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 idea.
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. And, in fact, the device was not entirely useless; when combined with a modem board, it became a crude but serviceable terminal. —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]
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 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 magic.
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.
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 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.”
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: /jedīgr/), 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 1999 — in the Unisys MCP for large systems. It is unknown to us whether the name is tribute or independent invention.
This was posted to Usenet by its author, Ed Nather (<nather@astro.as.utexas.edu>), 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,
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. (But 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 than his prose original...]
[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”.]
[2001: The Royal McBee LPG-30 turns out to have one other claim to fame. It turns out that meteorologist Edward Lorenz was doing weather simulations on an LGP-30 when, in 1961, he discovered the “Butterfly Effect” and computational chaos. This seems, somehow, appropriate.]
[2002: A copy of the programming manual for the LGP-30 lives at http://ed-thelen.org/comp-hist/lgp-30-man.html]