The Women who Programmed the ENIAC

Kelly Therese Pollock  0:00  
This is Unsung History, the podcast where we discuss people and events in American history that haven't always received a lot of attention. I'm your host, Kelly Therese Pollock. I'll start each episode with a brief introduction to the topic, and then talk to someone who knows a lot more than I do. Be sure to subscribe to Unsung History on your favorite podcasting app, so you never miss an episode. And please, tell your friends, family, neighbors, colleagues, maybe even strangers to listen too.

Today we're discussing the ENIAC, or Electronic Numerical Integrator and Computer, the first programmable general purpose electronic digital computer, and we're talking about the women who made it run. In 1943, the United States was fighting in World War II on multiple fronts, and there was a great demand for calculating numbers for artillery range tables for the United States Army's Ballistic Research Laboratory. With so many men involved in combat operations, the army started recruiting women math majors to do the grueling computing involved. At the same time, engineers worked on ways to run the calculations quicker and more efficiently. In 1942, physicist John Mauchly at the University of Pennsylvania's Moore School of Electrical Engineering, had proposed building a general purpose electronic computer in a paper titled "The Use of Vacuum Tube Devices in Calculating." An army liaison at the Moore School saw the proposal and realized the potential value. In April, 1943, the army signed a contract with the Moore School to build the ENIAC.

Mauchly was in charge of conceptual design, and Moore School graduate, J. Presper Eckert was the chief engineer. They began their work in secret under the codename Project PX, with a team of design engineers in the basement of the same Moore School building where the women computers were hard at work on ballistics tables.

The ENIAC was enormous by today's standards, with 40 large panels, each 32 square feet, taking up most of a 50 foot by 30 foot room. The ENIAC contained more than 17,000 vacuum tubes, 70,000 resistors, 10,000 capacitors, 6000 switches, and 1500 mechanical relays, and it required its own air conditioning system to cool down the tremendous amount of heat it put off. Once the machine existed, they needed a way to program it. Luckily, there was a talented group of women mathematicians already at work for the army at the Moore School location. Mathematician Lieutenant Herman Goldstine, who had convinced the army to fund the ENIAC, chose six of the women to work on the problem of how to program the ENIAC. Those six women were Kathleen "Kay" McNulty Mauchly Antonelli, Jean Jennings Bartik, Frances "Betty" Snyder Holberton, Marlyn Wescoff Meltzer, Frances "Fran" Bilas Spence, and Ruth Lichterman Teitelbaum. At first, the women were not even able to see the top secret ENIAC. So they studied the blueprints to figure out how the switches and cables worked, and how they could break down their mathematical equations into something that the ENIAC could calculate. They worked in three separate teams, with each team doing a deep dive into a different unit of the ENIAC, learning how it operated, and then coming back to the full group to teach that unit. Kay and Fran, who had both graduated from Chestnut Hill College in Philadelphia, and who were best friends, were one of the teams, working first on the high speed multiplier unit. Betty, a graduate of the University of Pennsylvania, and Jean a graduate of Northwest Missouri State Teachers College, together focused on the accumulator. And Marlyn, a graduate of Temple University, and Ruth, who graduated from Hunter College in New York City, likely taught the group about the divider and square router. Once they all learned those first units, they continued on in that fashion, learning more parts of the machine and figuring out how to make it work, until finally they were able to work on the machine itself, putting their theory into action. On February 1, 1946, after the end of World War II, the ENIAC project was finally announced to the public with a demonstration. According to the army press release, "A new machine that is expected to revolutionize the mathematics of engineering, and change many of our industrial design methods was announced today by the War Department. This machine is the first all electronic general purpose computer ever developed. It is capable of solving many technical and scientific problems, so complex and difficult that all previous methods of solution were considered impractical. Begun in 1943, at the request of the Ordnance Department to break a mathematical bottleneck in ballistic research, its peacetime uses extend to all branches of scientific and engineering work. "The original budget for the ENIAC was $61,700.In the end, it cost nearly $500,000, which in today's dollars, is around $8 million. In November, 1946, the massive ENIAC was dismantled and moved from Philadelphia, to the Aberdeen Proving Ground in Maryland. In 1947, Jean Bartik worked on the team that turned the ENIAC into the world's first stored program computer, meaning that the ENIAC Six were in the only group of programmers to work on it at the machine level. The six women's paths diverged once the ENIAC was moved to Maryland, and their contributions, classified as clerical work, were largely ignored, until today's guest recovered their story. In 1997, the women were finally inducted into the Women In Technology Hall of Fame. Joining me to help us learn more about the ENIAC Six is Kathy Kleiman, a leader in internet law and policy, founder of the ENIAC Programmers Project, and author of the 2022 book, "Proving Ground: the Untold Story of the Six Women Who Programmed the World's First Modern Computer." Hello, Kathy, thanks so much for joining me today.

