John J. Sweeney Jr. earned a law degree from the University of Pittsburgh, and never lost his passion for debate, but the study and teaching of mathematics was his true love.

His legal background became just one of many sources of information to draw upon as he pursued faculty work. He taught math first at the University of Pittsburgh and Duquesne University and then computer science at Indiana University of Pennsylvania from 1979 until retirement in 1998.

He was knowledgeable about computers, music and history, and enjoyed sharing what he'd learned.

Mr. Sweeney suffered a heart attack and died in his Indiana, Pa., home Friday. He was 80.

He grew up in Bellevue, finished at the top of his class at Avalon High School in 1946, and obtained a bachelor's degree in business from Pitt, followed by the law degree in 1953.

After service during the Korean War as an instructor at the Army's guided missile school in Huntsville, Ala., he worked for the Pittsburgh law firm of Puglise and Troiano. Because he enjoyed math more, however, he obtained a master's degree in it from Pitt in 1959 and started his university teaching career.

A proud Irish Catholic who had always enjoyed singing in church choirs, he liked putting his sonorous voice to use in classroom lectures as well. As the computer revolution progressed in the late 20th century, he saw his role as helping students understand its underpinnings based in the study of numbers, which he had mastered.

"He always sought to give people insight into the real math background behind it all," said his son, Patrick Sweeney of the South Side. "You break it down, and it's all about ones and zeros and how the computer calculates things, and he wanted to make sure that was not lost."

Bill Oblitey, an IUP faculty colleague and former chairman of Mr. Sweeney's department there, said he took special interest in privacy issues related to computers, long before that was a common topic of concern. He taught about computer security and numerical methods, in addition to more general computer science subjects, and was known as a talkative faculty member who would speak his mind freely.

Mr. Sweeney was once a Democratic committeeman in Wilkinsburg, and accustomed to trying to be persuasive.

"He would always have his say, and you couldn't easily argue him away. I mean, the guy's a lawyer," Mr. Oblitey said.

Mr. Sweeney was known as well for an extensive collection of records and CDs of classical music, jazz and opera, and encouraging others to listen with him -- usually with the volume high for his maximum pleasure.

On jaunts through the countryside, he showed a still wider scope of knowledge, easily pointing out names of mountains and other landmarks. He would stop to study historical markers. Much of his life was spent either learning or teaching.

He also is survived by his wife, Mary Beth; a daughter, Maureen E. Sweeney of Ben Avon; a sister, Eileen Rathgeb of Hannastown; and two grandchildren.

One hour of visitation will precede a 10:30 a.m. Mass today at St. Thomas More Church, 1200 Oakland Ave., Indiana, followed by burial in Union Dale Cemetery, North Side.

Memorial donations may be made to the Disabled American Veterans Memorial Program, P.O. Box 14301, Cincinnati, OH 45250; or the Greater Pittsburgh Community Food Bank, 1 N. Linden St., Duquesne, PA 15110.