The Women Behind ENIAC

A new book tells the story of how they broke a computer-science glass ceiling

6 min read
Two women programmers preparing a computer to be demonstrated.

Jean Jennings (left) and Frances Bilas, two of the ENIAC programmers, are preparing the computer for Demonstration Day in February 1946.

University Archives and Records Center/University of Pennsylvania

If you looked at the pictures of those working on the first programmable, general-purpose all-electronic computer, you would assume that J. Presper Eckert and John W. Mauchly were the only ones who had a hand in its development. Invented in 1945, the Electronic Numerical Integrator and Computer (ENIAC) was built to improve the accuracy of U.S. artillery during World War II. The two men and their team built the hardware. But hidden behind the scenes were six women—Jean Bartik, Kathleen Antonelli, Marlyn Meltzer, Betty Holberton, Frances Spence, and Ruth Teitelbaum—who programmed the computer to calculate artillery trajectories in seconds.

The U.S. Army recruited the women in 1942 to work as so-called human computersmathematicians who did calculations using a mechanical desktop calculator.

For decades, the six women were largely unknown. But thanks to Kathy Kleiman, cofounder of ICANN (the Internet Corporation for Assigned Names and Numbers), the world is getting to know the ENIAC programmers’ contributions to computer science. This year Kleiman’s book Proving Ground: The Untold Story of the Six Women Who Programmed the World’s First Modern Computer was published. It delves into the women’s lives and the pioneering work they did. The book follows an award-winning documentary, The Computers: The Remarkable Story of the ENIAC Programmers, which Kleiman helped produce. It premiered at the 2014 Seattle International Film Festival and won Best Documentary Short at the 2016 U.N. Association Film Festival.

Kleiman plans to give a presentation next year about the programmers as part of the IEEE Industry Hub Initiative’s Impact Speaker series. The initiative aims to introduce industry professionals and academics to IEEE and its offerings.

Planning for the event, which is scheduled to be held in Silicon Valley, is underway. Details are to be announced before the end of the year.

The Institute spoke with Kleiman, who teaches Internet technology and governance for lawyers at American University, in Washington, D.C., about her mission to publicize the programmers’ contributions. The interview has been condensed and edited for clarity.

Image of Kathy Kleiman and her book cover to the right. Kathy Kleiman delves into the ENIAC programmers’ lives and the pioneering work they did in her book Proving Ground: The Untold Story of the Six Women Who Programmed the World’s First Modern Computer.Kathy Kleiman

The Institute: What inspired you to film the documentary?

Kathy Kleiman: The ENIAC was a secret project of the U.S. Army during World War II. It was the first general-purpose, programmable, all-electronic computer—the key to the development of our smartphones, laptops, and tablets today. The ENIAC was a highly experimental computer, with 18,000 vacuum tubes, and some of the leading technologists at the time didn’t think it would work, but it did.

Six months after the war ended, the Army decided to reveal the existence of ENIAC and heavily publicize it. To do so, in February 1946 the Army took a lot of beautiful, formal photos of the computer and the team of engineers that developed it. I found these pictures while researching women in computer science as an undergraduate at Harvard. At the time, I knew of only two women in computer science: Ada Lovelace and then U.S. Navy Capt. Grace Hopper. [Lovelace was the first computer programmer; Hopper co-developed COBOL, one of the earliest standardized computer languages.] But I was sure there were more women programmers throughout history, so I went looking for them and found the images taken of the ENIAC.

The pictures fascinated me because they had both men and women in them. Some of the photos had just women in front of the computer, but they weren’t named in any of the photos’ captions. I tracked them down after I found their identities, and four of six original ENIAC programmers responded. They were in their late 70s at the time, and over the course of many years they told me about their work during World War II and how they were recruited by the U.S. Army to be “human computers.”

Eckert and Mauchly promised the U.S. Army that the ENIAC could calculate artillery trajectories in seconds rather than the hours it took to do the calculations by hand. But after they built the 2.5-meter-tall by 24-meter-long computer, they couldn’t get it to work. Out of approximately 100 human computers working for the U.S. Army during World War II, six women were chosen to write a program for the computer to run differential calculus equations. It was hard because the program was complex, memory was very limited, and the direct programming interface that connected the programmers to the ENIAC was hard to use. But the women succeeded. The trajectory program was a great success. But Bartik, McNulty, Meltzer, Snyder, Spence, and Teitelbaum’s contributions to the technology were never recognized. Leading technologists and the public never knew of their work.

