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mother of software.. ..................


spaceship programmer ..................


apollo 11 ...........................


debugger Extraordinaire ...............


modern legacy ........................


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*// an unexpected Founder Margaret Hamilton wasn’t supposed to invent the modern concept of software and land men on the moon. It was 1960, not a time when women were encouraged to seek out high-powered technical work. Hamilton, a 24-year-old with an undergrad degree in mathematics, had gotten a job as a programmer at MIT, and the plan was for her to support her husband through his stint at Harvard Law. After that, it would be her turn—she wanted a graduate degree in math.

Hamilton would bring her daughter Lauren by the lab on weekends and evenings. While 4-year-old Lauren slept on the floor of the office overlooking the Charles River, her mother programmed away, creating routines that would ultimately be added to the Apollo’s command module computer.

But the Apollo space program came along. And Hamilton stayed in the lab to lead an epic feat of engineering that would help change the future of what was humanly— and digitally—possible.

“People used to say to me, ‘How can you leave your daughter? How can you do this?’” Hamilton remembers. But she loved the arcane novelty of her job. She liked the camaraderie—the after-work drinks at the MIT faculty club; the geek jokes, like saying she was “going to branch left minus” around the hallway. Outsiders didn’t have a clue. But at the lab, she says, “I was one of the guys.”

As a working mother in the 1960s, Hamilton was unusual; but as a spaceship programmer, Hamilton was positively radical.

Then, as now, “the guys” dominated tech and engineering. Like female coders in today’s diversity-challenged tech industry,

Hamilton was an outlier. It might surprise today’s software makers that one of the founding fathers of their boys’ club was, in fact, a mother—and that should give them pause as they consider why the gender inequality of the Mad Men era persists to this day.

Hamilton and her daughter Lauren.

Margaret Hamilton at work in Draper Laboratory during the Apollo missions.

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When into what were like

I first got it, nobody knew it was that we doing. It was the Wild West.

Punch card is spit out into card stacker and a new one is loaded

4 Machine punches out corresponding holes for each character typed



IBM keypunch machine is loaded with blank punch cards

Required Tools: * Punch Cards * keyPunch machine * Mainframe computer

2 Keyboard is used to type up each line of program code

Punch cards are accumulated until entire program has been converted to numeric punches


6 Cards are fed chronologically into computer to load source code

7 Circuitry in computer recognizes punch patterns to read and execute the program

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*// Nasa woman MIT’s instrumentation lab received the contract for the Apollo guidance and control systems on Aug. 9, 1961, when the United States had accomplished only two spaceflights—both with just one crewmember on board, and both in suborbital space. The contract was awarded just weeks before then-President John F. Kennedy announced that he planned to have humans on the moon by the end of the decade. The guidance and control systems at NASA would apply to both the lunar module (which would land on the moon) and the command module (which would orbit the moon while the lunar module was on the surface, then house the astronauts on their journey home.) It was intended to guide the spacecraft once they had achieved Earth orbit.

*// Growing software

Hamilton inside a mockup of the Apollo 8 command module.

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As Hamilton’s career got under way, the software world was on the verge of a giant leap, thanks to the Apollo program launched by John F. Kennedy in 1961. At the MIT Instrumentation Lab where Hamilton worked, she and her colleagues were inventing core ideas in computer programming as they wrote the code for the world’s first portable computer. She became an expert in systems programming and won important technical arguments. “When I first got into [programming], There was no course in it. They didn’t teach it,” Hamilton says.

This was a decade before Microsoft and nearly 50 years before Marc Andreessen would observe that software is, in fact, “eating the world.” The world didn’t think much at all about software back in the early Apollo days. The original document laying out the engineering requirements of the Apollo mission didn’t even mention the word software, MIT aeronautics professor David Mindell writes in his book Digital Apollo. “Software was not included in the schedule, and it was not included in the budget.” Not at first, anyhow.

The process of actually coding in the programs was laborious, as well. The guidance computer used something known as “core rope memory”: wires were roped through metal cores in a particular way to store code in binary. “If the wire goes through the core, it represents a one,” Hamilton explained in the documentary Moon Machines. “And around the core it represents a

Margaret Hamilton with one of her former colleagues on April 19, 1962.

zero.” The programs were woven together by hand in factories. And because the factory workers were mostly women, core rope memory became known by engineers as “LOL memory,” LOL standing for “little old lady.” Each Apollo computer contained 4 kilobytes of read-write memory and 72 kilobytes of read-only memory.