Kathy Kleiman  9:01  
Kelly, it is a pleasure to be here.

Kelly Therese Pollock  9:03  
Yes, I am really excited to talk to you. I've been looking forward to this one for a while. So I wanted to start just by asking you, I know you have been researching these ENIAC Six for a really long time, I wanted to talk about how you first got into this project.

Kathy Kleiman  9:20  
That was a long time ago. I was an undergraduate. I was taking computer science courses, a lot of them. And as I went up in the levels of computer science, the number of women just went down, though sometimes maybe there was one other woman in the room, sometimes not. And so I wondered if there had been women in early computing. Did I have role models? And we know of two great women in computing. One is Lady Ada Lovelace, in the 19th century in the UK, and one is, she was then Captain Grace Hopper. She retired as Rear Admiral Grace Hopper from the Navy and she was in the 20th century. But that's one woman a century in computing, and that did not make me feel warm and fuzzy about my opportunities in the field. And so I went looking. I was taking a course on American women's history, and I had to write a paper. So I had an excuse to go looking for women in computing. And I went through all the secondary sources, the Encyclopedia of Computer Science and other things. And I didn't see any other women's names; but I also didn't see much history of programming. Most of the history of early computing written then, and still is a history of hardware; and that's a history of men building big machines. But I then went to primary sources. And in one an autobiography of someone who managed a group of women who hand calculated ballistics trajectories, during World War II for firing tables for cannons and artillery. At one point in his book, he says that he helped build a big, new modern computer and hired six of the women who were calculating the ballistics trajectories by hand to be its first programmers. And he names them. And I'm like, "Wait a second. Hold on. I've never heard of these women." And after that, I went searching for them. And all these years later, that this is my, my never ending undergraduate thesis is finally completed with this book coming out, called "Proving Ground: the Untold Story of the Six Women who Programmed the World's First Modern Computer."

Kelly Therese Pollock  11:24  
Yes, so you're able to find just this incredible wealth of information about these women that you know, as you say, there just wasn't that much out about them. They were sort of hidden in history. So talk to me some about how, how you actually were able to find these stories to put into this book.

Kathy Kleiman  11:45  
 I found the stories by, sounds silly, by being persistent. Initially, I found these beautiful pictures of the ENIAC computer. ENIAC stands for Electronic Numerical Integrator and Computer. This was the world's first general purpose programmable, all electronic, modern computer. And it was built at the University of Pennsylvania during World War II. And there were women in front of these pictures. And their names were not in the captions. So initially, I went to my professor who sent me to one of the founders of the Computer History Museum, which used to be in Boston, and now is in Silicon Valley. And she said that these were models. She made it very clear that the women in these pictures were models. And I was asking silly questions. But they didn't look like models. These looked like women, young, beautiful women who knew exactly what they were doing. They seem to have a very direct connection with this enormous computer. And so I called around the University of Pennsylvania and found an old retired professor named Saul Warren, so very well known and respected. And he said that there had been women working at the University of Pennsylvania at the Moore School of Electrical Engineering during World War II, and he thought that they might be the women I was looking for, and that there was about to be an anniversary of the ENIAC, a celebration of this incredible first computer, and they might be there and I might want to come down from Boston to Philadelphia, and attend the ceremony and look further for the people I was looking for. And I did go to that ceremony. I did go to the anniversary. And I did meet the very women that had been named in that book I mentioned, the autobiography I'd mentioned and I met a number of the ENIAC Six at the ENIAC anniversary. And after that, stayed in contact with them, and began to gather their stories, first for my senior thesis. and then later, about 10 years later, when their stories still hadn't been told, I decided it was time that we really had to tape them telling their stories, and we taped very extensive broadcast quality oral histories, which became the basis of the book and the documentary and everything else.

