Hackers

by Steven Levy

  This analog alchemist, the new hacker king, was showing a deeply impressed group of PDP-1 programmers how a solitary college freshman could wrest control of the nearly one hundred-year-old phone system, using it not for profit but for sheer joyriding exploration. Word spread of these exploits, and Nelson began to achieve heroic status around TMRC and the Kluge Room; soon some of the more squeamish PDP-1 people were doing some hand-wringing about whether he had gone too far. Greenblatt did not think so, nor did any true hacker: people had done that sort of thing around TMRC for years; and if Nelson took things a step beyond, that was a positive outgrowth of the Hacker Ethic. But when John McKenzie heard of it he ordered Nelson to stop, probably realizing that there was not much he could do to slow Stew Nelson’s eternal quest for systems knowledge. “How can you stop talent like that?” he later reflected. As it turned out, things were going to go much further before Stewart Nelson was through. In some ways, they would never stop.

  Nelson’s freshman pyrotechnics were not so startling in light of his life before MIT. Born in the Bronx, Nelson was the son of a physicist-turned-engineer who had done some pioneering work on color TV design. Stewart’s own interest in electronics, though, needed no parental urging. It was as natural as walking, and by the time he was five he was building crystal radios. At eight, he was working on dual-relay burglar alarms. He had little interest, socially or educationally, in school, but gravitated to the electronics shop, where he’d engage in relentless experimentation. It wasn’t long before the other kids’ mothers would ban their children from playing with Stewart—they were afraid that their progeny would be fried by a dose of electricity. These were inevitable dangers of fooling around with powerful vacuum tube circuits and state-of-the-art transistors powered by 110 V electrical lines. Stew on occasion would get shocks so severe that he’d be painfully jolted. He would later tell stories of his equipment flying halfway across the room and exploding into smithereens. After one particularly searing shock, he swore off playing with electricity. But after about two days he was back at it, a young loner working on fantastic projects.

  Stew loved the telephone. His family had moved to Haddonfield, New Jersey, and he soon found out that by clicking the switches on which the receiver rests, you could actually dial a number. Someone on the other end will be saying, “Hello . . . yes? Hello?" and you realize that this is not just a random piece of equipment, but something hooked to a system that you can endlessly explore. Stewart Nelson was soon building things that few of his neighbors in the mid-1950s had seen, like automatic dialers and gadgets that could connect to several phone lines, receiving a call on one line and automatically calling out on the other. He learned to handle telephone equipment with the deftness with which an artist wields his tools; witnesses would later report how Nelson, when confronted with a phone, would immediately dismantle it, first removing the filter which prevents the caller from hearing the dialing signals, and then making a few adjustments so that the phone would dial significantly faster. Essentially, he was reprogramming the telephone, unilaterally debugging Western Electric equipment.

  Stew’s father died when he was fourteen, and his mother moved them up to Poughkeepsie, New York. He struck a deal with his high school teachers wherein he would fix their radios and televisions in exchange for not having to go to class. Instead, he spent time at a small radio station starting up nearby—Nelson “pretty much put it together,” he later explained, connecting the elements, tuning the transmitter, finding sources of noise and hums in the system. When the radio station was running, he was the main engineer, and sometimes he would even be the disc jockey. Every glitch in the system was a new adventure, a new invitation to explore, to try something new, to see what might happen. To Stewart Nelson, wanting to find out what might happen was the ultimate justification, stronger than self-defense or temporary insanity.

  With that attitude, he fit in comfortably at the Tech Model Railroad Club and the PDP-1. There had already been avid interest in “phone hacking” around the club; with Nelson around, that interest could really flower. Besides being a technical genius, Nelson would attack problems with bird-dog perseverance. “He approached problems by taking action,” Donald Eastlake, a hacker in Nelson’s class, later recalled. “He was very persistent. If you try a few times and give up, you’ll never get there. But if you keep at it . . . There’s a lot of problems in the world which can really be solved by applying two or three times the persistence that other people will.”

