On 12 May 1941 the German engineer Konrad Zuse presented the Z3, widely regarded as the first working program-controlled, fully automatic computing machine. It was electromechanical, built from about 2,000 telephone relays, and worked in binary floating point with a 22-bit word. Its instructions were read from a punched film tape, so changing the calculation meant feeding in a different tape rather than rewiring the machine. The original was destroyed in an Allied air raid on Berlin in 1945.