NASA elected to send Apollo 8’s command module solo that December on an orbital mission to the moon, out of concerns that the Soviet Union would get there first. Apollo 9 tested out the lunar module and command module together in Earth orbit for the first time, and then the two spacecraft were tested again in lunar orbit for Apollo 10.

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Despite the laborious task, Hamilton and her team kept a sense of humor. Hamilton’s programming lingo: # Page 801 CAF TWO # TS WCHPHOLD TS WCHPHASE TC BANKCALL # CADR STOPRATE # TC DOWNFLAG # TC POSTJUMP # CADR BURNBABY

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LOL’s = Little Old Ladies

WCHPHASE = 2 ---> VERTICAL: P65,P66,P67

FLT’s = Funny Little Things MEGO = My Eyes Glazed Over


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*// liftoff As the Apollo project unfolded, the centrality of software in accomplishing the mission started to become clear. In 1965, Hamilton became responsible for the onboard flight software on the Apollo computers. It was an exciting time, and the US was depending on the work that she was doing. But sometimes the pressure kept Hamilton up at night. Once, after a late-night party, she rushed back to the computer lab to correct a piece of code she’d suddenly realized was flawed. “I was always imagining headlines in the newspapers, and they would point back to how it happened, and it would point back to me.” By mid-1968, more than 400 people were working on Apollo’s software, because software was how the US was going to win the race to the moon. As it turned out, software was going to help the world do so much more. As Hamilton and her colleagues were programming the Apollo spacecraft, they were also hatching what would become a $400 billion industry.

Margaret Hamilton, lead Apollo flight software design, standing next to listings of the Apollo Guidance Computer that she wrote herself.

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For Hamilton, programming meant punching holes in stacks of punch cards, which would be processed overnight in batches on a giant Honeywell mainframe computer that simulated the Apollo lander’s work. “We had to simulate everything before it flew,” Hamilton remembers. Once the code was solid, it would be shipped off to a nearby Raytheon facility where a group


July 16, 1969


9:32 AM EDT


Launch Complex 39A

of women, expert seamstresses known to the Apollo program as the “Little Old Ladies,” threaded copper wires through magnetic rings (a wire going through a core was a 1; a wire going around the core was a 0). Forget about RAM or disk drives; on Apollo, memory was literally hardwired and very nearly indestructible.

ated by humans but with “fly-by-wire” autopilot technology—a precursor to the computerized navigation systems that are now standard on jetliners.

The system stored more than 12,000 “words” in its permanent memory—the copper “ropes” threaded by the Raytheon workers—and had 1,024 words in its temporary, erasable memory. “It Apollo flights carried two near-idenwas the first time that an important tical machines: one used in the lunar computer had been in a spacecraft module—the Eagle that landed on the and given a lot of responsibility for the moon—and the other for the command mission,” says Don Eyles, who worked module that carried the astronauts on the lunar module code while at to and from Earth. These 70-pound MIT. “We showed that that could be Apollo computers were portable comdone. We did it in what today seems puters unlike any other. Conceived by an incredibly small amount of memory MIT engineers such as Hal Laning and and very slow computation speed.” Hamilton’s boss, Dick Batton, it was Without it, Neil Armstrong wouldn’t one of the first important computers to have made it to the moon. And without use integrated circuits rather than tran- the software written by Hamilton, sistors. As Mindell tells the story, it was Eyles, and the team of MIT engineers, the first computerized onboard navithe mainframe computer would have gation system designed to be operultimately been a dud.

# # #

Apollo 11 clears the launch tower on July 16, 1969.

Smoke and flames signal the opening of a historic journey as the Saturn V clears the launch pad.



# (12)

TCF P12IGN # BANK 36 P12TABLE VN 0674 # (0) SETLOC P40S TCF ULLGNOT # (1) P40TABLE VN 0640 BANK TCF COMFAIL3 # (2) TCF ULLGNOT # EBANK= WHICH TCF GOCUTOFF # (3) TCF COMFAIL4 # COUNT* $$/P40 TCF TASKOVER # (4) TCF GOPOST # # *********************************************** TCF P12SPOT # (5) TCF TASKOVER # # TABLES FOR THE IGNITION ROUTINE DEC 0 # (6) NO ULLAGE TCF P40SPOT # # *********************************************** EBANK= WHICH # Page 732 # 2CADR SERVEXIT # (7) DEC 2240 # # NOLI SE TANGERE

# (0) (1) (2) (3) (4) (5)



Buzz Aldrin poses for a portrait on the moon.

