Hitting the books: the women who made ENIAC more than a weapon

Anear Mary Sears and her team had revolutionized the field of oceanography, but before Katherine G. Johnson, Dorothy Vaughan and Mary Jackson helped put John Glenn into orbit, a group of female programmers working for the US government were faced with an impossible task: to train ENIAC, the world’s first modern computer, to do more than quickly calculate artillery trajectories. Although they were successful – and without the aid of a guidebook or more manual – their names and deeds were lost to the annals of history, until author Kathy Kleiman , through a Herculean research effort, bring their stories to light in Proving Ground: The Untold Story of the Six Women Who Programmed the World’s First Modern Computer.

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Book’s extract Proving Ground: The Untold Story of the Six Women Who Programmed the World’s First Modern Computer by Kathy Kleiman. Copyright © 2022 by First Byte Productions, LLC. Reprinted with permission from Grand Central Publishing. All rights reserved.


Demonstration day, February 15, 1946

Moore School was ready as people started arriving by train and streetcar. John and Pres, along with the engineers, deans and professors of the university, wore their finest suits and the army officers were in uniform with their sparkling medals. The six women wore their best business suits and dresses.

Kay and Fran were manning the front door of Moore School. As the scientists and technologists arrived, some from as far away as Boston, the two women gave them a warm welcome. They asked everyone to hang their heavy winter coats on the portable coat racks Moore School staff had left nearby. Then they directed them down the hall and around the corner of the ENIAC room.

Just before 11:00 a.m., Fran and Kay ran to be in the ENIAC room when the protest started.

As they slipped to the back of the room, everything was ready. At the front of the large ENIAC U there was room for a few speakers, a few rows of chairs and plenty of standing room for guests and ENIAC team members. Across the room, Marlyn, Betty and Jean stood in the back and the women smiled at each other. Their big moment was about to begin. Ruth stayed outside, pointing the stragglers in the right direction.

The room was packed and filled with an air of anticipation and wonder as people saw ENIAC for the first time.

The demo day started with a few presentations. Major General Barnes started with the BRL officers and deans of the Moore School, then introduced John and Pres as the co-inventors. Then Arthur came to the front of the room and introduced himself as the master of ceremonies for ENIAC events. He was running five programs, all using the remote control he held in his hand.

The first program was an add-on. Arthur pressed one of the buttons and the ENIAC came to life. Then he did a multiplication. His expert audience knew that ENIAC calculated it several times faster than any other machine in the world. Then he scanned the table of squares and cubes, then sines and cosines. So far, the demo day was the same as two weeks earlier, and for this discerning audience, the presentation was quite boring.

But Arthur was just getting started and the drama was about to begin. He told them that he would now execute a ballistic trajectory three times on the ENIAC.

He pressed the button and executed it once. The trajectory “went wonderfully”, recalls Betty. Then Arthur ran it again, a version of the trajectory without the punch card printing, and it ran much faster. Punch cards actually slowed things down a bit.

Then Arthur pointed everyone to the grids of tiny lights atop the accumulators and urged his attendees to watch them closely in the moments to come. He nodded at Pres, who was standing against the wall, and suddenly Pres turned off the lights. In the dark room, only a few small status lights were lit on the ENIAC units. Everything else was in darkness.

With a simple click, Arthur brought ENIAC to life. For twenty dazzling seconds, the ENIAC lit up. Those looking closely at the accumulators saw the 100 tiny lights flicker as they moved in a flash, first rising as the missile soared skyward, then descending as it returned to earth, the lights changed and sparkle forever. Those twenty seconds seemed both an eternity and a moment.

Then ENIAC finished, and darkness once again filled the room. Arthur and Pres waited a while, then Pres turned on the lights and Arthur dramatically announced that the ENIAC had just completed a trajectory faster than it would take for a missile to leave the artillery muzzle and hit his target. “Everyone gasped.”

Less than twenty seconds. This audience of scientists, technologists, engineers, and mathematicians knew how many hours it took to calculate a differential calculus equation by hand. They knew that ENIAC had calculated a week’s work in less than two dozen seconds. They knew the world had changed.

Climax over, everyone in the room was beaming. The army officers knew their risk had paid off. ENIAC engineers knew that their equipment was a success. The deans of the Moore School knew they no longer had to worry about being embarrassed. And the ENIAC programmers knew that their trajectory had worked perfectly. Years of work, effort, ingenuity and creativity had come together in twenty seconds of pure innovation.

Some would later call this moment the birth of the “Electronic Computing Revolution.” Others would soon call it the birth of the information age. After those precious twenty seconds, no one would give the large Mark I electromechanical computer or the differential analyzer a second look. After Demo Day, the country was clearly on the path to general-purpose, programmable, all-electronic computing. There was no other direction. There was no other future. John, Pres, Herman and some of the engineers answered questions from the guests and then the official session ended. But no one wanted to leave. Participants surrounded John and Pres, Arthur and Harold.

The women circulated. They had taken turns running punched cards through the tabulator and had stacks of trajectory printouts to share. They divided the sheets and moved around the room to distribute them. The participants were happy to receive a trajectory, a souvenir of the great moment they had just witnessed.

But no participant congratulated the women. Because no guest knew what he had done. Amid announcements and presentations from Army officers, Moore School deans, and ENIAC inventors, the programmers had been left out. “None of us girls were ever introduced as part of it” that day, Kay later noted.

Since no one had thought to name the six young women who programmed the ballistic trajectory, the public did not know their work: thousands of hours spent learning ENIAC’s units, studying its method of “direct programming “, to break down the ballistic trajectory into discrete steps, write the detailed pedaling sheets for the trajectory program, set up their program on ENIAC, and learn ENIAC “down to a vacuum tube”. Later, Jean said, they “got a lot of compliments” from the ENIAC team, but by then they were unknown to the guests in the room.

And at that time, it didn’t matter. They cared about the success of ENIAC and their team, and they knew they had played a role, a vital role, in the success of the day. It was a day that would go down in history, and they had been there and played an invaluable role.

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