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[though GLS and I can personally confirm only that they were
already common in the mid-1970s --- ESR].

:-ware: [from `software'] suff. Commonly used to form jargon terms
for classes of software. For examples, see {careware},
{crippleware}, {crudware}, {freeware}, {fritterware},
{guiltware}, {liveware}, {meatware}, {payware},
{psychedelicware}, {shareware}, {shelfware}, {vaporware},

:/dev/null: /dev-nuhl/ [from the UNIX null device, used as a data
sink] n. A notional `black hole' in any information space being
discussed, used, or referred to. A controversial posting, for
example, might end "Kudos to rasputin@kremlin.org, flames to
/dev/null". See {bit bucket}.

:0: Numeric zero, as opposed to `O' (the 15th letter of the English
alphabet). In their unmodified forms they look a lot alike, and
various kluges invented to make them visually distinct have
compounded the confusion. If your zero is center-dotted and
letter-O is not, or if letter-O looks almost rectangular but zero
more like an American football stood on end, you're probably
looking at a modern character display (though the dotted zero seems
to have originated as an option on IBM 3270 controllers). If your
zero is slashed but letter-O is not, you're probably looking at an
old-style ASCII graphic set descended from the default typewheel on
the venerable ASR-33 Teletype (Scandinavians, for whom slashed-O is
a letter, curse this arrangement). If letter-O has a slash across
it and the zero does not, your display is tuned for a very old
convention used at IBM and a few other early mainframe makers
(Scandinavians curse *this* arrangement even more, because it
means two of their letters collide). Some Burroughs/Unisys
equipment displays a zero with a *reversed* slash. And yet
another convention common on early line printers left zero
unornamented but added a tail or hook to the letter-O so that it
resembled an inverted Q or cursive capital letter-O. Are we
sufficiently confused yet?

:1TBS: // n. The "One True Brace Style"; see {indent style}.

:120 reset: /wuhn-twen'tee ree'set/ [from 120 volts, U.S. wall
voltage] n. To cycle power on a machine in order to reset or unjam
it. Compare {Big Red Switch}, {power cycle}.

:2: infix. In translation software written by hackers, infix 2 often
represents the syllable *to* with the connotation
`translate to': as in dvi2ps (DVI to PostScript), int2string
(integer to string), and texi2roff (Texinfo to [nt]roff).

:@-party: /at'par`tee/ [from the @-sign in an Internet address]
n. (alt. `@-sign party' /at'si:n par`tee/) A semi-closed
party thrown for hackers at a science-fiction convention (esp.
the annual Worldcon); one must have a {network address} to
get in, or at least be in company with someone who does. One of
the most reliable opportunities for hackers to meet face to face
with people who might otherwise be represented by mere phosphor
dots on their screens. Compare {boink}.

:@Begin: // See {\begin}.

:\begin: // [from the LaTeX command] With \end, used
humorously in writing to indicate a context or to remark on the
surrounded text. For example:

Predicate logic is the only good programming
language. Anyone who would use anything else
is an idiot. Also, all computers should be
tredecimal instead of binary.

The Scribe users at CMU and elsewhere used to use @Begin/@End in
an identical way (LaTeX was built to resemble Scribe). On USENET,
this construct would more frequently be rendered as `'
and `'.

:(Lexicon Entries End Here):

:Appendix A: Hacker Folklore

This appendix contains several legends and fables that illuminate the
meaning of various entries in the lexicon.

:The Meaning of `Hack':

"The word {hack} doesn't really have 69 different meanings", according
to MIT hacker Phil Agre. "In fact, {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 {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 {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 {pseudo} and {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 {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).

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 subverted.

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 {walking drives}).
* The card-punch output device would occasionally start up of
itself and punch a {lace card}. These would usually jam in
the punch.
* 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

Naturally, the operator called in the operating-system developers.
They found the bandit ghost jobs running, and X'ed them... and were
once again surprised. When Robin Hood was X'ed, 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.

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.

: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 {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 {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]

:A Story About `Magic': (by GLS)

Some years ago, I 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
{dike}d it out. We then revived the computer and it has run fine ever

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 {magic}.

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

:A Selection of 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. 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."


This story says a lot about the 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 (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 {gun} the job of the
{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

:The Story of Mel, a Real Programmer:

This was posted to USENET by its author, Ed Nather (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 {real programmer}.

[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."]

:Appendix B: 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).

: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.


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 obvious).

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

Very few actually fit the `National Lampoon' Nerd stereotype, though it
lingers on at MIT and may have been more common before 1975. These
days, backpacks are more common than briefcases, and the hacker `look'
is more whole-earth than whole-polyester.

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

:Reading Habits:

Omnivorous, but usually includes lots of science and science fiction.
The typical hacker household might subscribe to `Analog', `Scientific
American', `Co-Evolution Quarterly', and `Smithsonian'. 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.

: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.) Logic puzzles.
Ham radio. Other interests that seem to correlate less strongly but
positively with hackerdom include linguistics and theater teching.

: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 is a
notable exception, perhaps because it's non-contact and relatively
friendly). 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
(ice and roller). Hackers' delight in techno-toys also tends to draw
them towards hobbies with nifty complicated equipment that they can
tinker with.


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.

:Things Hackers Detest and Avoid:

IBM mainframes. Smurfs, Ewoks, and other forms of offensive cuteness.
Bureaucracies. Stupid people. Easy listening music. Television
(except for cartoons, movies, the old "Star Trek", and the new
"Simpsons"). Business suits. Dishonesty. Incompetence.
Boredom. COBOL. BASIC. Character-based menu interfaces.