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*// sounding alarms But a software incident almost derailed the landing, as Hamilton recalled in a 2009 interview with MIT. “Everything was going according to plan until something totally unexpected happened, just as the astronauts were in the process of landing on the moon,” she recalled. “All of a sudden, the normal mission sequences were interrupted by priority displays of 1201 and 1202 alarms, giving the astronauts a go/no-go decision (to land or not to land),” she added. “It quickly became clear that the software was not only informing everyone that there was a hardware-related problem, but that the software was compensating for it. With only minutes to spare, the decision was made to go for the landing.”

*// hamilton tech Also thanks to Hamilton and the work she led, notions of what humanity could do, and be, changed not just beyond the stratosphere but also here on the ground. Software engineering, a concept that Hamilton pioneered, has found its way from the moon landing to nearly every human endeavor. By the 1970s, Hamilton had moved on from NASA and the Apollo program. She went on to found and lead multiple software companies. Today her company, Hamilton Technologies, is just a few blocks away from MIT, where her career began—a hub of the code revolution that continues looking towards the stars to this day.

While a decision was made in the moment to let the astronauts land, Hamilton pointed out that a fault analysis was done to see where the error was made. It turned out that the astronaut checklist, which governed the actions the crew had to do before landing, had the crew set the rendezvous radar hardware switch in the wrong position. This overloaded the central processing unit during the landing, but fortunately, the software recovered in the heated moments before Apollo 11 touched down.

Our astronauts didn’t have much time, but thankfully they had margaret hamilton.

Hamilton sits with some of her staff in the Scama room at MIT, while supporting the Apollo mission.

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President Barack Obama laughts with Margaret Hamilton during a ceremony in the East Room of the White House in 2016.

*// Medal of freedom By the end of the decade, programming had more than proved its worth—and Hamilton and her colleagues at the future Draper Laboratory had played a critical role in landing man safely on the moon. That was just one achievement in a pioneering half-century in software engineering that landed Hamilton on stage Tuesday at the White House, where the 80-year-old Cambridge resident was one of 21 recipients of the Presidential Medal of Freedom, the nation’s highest civilian honor. This year’s honorees included Bill and Melinda Gates, Kareem Abdul-Jabbar, and Bruce Springsteen, part of a group President

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Obama hailed as “extraordinary Americans who have lifted our spirits, strengthened our union, pushed us toward progress.” The president recalled the historic flight of Apollo 11. Three minutes before the spacecraft was set to touch down on the moon, an alarm rang out. But software designed by a team that included Hamilton helped sort out what mattered most, determining that the alarm wasn’t signaling a major problem. “Our astronauts didn’t have much time, but thankfully they had Margaret Hamilton,” Obama said. “Margaret led the team that created the on-board flight software that allowed the Eagle to land safely.”

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Her software architecture echoes in countless technologies today, and her example speaks of the American spirit...

Hamilton, the president contin“Hamilton was honored by NASA ued, “symbolizes that generation in 2003, when she was presented of unsung women who helped a special award recognizing the send humankind into space. Her value of her innovations in the software architecture echoes in Apollo software development,” countless technologies today, and NASA wrote in 2016. “The award her example speaks of the Ameriincluded the largest financial can spirit of discovery that exists in award that NASA had ever every little girl and little boy who presented to any individual up to know that somehow to look bethat point.” yond the heavens is to look deep within ourselves and to figure out Hamilton later left MIT to start just what is possible.” her own software company, but her name is still most recognized When Margaret H. Hamilton for her lunar landing accomplishstarted writing computer code at ments. Her name was clearly MIT as a young working mother in visible when the entire Apollo 1960, the term “software engineer” 11 source code was released on did not exist, and programmers GitHub in 2016, catapulting her to occupied the fringes of a nascent fame among modern coders and aerospace field dominated by programmers on the internet. nuts-and-bolts engineering and draft work. For Hamilton, although Apollo 11 was monumental, she relished NASA was so impressed with the the challenge of doing her job for software used in Apollo that the it. “From my own perspective, the basis of it was adapted for Skylab software experience itself (de(the first U.S. space station), the signing it, developing it, evolving it, space shuttle (which ran more watching it perform and learning than 100 successful missions in from it for future systems) was at Earth orbit) and the first digital fly- least as exciting as the events surby-wire systems in aircraft. rounding the mission,” she said.

Margaret Hamilton holds a Lego figure (pictured left) of herself.

President Barack Obama presents the Presidential Medal of Freedom to Hamilton on Nov. 22, 2016.

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Margaret Hamilton at the MIT Museum in Cambridge, MA.

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