Kelly Therese Pollock  14:06  
And what were they like, these women? So you were, this was decades after they had done this work; but what were they like as you were talking to them, and what was sort of their, their emotions and feelings around this project that they'd been part of?

Kathy Kleiman  14:23  
Decades, it is decades later. And so they're in their 70s. I knew them into their 80s. And they were incredible. They were remarkable. Each one was so alive, so vibrant, so different, had such a distinct, clear voice. I just I really loved these women. I got to know four of the original ENIAC Six very well, and they were just incredible. And each voice was so different. Jean Jennings Bartik came from a farm in Missouri, and still talked like she was on the farm sometimes in Missouri. Kay McNulty Mauchly Antonelli had grown up in Philadelphia, but only from the age of three and older. She arrived from Ireland, not speaking a word of English when she was three. And so those stories were incredible and she was wonderful and charismatic and eloquent. Marlyn Westcott Meltzer was so down to earth and nice, and yet had these incredible recollections and memories of the ENIAC that were so much fun to hear. And probably the closest I was the closest Betty Snyder Holberton, who lived about half an hour away from me. I'm in the DC area. And she stayed in computing for 40 years. She never went home after the war. And she negotiated international treaties, she created programming languages we still use today. She created the first sort, sorting routine, just incredible, an incredible pioneer. And it was amazing to hear her story. 

Kelly Therese Pollock  16:05  
Yeah. So I want to talk some then about the context. You just mentioned the war. And so this, this comes about around the time of World War II, which is important, both because of the resources that the government and the military are willing to put behind these sorts of projects; but it's also important because of the opportunities available to women. Can you talk a little bit about that piece and how these women had this opportunity that prior to World War II, they wouldn't have had?

Kathy Kleiman  16:37  
Oh, great question. So before World War II, women math majors, actually, before World War II, there were separate Help Wanted sections. And I didn't know this. And this continued into World War II. There was a women's Help Wanted section and a men's Help Wanted section. And so most of the ENIAC Six were math majors in college. And they knew as they were approaching graduation, they could see it that the jobs for actuaries and accountants and CPAs were on the Men's Help wanted, on the men's Help Wanted side of the ledger. And so they wanted jobs in their fields. But they weren't really available. For those who are graduating before World War II, they weren't really available. But during World War II, the army for this project in Philadelphia and for other projects, goes out of its way to advertise for women math majors. And this is an incredible part of the homefront story that I didn't know. We're taught in school, actually, we're not taught much about the homefront. But we know a little bit. We know that men went off to war, and women are urged to go into the factories and farms to replace the men who have gone off to war. What I didn't know until I sat there going through page after page of microfiche in the basement of the Library of Congress of the Philadelphia papers was that women were actively recruited into STEM work. We needed women for science, technology and math, the same way we needed them in the factories and the farms. And so finally, doors are opening to opportunities in STEM that didn't exist before the war and they're opening abundantly during the war. And these women see these ads and are very excited to help the war effort and also to be able to jump into the the fields of mathematics and other fields, that they don't think that they you know, that they wouldn't have been able to before the war.

Kelly Therese Pollock  18:38  
And then that initial work that they're doing while really, really important, and of course, they're thrilled that they can meet, you know, contribute to this effort, is kind of grueling work, calculating these ballistics tables. Can you talk a little bit about sort of what they were actually doing at first?