Ethnic. Spicy. Oriental, esp. Chinese and most esp. Szechuan, Hunan,
and Mandarin (hackers consider Cantonese vaguely d'eclass'e). 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 Mexican.

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 10--15 years ago.


Vaguely left of center, 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.

: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 {Food},
above, and note that several common jargon terms are obviously mutated

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 AI
programs, robots, dolphins, and extraterrestrial aliens, mere color and
gender can't seem very important any more.


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.

:Ceremonial Chemicals:

Most hackers don't smoke tobacco, and use alcohol in moderation if at
all (though there is a visible contingent of exotic-beer fanciers, and a
few hackers are serious oenophiles). Limited use of non-addictive
psychedelic drugs, such as cannabis, LSD, psilocybin, and 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 `dumb them down'. On the third hand, many
hackers regularly wire up on caffeine and/or sugar for all-night hacking

: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 extremely sensitive to nuances
of language and very precise in their use of it. They are often better
at writing than at speaking.

: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).

:Sexual Habits:

Hackerdom tolerates a much wider range of sexual and lifestyle variation
than the mainstream culture. It includes a relatively large gay and bi
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.

: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 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 competent.

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.

: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
{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
{{ITS}} partisans look down on the ever-growing hordes of {{UNIX}}
hackers; UNIX aficionados despise {VMS} and {{MS-DOS}}; and hackers who
are used to conventional command-line user interfaces loathe
mouse-and-menu based systems such as the Macintosh. Hackers who don't
indulge in {USENET} consider it a huge waste of time and {bandwidth};
fans of old adventure games such as {ADVENT} and {Zork} consider {MUD}s
to be glorified chat systems devoid of atmosphere or interesting
puzzles; hackers who are willing to devote endless hours to USENET or
MUDs consider {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 {holy wars} -- {EMACS} vs. {vi},
{big-endian} vs. {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 {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.

The sort of person who uses phrases like `incompletely socialized'
usually thinks hackers are. Hackers regard such people with contempt
when they notice them at all.


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.

:Appendix C: Bibliography

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

:G"odel, 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 `G"odel,
Escher, Bach'. See {Eris}, {Discordianism}, {random numbers}, {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 {bogon}) and the significance of
the number 42 (see {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

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. Numerous minor factual errors also mar the
text; for example, Levy's claim that the original Jargon File derived
from the TMRC Dictionary (the File originated at Stanford and was
brought to MIT in 1976; the co-authors of the first edition had never
seen the dictionary in question). There are also numerous misspellings
in the book that inflame the passions of old-timers; as Dan Murphy, the
author of TECO, once said: "You would have thought he'd take the trouble
to spell the name of a winning editor right." Nevertheless, this
remains a useful and stimulating book that captures the feel of several
important hackish subcultures.

:The Devil's DP Dictionary:
Stan Kelly-Bootle
McGraw-Hill, 1981
ISBN 0-07-034022-6

This pastiche of Ambrose Bierce's famous work is similar in format to
the Jargon File (and quotes several entries from jargon-1) 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 "the boring art of coping with
a large number of trivialities."

: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
{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 Eclipse. 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 illuminates many
of its in-jokes and preoccupations.

:True Names ... and Other Dangers:
Vernor Vinge
Baen Books, 1987
ISBN 0-671-65363-6

Hacker demigod Richard Stallman believes the title story of this book
"expresses the spirit of hacking best". This may well be true; it's
certainly difficult to recall a better job. The other stories in this
collection are also fine work by an author who is perhaps one of today's
very best practitioners of hard SF.

:Cyberpunk: Outlaws and Hackers on the Computer Frontier:
Katie Hafner & John Markoff
Simon & Schuster 1991
ISBN 0-671-68322-5

This book gathers narratives about the careers of three notorious
crackers into a clear-eyed but sympathetic portrait of hackerdom's dark
side. The principals are Kevin Mitnick, "Pengo" and "Hagbard" of the
Chaos Computer Club, and Robert T. Morris (see {RTM}, sense 2) .
Markoff and Hafner focus as much on their psychologies and motivations
as on the details of their exploits, but don't slight the latter. The
result is a balanced and fascinating account, particularly useful when
read immediately before or after Cliff Stoll's {The Cuckoo's Egg}. It
is especially instructive to compare RTM, a true hacker who blundered,
with the sociopathic phone-freak Mitnick and the alienated, drug-addled
crackers who made the Chaos Club notorious. The gulf between {wizard}
and {wannabee} has seldom been made more obvious.

John Barry
MIT Press 1991
ISBN 0-262-02333-4

Barry's book takes a critical and humorous look at the `technobabble' of
acronyms, neologisms, hyperbole, and metaphor spawned by the computer
industry. Though he discusses some of the same mechanisms of jargon
formation that occur in hackish, most of what he chronicles is actually
suit-speak --- the obfuscatory language of press releases, marketroids,
and Silicon Valley CEOs rather than the playful jargon of hackers (most
of whom wouldn't be caught dead uttering the kind of pompous,
passive-voiced word salad he deplores).

:The Cuckoo's Egg:
Clifford Stoll
Doubleday 1989
ISBN 0-385-24946-2

Clifford Stoll's absorbing tale of how he tracked Markus Hess and the
Chaos Club cracking ring nicely illustrates the difference between
`hacker' and `cracker'. Stoll's portrait of himself, his lady Martha,
and his friends at Berkeley and on the Internet paints a marvelously
vivid picture of how hackers and the people around them like to live and
what they think.

#====================== THE JARGON FILE ENDS HERE ======================#

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