Mary Coombs: first female commercial computer programmer

“I am said to be the first female commercial programmer. It’s really nice to feel like a pioneer,” said Mary Coombs – who died aged 93 – of her pioneering career as a software developer for Lyons Electronic Office (LEO), one of first professional computers.

She was born Mary Blood in Muswell Hill, London, in 1929, daughter of Ruth and William Blood. Her father was a general practitioner. Looking back on her school days, she recalled, “The subject I was best at was definitely maths”, but she continued to read French and history at what was then Queen Mary College, University of London.

Coombs taught English and took secretarial courses in Switzerland, returning in 1952. When she found that the teaching position she wanted was not available, she took a temporary job with J Lyons & Co, the food company famous at the time for its 250 tearooms. across the British Isles.

Lyons might have seemed an unlikely candidate to be a pioneer in enterprise computing. However, it became one of the first companies to use computers to calculate ingredient quantities and costs. Based on the University of Cambridge’s Electronic Delay Storage Automatic Calculator (EDSAC) project, the Lyons Electronic Office (LEO) was a huge machine by today’s standards, occupying 2,500 square feet of space at Cadby Hall in Hammersmith, England. West London.

Coombs was the only woman among a dozen internal candidates who applied to work on LEO. “It was a simple – well, [a] kind of an intelligence test, really, to see if you could manipulate things, work out the logic of things, and so on. she recalls of the interview process. Of the 12 applicants, only she and her colleague Frank Land were hired and started working as programmers in 1952.

With a small amount of memory, software development for LEO was tricky business, requiring detailed knowledge of its valve-based electronic hardware as well as its binary “machine language”. She recalled, “LEO only provided 2 kilobytes [2000 characters] of space in which you had to cram all your instructions. Life was a continuous challenge to get a full program.

The LEO occupied 2,500 square feet of space at Cadby Hall in Hammersmith, West London

(LEO Computer Company)

On one occasion, Coombs discovered the unusual cause of a bug in the system, later recalling, “I remember one particularly long evening when it just kept going wrong, and we were there the whole evening, because you had to have a programmer involved in this, the engineers couldn’t do it themselves…and we finally found out that the executive elevator, which went up to the fifth floor…was in the way [electronically].”

Lyons soon realized he could offer his computing facilities to other businesses and organisations, forming LEO Computer Ltd in 1954. Coombs became involved in projects for British Oxygen, Ford Motor Company and Glyn, Mills & Co (now part of the Royal Bank of Scotland), and provided payroll services to the British Army and Royal Air Force.

Coombs continued his programming work on the LEO II (1957) and LEO III (1962). In 1963 LEO became part of English Electric and in 1968 a division of International Computers Limited (ICL). She continued to work with ICL, editing manuals for their computer systems, until the late sixties.

After retiring from ICL, Coombs returned to education, teaching at an elementary school from 1976 to 1985. She then worked as a buyer for a water treatment company.

The legacy of this important pioneering period in the development of British computing is carried on by the charity LEO Computers Society, which said in a statement: “Mary was the world’s first female corporate computer programmer, at joining the LEO team in 1952,” adding, “Mary was a good friend to the company and will be sorely missed.”

She married John Coombs, a computer programmer, in 1955. He died in 2012. They had a daughter, Anne, who died in childhood, and adopted three children, Andrew, Paul and Gillian.

Mary Coombs, computer programmer, born February 4, 1929, died February 28, 2022

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