McNulty, Kathleen Rita ('Kay') (1921–2006), pioneering computer programmer, was born on 12 February 1921 in the townland of Feymore, Creeslough, Co. Donegal, the third of six children (three boys and three girls) of James McNulty (1890–1977) and his wife Anne or Annie (née Nelis). Around 1908 James McNulty emigrated from Creeslough to Philadelphia and trained as a stonemason. Involved in Clan na Gael, he returned to Creeslough in 1915 to take part in the struggle for Irish independence. He became commandant of the Doe battalion of the Irish Volunteers, which, owing to confusion and poor communications, took no part in the 1916 rising. After the rising, he continued to recruit and organise Volunteers, and also worked with the local Sinn Féin club, helping to establish Doe Cooperative Society in Creeslough in 1920. In an attempt to seize guns from the home of a protestant JP in early 1919, McNulty was shot and seriously wounded. After a slow recovery, he returned to active service with the IRA and organised the sabotage of a railway bridge outside Creeslough (7 February 1921); fifteen British soldiers were injured in the resulting derailment. Arrested the day after his daughter was born, he was imprisoned in solitary confinement in Derry jail, under threat of execution, until released in the general amnesty of December 1921. He opposed the Anglo–Irish treaty and, unwilling to recognise the new government of the Irish Free State, returned to Philadelphia in 1923 to join a brother in a construction business; his wife and family travelled to America in October 1924. He was successful in his business, working with John B. Kelly, father of Princess Grace of Monaco, and was involved in the construction of important government buildings. He returned to Ireland in 1966, and died in Creeslough in 1977.
The household, in Chestnut Hill, Philadelphia, was Irish-speaking, and Kay first learned English from her two older brothers (she remembered her prayers in Irish for the rest of her life). She attended the parish grade school and then Hallahan Catholic Girls' High School, where she was an excellent student. Chestnut Hill College offered her a scholarship, and she graduated in spring 1942, having majored in mathematics. By then the US army had a pressing need for mathematicians to produce ballistics calculations and, with a scarcity of trained men, McNulty was one of a number of women taken on to work as 'computers' at the Moore School of Electrical Engineering at the University of Pennsylvania.
Calculating missile trajectories, using the desk calculators and tables then available, took each woman about forty hours, and hundreds of such calculations were required. McNulty and another woman were trained to use a recently-built differential analyser machine (an analogue device, reliant on mechanical operations), which speeded up calculations. A much more sophisticated machine, designed on quite novel principles, using electrical circuits to execute calculations, was being developed in great haste at the army's Aberdeen Proving Ground in Maryland. In June 1945 McNulty was one of six women selected to work on this room-sized ENIAC (Electronic Numerical Integrator and Computer). For the next few months, the women collaborated with the engineers who were still working on the design and construction of ENIAC; there were no manuals, only design blueprints, as the machine was still incomplete. McNulty and others devised the processing routines that enabled the machine to carry out calculations, more or less establishing the ways in which artificial intelligence subsequently developed. ENIAC had no memory capabilities: its programmes had to be input manually, using punch cards and realigning wiring and switches, for each calculation. McNulty is credited with suggesting the concept of subroutines, in which the master programmer element of the instructions to the machine was set to trigger the reuse of sections of code, enabling the logical circuits to carry more capacity. Once they began to perform calculations on the actual machine, McNulty and her colleagues became expert in diagnosing problems and finding where the machine's physical wiring or some of the 17,468 vacuum tubes or 5,000,000 hand-soldered connections had failed, as they did at first every few hours.
The public launch of the ENIAC machine as the first general-purpose electronic digital computer took place on 15 February 1946, causing great excitement in the scientific and business communities, as the potential importance of such machines was already evident. The event, however, relegated the women programmers to the role of hostesses, and official reports and early histories of computing made no mention of female operators. Tellingly, as mid-century America reversed the gains made in wartime by women in employment, science and public engagement, some contemporary observers even regarded the women in the project as 'refrigerator ladies': models employed to stand elegantly in front of machines that they did not understand. (Even in 1986, five of the women who had first programmed the 'beast' were not invited to the fortieth anniversary celebration of the birth of the electronic computing age. Kay McNulty was there, and gave an address, but did so as the widow of one of the men who had developed ENIAC. Only as the 1980s ended was the women's contribution to the development of computer systems acknowledged and celebrated.)
On 7 February 1948 Kay McNulty married John Mauchly. Her parents were not present, and were deeply upset by her decision to marry a non-catholic, fourteen years her senior, who had a son and a daughter by a first marriage. John Mauchly was one of the engineers chiefly responsible for designing the hardware of ENIAC; his first wife, also a gifted mathematician, had worked with him, but drowned while on holiday in 1946. Mauchly was also suffering chronic illness, hereditary haemorrhagic telangiectasia (which all but one of his and Kay's five children inherited), necessitating constant vigilance and frequent hospitalisation; he later developed diabetes.
Until her marriage, McNulty had continued to work on ENIAC through 1947 and 1948, testing the device during its re-assembly after a move to the Aberdeen Proving Ground. It is possible she was also involved in its development into a machine with a rudimentary capacity to store an operating system. In her autobiography, Kay noted without comment that her new husband gave her a cookbook on their honeymoon, and that she was thereafter expected to be the family cook; she left paid scientific work on her marriage.
McNulty's possible contribution to developing technology and information systems after her years on ENIAC is now difficult to trace. She may have provided some suggestions in discussions of her husband's pioneering work on the first computer designed for commercial use, UNIVAC, built by his company, Eckart-Mauchly. However, the couple were increasingly preoccupied by legal tussles over patents (which they lost) and difficulties with Mauchly's security clearance, and spent considerable time in disputes with former colleagues and attempts to establish companies and new projects. For the rest of her life, Kay was bitter about how the industry and the government treated her husband, and ardently defended his work and his claims to priority in the computer revolution. In 2002, she was able to accept John Mauchly's posthumous induction into the National Inventors Hall of Fame.
Kay and John Mauchly had four daughters and a son. While rearing her children, she volunteered in youth and church organisations and did some supply teaching in elementary schools. John Mauchly died on 8 January 1980. Kay married again on 27 December 1985; her second husband was a successful, Italian-born photographer, Severo Antonelli. Her years with him were busy and enjoyable, with travel and social engagements, until he developed Parkinson's disease. He died after two difficult years on 14 December 1995.
In her latter years, Kay McNulty Mauchly Antonelli was lionised as one of the invisible women scientists rediscovered in the late twentieth century, and developed considerable skills of communication and presentation as she was sought out to attend conferences and functions to discuss and record the role of the women pioneers of information science. Her online autobiography captures some of the excitement of the wartime work for which she became famous. In April 1999 she and an ENIAC colleague went on a lecture tour in Ireland, and were filmed for a feature documentary, Oh Kay computer (1999). She revisited Creeslough for the first time since 1924, and met many of her relatives there. During her visit, a prize for the best student in computer science was established in her honour at Letterkenny Institute of Technology.
In 1997 she and her five female colleagues were inducted into the Women in Technology Hall of Fame. After suffering from cancer, she died on 20 April 2006 in Wyndmoor, Pennsylvania. A computer science building was renamed in her honour in Dublin City University in 2017.