In fact, it was the calm Bloch rather than the spunky Hopper who had the more contentious relationship with Commander Aiken. “Dick was always getting in trouble,” Hopper claimed. “I would try to explain to him that Aiken was just like a computer. He’s wired a certain way, and if you are going to work with him you must realize how he is wired.”15 Aiken, who initially balked at having a woman on his officer corps, soon made Hopper not only his primary programmer but his top deputy. Years later he would recall fondly the contributions she made to the birth of computer programming. “Grace was a good man,” he declared.16
Among the programming practices that Hopper perfected at Harvard was the subroutine, those chunks of code for specific tasks that are stored once but can be called upon when needed at different points in the main program. “A subroutine is a clearly defined, easily symbolized, often repeated program,” she wrote. “Harvard’s Mark I contained subroutines for sine x, log10 x, and 10x, each called for by a single operational code.”17 It was a concept that Ada Lovelace had originally described in her “Notes” on the Analytical Engine. Hopper collected a growing library of these subroutines. She also developed, while programming the Mark I, the concept of a compiler, which would eventually facilitate writing the same program for multiple machines by creating a process for translating source code into the machine language used by different computer processors.
In addition, her crew helped to popularize the terms bug and debugging. The Mark II version of the Harvard computer was in a building without window screens. One night the machine conked out, and the crew began looking for the problem. They found a moth with a wingspan of four inches that had gotten smashed in one of the electromechanical relays. It was retrieved and pasted into the log book with Scotch tape. “Panel F (moth) in relay,” the entry noted. “First actual case of bug being found.”18 From then on, they referred to ferreting out glitches as “debugging the machine.”
By 1945, thanks largely to Hopper, the Harvard Mark I was the world’s most easily programmable big computer. It could switch tasks simply by getting new instructions via punched paper tape rather than requiring a reconfiguration of its hardware or cables. However, this distinction was largely unnoticed, both then and in history, because the Mark I (and even its 1947 successor, the Mark II) used slow and clackety electromechanical relays rather than electronic components such as vacuum tubes. “By the time anybody knew anything about her,” Hopper said of the Mark II, “she was a dead duck, and everybody was going electronic.”19
Computer innovators, like other pioneers, can find themselves left behind if they get stuck in their ways. The same traits that make them inventive, such as stubbornness and focus, can make them resistant to change when new ideas come along. Steve Jobs was famously stubborn and focused, yet he dazzled and baffled colleagues by suddenly changing his mind when he realized he needed to think different. Aiken lacked that agility. He was not nimble enough to pirouette. He had a naval commander’s instinct for centralized authority, so his crew was not as freewheeling as the Mauchly-Eckert team at Penn. Aiken also placed a premium on reliability rather than speed. So he clung to the use of time-tested and dependable electromechanical relays even after it became clear to the people at Penn and Bletchley Park that vacuum tubes were the wave of the future. His Mark I could execute only about three commands per second, while the ENIAC being built at Penn would execute five thousand commands in that time.
When he went to Penn to see ENIAC and attend some lectures, “Aiken was absorbed in his own way of doing things,” a report on the meeting noted, “and does not appear to have been aware of the significance of the new electronic machines.”20 The same was true of Hopper when she visited ENIAC in 1945. It seemed to her that the Mark I was superior because it was easily programmable. With ENIAC, she said, “you plugged the pieces and essentially you built a special computer for each job, and we were used to the concept of programming and controlling the computer by our program.”21 The time it took to reprogram ENIAC, which could be a whole day, wiped out the advantage it had in processing speed, unless it was doing the same task over and over.
But unlike Aiken, Hopper was open-minded enough that she soon changed her outlook. Advances were being made that year in ways to reprogram ENIAC more quickly. And the people in the forefront of that programming revolution, to Hopper’s delight, were women.
THE WOMEN OF ENIAC
All the engineers who built ENIAC’s hardware were men. Less heralded by history was a group of women, six in particular, who turned out to be almost as important in the development of modern computing. As ENIAC was being constructed at Penn in 1945, it was thought that it would perform a specific set of calculations over and over, such as determining a missile’s trajectory using different variables. But the end of the war meant that the machine was needed for many other types of calculations—sonic waves, weather patterns, and the explosive power of new types of atom bombs—that would require it to be reprogrammed often.
This entailed switching around by hand ENIAC’s rat’s nest of cables and resetting its switches. At first the programming seemed to be a routine, perhaps even menial task, which may have been why it was relegated to women, who back then were not encouraged to become engineers. But what the women of ENIAC soon showed, and the men later came to understand, was that the programming of a computer could be just as significant as the design of its hardware.
The tale of Jean Jennings is illustrative of the early women computer programmers.22 She was born on a farm on the outskirts of Alanthus Grove, Missouri (population: 104), into a family that had almost no money and deeply valued education. Her father taught in a one-room schoolhouse, where Jean became the star pitcher and lone girl on the softball team. Her mother, though she had dropped out of school in eighth grade, helped tutor algebra and geometry. Jean was the sixth of seven children, all of whom went to college. That was back when state governments valued education and realized the economic and social value of making it affordable. She attended Northwest Missouri State Teachers College in Maryville, where the tuition was $76 per year. (In 2013 it was approximately $14,000 per year for in-state residents, a twelve-fold increase after adjusting for inflation.) She started out majoring in journalism, but she hated her advisor so switched to math, which she loved.
When she finished in January 1945, her calculus teacher showed her a flyer soliciting women mathematicians to work at the University of Pennsylvania, where women were working as “computers”—humans who performed routinized math tasks—mainly calculating artillery trajectory tables for the Army. As one of the ads put it:
Wanted: Women With Degrees in Mathematics. . . . Women are being offered scientific and engineering jobs where formerly men were preferred. Now is the time to consider your job in science and engineering. . . . You will find that the slogan there as elsewhere is “WOMEN WANTED!”23
Jennings, who had never been out of Missouri, applied. When she received a telegram of acceptance, she boarded the midnight Wabash train heading east and arrived at Penn forty hours later. “Needless to say, they were shocked that I had gotten there so quickly,” she recalled.24