  Nelson was displaying an extension of the Hacker Ethic—if we all acted on our drive to discover, we’d discover more, produce more, be in control of more. Naturally, the phone system was his initial object of exploration at MIT. First the PDP-1 and later the PDP-6 were ideal tools to use in these excursions. But even as Nelson set off on these electronic journeys, he adhered to the unofficial hacker morality. You could call anywhere, try anything, experiment endlessly, but you should not do it for financial gain. Nelson disapproved of those MIT students who built “blue boxes”—hardware devices to make illegal calls—for the purpose of ripping off the phone company. Nelson and the hackers believed that they were helping the phone company. They would get hold of priority phone company lines to various locations around the country and test them. If they didn’t work, they would report it to the appropriate repair service.

  To do this, of course, you had to successfully impersonate technical employees of the Bell Telephone System, but the hackers became quite accomplished at that, especially after reading such contraband books as the classic Principles of Electricity and Electronics Applied to Telephone and Telegraph Work, or Notes on Distant Dialing, or recent issues of the Bell System Technical Journal.

  Armed with this information, you could travel around the world, saying to an operator, “I’m calling from the test board in Hackensack and I’d like you to switch me through to Rome. We’re trying to test the circuit.” She would “write up the number,” which would lead you to another number, and soon you would be asking a phone operator in Italy what the weather was like there. Or you’d use the PDP-1 in Blue Box Mode, letting it route and reroute your calls until you were connected to a certain phone number in England where callers would hear a children’s bedtime story, a number inaccessible from this country except by the blue box.

  In the mid-sixties, the phone company was establishing its system of toll-free area-code-800 numbers. Naturally, the hackers knew about this. With scientific precision, they would attempt to chart these undocumented realms: excursions to 800-land could send you to bizarre places, from the Virgin Islands to New York. Eventually someone from the phone company gave a call to the line near the computer, asking what were these four hundred or so calls to places that, as far as the phone company was concerned, did not exist. The unlucky Cambridge branch of the phone company had coped with MIT before, and would again—at one point, they burst into the ninth floor at Tech Square, and demanded that the hackers show them the blue box. When the hackers pointed to the PDP-6, the frustrated officials threatened to take the whole machine, until the hackers unhooked the phone interface and handed it over.

  Though Nelson’s initial interest in the PDP-1 was its phone hacking potential, he became more versatile with it, and was eventually programming all sorts of things. The more he programmed, the better he got, and the better he got, the more he wanted to program. He would sit by the console of the machine while some graduate student would fumble with a program, and he’d sort of peck around the grad student’s back, which would only make the graduate student fumble more, and finally he would burst out, “If I solve that problem for you, will you let me have the computer?” The grad student, who probably had been trying to crack the problem for weeks, would agree, not really believing this quirky fellow could solve it, but Nelson would already be pushing him away, sitting down at the console, bringing up the “TECO” editing program, and pounding in code at a blinding rate. In five minutes, he’d be done, leaping up to print it on the Model 33 teletyp
e near the machine, and in a rush of motion he’d rip the paper off the line printer, run back to the machine, pull off the tape with the grad student’s program, and send him off. Then he’d do his own hacking.

  He knew no bounds. He used both the PDP-1 in the Kluge Room and the newer machine at Project MAC. When others used the PDP-1 and its limited instruction set, they might have grumbled at having to use several instructions for a simple operation, and then figured out the subroutines to do the programs. Nelson could bum code with the best of them, but he wanted more instructions actually on the machine. Putting an instruction on the computer itself—in hardware—is a rather tricky operation. When the TX-0 was given its new instructions, it had to be shut down for a while until official priests, trained to the level of Pope, almost, performed the necessary brain surgery. This seemed only logical—who would expect a university to allow underclassmen to tamper with the delicate parts of a fantastically expensive computer?

