Colleagues and historians of the computer world honored Dr. Corbató for work that drastically expanded the usefulness of the computer and put its benefits at the reach of all. But he also made his mark on the modern world by conceiving and applying the idea of controlling computer access by passwords. They have been credited with protecting privacy against malice and mischief, but the effort to create and recall them has also been a source of anxiety and frustration.

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Passwords — words or phrases held in secret and known only to the select few — have been part of civilization since classical antiquity. They can be found in the Bible, in the rituals of fraternal groups, and in the lore of the Prohibition period where they provided those in the know with entry to speakeasies and access to forbidden alcohol.

But it appears likely that the indispensability of computers and computerized devices have created an unprecedented use and proliferation of the password. For Dr. Corbató, who was concerned about increasing access to computers while protecting individual privacy and data, passwords seemed a convenient solution.

“The key problem was that we were setting up multiple terminals which were to be used by multiple persons but with each person having his own private set of files” he told Wired magazine. “Putting a password on for each individual user as a lock seemed like a very straightforward solution.”

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The holder of a PhD in physics, Dr. Corbató found during his research at MIT that his interests were shifting from what he was calculating to how it was being calculated, drawing him into the discipline that would become known as computer science.

He entered the new arena in its early days, when the slide rule or the mechanical calculator were mainstays of computation. In 1956, when Corbató began at the MIT Computation Center, machines and their operations were characterized by such items as vacuum tubes, paper tape and stacks of the infamous punch cards — the last giving rise to the slogan “do not fold, spindle or mutilate.”

The machines were big, balky and relatively few in number. Those wishing to exploit the advantage of computers required great patience. They could expect to queue up for the prized opportunity to run programs on them in so-called batch operations one after the other. Dr. Corbató was credited with a major role in the introduction of time-sharing, which permits multiple access to the same device.

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Others were said to have also conceived the idea of time-sharing, but Dr. Corbató was described as having the vision and the persistence to see it through. In that, he was said to have paved the way for the modern age of computer use.

At MIT in 1961, Dr. Corbató and two colleagues, Robert Daley and Marjorie Merwin-Daggett, he built the initial version of the Compatible Time-Sharing System (CTSS). It was demonstrated that November.

“Corby was one of the most important researchers for making computing available to many people for many purposes,” MIT colleague Tom Van Vleck said in the university announcement of Dr. Corbató’s death. “He saw that these concepts don’t just make things more efficient; they fundamentally change the way people use information.”

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By 1963, an improved version of Dr. Corbató’s CTSS went into daily operation at MIT. It was followed by the introduction of another time shared system: Multiplexed Information and Computing Service (Multics), a prototype of a “computer utility” that provides computing and storage service to a large user community. In addition, Dr. Corbató, who remained affiliated with the Computation Center until 1966, was credited with the groundwork for a third system, known as Unix.

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The Association for Computing Machinery presented Dr. Corbató with the 1990 Alan M. Turing award “for his work in organizing the concepts and leading the development of the general purpose large-scale time-sharing system and resource-sharing computer systems CTSS and MULTICS.”

Fernando José Corbató was born in Oakland, Calif., on July 1, 1926. At the time, his parents were graduate students at the University of California in adjacent Berkeley.

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As a boy, he moved to Southern California when his father became a professor of Spanish literature at the University of California at Los Angeles. His mother was a homemaker.

He enlisted at 17 in the Navy, becoming an electronics technician working on radar and sonar systems during World War II. Afterward, he entered the California Institute of Technology and received a bachelor’s degree in physics in 1950. Continuing his physics education at MIT, he obtained a doctorate in 1956 and advanced to professor on the faculty. He was a former associate department head for computer science and engineering. He retired in 1996.

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His first wife, computer programmer Isabel Blandford, died in 1973. Two years later, he married Emily Gluck. In addition to his wife, of Newton, Mass., and Newbury, Mass., survivors include two daughters from his first marriage, Carolyn Corbató Stone of Huntington, Vt., and Nancy Corbató of Irvine, Calif.; two stepsons, David Gish of Oakland and Jason Gish of Newton; a brother; and five grandchildren.

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As seen through a speech he gave on receiving the 1990 Turing award, Dr. Corbató was a wry and good-natured man. He titled his lecture “On Building Systems That Will Fail,” which would have seemed prescient to many users of the computers of that day.

In building what he called “ambitious systems,” those for which designers had high hopes, he said, the question for designers to ask was not what to do “IF something will go wrong,” but rather how to respond “when it will go wrong.”