Meteorologist, oceanographer, Python solvem probler, experimenter, Raspberry Pi tinkerer, geek dad, manager, space enthusiast, ham radio lover, science columnist, ADHDer, synthetic intellect curious, linux admin cosplayer.

The Six ENIAC Programmers

Overview

During World War II, the Moore School of Engineering at the University of Pennsylvania hired approximately 200 women as “computers” – human calculators who computed ballistic trajectories for the Army’s Ballistic Research Laboratory. In 1945, six of these women were selected to program ENIAC (Electronic Numerical Integrator and Computer), the first general-purpose electronic digital computer. They were classified as “subprofessionals” while equally educated men received “professional” titles.

The six women were:

  1. Kathleen (Kay) McNulty (later Mauchly, then Antonelli)
  2. Betty Jean Jennings (later Bartik)
  3. Frances Elizabeth (Betty) Snyder (later Holberton)
  4. Marlyn Wescoff (later Meltzer)
  5. Frances (Fran) Bilas (later Spence)
  6. Ruth Lichterman (later Teitelbaum)

How They Programmed ENIAC

There was no programming manual, no programming language, and no precedent. The women taught themselves ENIAC’s functions by studying its logical and electrical block diagrams and by interviewing the engineers. Programming ENIAC meant physically setting 3000 switches and routing data through telephone switching cords and patch cables. They had to understand the machine at the hardware level – every vacuum tube, every accumulator, every data path. The precision required was extraordinary: timing accuracy to 1/5000th of a second.

The February 1946 Demonstration

On 15 February 1946, ENIAC was publicly unveiled. The ballistics trajectory program – developed by Jean Bartik and Betty Holberton – demonstrated that ENIAC could complete in 20 seconds a calculation that took 40 hours by hand. The demonstration was a triumph. But when the U.S. Army released photographs of the event, the women in the pictures were not identified. The captions named the men – particularly Eckert and Mauchly – but the women were unnamed.

Individual Biographies

1. Kathleen (Kay) McNulty Mauchly Antonelli (1921–2006)

Early Life

Born 12 February 1921 in Feymore, Creeslough, County Donegal, Ireland, during the Irish War of Independence. Third of six children of James and Anne (nee Nelis) McNulty. Her father was an IRA training officer who was arrested and imprisoned in Derry Gaol for two years on the night of her birth.

The family emigrated to the United States in October 1924, settling in Chestnut Hill, Philadelphia. At age three, Kay spoke only Irish and “would remember prayers in Irish for the rest of her life.”

Education

  • Parochial grade school in Chestnut Hill (1927–1933)
  • J. W. Hallahan Catholic Girls High School, Philadelphia (1933–1938)
  • Chestnut Hill College for Women: Graduated June 1942 with a mathematics degree – “one of only a few mathematics majors out of a class of 92 women”

ENIAC Work

Hired in June 1942 at the Moore School’s Ballistic Research Laboratory as a “human computer” at SP-4 pay grade ($1620 annually). Initially computed artillery trajectories using desk calculators, then operated the differential analyzer.

In June 1945, selected as one of the six ENIAC programmers. Received training at Aberdeen Proving Ground on IBM punched card equipment (June–August 1945).

Key contribution: Credited with inventing the subroutine to solve capacity constraints during trajectory computations. Programming involved discretizing differential equations with timing precision to 1/5000th of a second.

The team also discovered they had been “testing the conveniency of the H-bomb” – their ENIAC calculations were being used for thermonuclear weapon feasibility studies.

Personal Life

  • First marriage: John Mauchly (1948), “against the wishes of her parents.” Five children: Sally (1949), Kathy (1951), Bill (1953), Gini (1954), Eva (1958). Lived in Philadelphia and later at Little Linden farmhouse in Ambler, Pennsylvania. Mauchly died in 1980.
  • Second marriage: Photographer Severo Antonelli (1985). He died in 1996 from Parkinson’s disease; she suffered a heart attack while caring for him but recovered.

Later Career

Worked on BINAC and UNIVAC I software design. In later years, she gave lectures and interviews promoting recognition of the ENIAC programmers.

Death

Died of cancer in Wyndmoor, Pennsylvania, 20 April 2006, aged 85.

Honors

  • Women in Technology International (WITI) Hall of Fame (1997), with all five other ENIAC programmers
  • Accepted John Mauchly’s posthumous induction into the National Inventors Hall of Fame, Akron, Ohio (2002)
  • Dublin City University named their computing building after her (July 2017)
  • Irish Centre for High-End Computing named their primary supercomputer “Kay” (2019)
  • Commemorative plaque unveiled in Creeslough, County Donegal (3 April 2023)

2. Jean Jennings Bartik (1924–2011)

Early Life

Born 27 December 1924 in Gentry County, Missouri (specifically Alanthus Grove), as Betty Jean Jennings. Sixth of seven children. Her father, William Smith Jennings, was a schoolteacher and farmer; her mother was Lula May Spainhower. Attended a one-room school initially; gained local recognition for her softball skills.

