David Norman Freeman, 86, of Newtown Square, an IBM executive whose team developed DOS/360, a disk operating system for mainframe computers that remained in use for several decades, died Saturday, Nov. 16, of complications from cancer at Lankenau Medical Center.

In the 1960s, Mr. Freeman joined International Business Machines Corp.’s Endicott, N.Y. development laboratory, where he headed a team that worked on the project.

News of DOS/360 was first aired by IBM in late 1964 and delivered to buyers in June 1966. In its day, DOS/360 it the most widely used operating system in the world, according to a book by E.W. Pugh, L.R. Johnson, and John H. Palmer, IBM’s 360 and Early 370 Systems, published by MIT Press.

“It was an accomplishment he looked back on with pride,” his family said.

After several years at IBM, Mr. Freeman was recruited to lead development of the Duke University computer center in Chapel Hill, N.C. At that time, it was one of the few shared-use networks within an academic setting in this country.

Although he thrived at Duke, Mr. Freeman was much in demand as a facilitator for the large computer systems that were being set up in the 1960s. While on an academic visit to Philadelphia in 1969, he was offered a position as director of computer services at the University of Pennsylvania.

Mr. Freeman accepted the job on the spot and quickly bought a home in the southeast corner of Radnor Township without showing it to his wife, Ellen. The white Colonial house, whose postal address is Newtown Square, has remained in the family for 50 years.

In 1971, Mr. Freeman took a job merging academic and administrative computing systems into a single center at Rutgers University’s New Brunswick campus, the New Brunswick Home News Tribune said in an Oct. 26 article. His title was director and professor of computing.

Daunted by the long commute from Newtown Square to New Brunswick, Mr. Freeman shifted to the private sector in 1973, joining the Wayne-based Ketron Inc., a computer consulting firm, as vice president. The company conducted studies of different topics, including deployment of buses to save school districts money.

He stayed with the firm for 20 years before retiring in 1993.

Born in Boston to Norman Easton Freeman and Charlotte Hume Freeman, he grew up in Wynnewood and then Mill Valley, Calif. He graduated at age 16 from Tamalpais High School in California, and then completed a postgraduate year at Phillips Exeter Academy in New Hampshire before enrolling at Yale University.

He earned a bachelor’s degree from Yale in 1955 and a master’s degree from Cornell University in 1958, both in mathematics. In 1963, he earned one of the first Ph.D.s in computer science to be granted by Cornell.

On a ski trip to Killington, Vt., during his junior year of college, Mr. Freeman met Ellen Wood, a Smith College freshman. They became engaged when she was 19. On the advice of Wood’s father, the two postponed their wedding from 1955 until after her graduation in 1957.

A year into the marriage, Mr. Freeman completed basic training with the Army Reserve. The couple had three children.

Aside from his work, Mr. Freeman held leadership roles with Bryn Mawr Presbyterian Church, Radnor ABC (A Better Chance), Radnor Memorial Library, the Main Line Red Cross, and Friends of Independence National Historical Park. He was a Democratic committeeman in Radnor Township for 35 years.

He enjoyed reading, the cultural life of Philadelphia, cross-country drives, and international travel.

Mr. Freeman took pleasure in being the family’s patriarch and enjoyed spending time with his children and grandchildren. “Small gatherings were good. Big gatherings were even better,” he liked to say.

Besides his wife, he is survived by children Jon, Anne Clothier, and Greg; eight grandchildren; a great-grandchild; and three sisters.

A visitation from 5 to 7 p.m. Friday, Nov. 22, at the McConaghy Funeral Home, 328 W. Lancaster Ave., Ardmore, will be followed by a 10 a.m. funeral service Saturday, Nov. 23, in the sanctuary at Bryn Mawr Presbyterian Church, 625 Montgomery Ave., Bryn Mawr, Pa. 19010. Interment is private.

Memorial donations may be made to the Bryn Mawr Presbyterian Church Foundation at the address above.