The PDP-1 the game was written on stood in the "kluge room" on the second floor of Building 26 at MIT, the home of the Research Laboratory of Electronics and, before the PDP-1 arrived in 1961, of the TX-0 on which the first hackers had learned the machine. The Hingham Institute where the idea was hatched was a barely habitable tenement at 8 Hingham Street in Cambridge, and the computer itself had been donated by DEC, the young Digital Equipment Corporation, from the old woollen mill it occupied in Maynard, Massachusetts.

Most of the people who built Spacewar! came out of a single student society, the Tech Model Railroad Club, and in particular its Signals and Power Subcommittee, the members who cared less for the trains on top of the layout than for the relays and switches beneath it. The club met in room 20E-214, on the third floor of Building 20, the temporary wartime structure known as the "Plywood Palace," demolished in 1998; the machines they hacked, the TX-0 and then the PDP-1, sat elsewhere on campus, in Building 26. In that clubroom, and in the slang and habits its members carried to the machines, the word "hack" took on its honorific sense and the first hacker culture took shape, including the conviction, later a hacker watchword, that "information wants to be free," an idea credited to club members Peter Samson and Jack Dennis. Samson, Kotok, Saunders, and Piner were all of the club, as were others who circled the machine without a credit on the game, among them Bob Wagner.

The club's slang, including the honorific sense of "hack", was catalogued by Peter Samson in the TMRC Dictionary, archived here from the originals: 1959 and 1960 (originals at gricer.com/tmrc).

A few figures stand just outside the credit but inside the story: the professor who gave the hackers their machines, and, in the same building, the two men imagining what such machines might one day think.

Jack Dennis (b. 1931, d. 2026)

A Tech Model Railroad Club member who became MIT faculty, Dennis is the man who let the hackers in. He brought the Signals and Power crowd to the TX-0, hired the best of them as its systems programmers, and wrote, largely single-handed, the time-sharing system for the PDP-1 on which Spacewar! grew. If anyone opened the machines to the people who wrote the game, it was him.

John McCarthy (b. 1927, d. 2011)

Invented Lisp (1958) and led MIT's early artificial-intelligence work. He employed Russell as his assistant, and it was his theoretical eval that Russell turned into a running interpreter. The line from Spacewar! to symbolic AI runs through him.

Marvin Minsky (b. 1927, d. 2016)

A founder of artificial intelligence at MIT. His display hack, the Minskytron (1962), drew hypnotic curves on the same Type 30 tube and gave the hyperspace warp its distinctive look, the "Minskytron signature."

Ed Fredkin (b. 1934, d. 2023)

Not a Spacewar! author, but central to the machine it ran on. At Bolt Beranek and Newman, which bought DEC's very first PDP-1, Fredkin specified the machine's character set, character codes and I/O, and designed the zero-latency swapping drum that made PDP-1 time-sharing possible; he also wrote its assembler, FRAP. A close friend of Minsky and McCarthy, he later directed MIT's Project MAC (1971–74), and devised TRIE memory and the reversible Fredkin gate (Wikipedia). More on the machine ›

The PDP-1 was built by Digital Equipment Corporation, founded in a corner of a Maynard woolen mill in 1957. Women were not rare there: of the first hundred employees, thirty-six were women, many of them former mill workers who now assembled the circuit boards. Alma Pontz (employee #5) was the first woman hired; Gloria Porrazzo (#6) ran the module assembly line, whose fifty-odd workers were known as "Gloria's Girls"; Angela Cossette, hired in 1963 to run the DEC Users' Society (DECUS), became the company's first woman manager.

Barbera Stephenson (employee #71)

An MIT electrical-engineering graduate, hired by Ken Olsen in 1960 as Digital's first woman engineer. She wrote the first DEC module handbooks, the do-it-yourself manuals that taught customers digital logic, testing the prose by "teaching Boolean algebra to all the secretaries," and later the Analog-to-Digital Conversion handbook and the Digital Logic Laboratory Workbook, whose final exercise was to "build your own mini-computer" (1965). As an applications engineer she supported the early PDP-1 installations in person. Customers balked: "I'd say 'I'm an engineer' and they'd say, 'No, I want to speak with a real engineer.'" Sources: her DEC oral history and David A. Mark, "Women at Digital Equipment Corporation" (2014).

Gender and Spacewar

As Nooney argues, gender in early computing worked as an infrastructure: it shaped who had access to a PDP-1 at two in the morning, whose presence in the machine room read as "hacking" and whose did not, and so whose work the record kept. The point is sharpened by proximity. Two buildings away, in these same years, two women were doing foundational scientific computation for the meteorologist Edward Lorenz (b. 1917, d. 2008): Margaret Hamilton (b. 1936), who would go on to lead the Apollo flight software, and then, when Hamilton moved on in 1961, Ellen Fetter (b. 1940), a Mount Holyoke mathematics graduate whose runs traced out what became the Lorenz attractor, the founding image of chaos theory. Their machine was not the PDP-1 but a Royal McBee LGP-30, an 800-pound machine with its own office on the fifth floor of Building 24. Further out, at Lincoln Laboratory, Mary Allen Wilkes (b. 1937) was programming the LINC. And one woman was closer than any corridor: Marge French, who did what one history calls "non-hacking computer work" for a research project in this very milieu and who married one of the authors, Bob Saunders. She survives in the record chiefly as a hacker's wife. Women were doing foundational work on interactive machines at MIT in these same years, close enough to be down a corridor, and the room that wrote the game stayed shut to them anyway. More on this ›