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Women’s History Month: Mary Coombs, First Female Computer Programmer

On the 28th of February this year we lost the world’s first female computer programmer, Mary Coombs, who died at age 93. She lived a great life and made history, so this Women’s History Month I wanted to celebrate her and her story.

Early Life 

Mary Coombs was born in 1929 in Muswell Hill in London to her parents William and Ruth Blood. Mathematics was her strongest subject at school, however, she had a passion for French and History, which she then studied at Queen Mary University in London. Once she graduated with a BA Honours she went to Switzerland for a summer to teach English. 

J. Lyons & Co

In 1952, on her return to London, she got a temp job at the food chain J. Lyons & Co, in their ice cream sales office. Due to her talents in mathematics she progressed there rather quickly, becoming a management trainee in their statistical office. 

J. Lyons was the country’s largest caterer and at the time that Coombs worked there, they wanted to apply computing to their business operations. Their chief accountant, John Simmons, recognised that there would be huge potential in automating the company’s operations. He decided that the company should invest in the computer developments that were happening at Cambridge University. This collaboration birthed the Lyons Electronic Office (aka LEO), the world’s first computer used for business applications. 

J. Lyons were looking for people to program the LEO, and so, put out a message announcing a “computer appreciation course”. Out of the 10 applicants, Coombs was the only female to apply, and was one of the two people who were offered the programming job. In an interview with the British Library, she had previously stated that “it was a simple, well, sort of intelligence test really, to see whether you could manipulate things, work out the logic of things and so on.”

Coombs the Programmer

Once she got the programming job, Coombs took part in a week long training course where, as she said, “we learnt about binary, we learnt about how the actual computer was organised, we learnt about what were known as the initial orders, which were instructions which we used to take everything in and set it up on the computer.” 

In 1952, Coombs started working on LEO programs alongside John Grover, Leo Fantl and Derek Hemy. Coombs progressed to supervisor level and she would locate and repair coding errors in the programs created by others. The LEO was a room-sized computer, which was rather unreliable. It wasn’t fully ready until December 1953 and Coombs had spent her first couple months writing test programs well into the night. 

Her big task for J. Lyons was on payroll, as they had over 10,000 employees, The program was written in alphanumeric code and was needed to produce payslips that were in pre-decimal currency. It had to take into account the tax deductions, holiday and sick pay, and calculate the breakdown of cash to go into the pay pockets. After successfully programming this alongside her team, she went on to do this for the Ford Motor Company, just one of many companies queuing up to use LEO. 

In 1954, the LEO was commercialised for sale to other companies under the name Leo Computer Ltd. Coombs also went on to work on the LEO II & III, with the LEO II being the world’s first commercially available business computer. She continued to work on the LEO computers until the company became International Computers Limited (ICL) in 1968. 

Coombs the Wife and Mother

Mary Blood became May Coombs after marrying John Coombs, a fellow programmer, in 1955. Together, they had a daughter, Anne, in 1961. Anne was born with a disability, and in order to help meet her needs, Coombs started to program for the company part-time from home. Unfortunately due to a disability Anne died at the age of six. After this, Mary and John Decided to adopt children, Andrew, Gillian and Paul.

In 1969, after three years out of work, Coombs went on to become a primary school teacher. After this, she worked in the water treatment industry as an equipment buyer, until she retired in 1993. Coombs has often spoken about the difficulties in balancing work and family, as well as the general topic of women in computing. She had said “I don’t know whether it’s just the people I know, but I can’t think of any of the female children of my friends who have gone into computers…It probably has something to do with the content of the various degree courses…women may think of them as being more masculine preserves…I think when people are of equal ability, it doesn’t matter what sex they are, or it shouldn’t matter.” 

Coombs’ husband died in 2012, and they are survived by their children and three grandchildren. 


“Mary Coombs obituary”. Ferry, G. March 2022

“Mary Coombs, first woman commercial programmer, dies at 93”. Claburn, T. March 2022 Accessed March 2022 Accessed March 2022

“Mary Coombs, first female business computer programmer, dies at 93”. Kundaliya, D. March 2022

  • Written by Mikita Maru, March 18 2022