher as he was eating his
morning meal.

"I would like to give you this personality test", said the outsider,
"because I want you to be happy."

Drescher took the paper that was offered him and put it into the
toaster, saying: "I wish the toaster to be happy, too."

Node:OS and JEDGAR, Next:[15212]The Story of Mel, Previous:[15213]Some
AI Koans, Up:[15214]Appendix A


This story says a lot about the ITS ethos.

On the ITS system there was a program that allowed you to see what was
being printed on someone else's terminal. It spied on the other guy's
output by examining the insides of the monitor system. The output spy
program was called OS. Throughout the rest of the computer science
world (and at IBM too) OS means `operating system', but among old-time
ITS hackers it almost always meant `output spy'.

OS could work because ITS purposely had very little in the way of
`protection' that prevented one user from trespassing on another's
areas. Fair is fair, however. There was another program that would
automatically notify you if anyone started to spy on your output. It
worked in exactly the same way, by looking at the insides of the
operating system to see if anyone else was looking at the insides that
had to do with your output. This `counterspy' program was called
JEDGAR (a six-letterism pronounced as two syllables: /jed'gr/), in
honor of the former head of the FBI.

But there's more. JEDGAR would ask the user for `license to kill'. If
the user said yes, then JEDGAR would actually [15215]gun the job of
the [15216]luser who was spying. Unfortunately, people found that this
made life too violent, especially when tourists learned about it. One
of the systems hackers solved the problem by replacing JEDGAR with
another program that only pretended to do its job. It took a long time
to do this, because every copy of JEDGAR had to be patched. To this
day no one knows how many people never figured out that JEDGAR had
been defanged.

Interestingly, there is still a security module named JEDGAR alive as
of late 1994 -- in the Unisys MCP for large systems. It is unknown to
us whether the name is tribute or independent invention.

Node:The Story of Mel, Previous:[15217]OS and JEDGAR,
Up:[15218]Appendix A

The Story of Mel

This was posted to Usenet by its author, Ed Nather
([15219]utastro!nather), on May 21, 1983.
A recent article devoted to the macho side of programming
made the bald and unvarnished statement:

Real Programmers write in FORTRAN.

Maybe they do now,
in this decadent era of
Lite beer, hand calculators, and ``user-friendly'' software
but back in the Good Old Days,
when the term ``software'' sounded funny
and Real Computers were made out of drums and vacuum tubes,
Real Programmers wrote in machine code.
Not FORTRAN. Not RATFOR. Not, even, assembly language.
Machine Code.
Raw, unadorned, inscrutable hexadecimal numbers.

Lest a whole new generation of programmers
grow up in ignorance of this glorious past,
I feel duty-bound to describe,
as best I can through the generation gap,
how a Real Programmer wrote code.
I'll call him Mel,
because that was his name.

I first met Mel when I went to work for Royal McBee Computer Corp.,
a now-defunct subsidiary of the typewriter company.
The firm manufactured the LGP-30,
a small, cheap (by the standards of the day)
drum-memory computer,
and had just started to manufacture
the RPC-4000, a much-improved,
bigger, better, faster --- drum-memory computer.
Cores cost too much,
and weren't here to stay, anyway.
(That's why you haven't heard of the company,
or the computer.)

I had been hired to write a FORTRAN compiler
for this new marvel and Mel was my guide to its wonders.
Mel didn't approve of compilers.

``If a program can't rewrite its own code'',
he asked, ``what good is it?''

Mel had written,
in hexadecimal,
the most popular computer program the company owned.
It ran on the LGP-30
and played blackjack with potential customers
at computer shows.
Its effect was always dramatic.
The LGP-30 booth was packed at every show,
and the IBM salesmen stood around
talking to each other.
Whether or not this actually sold computers
was a question we never discussed.

Mel's job was to re-write
the blackjack program for the RPC-4000.
(Port? What does that mean?)
The new computer had a one-plus-one
addressing scheme,
in which each machine instruction,
in addition to the operation code
and the address of the needed operand,
had a second address that indicated where, on the revolving drum,
the next instruction was located.

In modern parlance,
every single instruction was followed by a GO TO!
Put that in Pascal's pipe and smoke it.

Mel loved the RPC-4000
because he could optimize his code:
that is, locate instructions on the drum
so that just as one finished its job,
the next would be just arriving at the ``read head''
and available for immediate execution.
There was a program to do that job,
an ``optimizing assembler'',
but Mel refused to use it.

``You never know where it's going to put things'',
he explained, ``so you'd have to use separate constants''.

It was a long time before I understood that remark.
Since Mel knew the numerical value
of every operation code,
and assigned his own drum addresses,
every instruction he wrote could also be considered
a numerical constant.
He could pick up an earlier ``add'' instruction, say,
and multiply by it,
if it had the right numeric value.
His code was not easy for someone else to modify.

I compared Mel's hand-optimized programs
with the same code massaged by the optimizing assembler program,
and Mel's always ran faster.
That was because the ``top-down'' method of program design
hadn't been invented yet,
and Mel wouldn't have used it anyway.
He wrote the innermost parts of his program loops first,
so they would get first choice
of the optimum address locations on the drum.
The optimizing assembler wasn't smart enough to do it that way.