Kathy Kleiman  18:58  
Sure, they were hand calculating ballistics trajectories, so that's the path of the missile from the time it leaves the muzzle, muzzle of a gun to hit the target. And at that point, our cannons, in this case, they're mostly calculating howitzers, howitzers just go from eight to 14 miles. And at that distance, the weather on the battlefield has a distinct impact on the arc of the trajectory. So if it's raining, snowing, if there's a crosswind, it changes where you have to aim the gun to hit the target. And it turns out that a differential calculus equation that had been created during World War I could give you a very accurate angle to shoot the gun, to set and shoot the gun. But it took 30 to 40 hours to do by hand.  These teams of 10 women apiece, they're classified. Their title for the army is computer because they're hand computing and they're using these really noisy desktop calculators that that did their calculations by interlocking gears. And when the gears turn, it's very noisy, and they're lucky enough actually to have electrical, mechanical, desktop calculators. So it's electricity that's turning the gears. But they're they're punching these numbers painstakingly into these machines which have no memory. So they're writing the answers down on their sheets. And then they're re punching numbers and then recalculating. And they're kind of painstakingly going through one, one line of the calculation at a time. And then again, it takes about 30 to 40 hours to do one of these calculations by hand, and the military needs hundreds of them just to do one firing table for one guy. They are soon put on two shifts a day to keep the machines, the electromechanical calculators working as many hours as possible. There's one shift that comes in, in the morning, stays till the afternoon and another shift that comes in in the afternoon and stays till night.

Kelly Therese Pollock  21:00  
And then I remember you mentioning in the book that depending on sort of where the front of the war was at any given point, so like, if there's a theater in Africa where fighting is going on, that that changes everything. And then you need a whole new table for what that looks like, those trajectories.

Kathy Kleiman  21:15  
Oh my gosh, yes. But they didn't realize that upfront. So they calculated this whole table, sent it to North Africa. And then not the women, of course, but you know, people in the army realized that the testing that had been done in Maryland wasn't right for the for the kind of spongy soil of the desert. And so the women were told that they had to very quickly, as quickly as possible, recalculate those tables. And Marlyn in particular, distinctly remembered the being told about the circumstances and that they would have to get to work recalculating all of this equation.

Kelly Therese Pollock  21:54  
So it's in this context, then that the idea for ENIAC comes about that this could be a huge time saver. So what is it about ENIAC that is unique? It's not the first computer of any kind, but what makes it sort of new on the scene?

Kathy Kleiman  22:13  
New on the scene, new to our world, the great great grandfather or grandmother of everything that we use today, our, you know, our desktops, our laptops, our smartphones. So what made it unique? Well, first, it's all electronic, digital. Every computer up till that time had been electromechanical. It had gears or switches or some other types of mechanical operations. So being all electronic, it's super fast, much faster than anything that existed at the time. But also, it's programmable. The idea that hardware could be reused again and again, for different types of human programs, is the great vision of a man named Dr. John Mauchly, who believed in a general purpose programmable computer that would make our lives much simpler and allow us to calculate problems much greater than we had been able to calculate before. He was particularly interested in weather problems that to this day are done on supercomputers. And so he had this vision, and the army had a desperate need to speed up the calculations. And they all happened to be at the University of Pennsylvania in the Moore School of Electrical Engineering at the same time, and serendipity came into play. And the army found out about his ideas and ultimately funded them.

Kelly Therese Pollock  23:42  
So we should sort of help people visualize this. Nowadays, you know, I have a computer I can stick in my pocket, right? But that is not what we're talking about here. What does this physically look like, this ENIAC computer?

Do you mind if I tell you in the words of the women? Sure. Fantastic. So initially, the men build this machine behind closed doors in a lab in the back of the first floor of Moore School of Electrical Engineering. And the women don't have the security clearance to see it even when six of the 100 computers are assigned to program the ENIAC to do the differential calculus equation, they're still, they're still not allowed to see the machine. They have wiring diagrams, block diagrams. But one day they're finally allowed in, past the locked doors into into the ENIAC, and they walked in, and they lit up when they told me these stories. So there's the ENIAC in front of them eight feet tall, 80 feet long, its 40 units, arranged in a big view. Each unit is eight feet tall and two feet wide. And some of the units have lights on them and the, and the lights can flash, and there's wiring connecting the different units together and it had a hum. It had its own sound, but eight feet tall, 80 feet long and black steel. Betty Holberton kind of said, "It was a monstrous thing!" You can imagine what a computer is today compared to that.

