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Meet the 'Refrigerator Ladies' Who Programmed the ENIAC

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In 1945, Betty “Jean” Jennings wanted out of Missouri. A math student at Northwest Missouri State Teachers College (now Northwest Missouri State University), the last thing the farm-bred 20-year-old wanted to do was stay inside a classroom and teach. She wanted adventure. So when an advisor showed her a mysterious classified ad in a math journal soliciting mathematicians to come work in Pennsylvania, Jean jumped at the chance.

She applied for the job, was accepted, and hopped the next steam locomotive to Philadelphia. Little did she know that her leap of faith would help launch the modern computer. Although she and the women like her would be all but forgotten, Jean Jennings’s pioneering work helped create the technology that made the information age buzz.

Uncovering the Women Behind ENIAC

In the mid-1980s, Kathy Kleiman felt isolated and discouraged. A computer science undergrad at Harvard, she began noticing a dramatic drop-off in the number of women in her classes as the course level went up. It was not an auspicious sign for her future in programming.

“I found myself wondering if women had much of a role in the history of computing at all,” Kleiman says. “So I turned to history to see if I could find any role models.”


In her research she stumbled upon a famous black-and-white photo of the first all-electric computer. Published in major newspapers across the country in 1946, the caption identified the men in the image, but no one else. Kleiman was perplexed. Why were the men in the photo the only ones identified? Who were the women?

She took her questions to a historian of computing, but it turned out no one knew who the women were. “I was told they were models—‘Refrigerator Ladies’—posing in front of the machine to make it look good,” Kleiman says. This was a common marketing tactic used to sell kitchen appliances like refrigerators at the time. “But they didn’t look like models to me. In fact, that was the farthest thing from the truth.”

The Birth of the Electric Computer

In World War II the Army was tasked with a Herculean job: calculate the trajectories of ballistic missiles—the arcs that artillery shells take from the time they leave cannon muzzles to the time they reach their target—by hand. These differential calculus equations (a PDF of those calculations can be seen here) were used to target the weapons, and as the firepower increased in the field, so did the demand for the ballistics firing tables. The problem was that each equation took 30 hours to complete, and the Army needed thousands of them.

So they started recruiting every mathematician they could find. They placed ads in newspapers, first in Philadelphia, then in New York City, then far out west in places like Missouri, seeking women “computers” who could hand-compute the equations using mechanical desktop calculators. They would need to relocate to the University of Pennsylvania.

“If they could calculate a differential calculus equation, they were hired,” Kleiman says. Male mathematicians were already working on other projects, so the Army specifically recruited women, even hiring ones who hadn’t graduated college yet. “Like everything else during early WWII, where they needed lots of people, like in factories and farms, they hired women,” she says. At the height of the program, the Army employed more than 100 women calculators. One of the last women to join the team was a farm girl named Jean Jennings.

But the calculations weren’t coming out fast enough, so the Army funded an experimental project to automate the trajectory calculations. Engineers John Presper Eckert and John W. Mauchly began designing the Electronic Numerical Integrator and Computer, or ENIAC as it was called.

“Few in the Army thought the highly-experimental ENIAC would work, but the need was great and it was a time to experiment,” Kleiman says. That experimenting paid off: The 80-foot long, 8-foot tall, black metal behemoth, which contained hundreds of wires, 18,000 vacuum tubes, 40 8-foot cables, and 3000 switches, would become the first all-electric computer.

Making it Work

When the ENIAC was nearing completion in the spring of 1945, the Army randomly selected five women computers out of the 100 or so workers (later adding a sixth woman to the team) and tasked them with programming the thing. “The engineers handed the women the logistical diagrams of ENIAC’s 40 panels and and the women learned from there," Kleiman says. "They had no programming languages or compilers. Their job was to program ENIAC to perform the firing table equations they knew so well.”

The six women—Francis “Betty” Snyder Holberton, Betty “Jean” Jennings Bartik, Kathleen McNulty Mauchly Antonelli, Marlyn Wescoff Meltzer, Ruth Lichterman Teitelbaum, and Frances Bilas Spence—had no precedent and only schematics to work with.

“There was no language, no operating system, no anything,” Kleiman says. “The women had to figure out what the computer was, how to interface with it, and then break down a complicated mathematical problem into very small steps that the ENIAC could then perform.” They physically hand-wired the machine, an arduous task using switches, cables, and digit trays to route data and program pulses.

“The ENIAC was a son of a bitch to program,” Jean Jennings has said.

The ballistic calculations went from taking 30 hours to complete by hand to taking mere seconds to complete on the ENIAC.

On February 14, 1946, six months after the end of the war, the Army revealed their amazing feat of engineering in a public relations extravaganza. (The ENIAC was not completed in time to use during World War II.) ENIAC was front-page news across the country, a milestone in modern computing, with praise going to the military, the Moore School of Electrical Engineering at the University of Pennsylvania, and Eckert and Mauchly, the hardware engineers. The programmers, all women, were not introduced at the event. And even though some of them appeared in photographs at the time, everyone assumed they were just models. 

After the war, the government ran a campaign asking women to leave their jobs at the factories and the farms so returning soldiers could have their old jobs back. Most women did, leaving careers in the 1940s and 1950s and staying at home. But no returning soldier knew how to program the ENIAC.

“We were like fighter pilots,” programmer Kathleen McNulty has said. “You couldn’t just take any ordinary pilot and stick him into a fighter [jet] and say, ‘Go to it now, man.’ That was not the way it was going to be.”

“The Army didn’t want to let this group of women go,” Kleiman says. “All of these women had gone to college at a time when most men in this country didn’t even go to college. So the Army strongly encouraged them to stay, and for the most part, they did, becoming the first professional programmers, the first teachers of modern programming, and the inventors of tools that paved the way for modern software.”