Mel never wrote time-delay loops, either,
even when the balky Flexowriter
required a delay between output characters to work right.
He just located instructions on the drum
so each successive one was just past the read head
when it was needed;
the drum had to execute another complete revolution
to find the next instruction.
He coined an unforgettable term for this procedure.
Although ``optimum'' is an absolute term,
like ``unique'', it became common verbal practice
to make it relative:
``not quite optimum'' or ``less optimum''
or ``not very optimum''.
Mel called the maximum time-delay locations
the ``most pessimum''.

After he finished the blackjack program
and got it to run
(``Even the initializer is optimized'',
he said proudly),
he got a Change Request from the sales department.
The program used an elegant (optimized)
random number generator
to shuffle the ``cards'' and deal from the ``deck'',
and some of the salesmen felt it was too fair,
since sometimes the customers lost.
They wanted Mel to modify the program
so, at the setting of a sense switch on the console,
they could change the odds and let the customer win.

Mel balked.
He felt this was patently dishonest,
which it was,
and that it impinged on his personal integrity as a programmer,
which it did,
so he refused to do it.
The Head Salesman talked to Mel,
as did the Big Boss and, at the boss's urging,
a few Fellow Programmers.
Mel finally gave in and wrote the code,
but he got the test backwards,
and, when the sense switch was turned on,
the program would cheat, winning every time.
Mel was delighted with this,
claiming his subconscious was uncontrollably ethical,
and adamantly refused to fix it.

After Mel had left the company for greener pa$ture$,
the Big Boss asked me to look at the code
and see if I could find the test and reverse it.
Somewhat reluctantly, I agreed to look.
Tracking Mel's code was a real adventure.

I have often felt that programming is an art form,
whose real value can only be appreciated
by another versed in the same arcane art;
there are lovely gems and brilliant coups
hidden from human view and admiration, sometimes forever,
by the very nature of the process.
You can learn a lot about an individual
just by reading through his code,
even in hexadecimal.
Mel was, I think, an unsung genius.

Perhaps my greatest shock came
when I found an innocent loop that had no test in it.
No test. None.
Common sense said it had to be a closed loop,
where the program would circle, forever, endlessly.
Program control passed right through it, however,
and safely out the other side.
It took me two weeks to figure it out.

The RPC-4000 computer had a really modern facility
called an index register.
It allowed the programmer to write a program loop
that used an indexed instruction inside;
each time through,
the number in the index register
was added to the address of that instruction,
so it would refer
to the next datum in a series.
He had only to increment the index register
each time through.
Mel never used it.

Instead, he would pull the instruction into a machine register,
add one to its address,
and store it back.
He would then execute the modified instruction
right from the register.
The loop was written so this additional execution time
was taken into account ---
just as this instruction finished,
the next one was right under the drum's read head,
ready to go.
But the loop had no test in it.

The vital clue came when I noticed
the index register bit,
the bit that lay between the address
and the operation code in the instruction word,
was turned on ---
yet Mel never used the index register,
leaving it zero all the time.
When the light went on it nearly blinded me.

He had located the data he was working on
near the top of memory ---
the largest locations the instructions could address ---
so, after the last datum was handled,
incrementing the instruction address
would make it overflow.
The carry would add one to the
operation code, changing it to the next one in the instruction set:
a jump instruction.
Sure enough, the next program instruction was
in address location zero,
and the program went happily on its way.

I haven't kept in touch with Mel,
so I don't know if he ever gave in to the flood of
change that has washed over programming techniques
since those long-gone days.
I like to think he didn't.
In any event,
I was impressed enough that I quit looking for the
offending test,
telling the Big Boss I couldn't find it.
He didn't seem surprised.

When I left the company,
the blackjack program would still cheat
if you turned on the right sense switch,
and I think that's how it should be.
I didn't feel comfortable
hacking up the code of a Real Programmer.

This is one of hackerdom's great heroic epics, free verse or no. In a
few spare images it captures more about the esthetics and psychology
of hacking than all the scholarly volumes on the subject put together.
For an opposing point of view, see the entry for [15220]Real

[1992 postscript -- the author writes: "The original submission to the
net was not in free verse, nor any approximation to it -- it was
straight prose style, in non-justified paragraphs. In bouncing around
the net it apparently got modified into the `free verse' form now
popular. In other words, it got hacked on the net. That seems
appropriate, somehow." The author adds that he likes the `free-verse'
version better...]

[1999 update: Mel's last name is now known. The manual for the LGP-30
refers to "Mel Kaye of Royal McBee who did the bulk of the programming
[...] of the ACT 1 system".]

Node:Appendix B, Next:[15221]Appendix C, Previous:[15222]Appendix A,

A Portrait of J. Random Hacker

This profile reflects detailed comments on an earlier `trial balloon'
version from about a hundred Usenet respondents. Where comparatives
are used, the implicit `other' is a randomly selected segment of the
non-hacker population of the same size as hackerdom.

