Co-creator of SNOBOL and pioneer in string processing languages, Griswold made lasting contributions to non-numerical computation. He worked for Bell Labs in 1962, where he studied ideas for non-numerical computation. SNOBOL was the outcome; it was a radically different language in its time and still is. He became the head of the Labs' Programming Research and Development department in 1967.
In 1971, Griswold was hired by the University of Arizona to be its first professor of computer science, subsequently organized the department, and was its head until 1981. While at Arizona, he developed Icon. The earlier Ratfor implementation of Icon was discarded and the language rewritten from scratch in C and UNIX.