Zuse Z3

What it is

The Z3 was a program-controlled binary computer built by the civil engineer Konrad Zuse in Berlin. He presented it on 12 May 1941 to scientists from the Deutsche Versuchsanstalt für Luftfahrt, the German aviation research institute. It is widely described as the world's first working programmable, fully automatic digital computer.

How it works

Instead of valves, the Z3 used telephone relays, about 2,000 to 2,600 depending on the source, with roughly 1,400 forming the memory. It worked in binary floating point arithmetic, a choice far ahead of its time, and ran at about five to ten operations per second. Programs were read from punched celluloid film, and results appeared on a lamp display.

Why it stands out

• It used binary floating point numbers, the representation that almost all modern processors use.
• One of its first jobs was helping aviation engineers with wing flutter calculations.
• In a rejected 1936 patent application Zuse also described storing program instructions in memory, years before the stored-program concept became associated with John von Neumann.
• The claim to be first is contested. Britain's Colossus (1943) and the Atanasoff Berry Computer (1942) were electronic, and the Z3 lacked conditional branching. Raúl Rojas showed in 1998 that it is Turing complete only in principle.

Where you meet it

Every computer that represents numbers in binary floating point follows the path Zuse chose. The original Z3 was destroyed in an Allied bombing raid on Berlin in December 1943. Zuse's company, Zuse KG, built a working replica in the 1960s that is on permanent display at the Deutsches Museum in Munich.

Sources

• Zuse Internet Archive (ZIB): Z3
• Wikipedia: Z3 (computer)
• Centre for Computing History: Zuse Z3 completed