Stephen Cole Kleene was an American mathematician. Kleene was born in 1909 in Hartford, Connecticut. Kleene was educated at Amherst College and earned a Ph.D. in mathematics at Princeton University in 1934. After teaching briefly at Princeton, he joined the University of Wisconsin at Madison as an instructor in 1935 and became a full professor there in 1948. Kleene’s research was devoted to the theory of algorithms and recursive functions. Kleene, together with Alonzo Church, Kurt Godel, Alan Turing, and others, developed the field of recursion theory, which made it possible to prove whether certain classes of mathematical problems are solvable or unsolvable. Recursion theory in turn led to the theory of computable functions, which governs those functions that can be calculated by a digital computer. Kleene was the author of Introduction to Metamathematics (1952) and Mathematical Logic (1967).        In 1990 he was awarded the National Medal of Science. He died on January 25, 1994 in Madison, Wisconsin, United States.