I mean, as I was reading this, and I'm trying to picture, you know, the what this experience is like, and then this idea of, they're not just programming the computers, but they are the ones who figure out how to program. I took programming in high school, and it was like, here's a programming language, you learn this language, you type in these things, and then the program runs and does this stuff. But that's not what we're talking about here. So you mentioned they couldn't even see the machine. So this includes when they're trying to figure out how to program the machine, they don't even have physical access to it. So what is it that they're doing here to try to figure out how to actually use the ENIAC? 

It's a great question. And I love that you were in programming classes too. What you and I had, when we were in our programming classes were programming languages. And whether it was Basic, or Pascal, or C or LISP, you know, we got to use programming languages, to communicate our commands to the computer. So the ENIAC Six didn't have that, and initially, the ENIAC didn't have that. It would change, but during World War II, when it was first built, the method of communicating a problem to the ENIAC was something called direct programming. So first, the women did what you and I did in our programming classes. They sat down, and they broke down the ballistics trajectory equations, differential calculation, this differential calculus equation that they knew so well. They knew how to do it, to calculate it on a desktop calculator. But there's still a lot of intuition and human knowledge involved with that. A computer, as you and I know, only does what you tell it to do. And so they had to break it down even more, much, much more into the steps ENIAC could handle. And then they physically put their program on the ENIAC with six wires, particularly the six digit wires. So a number would pass from an accumulator, and an accumulator could add and subtract to say, a multiplier. Let's say the sum of the accumulator was needed at the next step in the multiplier, the six digit wire would literally go from the accumulator to the multiplier or down to a tray that would carry the the number which they called the digit, and pass it to the multiplier. And they created special flowcharts, which they called pedaling sheets to keep track of all this detail. But they had to put that six digit wire in, they had to put a digit tray in. And they also had to put in something called a program pulse. They had to tell each unit when to run, and that's going to be kind of a pulse that comes in at a certain moment. And they were responsible for all of that. 

And then how did they know it was working? So I think, you know, a lot of our use of computers is kind of on blind faith now, like I type in a calculation into my spreadsheet or whatever. And I just assume that of course, it's right. But you're using this brand new machine that nobody knows if it is going to work the way it's supposed to. You're figuring out how to program it. How do they know that in fact, what they're doing is working?

Kathy Kleiman  28:35  
Really good question. And one of the reasons we take for granted, but you said that you put two numbers into a spreadsheet, and then put the formula in in the correct format for Excel. And then you trust that the number's right, is that we know someone's tested and retested and reread that process. But when you and I write our own programs, we often use test data. And we'll hand calculate the whatever it is we want the computer to do first with a set of test data, and then run that test data through the program and see if we get the same answer. And if we don't, then we figure out did we make a mistake in our hand calculations or is there a bug somewhere in the program? And that's what the women did. Marlyn Wescott Meltzer and Ruth Lichterman Teitelbaum spun off, and they created what we now called the bench test. And they ran through a sample ballistics trajectory at a certain, you know, in certain cross winds and certain temperatures and humidity. And they hand calculated that just as they did, just that they've done on a mechanical desktop calculator, but using the steps that ENIAC would take, and that gave Betty and Jean, who are kind of the technical leads of the trajectory program, but Kay was also very involved as was Fran, and that gave them sample answers. So at various steps along the way, so that at each step of the program, they could kind of test to see if the interim results were accurate, according to Marlyn and Ruth's bench test, and if they weren't, maybe there was a cable they had to adjust, maybe there was a switch they needed to set, you know, flip it from ADD to SUBTRACT, maybe there was a program pulse they needed to wire just at that moment. You would figure it out, and then go on to the next step and have that sample answer for the next step.

Kelly Therese Pollock  30:29  
So I want to talk some then about sort of the the impact and the legacy. You know, when I was in programming classes in the mid 90s, I was the only girl in those classes, I was the only girl at programming competitions. So I think a little bit about what it would have meant to me to know that early programmers were women, but moreover, I think what it would have meant to all the girls who weren't getting involved in programming. Can you talk some about what what it means that we, we didn't know this story for so long, what it would have meant to generations of girls and women to know these kinds of stories earlier?

