The development of computer software is a history strongly represented by women who have played significant rôles in its development. Ada Lovelace is the best known and Grace Hopper is also becoming a legend among the cognoscenti.   Less heralded by history was a group of six women who worked in wartime secrecy at the University of Pennsylvania, where John Mauchly and Presper Eckert led a team that was building ENIAC, the world’s first programmable, all-electronic, general-purpose computer.

 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 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. She was born on a farm on the outskirts of Alanthus Grove, Maryville, into a family that had almost no money but deeply valued education. When Jean finished college in January 1945, her calculus teacher showed her a flier soliciting women mathematicians to work at the University of Pennsylvania, where women were working as “computers”—humans who performed routine maths tasks. 

One of the ads read:

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’.

 When Jennings started work at Penn in March 1945 there were approximately seventy other women at Pennsylvania working on desktop adding machines and scribbling numbers on huge sheets of paper.  A few months after she arrived, a memo was circulated among the women advertising six job openings to work on the mysterious machine that was behind locked doors on the first floor of Penn’s Moore School of Engineering, the ENIAC. She had no idea what the job was or what the ENIAC was, all she hoped was that she might be getting in on the ground floor of something new.  She believed in herself and wanted to do something more exciting than calculating trajectories.

When Jean Jennings got that job she was set to work together with Marlyn Wescoff, Ruth Lichterman, Betty Snyder, Frances Bilas, and Kay McNulty to figure out how the machine worked and then how to programme it.   They made careful diagrams and charts for each new configuration of cables and switches. What they were doing then was the beginning of a programme, though they did not yet have that word for it.

Around the same time that Grace Hopper was doing so at Harvard, the women of ENIAC were developing the use of subroutines. Because it was being used for atom bomb calculations and other classified tasks, ENIAC was kept secret until February 1946, when the Army and Penn scheduled a gala unveiling for the public and the press.  At the demonstration, ENIAC was able to spew out in 15 seconds a set of missile trajectory calculations that would have taken human computers several weeks. The women had programmed the ENIAC.  The unveiling of ENIAC made the front page of the New York Times under the headline ELECTRONIC COMPUTER FLASHES ANSWERS, MAY SPEED ENGINEERING.

Later Jennings complained, in the tradition of Ada Lovelace, that many of the newspaper reports overstated what ENIAC could do by calling it a giant brain and implying that it could think. The ENIAC wasn’t a brain in any sense, it couldn’t reason, as computers still cannot reason, but it could give people more data to use in reasoning.

That night there was a candlelit dinner at Pennsylvania’s venerable Houston Hall. It was filled with scientific luminaries, military brass, and most of the men who had worked on ENIAC. But Jean Jennings and Betty Snyder  were not there, nor were any of the other women programmers.

Shortly before she died in 2011, Jean Jennings reflected proudly on the fact that all the programmers who created the first general-purpose computer were women. It happened because a lot of women back then had studied maths, and their skills were in demand, she explained. There was also an irony involved, the boys with their toys thought that assembling the hardware was the most important task, and thus a man’s job. If the ENIAC’s administrators had known how crucial programming would be to the functioning of the electronic computer and how complex it would prove to be, they might have been more hesitant about giving such an important role to women.


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