Many encyclopedias and other reference works state that the first large-scale automatic digital computer was the Harvard Mark 1, which was developed by Howard H. Aiken (and team) in America between 1939 and 1944. However, in the aftermath of World War II it was discovered that a program controlled computer called the Z3 had been completed in Germany in 1941, which means that the Z3 pre-dated the Harvard Mark I.

The Z3’s architect was a German engineer called Konrad Zuse, who developed his first machine, the Z1, in his parents’ living room in Berlin in 1938. Although based on relays, the Z3 was very sophisticated for its time; for example, it utilized the binary number system and could perform floating-point arithmetic.