An important point: Except in some relatively minor respects such as
slang vocabulary, hackers don't get to be the way they are by
imitating each other. Rather, it seems to be the case that the
combination of personality traits that makes a hacker so conditions
one's outlook on life that one tends to end up being like other
hackers whether one wants to or not (much as bizarrely detailed
similarities in behavior and preferences are found in genetic twins
raised separately).
* [15224]General Appearance:
* [15225]Dress:
* [15226]Reading Habits:
* [15227]Other Interests:
* [15228]Physical Activity and Sports:
* [15229]Education:
* [15230]Things Hackers Detest and Avoid:
* [15231]Food:
* [15232]Politics:
* [15233]Gender and Ethnicity:
* [15234]Religion:
* [15235]Ceremonial Chemicals:
* [15236]Communication Style:
* [15237]Geographical Distribution:
* [15238]Sexual Habits:
* [15239]Personality Characteristics:
* [15240]Weaknesses of the Hacker Personality:
* [15241]Miscellaneous:

Node:General Appearance, Next:[15242]Dress, Up:[15243]Appendix B

General Appearance

Intelligent. Scruffy. Intense. Abstracted. Surprisingly for a
sedentary profession, more hackers run to skinny than fat; both
extremes are more common than elsewhere. Tans are rare.

Node:Dress, Next:[15244]Reading Habits, Previous:[15245]General
Appearance, Up:[15246]Appendix B


Casual, vaguely post-hippie; T-shirts, jeans, running shoes,
Birkenstocks (or bare feet). Long hair, beards, and moustaches are
common. High incidence of tie-dye and intellectual or humorous
`slogan' T-shirts (only rarely computer related; that would be too

A substantial minority prefers `outdoorsy' clothing -- hiking boots
("in case a mountain should suddenly spring up in the machine room",
as one famous parody put it), khakis, lumberjack or chamois shirts,
and the like.

Very few actually fit the "National Lampoon" Nerd stereotype, though
it lingers on at MIT and may have been more common before 1975. At
least since the late Seventies backpacks have been more common than
briefcases, and the hacker `look' has been more whole-earth than

Hackers dress for comfort, function, and minimal maintenance hassles
rather than for appearance (some, perhaps unfortunately, take this to
extremes and neglect personal hygiene). They have a very low tolerance
of suits and other `business' attire; in fact, it is not uncommon for
hackers to quit a job rather than conform to a dress code.

Female hackers almost never wear visible makeup, and many use none at

Node:Reading Habits, Next:[15247]Other Interests,
Previous:[15248]Dress, Up:[15249]Appendix B

Reading Habits

Omnivorous, but usually includes lots of science and science fiction.
The typical hacker household might subscribe to "Analog", "Scientific
American", "Whole-Earth Review", and "Smithsonian" (most hackers
ignore "Wired" and other self-consciously `cyberpunk' magazines,
considering them [15250]wannabee fodder). Hackers often have a reading
range that astonishes liberal arts people but tend not to talk about
it as much. Many hackers spend as much of their spare time reading as
the average American burns up watching TV, and often keep shelves and
shelves of well-thumbed books in their homes.

Node:Other Interests, Next:[15251]Physical Activity and Sports,
Previous:[15252]Reading Habits, Up:[15253]Appendix B

Other Interests

Some hobbies are widely shared and recognized as going with the
culture: science fiction, music, medievalism (in the active form
practiced by the Society for Creative Anachronism and similar
organizations), chess, go, backgammon, wargames, and intellectual
games of all kinds. (Role-playing games such as Dungeons and Dragons
used to be extremely popular among hackers but they lost a bit of
their luster as they moved into the mainstream and became heavily
commercialized. More recently, "Magic: The Gathering" has been widely
popular among hackers.) Logic puzzles. Ham radio. Other interests that
seem to correlate less strongly but positively with hackerdom include
linguistics and theater teching.

Node:Physical Activity and Sports, Next:[15254]Education,
Previous:[15255]Other Interests, Up:[15256]Appendix B

Physical Activity and Sports

Many (perhaps even most) hackers don't follow or do sports at all and
are determinedly anti-physical. Among those who do, interest in
spectator sports is low to non-existent; sports are something one
does, not something one watches on TV.

Further, hackers avoid most team sports like the plague. Volleyball
was long a notable exception, perhaps because it's non-contact and
relatively friendly; Ultimate Frisbee has become quite popular for
similar reasons. Hacker sports are almost always primarily
self-competitive ones involving concentration, stamina, and micromotor
skills: martial arts, bicycling, auto racing, kite flying, hiking,
rock climbing, aviation, target-shooting, sailing, caving, juggling,
skiing, skating, skydiving, scuba diving. Hackers' delight in
techno-toys also tends to draw them towards hobbies with nifty
complicated equipment that they can tinker with.

