# Konrad Zuse and the Z3: The First Programmable Computer

## Overview

Konrad Zuse (1910–1995) was a German civil engineer and computer pioneer who, largely
in isolation from the Anglo-American computing efforts of the 1940s, designed and built
a series of computing machines in his parents' living room in Berlin.

## The Z1 (1938)

Zuse's first machine, the Z1, was a mechanical binary calculator built almost entirely
from sheet metal cut by hand. It was unreliable due to manufacturing tolerances but
demonstrated the core concept: binary floating-point arithmetic using mechanical relays.
The Z1 was destroyed in the Allied bombing of Berlin in 1943.

## The Z3 (1941)

The Z3, completed in May 1941, is recognised by most historians as the world's first
working **programmable, fully automatic digital computer**. Key specifications:

- **Technology:** 2,600 telephone relay switches
- **Word length:** 22-bit floating-point
- **Clock speed:** approximately 5–10 Hz (one multiplication per 3 seconds)
- **Programming:** punched film (35 mm cinema strip) — sequences of operations
  encoded as holes in the tape
- **Memory:** 64 words (limited by relay count)

Unlike Colossus (1943) or ENIAC (1945), the Z3 was a **general-purpose stored-program
machine** in principle, though its tape-based programming was more limited than the
stored memory designs that followed.

## Turing Completeness

In 1998, Raúl Rojas demonstrated that the Z3 was Turing-complete — any computable
function could be expressed in its instruction set using conditional loops created by
looping the tape. Zuse himself was unaware of Alan Turing's work and arrived at
similar theoretical foundations independently.

## Commercial Success: The Z4

After World War II, Zuse built the Z4 (1950), which was leased to the ETH Zürich —
making it the first commercially used computer in continental Europe. The Z4 ran
reliably for years, processing structural engineering calculations.

## Plankalkül: The First High-Level Programming Language

Between 1942 and 1945, Zuse designed **Plankalkül** (Plan Calculus), a high-level
programming language with variables, subroutines, and data structures. It was not
published until 1972 and not fully implemented until 2000 — decades after FORTRAN,
COBOL, and LISP. Nonetheless, Plankalkül is considered the first design of a
high-level programming language.

## Legacy

Zuse founded Zuse KG in 1949, one of the first computer companies in Europe, and
continued building relay and transistor-based machines through the 1950s and 1960s.
His work demonstrates that the development of the digital computer was not solely an
Anglo-American achievement — it emerged independently on both sides of the Atlantic
under wartime pressure and without cross-pollination of ideas.
