In 1969, he was part of a team of young engineers who built the first machine to switch data among computers using the Arpanet, the precursor to the internet.
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David Walden, a computer scientist who helped develop a machine that would evolve to become the backbone of the internet for decades, died on April 27 at his home in East Sandwich, Mass. He was 79.
The cause was complications of mantle cell lymphoma, his wife, Sara Walden, said.
In 1969, Mr. Walden was part of a small team of talented young engineers whose mission was to build the Interface Message Processor. Its function was to switch data among computers linked to the nascent Arpanet, the precursor to the internet. The first I.M.P. was installed that year at the University of California, Los Angeles. The I.M.P.s would be crucial to the internet until the Arpanet was decommissioned in 1989.
Mr. Walden was the first computer programmer to work with the team. “The I.M.P. guys,” as they came to call themselves, developed the computer in nine frenetic months under a contract secured by Bolt Beranek and Newman (now Raytheon BBN), a technology company in Cambridge, Mass.
The I.M.P.s served as translators between mainframe computers at different locations and the network itself. Each I.M.P. translated what came over the network into the particular language of that location’s main computer. The translation work of the I.M.P. evolved into today’s network routers.
The work of Mr. Walden and his colleagues was unprecedented. “They had no models to draw on,” said Marc Weber, a curatorial director at the Computer History Museum in Mountain View, Calif. “They were creating out of whole cloth a new class of machine.”
He added, “They took a very new idea at the time and turned it into a living, breathing, working machine with its own software and protocols that became an essential component of the network that grew to connect all of us.”
David Corydon Walden was born on June 7, 1942, in Longview, Wash., in the southwest part of the state. His mother, Velva (Diede) Walden, taught elementary school; his father, Clarence, taught high school chemistry and physics. The family moved to the San Francisco Bay Area when Mr. Walden was 4.
An avid bridge player from a young age, Mr. Walden helped support himself as a student at the University of California, Berkeley, by working at a local bridge club. But so consuming was his passion for the game that he left college after one semester because of poor grades, his wife said.
Mr. Walden eventually enrolled at San Francisco State College (now University) and received his bachelor’s degree in mathematics in 1964. His interest in computing grew from a course he took in numerical analysis that involved working on an IBM computer.
After college, he went to work for the Massachusetts Institute of Technology’s Lincoln Laboratory as a computer programmer in the Space Communications Division.
In 1965, he met Sara Elizabeth Cowles, an education administrator, and they married the next year. He was hired at Bolt Beranek and Newman in 1967. Soon after, the company won a contract to build the first I.M.P.
“It was a very small group working together all the time,” Mr. Walden said in a 1990 interview with the Charles Babbage Institute at the University of Minnesota, an archive and research center specializing in information technology.
“We were in and out of each other’s offices and helping each other debug,” he added.
Every discovery drew excitement. “We’d run in and say, ‘Look, I got this running!’” he said.
Mr. Walden left Bolt Beranek for a year in 1970 to work at Norsk Data, helping that company build a computer modeled after the I.M.P. He returned to Bolt Beranek in 1971 and stayed until 1995. He later became an expert in the field of management. An avid computer historian, he was an editor at the IEEE Annals of the History of Computing, published by what was originally the Institute of Electrical and Electronics Engineers.
Although he did not hold an advanced degree, Mr. Walden received an honorary doctorate from California State University in 2014 for his work on the Arpanet. “He remarked to me on more than one occasion that he never thought he would get that kind of honor,” Alex McKenzie, a former colleague of Mr. Walden’s, said in an interview.
In addition to his wife, Mr. Walden is survived by his son, Luke; his brother, Daniel; his sister, Velma Walden Hampson; and two grandchildren.