Education

  • Stanberry High School, graduated 1941 at age 16, as salutatorian.
  • B.S. in Mathematics: Northwest Missouri State Teachers College, 1945 – the only female mathematics graduate that year.

ENIAC Work

In 1945, the U.S. Army recruited her for ballistics calculations at the University of Pennsylvania. She became one of the six original ENIAC programmers.

The team taught themselves programming by studying schematics and interviewing engineers. Bartik’s partnership with Betty Holberton produced the ballistics trajectory program demonstrated publicly on 15 February 1946, proving ENIAC could complete in 20 seconds what took 40 hours by hand.

Key contribution: Developed subroutines, nesting, and other fundamental programming techniques. Played a central role in converting ENIAC into a stored-program computer by March 1948, working with Adele Goldstine and Dick Clippinger.

Bartik later supported J. Presper Eckert’s claim that the stored-program concept predated von Neumann’s involvement.

Personal Life

Married William Bartik in December 1946. They later divorced.

Later Career

  • Contributed to BINAC and UNIVAC development after ENIAC.
  • Worked at Auerbach Corporation (1967–1975), writing technical reports on minicomputers.
  • Held positions at various technology firms before retiring from computing in 1986.
  • Worked as a real estate agent for 25 years (1986–2011).

Memoir

Published her autobiography Pioneer Programmer: Jean Jennings Bartik and the Computer that Changed the World (2013, posthumously).

Death

Died 23 March 2011 of congestive heart failure in Poughkeepsie, New York, at age 86.

Honors

  • WITI Hall of Fame (1997)
  • Computer History Museum Fellowship (2008)
  • IEEE Computer Pioneer Award (2008)
  • The Drupal content management framework’s default theme is named “Bartik” in her honor.

3. Frances Elizabeth (Betty) Snyder Holberton (1917–2001)

Early Life

Born 7 March 1917 in Philadelphia, Pennsylvania, as Frances Elizabeth Snyder. Third of eight children of John Amos Snyder (1884–1963) and Frances J. Morrow (1892–1981).

Education

Studied journalism at the University of Pennsylvania. She chose journalism because “its curriculum let her travel far afield.” On her first day in a mathematics course, her professor asked whether she “wouldn’t be better off at home raising children.”

ENIAC Work

Selected as one of six ENIAC programmers from the pool of approximately 200 women “computers” at the Moore School.

Key contributions:

  • Invented the breakpoint in computer debugging – a concept that remains fundamental to software development to this day.
  • Designed the sort/merge generator, using playing cards to develop decision trees for binary sort functions.
  • Wrote the first statistical analysis package, used for the 1950 U.S. Census.

Post-ENIAC Career

Holberton’s career after ENIAC was arguably the most distinguished of the six programmers:

  • Worked on UNIVAC development; redesigned UNIVAC’s control panels and changed the computer’s exterior color from black to gray-beige (a more practical choice for office environments).
  • Collaborated with John Mauchly on the C-10 instruction set for BINAC, considered “the prototype of all modern programming languages.”
  • Helped develop COBOL and FORTRAN standards alongside Grace Hopper.
  • 1959–1966: Chief of Programming Research Branch at David Taylor Model Basin.
  • Active in FORTRAN 77 and Fortran 90 revisions at the National Bureau of Standards (NBS/NIST).

Personal Life

Married John Vaughan Holberton. Two daughters: Pamela and Priscilla.

Death

Died 8 December 2001 in Rockville, Maryland, at age 84, from heart disease, diabetes, and stroke complications.

Honors

  • Augusta Ada Lovelace Award (1997) – the sole original ENIAC programmer to receive this award individually that year
  • IEEE Computer Pioneer Award (1997)
  • WITI Hall of Fame (1997)
  • The Holberton School (founded 2015) is named in her honor.

4. Marlyn Wescoff Meltzer (1922–2008)

Early Life

Born 1922 in Philadelphia, Pennsylvania. (Exact birth date not widely recorded.)

Education

Graduated from Temple University in 1942.

ENIAC Work

Hired by the Moore School after graduation to perform weather calculations using adding machines. In 1943, transitioned to ballistic trajectory calculations using mechanical calculators. In 1945, selected as one of six ENIAC programmers.

As part of the team, she programmed “the first general-purpose electronic digital computer,” though as with her colleagues, “little recognition was attributed to the women working on the computer.”

Personal Life

Resigned from the ENIAC team in 1947 to marry, before the machine relocated to Aberdeen Proving Ground. She did not continue in computing.

Later Life

Engaged extensively in volunteer work: service at Shir Ami Library, Meals on Wheels delivery, and knitting over 500 chemotherapy hats for Susan G. Komen For the Cure.

Death

Died 7 December 2008 in Yardley, Pennsylvania, at age 86.

Honors

  • WITI Hall of Fame (1997)
  • Featured in documentaries Top Secret Rosies (2010) and The Computers (2013).

