Berlin - It's hard to imagine today, but Berlin-Kreuzberg was, along with Bletchley Park near London and Los Alamos in New Mexico, the site of pioneering computer research that laid the groundwork for the digital world of today. 

Alongside Britain's Alan Turing and John von Neuman, a Hungarian mathematician who emigrated to the US, Berliner Konrad Zuse built the world's first functioning digital computer.

As a structural engineer at the Henschel aircraft factory in Berlin, he had a permanent position, an enviable status in the economically depressed Germany of the early 1930s. But performing repetitive structural calculations bored the mechanical and civil engineer so much he quit his job in 1935 to become an inventor.

In his parents' living room, he developed a calculating machine to perform tedious calculations automatically, a forerunner of digital calculators. Known as the Z3, it went into operation for the first time exactly 80 years ago - on 12 May 1941.

A mechanical brain

Zuse wanted nothing less than to design a "mechanical brain". The 25-year-old broke new conceptual ground as the machine was to use the binary system, i.e. perform calculations using zeros and ones or - put differently - the states "true or false". Zuse hoped to use binary logic to control sequences. The method later formed the basis of the digital age.

To handle structural calculations, Zuse created a compact memory system for 16 numbers. In his initial attempts at building a mechnical computing machine, he drew on an experience from his youth. After graduating from high school, he assembled a complex coal crane using a metal construction kit from Stabil, for which he received a certificate of honour from the company. Zuse's first calculator - the Z1 from 1938 - consisted of a complex system of layered metal strips.

"The Z1 was stuck most of the time," writes Berlin computer scientist and historian Ralf Bülow in a blog post for the world's largest computer museum, the Heinz Nixdorf MuseumsForum in Paderborn for the Z3 anniversary.

Mike Peel/CC-BY-SA-4.0.license
A replica of the Z1 at the German Museum of Technology in Berlin.

Two hundred electromagnetic relays

In his second attempt, Zuse abandoned an exclusively mechanical solution. This time, around 200 electromagnetic relays were to take over the computational work. The Z2 functioned better than the Z1, but was not reliable enough for commercial use. It did, however, spark the interest of Alfred Teichmann of the Institute for Strength at the German Aviation Research Institute (DVL).

At the institute located at the Johannisthal airfield in Berlin-Adlershof, Teichmann was primarily concerned with the phenomenon of flutter. "This is what aviation experts had been calling the rhythmic vibration in aircraft wings and tail units that had been occuring at certain speeds since the 1920s. In the worst case, the aircraft crashed," writes Bülow. The DVL engineers tried to get the flutter under control by making design improvements. For example, weights integrated in the wings were moved to change the centre of gravity. But this required a lot of calculation. When Teichmann saw the Z2, he recognised the possibilities for flutter research. Zuse was commissioned to build a larger computer.

Zuse needed another year to develop the successor model, the Z3. The machine was a great success, although it was largely ignored in the German war economy. Nonetheless, the Z3 has gone down in computer history as the first freely programmable and programme-controlled calculating machine. In short, the Zuse Z3 was the first digital computer of the modern era.

The test run took place 80 years ago, on 12 May 1941 at Methfesselstraße 7 in Kreuzberg where Zuse had set up his workshop. "There were 2,000 relays in the Z3's calculator and memory unit; there was a small control panel for inputting and outputting the numbers, and programming was done with perforated film strips," Bülow writes. "If you allow for the use of electromagnetic technology, the Z3 was the first functioning computer."

Deutsches Museum, Munich/CC BY-SA 3.0 license
A replica of the Z3 at the Deutsches Museum, Munich.

Z3 destroyed in a bombing raid

The Z3 was never put to productive use. The machine was demonstrated several times, but destroyed in 1943 during an Allied aerial bombing raid on Berlin. Zuse launched various entrepreneurial projects after the war, but enjoyed no long-term success. He died in Hünfeld, Hesse in 1995. The first computer based on vacuum tube technology, the ENIAC developed by John Mauchly and John Presper Eckert in the United States, was completed in 1946. The "Electrical Numerical Integrator And Calculator" was intended - as the name suggests - to speed up numerical integration, i.e. the calculation of an area beneath a curve in the coordinate system. This was not an abstract mathematical exercise. Rather, it was intended to help US troops quickly calculate the trajectories of artillery shells during the Second World War.

However, the machine wasn't completed until after fighting ceased. With the advent of the Cold War, though, the ENIAC was used by US scientists in Los Alamos to calculate the destructive power of the first hydrogen bomb.

picture alliance / Karl Staedele/dpa
Konrad Zuse in 1982.

The Kreuzberg Google campus that wasn't

A 1:1 model of the ENIAC can be admired at the HNF in Paderborn. A functioning replica of the Z3 sits in the Deutsches Museum in Munich. Another replica built by the computer pioneer's son, Prof. Dr. Horst Zuse, in 2010 to celebrate what would have been his father's 100th birthday is on display at the German Museum of Technology in Berlin. He followed his father's career path and is an accomplished computer scientist and pioneer of software quality assurance.

In 2017, Google announced it was setting up a campus in Kreuzberg, but in 2018 the project was cancelled after fierce protests by locals. According to insiders at Google, the Kreuzberg location was chosen partially because of its proxity to where Konrad Zuse did his pioneering work.

Berlin news in English.