  No one. In fact, Dan Edwards, one of Minsky’s graduate students who had done some hacking on Spacewar, had set himself up as protector of the hardware. According to Gosper, Edwards had declared that “Anyone who does as much as change a ribbon in the typewriter is going to get permanently barred from this place!” But hackers did not care what the university allowed or didn’t allow. What Dan Edwards thought was of even less concern: his position of authority, like that of most bureaucrats, was deemed an accident.

  Nelson thought that adding an “add to memory” instruction would improve the machine. It would take months, perhaps, to go through channels to do it, and if he did it himself he would learn something about the way the world worked. So one night Stewart Nelson spontaneously convened the Midnight Computer Wiring Society. This was an entirely ad hoc organization which would, when the flow of history required it, circumvent the regulations of the Massachusetts Institute of Technology against unauthorized tampering with expensive computers. The MCWS, which that night consisted of Nelson, a student worker, and several interested bystanders, opened up the cabinet and proceeded to rewire the PDP-1. Nelson fused a couple of diodes between the “add” line and the “store” line outputs of the instruction decoder, and had himself a new op-code, which presumably supported all the previous instructions. He then proceeded to reassemble the machine to an apparent pristine state.

  The machine was taken through its paces by the hackers that night, and worked fine. But the next day an Officially Sanctioned User named Margaret Hamilton showed up on the ninth floor to work on something called a Vortex Model for a weather-simulation project she was working on. Margaret Hamilton was just beginning a programming career, which would see her eventually in charge of onboard computers on the Apollo moon shot, and the Vortex program at that time was a very big program for her. She was well aware of the hackers’ playfulness around the ninth floor, and she was moderately friendly with some of them, even though they would eventually blend into one collective personality in her memory: one unkempt, though polite, young male whose love for the computer had made him lose all reason.

  The assembler that Margaret Hamilton used with her Vortex program was not the hacker-written MIDAS assembler, but the DEC-supplied DECAL system that the hackers considered absolutely horrid. So of course Nelson and the MCWS, when testing the machine the previous night, had not used the DECAL assembler. They had never even considered the possibility that the DECAL assembler accessed the instruction code in a different manner than MIDAS, a manner that was affected to a greater degree by the slight forward voltage drop created by the addition of two diodes between the add line and the store line. Margaret Hamilton, of course, was unaware that the PDP-1 had undergone surgery the previous night. So she did not immediately know the reason why her Vortex program, after she fed it in with the DECAL assembler . . . broke. Stopped working. Died. Mysteriously, a perfectly good program had bombed. Though programs often did that for various reasons, this time Margaret Hamilton complained about it, and someone looked into why, and someone else fingered the Midnight Computer Wiring Society. So there were repercussions. Reprimands.

  That was not the end of the Midnight Computer Wiring Society. Edwards and his ilk could not stay up all night to watch the machines. Besides, Minsky and the others in charge of Project MAC knew that the hackers’ nocturnal activities were turning into a hands-on postgraduate course on logic design and hardware skills. Partially because Nelson and the others got good enough so disasters like the Great Margaret Hamilton Program Clobber were less likely to occur, the official AI lab ban against hardware tampering gradually faded away to the status of one of those antiquated laws that nobody bothers to take off the books, like a statute forbidding you from publicly beating a horse on Sunday. Eventually the Midnight Computer Wiring Society felt free enough to change instructions, make new hardware connections, and even rig the computer to the room lights on the ninth floor, so that when you fired up the TECO text-editing program, the lights automatically dimmed so that you could read the CRT display more easily.

  This last hack had an unexpected consequence. The TECO editor rang a bell on the teletype to signal when the user made an error. This normally was no problem, but on certain days the machine got flaky, and was extremely sensitive to power line variations—like those generated by the bell on the teletype. Those times, when someone made a mistake with TECO, the bell would ring, and the machine would be thrown into randomness. The computer would be out of control; it would type spastically, ringing the bell, and most unsettling, turning the room lights on and off. The computer had run amok! Science-fiction Armageddon!