The popularity of martial arts in the hacker culture deserves special
mention. Many observers have noted it, and the connection has grown
noticeably stronger over time. In the 1970s, many hackers admired
martial arts disciplines from a distance, sensing a compatible ideal
in their exaltation of skill through rigorous self-discipline and
concentration. As martial arts became increasingly mainstreamed in the
U.S. and other western countries, hackers moved from admiring to doing
in large numbers. In 1997, for example, your humble editor recalls
sitting down with five strangers at the first Perl conference and
discovering that four of us were in active training in some sort of
martial art - and, what is more interesting, nobody at the table found
this particularly odd.

Today (2000), martial arts seems to have become established as the
hacker exercise form of choice, and the martial-arts culture combining
skill-centered elitism with a willingness to let anybody join seems a
stronger parallel to hacker behavior than ever. Common usages in
hacker slang un-ironically analogize programming to kung fu (thus, one
hears talk of "code-fu" or in reference to specific skills like
"HTML-fu"). Albeit with slightly more irony, today's hackers readily
analogize assimilation into the hacker culture with the plot of a Jet
Li movie: the aspiring newbie studies with masters of the tradition,
develops his art through deep meditation, ventures forth to perform
heroic feats of hacking, and eventually becomes a master who trains
the next generation of newbies.

Node:Education, Next:[15257]Things Hackers Detest and Avoid,
Previous:[15258]Physical Activity and Sports, Up:[15259]Appendix B


Nearly all hackers past their teens are either college-degreed or
self-educated to an equivalent level. The self-taught hacker is often
considered (at least by other hackers) to be better-motivated, and may
be more respected, than his school-shaped counterpart. Academic areas
from which people often gravitate into hackerdom include (besides the
obvious computer science and electrical engineering) physics,
mathematics, linguistics, and philosophy.

Node:Things Hackers Detest and Avoid, Next:[15260]Food,
Previous:[15261]Education, Up:[15262]Appendix B

Things Hackers Detest and Avoid

IBM mainframes. All the works of Microsoft. Smurfs, Ewoks, and other
forms of offensive cuteness. Bureaucracies. Stupid people. Easy
listening music. Television (with occasional exceptions for cartoons,
movies, and good SF like "Star Trek" classic or Babylon 5). Business
suits. Dishonesty. Incompetence. Boredom. COBOL. BASIC.
Character-based menu interfaces.

Node:Food, Next:[15263]Politics, Previous:[15264]Things Hackers Detest
and Avoid, Up:[15265]Appendix B


Ethnic. Spicy. Oriental, esp. Chinese and most esp. Szechuan, Hunan,
and Mandarin (hackers consider Cantonese vaguely déclassé). Hackers
prefer the exotic; for example, the Japanese-food fans among them will
eat with gusto such delicacies as fugu (poisonous pufferfish) and
whale. Thai food has experienced flurries of popularity. Where
available, high-quality Jewish delicatessen food is much esteemed. A
visible minority of Southwestern and Pacific Coast hackers prefers

For those all-night hacks, pizza and microwaved burritos are big.
Interestingly, though the mainstream culture has tended to think of
hackers as incorrigible junk-food junkies, many have at least mildly
health-foodist attitudes and are fairly discriminating about what they
eat. This may be generational; anecdotal evidence suggests that the
stereotype was more on the mark before the early 1980s.

Node:Politics, Next:[15266]Gender and Ethnicity, Previous:[15267]Food,
Up:[15268]Appendix B


Vaguely liberal-moderate, except for the strong libertarian contingent
which rejects conventional left-right politics entirely. The only safe
generalization is that hackers tend to be rather anti-authoritarian;
thus, both conventional conservatism and `hard' leftism are rare.
Hackers are far more likely than most non-hackers to either (a) be
aggressively apolitical or (b) entertain peculiar or idiosyncratic
political ideas and actually try to live by them day-to-day.

Node:Gender and Ethnicity, Next:[15269]Religion,
Previous:[15270]Politics, Up:[15271]Appendix B

Gender and Ethnicity

Hackerdom is still predominantly male. However, the percentage of
women is clearly higher than the low-single-digit range typical for
technical professions, and female hackers are generally respected and
dealt with as equals.

In the U.S., hackerdom is predominantly Caucasian with strong
minorities of Jews (East Coast) and Orientals (West Coast). The Jewish
contingent has exerted a particularly pervasive cultural influence
(see [15272]Food, above, and note that several common jargon terms are
obviously mutated Yiddish).

The ethnic distribution of hackers is understood by them to be a
function of which ethnic groups tend to seek and value education.
Racial and ethnic prejudice is notably uncommon and tends to be met
with freezing contempt.

When asked, hackers often ascribe their culture's gender- and
color-blindness to a positive effect of text-only network channels,
and this is doubtless a powerful influence. Also, the ties many
hackers have to AI research and SF literature may have helped them to
develop an idea of personhood that is inclusive rather than exclusive
-- after all, if one's imagination readily grants full human rights to
future AI programs, robots, dolphins, and extraterrestrial aliens,
mere color and gender can't seem very important any more.

Node:Religion, Next:[15273]Ceremonial Chemicals,
Previous:[15274]Gender and Ethnicity, Up:[15275]Appendix B


Agnostic. Atheist. Non-observant Jewish. Neo-pagan. Very commonly,
three or more of these are combined in the same person. Conventional
faith-holding Christianity is rare though not unknown.

