The Six Female Programmers Behind the ENIAC

March 22, 2022 by Robert Keim

Thanks to research conducted by computer scientist Kathy Kleiman, we can all know the story of the brilliant women who were instrumental in the creation of the world’s first general-purpose digital computer.

I studied assembly language in college, and at the beginning of my career, I even did a bit of firmware development in assembly. But nowadays, I regard assembly programming as a sort of Heraclean feat—something one does to demonstrate superhuman coding prowess rather than merely accomplish an engineering task.

And yet, writing firmware in assembly language seems almost trivially straightforward compared to the programming acrobatics required to turn the first electronic processing systems into functional computers. There were no IDEs back then, no fancy debuggers, no ergonomic keyboards tapping out human-readable code taken from thoroughly documented instruction set architectures. Instead, they had wires, vacuum tubes, paper punch cards, blueprints, and apparently much more patience and dedication than I do.

This makes it all the more surprising, and perhaps distressing, that modern society almost forgot about the six women who were essential to the success of a groundbreaking computing system called ENIAC.


ENIAC and some members of the development team

ENIAC and some members of the development team, including (in the background) Jean Jennings Bartik. Image used courtesy of the Los Alamos National Laboratory


What Was ENIAC?

The Electronic Numerical Integrator And Computer (ENIAC) was a pre-transistor processing system recognized as the first equivalent to what we now consider a “computer”—i.e., a digital and primarily electrical device that can manipulate data, perform mathematical operations, and follow a sequence of customized instructions created by a human being.

ENIAC, which was powered by a dedicated generator and weighed over sixty thousand pounds, was a vast network of (hand-soldered) vacuum tubes, crystal diodes, capacitors, resistors, and relays. Though built from technology that nowadays seems hopelessly primitive, ENIAC emerged from techniques and logic circuits that are familiar to engineers of the twenty-first century: punch cards provided an input/output interface, arithmetic units performed binary calculations, flip-flops were connected into counters, registers stored digital data, and operation was governed by a clock signal.


This is both a wiring diagram and a programming chart for an ENIAC application

This is both a wiring diagram and a programming chart for an ENIAC application. Image used courtesy of Columbia University


Program flow, on the other hand, is perhaps not so familiar. It’s difficult for me to fully assess the extent to which ENIAC “software” is conceptually comparable to modern software—because I can’t fully comprehend the process of programming ENIAC, and my research is impeded by the fact that said process sounds like an absolute nightmare.

Thus, I heartily congratulate the women who took this burden upon themselves and succeeded marvelously. My hat is off to Frances Snyder Holberton, Jean Jennings Bartik, Kathleen McNulty Mauchly Antonelli, Marlyn Wescoff Meltzer, Ruth Lichterman Teitelbaum, and Frances Bilas Spence.


The Women and Their Work

The ENIAC programmers were selected from a group of women whose mathematical aptitude qualified them for jobs as human “computers.” They were officially called computers; at the time the word didn’t have a universal association with electronic devices, and it made sense since their job was to compute mathematical solutions.


The ENIAC's first programmers were women

The ENIAC's first programmers were women. Image (modified) used courtesy of the University of Pennsylvania Archives

The six women integrated into the ENIAC project already had uncommon mathematical abilities, but they needed to supplement this expertise with thorough knowledge of the machine’s logical architecture, electrical behavior, and physical layout. Though reductively described as “machine operators,” the women were in fact computer programmers—at a time when programming languages did not exist. They configured and interconnected ENIAC’s components according to required computational functionality, and they were responsible for handling punch-card input, troubleshooting, and even replacing vacuum tubes (which failed frequently).


Sophisticated ENIAC programs

Sophisticated ENIAC programs required a prodigious quantity of punch cards. Image used courtesy of the Los Alamos National Laboratory


ENIAC was built during World War II, and the pressing math problems of the day were military in nature. The ENIAC women were originally hired as (human) computers and tasked by the U.S. Army with calculating artillery trajectories. By 1946, they had programmed ENIAC to do the same thing—but at a speed that far surpassed the capabilities of the human brain. 

This actually wasn’t the first successful ENIAC program: in 1945, ENIAC helped the Los Alamos folks perform calculations related to the feasibility of a thermonuclear bomb. How strange and disconcerting that the first program executed by the first general-purpose electronic computer was an exploratory analysis of a potentially apocalyptic technology that would eventually take shape as the most destructive weapon ever created by human beings.

ENIAC was not controlled by a program stored in memory, as with modern processors. According to an article from Columbia University, ENIAC “was programmed by a combination of plugboard wiring and three ‘portable function tables,’” and “each function table [had] 1200 ten-way switches, used for entering tables of numbers.” Translating a computational procedure into ENIAC connections was a slow and complicated process; creating and verifying the physical connections was also complicated and tedious. The first ENIAC programmers were pioneers in a hostile land.


Recognition: Better Late Than Never

The women who programmed ENIAC were not adequately recognized for their achievements until decades after their historic contribution to the advancement of digital processing systems.

Eventually, Kathy Kleiman learned about their lives and shared their stories, and a long-overdue period of awards and honors began. In 1997 all six of the ENIAC programmers were inducted into the Women in Technology Hall of Fame, and currently, the U.S. Army has supercomputers named Jean, Kay, and Betty, after three of the women who helped to make the Army’s—and the world’s—first computer a reality.



This article is part of a series that All About Circuits will publish throughout Women's History Month, celebrating key female figures in electrical engineering. Stay tuned for more feature stories. You can find what we've already covered below. 

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    MisterBill2 March 25, 2022

    Wow, it had not hit me that originally the computers did not take textual code commands. I did once have one of those back program panels to enter some sort of commands to a some sort of computer.
    Certainly the amount of insight that these women had was far more than just math ability.  And it was new territory, as well. Programming in machine language is hard enough, really.

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    MisterBill2 March 25, 2022

    The closest that we come to that sort of programming today might be adder logic, which could, in theory, be realized with electro-mechanical relays.  But relay math gets big very rapidly. These women were incredible.

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