Walter Savitch

Walter John Savitch was best known for defining the complexity class NL, and for Savitch's theorem, which defines a relationship between the NSPACE and DSPACE complexity classes. His work in establishing complexity classes has helped to create the background against which non-deterministic and probabilistic reasoning can be performed.
He also did extensive work in the field of natural [language processing] and mathematical linguistics. He was focused on computational complexity as it applies to genetics and biology for over 10 years.
Aside from his work in theoretical computer science, Savitch wrote a number of textbooks for learning to program in C/C++, Java, Ada, Pascal and others.
Savitch received his PhD in mathematics from University of [California, Berkeley] in 1969 under the supervision of Stephen Cook. Since then he was a professor at University of California, San Diego in the computer science department.