Named in memory of Alan Mathison Turing (1912–1954), English mathematician and logician, a pioneer in the study of computability. In a fundamental paper published in 1936, he introduced the concept of an abstract computing machine and showed how such a machine can be programed to simulate the behavior of any other computing device. This concept, now referred to as a “universal Turing machine”, was introduced years before the advent of programable computers, and it was used to demonstrate the existence of noncomputable numbers and undecidable mathematical propositions. (M 34633) _ _.