5. Frances (Fran) Bilas Spence (1922–2012)

Early Life

Born 2 March 1922 in Philadelphia, Pennsylvania.

Education

  • South Philadelphia High School for Girls (graduated 1938).
  • Initially enrolled at Temple University, then transferred to Chestnut Hill College on scholarship.
  • Graduated from Chestnut Hill College with a degree in mathematics and a physics minor (1942). It was at Chestnut Hill that she met her future ENIAC colleague Kathleen (Kay) McNulty.

ENIAC Work

Hired by the Moore School of Engineering as one of six female programmers for ENIAC. Worked on programming calculations and operated a Differential Analyzer for ballistics equations.

When ENIAC debuted publicly on 15 February 1946, “the US Army failed to mention the names of the female programmers.” Her contributions, like those of her colleagues, went uncredited for decades.

Personal Life

In 1947, married Homer W. Spence, an Army electrical engineer from Aberdeen Proving Ground. Three sons: Joseph, Richard, and William. She left the ENIAC project after marriage to raise her family.

Death

Died 18 July 2012, at age 90. Buried at the Cemetery of the Holy Rood in Westbury, New York.

Honors

  • WITI Hall of Fame (1997)

6. Ruth Lichterman Teitelbaum (1924–1986)

Early Life

Born 1 February 1924 in The Bronx, New York, to Jewish immigrant parents from Russia. Her father, Simon, was a teacher.

Education

Graduated from Hunter College with a Bachelor of Science in Mathematics.

ENIAC Work

Hired by the Moore School to calculate ballistic trajectories. In June 1943, selected as one of the six ENIAC programmers. She and Marlyn Meltzer “helped prepare the ballistics software.” The programmers physically programmed ENIAC using 3000 switches and telephone switching cords to route data.

Post-ENIAC

After the 1946 public unveiling, Ruth traveled to the Ballistic Research Laboratory at Aberdeen Proving Ground, where she remained for two additional years to train successor programmers on ENIAC. She was one of the few original programmers who continued working with the machine after its relocation.

Personal Life

Married Adolph Teitelbaum on 17 September 1948.

Death

Died 9 August 1986 in Dallas, Texas, at age 62. She was the first of the six programmers to die.

Honors

  • WITI Hall of Fame (1997, posthumous)

Decades of Non-Recognition

For nearly fifty years, the contributions of the six ENIAC programmers went unrecognized. At the 15 February 1946 demonstration, the Army released photographs showing the women at work on ENIAC, but the captions identified only the men. Contemporary accounts treated programming as “clerical” work, unworthy of mention alongside the “real” achievement of building the hardware.

The women were not invited to the ENIAC’s 50th Anniversary celebration in 1996.

Kathy Kleiman and the Recovery of Their Story

Discovery

Kathy Kleiman, as a Harvard undergraduate and a female programmer searching for role models, found photographs of ENIAC taken before demonstration day. The pictures showed men and women alike, but while some of the men – particularly Eckert and Mauchly – were named in the captions, none of the women were identified. When Kleiman asked computer historians about the women, she was told they were probably models posing with the machine. She tracked them down and discovered they were not models – they were the programmers.

The ENIAC Programmers Project

Kleiman founded the ENIAC Programmers Project. Over a decade, she met with four of the original six programmers and recorded extensive interviews about their work.

The Documentary: The Computers

The ENIAC Programmers Project produced a 20-minute documentary, The Computers: The Remarkable Story of the ENIAC Programmers. It premiered at the Seattle International Film Festival in 2014 and won Best Documentary Short from the United Nations Association Film Festival in 2016.

The Book: Proving Ground (2022)

Kleiman published Proving Ground: The Untold Story of the Six Women Who Programmed the World’s First Modern Computer (Grand Central Publishing, 2022), a full-length account that restores the six women to their rightful place in computing history.

Collective Honors and Recognition

  • 1997: All six inducted into the Women in Technology International (WITI) Hall of Fame.
  • 2008: Jean Bartik and Betty Holberton received Computer History Museum Fellowships and IEEE Computer Pioneer Awards.
  • 2010: Featured in the documentary Top Secret Rosies: The Female Computers of WWII.
  • 2013: Featured in The Computers documentary.
  • 2022: Kleiman’s Proving Ground published.

Connections to Others in the Story

  • Adele Goldstine: Trained all six programmers in ballistic trajectory calculations; wrote the ENIAC technical manual based on their work.
  • John Mauchly: ENIAC’s conceptual designer; later married Kay McNulty (1948).
  • J. Presper Eckert: ENIAC’s chief engineer; built the machine they programmed.
  • Herman Goldstine: Army liaison who helped fund ENIAC and managed the project.
  • John von Neumann: Consultant who worked with the programmers on the stored-program conversion; the women’s ENIAC work supported his meteorology and H-bomb calculations.
  • Jean Bartik supported Eckert’s claim that the stored-program concept predated von Neumann’s involvement.

Sources