The Long Lost Manual for the World's Oldest Preserved Computer Has Been Found

The Zuse Z4, a digital computer built in 1945 and currently preserved at the Deutsches Museum in Munich, finally has a manual to fully reveal its secrets.
September 22, 2020, 3:52pm
The Long Lost Manual for the World's Oldest Preserved Computer Has Been Found
The Z4 on display. Image: Clemens Pfeiffer/Wikimedia

The missing manual for one of the world’s first digital computers has been found in a pile of documents in Zurich, according to a blog post from the Association of Computing Machinery written by retired ETH Zurich lecturer Herbert Bruderer.

According to Bruderer, the Zuse Z4 is considered the oldest preserved digital computer in the world. Built in 1945, the Z4 is one of those machines that takes up a whole room, runs on magnetic tapes, and needs multiple people to operate. Today it sits in the Deutsches Museum in Munich, unused. Until now, historians and curators only had a limited knowledge of its secrets because the manual was lost long ago.


The Z4 was the last computer the Nazis invented. Ahead of the Soviet invasion of Berlin, the Wehrmacht evacuated the machine west to Göttingen. It’s inventor Konrad Zuse—inventor of the world’s first programmable computer, the Z3—completed work on the Z4 in Göttingen but had to move the machine again ahead of the Allies. From there, the Nazis wanted Zuse and his Z4 to move to the Mittelbau Dora, where slaves were building V1 and V2 rockets.

Zuse refused and escaped South to the small German town of Bad Hindelang. He hid the computer in a barn and waited out the war selling woodcuts to local farmers and American troops.

After the end of World War II, Zuse became regarded as the father of modern commercial computers and the Z4 was his flagship machine. It was one of the only computers on continental Europe and everyone wanted it. Eventually, the Z4 ended up at the Institute of Applied Mathematics at the Swiss Federal Institute of Technology (ETH) in Zurich where it did calculations for Swiss aviation engineers. It was there, among the historical documents related to planes from the 1950s, that researchers found the Z4’s manual just this year.

Evelyn Boesch from the ETH Zurich University discovered the manual among her father’s documents in March, Bruderer said in his blog post.

Boesch’s father was René Boesch, a researcher working on airplanes in the 1950s under the engineer Manfred Rauscher. “The research revealed that the documents included a user manual for the Z4 and notes on flutter calculations,” Bruderer said in the blog post. “According to the Historical Lexicon of Switzerland, Rauscher, who was professor of Aircraft Statics and Construction at ETH Zurich from 1950 to 1974, was a consultant on the P-16 fighter aircraft.”


According to Boesch’s notes, the Z4 performed around 100 jobs between 1950 and 1955. “These included calculations on the trajectory of rockets, on aircraft wings, on flutter vibrations, [and] on nosedive,” Bruderer said.

At the time, the Z4 was a powerful machine. It could run addition and subtraction in half a second, multiplication in 3 seconds, and perform division and square roots in six seconds. It averaged 1,000 mathematical operations an hour. Zuse invented more computers but never reached the heights of commercial success his successors would hit. He died in 1995.