Even hackers who identify with a religious affiliation tend to be
relaxed about it, hostile to organized religion in general and all
forms of religious bigotry in particular. Many enjoy `parody'
religions such as Discordianism and the Church of the SubGenius.

Also, many hackers are influenced to varying degrees by Zen Buddhism
or (less commonly) Taoism, and blend them easily with their `native'

There is a definite strain of mystical, almost Gnostic sensibility
that shows up even among those hackers not actively involved with
neo-paganism, Discordianism, or Zen. Hacker folklore that pays homage
to `wizards' and speaks of incantations and demons has too much
psychological truthfulness about it to be entirely a joke.

Node:Ceremonial Chemicals, Next:[15276]Communication Style,
Previous:[15277]Religion, Up:[15278]Appendix B

Ceremonial Chemicals

Most hackers don't smoke tobacco, and use alcohol in moderation if at
all. However, there has been something of a trend towards exotic beers
since about 1995, especially among younger Linux hackers apparently
influenced by Linus Torvalds's fondness for Guiness.

Limited use of non-addictive psychedelic drugs, such as cannabis, LSD,
psilocybin, nitrous oxide, etc., used to be relatively common and is
still regarded with more tolerance than in the mainstream culture. Use
of `downers' and opiates, on the other hand, appears to be
particularly rare; hackers seem in general to dislike drugs that make
them stupid. But [15279]on the gripping hand, many hackers regularly
wire up on caffeine and/or sugar for all-night hacking runs.

Node:Communication Style, Next:[15280]Geographical Distribution,
Previous:[15281]Ceremonial Chemicals, Up:[15282]Appendix B

Communication Style

See the discussions of speech and writing styles near the beginning of
this File. Though hackers often have poor person-to-person
communication skills, they are as a rule quite sensitive to nuances of
language and very precise in their use of it. They are often better at
writing than at speaking.

Node:Geographical Distribution, Next:[15283]Sexual Habits,
Previous:[15284]Communication Style, Up:[15285]Appendix B

Geographical Distribution

In the United States, hackerdom revolves on a Bay Area-to-Boston axis;
about half of the hard core seems to live within a hundred miles of
Cambridge (Massachusetts) or Berkeley (California), although there are
significant contingents in Los Angeles, in the Pacific Northwest, and
around Washington DC. Hackers tend to cluster around large cities,
especially `university towns' such as the Raleigh-Durham area in North
Carolina or Princeton, New Jersey (this may simply reflect the fact
that many are students or ex-students living near their alma maters).

Node:Sexual Habits, Next:[15286]Personality Characteristics,
Previous:[15287]Geographical Distribution, Up:[15288]Appendix B

Sexual Habits

Hackerdom easily tolerates a much wider range of sexual and lifestyle
variation than the mainstream culture. It includes a relatively large
gay and bisexual contingent. Hackers are somewhat more likely to live
in polygynous or polyandrous relationships, practice open marriage, or
live in communes or group houses. In this, as in general appearance,
hackerdom semi-consciously maintains `counterculture' values.

Node:Personality Characteristics, Next:[15289]Weaknesses of the Hacker
Personality, Previous:[15290]Sexual Habits, Up:[15291]Appendix B

Personality Characteristics

The most obvious common `personality' characteristics of hackers are
high intelligence, consuming curiosity, and facility with intellectual
abstractions. Also, most hackers are `neophiles', stimulated by and
appreciative of novelty (especially intellectual novelty). Most are
also relatively individualistic and anti-conformist.

Although high general intelligence is common among hackers, it is not
the sine qua non one might expect. Another trait is probably even more
important: the ability to mentally absorb, retain, and reference large
amounts of `meaningless' detail, trusting to later experience to give
it context and meaning. A person of merely average analytical
intelligence who has this trait can become an effective hacker, but a
creative genius who lacks it will swiftly find himself outdistanced by
people who routinely upload the contents of thick reference manuals
into their brains. [During the production of the first book version of
this document, for example, I learned most of the rather complex
typesetting language TeX over about four working days, mainly by
inhaling Knuth's 477-page manual. My editor's flabbergasted reaction
to this genuinely surprised me, because years of associating with
hackers have conditioned me to consider such performances routine and
to be expected. --ESR]

Contrary to stereotype, hackers are not usually intellectually narrow;
they tend to be interested in any subject that can provide mental
stimulation, and can often discourse knowledgeably and even
interestingly on any number of obscure subjects -- if you can get them
to talk at all, as opposed to, say, going back to their hacking.

It is noticeable (and contrary to many outsiders' expectations) that
the better a hacker is at hacking, the more likely he or she is to
have outside interests at which he or she is more than merely

Hackers are `control freaks' in a way that has nothing to do with the
usual coercive or authoritarian connotations of the term. In the same
way that children delight in making model trains go forward and back
by moving a switch, hackers love making complicated things like
computers do nifty stuff for them. But it has to be their nifty stuff.
They don't like tedium, nondeterminism, or most of the fussy, boring,
ill-defined little tasks that go with maintaining a normal existence.
Accordingly, they tend to be careful and orderly in their intellectual
lives and chaotic elsewhere. Their code will be beautiful, even if
their desks are buried in 3 feet of crap.