I think I can only talk about me. And it meant the world to me to know these women's stories. And I felt inspired to first stay in computing. Then I went to Wall Street into information technology. We ran big data centers and international data communications on Wall Street. And sometimes some of the guys would look at me like, "What are you doing here?" and I'm like, "I have every right to be here. Every right! Women helped create this field." And then after that, I became a leader in internet law, also very male dominated field.. And the fact that women had been pioneers in programming continue to inspire me. Even when I looked around the room, and it was all men, I thought, "You know, I have every right to be here and women need to be here." So I'm thrilled to be able to tell these stories now. And I want to inspire both girls and boys to believe that programming and STEM careers lie within their reach. And that all the stereotypes we think of as to what gender and what race are just wrong. We need everybody in computing, today. We are creating software for the world. And the internet is communicating everything, both commercial and non commercial activity to the world. And so we need the best minds from around the world. And we need our best people. And so I just hope that everyone is inspired by the ENIAC programmers story. I'm sorry, it took so long to get it to the world. But I hope everyone kind of gets to take these six women with them on the rest of their journey and know they have every right to be in the field that they're going to.

Do you have any thoughts about whether there are more stories out there like this, that that we might be missing that women who, you know, once the war was over, once the individual project was over, everyone sort of forgot their contribution?

Kathy Kleiman  33:08  
Yes, there are tons of stories. And because programming was a pink collar profession, for at least the first decade, if not more. So in the 1950s. It was mostly women doing programming. So one of my first oral histories was actually Millie Koss, who was a programmer at UNIVAC. And she worked under Grace Hopper. And later when I met her, she was VP of Information Technology for Harvard University. She had been in computing for decades. And so she told me some of the stories of what she did, how she came to be in computing in the 1950s, and also that her team was, if not all women, virtually all women. And the great stories, we know, we know the names of amazing women in the 1960s and 1970s. And yet still, so computer historians tell us that women did nothing important in those eras in computing. I just don't understand how we can know about Jean Sammet, Fran Allen, and Selma Esther and and just so many others, and then someone says that. It's just ridiculous. We really, really need not just to tell, but retell and amplify and put neon lights on the amazing stories of women in the 40s, 50s, and 60s, and 70s computers.

Kelly Therese Pollock  34:34  
 Well, speaking of sharing these stories with the world, how can everyone get your book?

Oh, thank you for asking. So my book is being published by Grand Central Publishing, and by the time this podcast is out, it will be on the shelves, hopefully it bookstores around the country. And it's again called "Proving Ground: The Untold Story of the Six Women Who Programmed the World's First Modern Computer" by Kathy Kleiman. And also you can order it online. And Grand Central publishing has a main page, and links to Target, Walmart, and Barnes and Noble, and everyplace else that you can order the book. And I am hoping people will order it and share these stories so that everyone knows them. 

Yeah, and I will put links up on our website as well. And I really, I love the book. In addition to loving the story itself, it's just really fun to get sort of a sense of what life was like during World War II and immediately after at the homefront and what life was like for these women and these opportunities that they had. So I really enjoyed that sort of glimpse of Americana.

Kathy Kleiman  35:46  
I'm so glad. I really did try to bring their their adventures to life. 

Kelly Therese Pollock  35:51  
Yeah. Well, Kathy, thank you so much. It was a pleasure to speak with you and I am so glad to have learned about these women.

Kelly, thank you for the opportunity to share these incredible stories, and some of my favorite women and I hope everyone enjoys the story of the ENIAC Six.

Teddy  36:14  
Thanks for listening to Unsung History. You can find the sources used for this episode @UnsungHistorypodcast.com. To the best of our knowledge, all audio and images used by Unsung History are in the public domain or are used with permission. You can find us on Twitter, or Instagram @Unsung__History, or on Facebook @UnsungHistorypodcast. To contact us with questions or episode suggestions, please email Kelly@UnsungHistorypodcast.com. If you enjoyed this podcast, please rate and review and tell your friends.