Edsger Wybe Dijkstra, 72, a University of Texas professor who was considered a pioneer of computer science, died of cancer Wednesday in Austin. He was renowned for his work in software development and computers, including his early insight that mathematical logic is the basis for programming.

He was also well known for his work regarding the building of computer operating systems and other areas in the field, including his shortest path algorithm.

Ronald McCroby, 68, a master whistler who performed with orchestras and jazz groups, died in Aurora, Ohio, on Monday of a heart attack.

"He didn't whistle like a bird or anything like that, he whistled like an instrument, like a flute or piccolo," said his wife, Barbara. "He used to tell people he played the 'puccolo' - coined from the words piccolo and pucker."

Whistling was an art form to Mr. McCroby. He performed on The Merv Griffin Show, and for Johnny Carson on The Tonight Show five times. He also performed at the Kennedy Center in Washington, and in the Monterey Jazz Festival in California.

He also did voice-overs as a whistling penguin on the Scooby Doo cartoon series, Winnie the Pooh for Disney ads and Tenderheart Bear on American Greetings Care Bear commercials.