Hackers are generally only very weakly motivated by conventional
rewards such as social approval or money. They tend to be attracted by
challenges and excited by interesting toys, and to judge the interest
of work or other activities in terms of the challenges offered and the
toys they get to play with.

In terms of Myers-Briggs and equivalent psychometric systems,
hackerdom appears to concentrate the relatively rare INTJ and INTP
types; that is, introverted, intuitive, and thinker types (as opposed
to the extroverted-sensate personalities that predominate in the
mainstream culture). ENT[JP] types are also concentrated among hackers
but are in a minority.

Node:Weaknesses of the Hacker Personality, Next:[15292]Miscellaneous,
Previous:[15293]Personality Characteristics, Up:[15294]Appendix B

Weaknesses of the Hacker Personality

Hackers have relatively little ability to identify emotionally with
other people. This may be because hackers generally aren't much like
`other people'. Unsurprisingly, hackers also tend towards
self-absorption, intellectual arrogance, and impatience with people
and tasks perceived to be wasting their time.

As cynical as hackers sometimes wax about the amount of idiocy in the
world, they tend by reflex to assume that everyone is as rational,
`cool', and imaginative as they consider themselves. This bias often
contributes to weakness in communication skills. Hackers tend to be
especially poor at confrontation and negotiation.

Because of their passionate embrace of (what they consider to be) the
[15295]Right Thing, hackers can be unfortunately intolerant and
bigoted on technical issues, in marked contrast to their general
spirit of camaraderie and tolerance of alternative viewpoints
otherwise. Old-time [15296]ITS partisans look down on the ever-growing
hordes of [15297]Unix hackers; Unix aficionados despise [15298]VMS and
[15299]MS-DOS; and hackers who are used to conventional command-line
user interfaces loudly loathe mouse-and-menu based systems such as the
Macintosh. Hackers who don't indulge in [15300]Usenet consider it a
huge waste of time and [15301]bandwidth; fans of old adventure games
such as [15302]ADVENT and [15303]Zork consider [15304]MUDs to be
glorified chat systems devoid of atmosphere or interesting puzzles;
hackers who are willing to devote endless hours to Usenet or MUDs
consider [15305]IRC to be a real waste of time; IRCies think MUDs
might be okay if there weren't all those silly puzzles in the way.
And, of course, there are the perennial [15306]holy wars --
[15307]EMACS vs. [15308]vi, [15309]big-endian vs.
[15310]little-endian, RISC vs. CISC, etc., etc., etc. As in society at
large, the intensity and duration of these debates is usually
inversely proportional to the number of objective, factual arguments
available to buttress any position.

As a result of all the above traits, many hackers have difficulty
maintaining stable relationships. At worst, they can produce the
classic [15311]computer geek: withdrawn, relationally incompetent,
sexually frustrated, and desperately unhappy when not submerged in his
or her craft. Fortunately, this extreme is far less common than
mainstream folklore paints it -- but almost all hackers will recognize
something of themselves in the unflattering paragraphs above.

Hackers are often monumentally disorganized and sloppy about dealing
with the physical world. Bills don't get paid on time, clutter piles
up to incredible heights in homes and offices, and minor maintenance
tasks get deferred indefinitely.

1994-95's fad behavioral disease was a syndrome called Attention
Deficit Disorder (ADD), supposedly characterized by (among other
things) a combination of short attention span with an ability to
`hyperfocus' imaginatively on interesting tasks. In 1998-1999 another
syndrome that is said to overlap with many hacker traits entered
popular awareness: Asperger's syndrome (AS). This disorder is also
sometimes called `high-function autism', though researchers are
divided on whether AS is in fact a mild form of autism or a distinct
syndrome with a different etiology. AS patients exhibit mild to severe
deficits in interpreting facial and body-language cues and in modeling
or empathizing with others' emotions. Though some AS patients exhibit
mild retardation, others compensate for their deficits with high
intelligence and analytical ability, and frequently seek out technical
fields where problem-solving abilities are at a premium and people
skills are relatively unimportant. Both syndromes are thought to
relate to abnormalities in neurotransmitter chemistry, especially the
brain's processing of serotonin.

Many hackers have noticed that mainstream culture has shown a tendency
to pathologize and medicalize normal variations in personality,
especially those variations that make life more complicated for
authority figures and conformists. Thus, hackers aware of the issue
tend to be among those questioning whether ADD and AS actually exist;
and if so whether they are really `diseases' rather than extremes of a
normal genetic variation like having freckles or being able to taste
DPT. In either case, they have a sneaking tendency to wonder if these
syndromes are over-diagnosed and over-treated. After all, people in
authority will always be inconvenienced by schoolchildren or workers
or citizens who are prickly, intelligent individualists - thus, any
social system that depends on authority relationships will tend to
helpfully ostracize and therapize and drug such `abnormal' people
until they are properly docile and stupid and `well-socialized'.

