When was the Turing machine discovered?

• A. In the 1930s
• B. In the 1920s
• C. In the 1940s
• D. In the 1950s

Answer: (A)

The idea being tested is when the Turing machine was introduced as a formal model of computation. Alan Turing presented the Turing machine in 1936 to formalize what could be computed and to tackle the Entscheidungsproblem. Because the model was defined in 1936, it belongs to the 1930s. The other decades don’t fit: the concept didn’t originate in the 1920s, and while larger computer machines emerged in the 1940s and beyond, the Turing machine itself was first described in the 1930s.