“There was a rally,” Peter D. Lax said, recalling a moment from half a lifetime ago — half his lifetime, anyway. He is 89 now and talking about the spring of 1970, when a computer at New York University was, as Dr. Lax’s biographer put it, “kidnapped.”

That word sounds almost prankish. A computer that weighed tons, as that one surely did, could not have been kidnapped and carried off, the way Helen was in ancient Greece. But Dr. Lax remembers nothing prankish. “As I found out at the end,” he said the other day, “they hung bombs on the computer.”

N.Y.U. students angry about the Vietnam War and the shootings at Kent State University — where National Guard troops sent in by Gov. James A. Rhodes of Ohio had fired into a crowd of demonstrators, killing four students and wounding nine others — seized the building at N.Y.U. that housed the computer, Warren Weaver Hall, at 251 Mercer Street, at West Fourth Street.

“We had a one-minute warning,” recalled Dr. Lax, a mathematician who was the director of the university’s computer center at the time. “The son of a friend ran in” and shouted that the demonstrators were coming for the computer, he said. “It was too late to call the police and fortify.”