Zuse Z3 (1941)
The world's first working programmable, fully automatic digital computer. Built by
Konrad Zuse using 2,600 telephone relays, it featured binary floating-point arithmetic
(22-bit word: 1 sign, 7 exponent, 14 mantissa), a 64-word memory, and programs fed
via punched 35mm film tape.
Completed on May 12, 1941 in Berlin. It could perform addition in 0.8 seconds and multiplication in 3 seconds. Destroyed by Allied bombing in 1944. In 1998, it was proven to be Turing-complete (via a theoretical trick with its loop capability). Zuse received almost no wartime funding -- the German military thought the war would be over before computers could be useful.