So hackers tend to believe they have good reason for skepticism about
clinical explanations of the hacker personality. That being said, most
would also concede that some hacker traits coincide with indicators
for ADD and AS - the status of caffeeine as a hacker beverage of
choice may be connected to the fact that it bonds to the same neural
receptors as Ritalin, the drug most commonly prescribed for ADD. It is
probably true that boosters of both would find a rather higher rate of
clinical ADD among hackers than the supposedly mainstream-normal 3-5%
(AS is rarer and there are not yet good estimates of incidence as of

Node:Miscellaneous, Previous:[15312]Weaknesses of the Hacker
Personality, Up:[15313]Appendix B


Hackers are more likely to have cats than dogs (in fact, it is widely
grokked that cats have the hacker nature). Many drive incredibly
decrepit heaps and forget to wash them; richer ones drive spiffy
Porsches and RX-7s and then forget to have them washed. Almost all
hackers have terribly bad handwriting, and often fall into the habit
of block-printing everything like junior draftsmen.

Node:Appendix C, Next:[15314]Bibliography, Previous:[15315]Appendix B,

Helping Hacker Culture Grow

If you enjoyed the Jargon File, please help the culture that created
it grow and flourish. Here are several ways you can help:

o If you are a writer or journalist, don't say or write [15317]hacker
when you mean [15318]cracker. If you work with writers or journalists,
educate them on this issue and push them to do the right thing. If you
catch a newspaper or magazine abusing the work `hacker', write them
and straighten them out (this appendix includes a model letter).

o If you're a techie or computer hobbyist, get involved with one of
the free Unixes. Toss out that lame Microsoft OS, or confine it to one
disk partition and put Linux or FreeBSD or NetBSD on the other one.
And the next time your friend or boss is thinking about some
proprietary software `solution' that costs more than it's worth, be
ready to blow the competition away with open-source software running
over a Unix.

o Contribute to organizations like the Free Software Foundation that
promote the production of high-quality free and open-source software.
You can reach the Free Software Foundation at gnu@gnu.org, by phone at
+1-617-542-5942, or by snail-mail at 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA.

o Support the League for Programming Freedom, which opposes over-broad
software patents that constantly threaten to blow up in hackers'
faces, preventing them from developing innovative software for
tomorrow's needs. You can reach the League for Programming Freedom at
lpf@uunet.uu.net. by phone at +1 617 621 7084, or by snail-mail at 1
Kendall Square #143, P.O.Box 9171, Cambridge, Massachusetts 02139 USA.

o Join the continuing fight against Internet censorship, visit the
Center for Democracy and Technology Home Page at

o If you do nothing else, please help fight government attempts to
seize political control of Internet content and restrict strong
cryptography. The so-called `Communications Decency Act' was declared
unconstitutional by the Supreme Court, but U.S. cryptography policy
still infringes our First Amendment rights. Surf to the Center for
Democracy and technology's home page at [15320]http://www.cdt.org to
see what you can do to help fight censorship of the net.

Here's the text of a letter RMS wrote to the Wall Street Journal to
complain about their policy of using "hacker" only in a pejorative
sense. We hear that most major newspapers have the same policy. If
you'd like to help change this situation, send your favorite newspaper
the same letter - or, better yet, write your own letter.

Dear Editor:

This letter is not meant for publication, although you can publish
it if you wish. It is meant specifically for you, the editor, not
the public.

I am a hacker. That is to say, I enjoy playing with computers --
working with, learning about, and writing clever computer programs.
I am not a cracker; I don't make a practice of breaking computer

There's nothing shameful about the hacking I do. But when I tell
people I am a hacker, people think I'm admitting something naughty
-- because newspapers such as yours misuse the word "hacker",
giving the impression that it means "security breaker" and nothing
else. You are giving hackers a bad name.

The saddest thing is that this problem is perpetuated deliberately.
Your reporters know the difference between "hacker" and "security
breaker". They know how to make the distinction, but you don't let
them! You insist on using "hacker" pejoratively. When reporters try
to use another word, you change it. When reporters try to explain
the other meanings, you cut it.

Of course, you have a reason. You say that readers have become used
to your insulting usage of "hacker", so that you cannot change it
now. Well, you can't undo past mistakes today; but that is no
excuse to repeat them tomorrow.

If I were what you call a "hacker", at this point I would threaten
to crack your computer and crash it. But I am a hacker, not a
cracker. I don't do that kind of thing! I have enough computers to
play with at home and at work; I don't need yours. Besides, it's
not my way to respond to insults with violence. My response is this

You owe hackers an apology; but more than that, you owe us ordinary

Sincerely, etc.

Node:Bibliography, Previous:[15321]Appendix C, Up:[15322]Top


Here are some other books you can read to help you understand the
hacker mindset.

Escher, Bach: An Eternal Golden BraidGödel, Escher, Bach: An Eternal
Golden Braid
Douglas Hofstadter
Basic Books, 1979
ISBN 0-394-74502-7

This book reads like an intellectual Grand Tour of hacker
preoccupations. Music, mathematical logic, programming, speculations
on the nature of intelligence, biology, and Zen are woven into a
brilliant tapestry themed on the concept of encoded self-reference.
The perfect left-brain companion to "Illuminatus".

