Part 60

"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 said.

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."

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OS and JEDGAR

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 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 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.

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The Story of Mel

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. Directly.

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." 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".]

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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:

Dress:

Reading Habits:

Other Interests:

Physical

## Activity and Sports:

Education:

Things Hackers Detest and Avoid:

Food:

Politics:

Gender and Ethnicity:

Religion:

Ceremonial Chemicals:

Communication Style:

Geographical Distribution:

Sexual Habits:

Personality Characteristics:

Weaknesses of the Hacker Personality:

Miscellaneous:

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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.

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Dress

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 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 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 all.

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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 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.

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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.

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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.

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Education

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.

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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.

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Food

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 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 before the early 1980s.

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Politics

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.

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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 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.

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Religion

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' religions.

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.

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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 on the gripping hand, many hackers regularly wire up on caffeine and/or sugar for all-night hacking runs.

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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.