The Clicking Computer: How the Lost Z3 Was Resurrected ✛ ✎

Original: "The Reconstructions of Konrad Zuse's Z3 Computer"

arXiv:2607.13089 · 2026-07-13 · arXiv non-exclusive · independent analysis · 2 min

cs.GL cs.AR History and Philosophy of Physics

Destroyed in the war, the Z3 comes back to life through replicas that show how early computing machines worked.

Berlin, December 1943. A bomb hits a building, and the first automatic programmable computer, the Z3, vanishes in the flames. Its creator, Konrad Zuse, does not rebuild the machine. But the idea of the Z3—like a lost painting, with only sketches remaining — waits for its moment. Years later, engineers reconstruct the logic of this masterpiece from surviving blueprints and circuit descriptions.

2500 relay switches in one replica — roughly like stars in the sky on a clear night. Each clicks in its own rhythm, and the machine comes alive, like a mechanical orchestra.

Inside the Z3, relays (electromagnetic switches) do the work. They open and close rapidly, sending electrical signals along wires without interference. Commands are read from a punched tape. This way, the computer cycles through numbers, performs calculations, and refines its algorithm — all strictly step by step. The process is controlled by a digital computing unit, where bits race through logic circuits like blood through vessels.

Modern replicas don't hide the mechanics: in the 2024 Swiss version, you can see the rotating shafts of stepping switches. This is a digital computing machine that openly shows its workings. Such replicas are teaching tools: students see how simple switches come together to form a computer. Slow, visible operation is ideal for learning.

The original Z3 weighed a ton, consumed 4000 watts, and performed just 3–4 additions per second. Your smartphone is billions of times faster but runs silently, whereas the Z3 sang relay music.

Eighty years after the bombing, the relays click again. The painting once thought lost has been given new life — not as an exhibit, but as a living tool of knowledge.

The original Z3 weighed a ton and did only 3–4 additions per second — any modern pocket calculator is quicker. But it could work with very large and very small numbers thanks to a clever way of writing numbers.

It's like something out of steampunk science fiction — a mechanical computer, but actually built in 1941.

(-1)^s \times 1.m \times 2^{(e-64)}

Number representation in the Z3: s is the sign, m the mantissa, e the exponent with an offset of 64.

Concepts

Turing machine numerical simulation Vlasov equation

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The Clicking Computer: How the Lost Z3 Was Resurrected ✛ ✎