The Army opened the ENIAC up to perform other types of non-military calculations after the war and Betty Holberton and Jean Jennings converted it to a stored-program machine. Betty went on to invent the first sort routine and help design the first commercial computers, the UNIVAC and the BINAC, alongside Jean.

Setting History Straight

In the 1990s Kleiman learned that most of the ENIAC programmers were not invited to the ENIAC’s 50th anniversary event. So she made it her mission to track them down and record their oral histories. Today, Kleiman, an Internet lawyer, is putting the finishing touches on her documentary and book on the six ENIAC programmers. The documentary, intended to inspire young women and men to get involved in programming, is set to be released in the coming months.

“They were shocked to be discovered,” Kleiman says. “They were thrilled to be recognized, but had mixed impressions about how they felt about being ignored for so long.”

Jean Jennings, the last surviving programmer from the original six, passed away on March 23, 2011 at 86. Northwest Missouri State University, her alma mater, named its computing museum in her honor.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Library of Congress
10 Facts About the Tomb of the Unknown Soldier
May 29, 2017
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Library of Congress

On Veterans Day, 1921, President Warren G. Harding presided over an interment ceremony at Arlington National Cemetery for an unknown soldier who died during World War I. Since then, three more soldiers have been added to the Tomb of the Unknowns (also known as the Tomb of the Unknown Soldier) memorial—and one has been disinterred. Below, a few things you might not know about the historic site and the rituals that surround it.


Wikimedia Commons // Public Domain

To ensure a truly random selection, four unknown soldiers were exhumed from four different WWI American cemeteries in France. U.S. Army Sgt. Edward F. Younger, who was wounded in combat and received the Distinguished Service Medal, was chosen to select a soldier for burial at the Tomb of the Unknowns in Arlington. After the four identical caskets were lined up for his inspection, Younger chose the third casket from the left by placing a spray of white roses on it. The chosen soldier was transported to the U.S. on the USS Olympia, while the other three were reburied at Meuse Argonne American Cemetery in France.


One had served in the European Theater and the other served in the Pacific Theater. The Navy’s only active-duty Medal of Honor recipient, Hospitalman 1st Class William R. Charette, chose one of the identical caskets to go on to Arlington. The other was given a burial at sea.


WikimediaCommons // Public Domain

The soldiers were disinterred from the National Cemetery of the Pacific in Hawaii. This time, Army Master Sgt. Ned Lyle was the one to choose the casket. Along with the unknown soldier from WWII, the unknown Korean War soldier lay in the Capitol Rotunda from May 28 to May 30, 1958.


Medal of Honor recipient U.S. Marine Corps Sgt. Maj. Allan Jay Kellogg, Jr., selected the Vietnam War representative during a ceremony at Pearl Harbor.


Wikipedia // Public Domain

Thanks to advances in mitochondrial DNA testing, scientists were eventually able to identify the remains of the Vietnam War soldier. On May 14, 1998, the remains were exhumed and tested, revealing the “unknown” soldier to be Air Force 1st Lt. Michael Joseph Blassie (pictured). Blassie was shot down near An Loc, Vietnam, in 1972. After his identification, Blassie’s family had him moved to Jefferson Barracks National Cemetery in St. Louis. Instead of adding another unknown soldier to the Vietnam War crypt, the crypt cover has been replaced with one bearing the inscription, “Honoring and Keeping Faith with America’s Missing Servicemen, 1958-1975.”


The Tomb was designed by architect Lorimer Rich and sculptor Thomas Hudson Jones, but the actual carving was done by the Piccirilli Brothers. Even if you don’t know them, you know their work: The brothers carved the 19-foot statue of Abraham Lincoln for the Lincoln Memorial, the lions outside of the New York Public Library, the Maine Monument in Central Park, the DuPont Circle Fountain in D.C., and much more.


Tomb Guards come from the 3rd U.S. Infantry Regiment "The Old Guard". Serving the U.S. since 1784, the Old Guard is the oldest active infantry unit in the military. They keep watch over the memorial every minute of every day, including when the cemetery is closed and in inclement weather.


Members of the Old Guard must apply for the position. If chosen, the applicant goes through an intense training period, in which they must pass tests on weapons, ceremonial steps, cadence, military bearing, uniform preparation, and orders. Although military members are known for their neat uniforms, it’s said that the Tomb Guards have the highest standards of them all. A knowledge test quizzes applicants on their memorization—including punctuation—of 35 pages on the history of the Tomb. Once they’re selected, Guards “walk the mat” in front of the Tomb for anywhere from 30 minutes to two hours, depending on the time of year and time of day. They work in 24-hour shifts, however, and when they aren’t walking the mat, they’re in the living quarters beneath it. This gives the sentinels time to complete training and prepare their uniforms, which can take up to eight hours.


The Tomb Guard badge is the least awarded badge in the Army, and the second least awarded badge in the overall military. (The first is the astronaut badge.) Tomb Guards are held to the highest standards of behavior, and can have their badge taken away for any action on or off duty that could bring disrespect to the Tomb. And that’s for the entire lifetime of the Tomb Guard, even well after his or her guarding duty is over. For the record, it seems that Tomb Guards are rarely female—only three women have held the post.


Everything the guards do is a series of 21, which alludes to the 21-gun salute. According to

The Sentinel does not execute an about face, rather they stop on the 21st step, then turn and face the Tomb for 21 seconds. They then turn to face back down the mat, change the weapon to the outside shoulder, mentally count off 21 seconds, then step off for another 21 step walk down the mat. They face the Tomb at each end of the 21 step walk for 21 seconds. The Sentinel then repeats this over and over until the Guard Change ceremony begins.