  The hackers considered this extremely humorous.

  The people in charge of the lab, particularly Marvin Minsky, were very understanding about these things. Marvin, as the hackers called him (they invariably called each other by last name), knew that the Hacker Ethic was what kept the lab productive, and he was not going to tamper with one of the crucial components of hackerism. On the other hand, there was Stew Nelson, constantly at odds with the rules, a hot potato who got hotter when he was eventually caught red-handed at phone hacking. Something had to be done. So Minsky called up his good friend Ed Fredkin, and told him he had this problem with an incredibly brilliant nineteen-year-old who had a penchant for getting into sophisticated mischief. Could Fredkin hire him?

  • • • • • • • •

  Besides being a close friend of Marvin Minsky and the founder of Information International Incorporated (Triple-I), Ed Fredkin considered himself the greatest programmer in the world.

  A dark-haired man with warm brown eyes behind glasses that rested on a nose with a slight intellectual hook, Fredkin had never finished college. He’d learned computers in the Air Force in 1956, as one of the first men working on the SAGE computer air defense system, then reputed to be the most complicated system known to man. Fredkin and nineteen others began an intensive course in the budding field of computation—memory drums, logic, communications, and programming. Fredkin later recalled, in his soothing, story-teller voice, “After a week, everyone dropped out but me.”

  Ed Fredkin did not fall into computers head-over-heels as had Kotok, Samson, Greenblatt, or Gosper—in some ways he was a very measured man, too much an intellectual polyglot to fixate solely on computers. But he was intensely curious about them, so after leaving the service he took a job at MIT-affiliated Lincoln Lab, where he soon earned the reputation of top program bummer around. He could consistently come up with original algorithms, some of which became well known as standard programming protocols. He also was one of the first to see the significance of the PDP-1—he knew about it before the prototype was built, and ordered the very first one. He was talked out of the purchase by Bolt Beranek and Newman, who instead hired him to program the machine and write an assembler. Fredkin did so and modestly considered it a masterpiece of programming. Besides systems work, Fredkin engaged in the kind of math hacking that would later be Bill Gosper’s forte, and he did some early theorizing on automatons. But not b
eing a pure hacker—he had business instincts and a family to support—he left BBN to start his own company, Information International, which would perform all sorts of digital troubleshooting and special computer consultations. The company was eventually based in Los Angeles, but for a long time it had facilities in Tech Square, two floors below the PDP-6.

  Fredkin was delighted with the hacker community at Tech Square; they had taken hackerism beyond its previous state, found only part-time in the few places in the world (such as MIT, DEC, the Army, BBN) where computers were accessible to people for whom computing was an end in itself. Around MIT, hackerism was full-time. Fredkin Came to love the hackers—he could speak their language and admire their work. Sometimes he would accompany them on their Chinatown excursions, and on those occasions the discussions could get quite freewheeling. Many of the hackers were avid science-fiction fans (note the origins of Spacewar), but Fredkin was able to link the wonders of Heinlein and Asimov to the work that the hackers were doing—making computers into powerful systems and building a software groundwork for artificial intelligence. Fredkin had a talent for sparking their imaginations, as he did when he mused that one day people would have tiny robots on their heads which would snip off hair when it reached the precise length for the desired coiffure. (Fredkin would cause a national ruckus when he repeated this prediction on a television talk show.)

  As much as Fredkin admired the hackers, though, he still thought he was the best programmer. While the Hacker Ethic encouraged group effort for general improvement, every hacker wanted to be recognized as a wizard, and fast programs and blazing code-crafting efforts would be eagerly displayed and discussed. It was a heady ego boost to be at the top of the hacking hill, where Fredkin considered himself. Hacking, to Fredkin, was above all a pride in craftsmanship.