I. "The Eye in the Pyramid"
II. "The Golden Apple"
III. "Leviathan".
Robert Shea and Robert Anton Wilson
Dell, 1988
ISBN 0-440-53981-1

This work of alleged fiction is an incredible berserko-surrealist
rollercoaster of world-girdling conspiracies, intelligent dolphins,
the fall of Atlantis, who really killed JFK, sex, drugs, rock'n'roll,
and the Cosmic Giggle Factor. First published in three volumes, but
there is now a one-volume trade paperback, carried by most chain
bookstores under SF. The perfect right-brain companion to Hofstadter's
"Gödel, Escher, Bach". See [15323]Eris, [15324]Discordianism,
[15325]random numbers, [15326]Church of the SubGenius.

The Hitchhiker's Guide to the Galaxy
Douglas Adams
Pocket Books, 1981
ISBN 0-671-46149-4

This `Monty Python in Space' spoof of SF genre traditions has been
popular among hackers ever since the original British radio show. Read
it if only to learn about Vogons (see [15327]bogon) and the
significance of the number 42 (see [15328]random numbers) -- and why
the winningest chess program of 1990 was called `Deep Thought'.

The Tao of Programming
James Geoffrey
Infobooks, 1987
ISBN 0-931137-07-1

This gentle, funny spoof of the "Tao Te Ching" contains much that is
illuminating about the hacker way of thought. "When you have learned
to snatch the error code from the trap frame, it will be time for you
to leave."

Steven Levy
Anchor/Doubleday 1984
ISBN 0-385-19195-2

Levy's book is at its best in describing the early MIT hackers at the
Model Railroad Club and the early days of the microcomputer
revolution. He never understood Unix or the networks, though, and his
enshrinement of Richard Stallman as "the last true hacker" turns out
(thankfully) to have been quite misleading. Despite being a bit dated
and containing some minor errors (many fixed in the paperback
edition), this remains a useful and stimulating book that captures the
feel of several important hacker subcultures.

The Computer Contradictionary
Stan Kelly-Bootle
MIT Press, 1995
ISBN 0-262-61112-0

This pastiche of Ambrose Bierce's famous work is similar in format to
the Jargon File (and quotes several entries from TNHD-2) but somewhat
different in tone and intent. It is more satirical and less
anthropological, and is largely a product of the author's literate and
quirky imagination. For example, it defines `computer science' as "a
study akin to numerology and astrology, but lacking the precision of
the former and the success of the latter" and `implementation' as "The
fruitless struggle by the talented and underpaid to fulfill promises
made by the rich and ignorant"; `flowchart' becomes "to obfuscate a
problem with esoteric cartoons". Revised and expanded from "The
Devil's DP Dictionary", McGraw-Hill 1981, ISBN 0-07-034022-6; that
work had some stylistic influence on TNHD-1.

The Devouring Fungus: Tales from the Computer Age
Karla Jennings
Norton, 1990
ISBN 0-393-30732-8

The author of this pioneering compendium knits together a great deal
of computer- and hacker-related folklore with good writing and a few
well-chosen cartoons. She has a keen eye for the human aspects of the
lore and is very good at illuminating the psychology and evolution of
hackerdom. Unfortunately, a number of small errors and awkwardnesses
suggest that she didn't have the final manuscript checked over by a
native speaker; the glossary in the back is particularly embarrassing,
and at least one classic tale (the Magic Switch story, retold here
under [15329]A Story About Magic in Appendix A is given in incomplete
and badly mangled form. Nevertheless, this book is a win overall and
can be enjoyed by hacker and non-hacker alike.

The Soul of a New Machine
Tracy Kidder
Little, Brown, 1981
(paperback: Avon, 1982
ISBN 0-380-59931-7)

This book (a 1982 Pulitzer Prize winner) documents the adventure of
the design of a new Data General computer, the MV-8000 Eagle. It is an
amazingly well-done portrait of the hacker mindset -- although largely
the hardware hacker -- done by a complete outsider. It is a bit thin
in spots, but with enough technical information to be entertaining to
the serious hacker while providing non-technical people a view of what
day-to-day life can be like -- the fun, the excitement, the disasters.
During one period, when the microcode and logic were glitching at the
nanosecond level, one of the overworked engineers departed the
company, leaving behind a note on his terminal as his letter of
resignation: "I am going to a commune in Vermont and will deal with no
unit of time shorter than a season."

Life with UNIX: a Guide for Everyone
Don Libes and Sandy Ressler
Prentice-Hall, 1989
ISBN 0-13-536657-7

The authors of this book set out to tell you all the things about Unix
that tutorials and technical books won't. The result is gossipy,
funny, opinionated, downright weird in spots, and invaluable. Along
the way they expose you to enough of Unix's history, folklore and
humor to qualify as a first-class source for these things. Because so
much of today's hackerdom is involved with Unix, this in turn

Book of the day: