The cause was heart failure, said his wife, Sharon B. Codd.
Computers can store vast amounts of data. But before Codd's work found its way into commercial products, electronic databases were "completely ad hoc and higgledy-piggledy," said Chris Date, a database expert and former business partner of Codd's, who was known as Ted.
Codd's idea, based on mathematical set theory, was to store data in cross-referenced tables, allowing the information to be presented in multiple permutations. For instance, a user could ask the computer for a list of all baseball players from both the National League and the American League with batting averages over .300.
Relational databases now lie at the heart of systems ranging from hospitals' patient records to airline flights and schedules.
While working as a researcher at the IBM San Jose Research Laboratory in the 1960s and '70s, Codd wrote several papers outlining his ideas. To his frustration, IBM largely ignored his work, as the company was investing heavily at the time in commercializing a different type of database system.
"His approach was not, shall we say, welcomed with open arms at IBM," said Harwood Kolsky, a physicist who worked with Codd at IBM in the 1950s and '60s. "It was a revolutionary approach."
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"The sad thing is that Ted never became rich out of his idea," Date said. "Other people did, but not Ted."
Edgar Frank Codd was born the youngest of seven children in Portland Bill, in Dorset, England, in 1923. His father was a leather manufacturer, his mother a schoolteacher.
He attended Oxford University on a full scholarship, studying mathematics and chemistry. During World War II, he was a pilot with the Royal Air Force. In 1948 he moved to New York and, hearing that IBM was hiring mathematicians, obtained a job there as a researcher.
A few years later, in 1953, angered by Sen. Joseph R. McCarthy's pursuit of Americans that he said had Communist ties or sympathies, Codd moved to Ottawa for several years.
After returning to the United States, he began graduate studies at the University of Michigan at Ann Arbor, where he received his doctorate in computer science in 1965. In 1967, he moved to California to work in the IBM San Jose Research Laboratory.
He and his first wife, Elizabeth, were divorced in 1978. In 1990, Codd married Sharon Weinberg, a mathematician and IBM colleague.
In 1981, he received the A. M. Turing Award, the highest honor in the computer science field.
Codd is survived by his wife of Williams Island; a daughter, Katherine Codd Clark of Palo Alto, Calif.; three sons, Ronald of Alamo, Calif., Frank of Castro Valley, Calif., and David of Boca Raton, Fla.; and six grandchildren.
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