I was inspired by their story and wanted to share it. I raised funds, researched and recorded 20 hours of broadcast-quality oral histories with the ENIAC programmers—which eventually became the documentary. It allows others to see the women telling their story.

“If we open the doors to history, I think it would make it a lot easier to recruit the wonderful people we are trying to urge to enter engineering, computer science, and related fields.”

Why was the accomplishment of the six women important?

Kleiman: The ENIAC is considered by many to have launched the information age.

We generally think of women leaving the factory and farm jobs they held during World War II and giving them back to the men, but after ENIAC was completed, the six women continued to work for the U.S. Army. They helped world-class mathematicians program the ENIAC to complete “hundred-year problems” [problems that would take 100 years to solve by hand]. They also helped teach the next generation of ENIAC programmers, and some went on to create the foundations of modern programming.

What influenced you to continue telling the ENIAC programmers’ story in your book?

Kleiman: After my documentary premiered at the film festival, young women from tech companies who were in the audience came up to me to share why they were excited to learn the programmers’ story. They were excited to learn that women were an integral part of the history of early computing programming, and were inspired by their stories. Young men also came up to me and shared stories of their grandmothers and great-aunts who programmed computers in the 1960s and ’70s and inspired them to explore careers in computer science.

I met more women and men like the ones in Seattle all over the world, so it seemed like a good idea to tell the full story along with its historical context and background information about the lives of the ENIAC programmers, specifically what happened to them after the computer was completed.

What did you find most rewarding about sharing their story?

Kleiman: It was wonderful and rewarding to get to know the ENIAC programmers. They were incredible, wonderful, warm, brilliant, and exceptional people. Talking to the people who created the programming was inspiring and helped me to see that I could work at the cutting edge too. I entered Internet law as one of the first attorneys in the field because of them.

What I enjoy most is that the women’s experiences inspire young people today just as they inspired me when I was an undergraduate.

collage of vintage photographs of six women.Clockwise from top left: Jean Bartik, Kathleen Antonelli, Betty Holberton, Ruth Teitelbaum, Marlyn Meltzer, Frances Spence.Clockwise from top left: The Bartik Family; Bill Mauchly, Priscilla Holberton, Teitelbaum Family, Meltzer Family, Spence Family

Is it important to highlight the contributions made throughout history by women in STEM?

Kleiman: [Actor] Geena Davis founded the Geena Davis Institute on Gender in Media, which works collaboratively with the entertainment industry to dramatically increase the presence of female characters in media. It’s based on the philosophy of “you can’t be what you can’t see.”

That philosophy is both right and wrong. I think you can be what you can’t see, and certainly every pioneer who has ever broken a racial, ethnic, religion, or gender barrier has done so. However, it’s certainly much easier to enter a field if there are role models who look like you. To that end, many computer scientists today are trying to diversify the field. Yet I know from my work in Internet policy and my recent travels across the country for my book tour that many students still feel locked out because of old stereotypes in computing and engineering. By sharing strong stories of pioneers in the fields who are women and people of color, I hope we can open the doors to computing and engineering. I hope history and herstory that is shared make it much easier to recruit young people to join engineering, computer science, and related fields.

Are you planning on writing more books or producing another documentary?

Kleiman: I would like to continue the story of the ENIAC programmers and write about what happened to them after the war ended. I hope that my next book will delve into the 1950s and uncover more about the history of the Universal Automatic Computer, the first modern commercial computer series, and the diverse group of people who built and programmed it.

The Conversation (2)
Larry Searing04 Jan, 2023
LM

See also the 2010 PBS DVD "Top secret Rosies : the female computers of World War II," which may be available at your local library or from PBS, covering much of the same story about the women computers.

Goeran Andersson24 Nov, 2022
INDV

A great achievement by these early programmers, but ENIAC was not the first computer in the world. The British developed the COLOSSUS in 1943 to be used for breaking the German ciphers produced by the so called "Lorenz gerät".

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
Vertical
A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay
Blue

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.

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