Konrad Zuse

“Of one thing I am sure – computer development has still a long way to go. Young people have got plenty of work ahead of them yet!” (K.Zuse)

The German engineer Konrad Zuse developed the first functional computer in his parents’ living room just before World War II. His first machines were all built in relative isolation and predate the American ENIAC, the British Colossus, Howard Aiken’s Harvard Mark I and even the Atanasoff-Berry Computer.

Konrad Zuse was born on June 22, 1910, in Berlin, Germany, as the son of a German postal clerk. In 1912 his parents moved to Braunsberg where the young Zuse would receive his first schooling. Later the family moved to Hoyerswerda where Zuse received his high school diploma in 1928. Following his childhood dreams of designing rockets he started his studies in civil engineering at the Technische Hochschule Berlin-Charlottenburg where he graduated in 1935. During his engineering studies he had become frustrated by the many tedious calculations he had to perform and he soon had developed a set of forms with rectangular boxes in which he could record the many intermediate results for a complex formula. Still not satisfied he then turned his mind to how he could automate this process and design a machine that could do the work for him. After his graduation he joined the Henschel Aircraft Company as a design engineer but after one year he resigned in order to concentrate on the construction of his calculating machine.

The Z1

It should be stressed that Zuse was an engineer and as such he was not familiar with work done earlier by Babbage on his Analytical Engine. This makes his achievements even more remarkable as he basically started from scratch without any preconceived ideas. In 1936 he set up his small workshop in his parents’ living room and with assistance from a few close friends who lent him a helping hand and a bit of money, Zuse started development of his calculating machine. He decided that his machine should not be based on a decimal pinwheel, like the mechanical calculators and tabulators of that time, but rather on a yes-no type system controlled by small pins slotting in and out of metal plates. He didn’t realize that he was developing the first electro-mechanical binary calculator. Rather than using punched paper tape to input the computer’s program – difficult to obtain in pre-war Germany – Zuse used second-hand 35mm celluloid film strips supplied by one of his friends who happened to be a film projectionist. He used a hand-punch for punching the holes in the tape. He called the first machine the V-1 (Versuchsmodell-1 or experimental model 1). Subsequent models were simply named V-2 and V-3. In order to eliminate possible confusion with the infamous flying bombs developed during the war by his friend Wernher von Braun, he changed the names of his models after the war to Z1, Z2, etc. The Z1 was completed in 1938 and was the first binary calculating machine, operating with floating-point numbers consisting of a 16-bit (catering for 4 digits) mantisse, a 7-bit exponent and a 1-bit sign. The machine could store 64 such 24-bit floating-point numbers. The output was shown on a 4-decimal-digit display board using an annunciator. This machine did not survive the war but a replica which was built by Zuse in the late eighties can be seen today at the Museum for Transport and Technology in Berlin.

The Z2 and Z3

As the workshop at his home was not adequate to produce a perfectly working Z1, Zuse was already thinking of the next version, the Z2. Although he was advised to use vacuum tubes in the new machine, it was virtually impossible in 1938 Germany to obtain the one thousand vacuum tubes he deemed necessary. So, instead of tubes Zuse decided to use relays. Not being able to afford new relays, he managed to find enough second-hand telephone relays to continue the development for the Z2. All went well till 1939 when Zuse was called up for the German Wehrmacht. Several attempts were made to get him out of military service – he even proposed to develop a vacuum tube based anti-aircraft system for them. The army staff showed little interest in this system as Zuse indicated he would need about two years to build the system, by which time the army believed the war would have been won. Still, it would take more than six months before he was released to return to the Henschel Aircraft Company. This enabled him to spend his spare time on constructing the Z2. The Z2 was completed in 1940, reason for Zuse to found his own company, Zuse Apparatebau, for the production of his computers.

In 1941 Zuse built the Z3, using 2,400 relays. It was the first fully functioning, programmable, digital computer, with the ability to add, subtract, multiply, divide and calculate a square root. [This is quite amazing, as the 4K memory IBM 1401 mainframe this author has been programming in the mid sixties didn’t have a multiply or divide function, although this was available as an additional option from IBM.] The Z3 had a speed of 3-4 additions or subtractions per second, while a multiplication took about 4 seconds (the 1939 Atanasoff-Berry Computer had a speed of 1 addition per second.) The floating-point numbers were limited to 4 decimal digits which severely limited its application. The machine included routines for converting binary floating-point numbers to decimal and vice versa. Like its predecessors, the Z3 did not survive the war as Zuse’s company, including the Z3, was destroyed during an air bombing raid in December 1943. A replica built 20 years later can be found in the Deutsches Museum in Münich.

The Z4

The Deutsche Versuchsanstalt für Luftfahrt (German Research Institute for Aviation) had given Zuse some financial support in developing the Z3, so in 1942 he started working on his next model, the Z4. It was planned very similar to the Z3 with a mechanical memory and an increased capacity of 1,024 words of 32 bits each. As the war progressed, procurement of the necessary materials proved increasingly difficult, but towards the end of the war the Z4 neared completion. With the bombing raids on Berlin increasing, Zuse decided in early 1945 to remove his machine from Berlin and found a place in Göttingen at the Aerodynamische Versuchsanstalt (Aerodynamic Research Institute). With the allied forces approaching Göttingen a few weeks later the Ministry of Aviation ordered him to remove the machine to an underground storage facility in the Harz mountains. On arriving Zuse didn’t find it a suitable environment and he continued south on a harrowing journey. They finally landed up in the small village of Hinterstein in the Allgäuer Alps close to the Austrian border where the Z4 was hidden for the remainder of the war.

After the war

After the war the allied forces interviewed all German engineers, including Zuse, but the story on his machines did not convince the interviewers that there was any scientific value in his computing machines. Although developed during the war, in 1945 Zuse published the first-ever high-level programming language Plankalkül (Plan Calculus) and used it to develop the world’s first chess playing program. Plankalkül was an algorithmic language which already could handle multi-dimensional arrays (or tables). It was a remarkable achievement if one keeps in mind that the next high-level language, FORTRAN (for FORmula TRANslation), only came to light in the fifties. Plankalkül was never widely used as there was no compiler/interpreter available to translate the high-level instructions into machine language – it was only in 2000 that a team of the Free University of Berlin managed to develop this facility. In 1949 Zuse re-established his own company under the name Zuse KG (Kommandit Gesellschaft meaning limited partnership) and completed the Z4. Adding a few functionalities, including conditional branching, the revamped Z4 was taken to Switzerland in 1950 and installed at the Eidgenossisch Technische Hochschule (Federal Technical University) in Zürich, Switzerland, where it stayed in use till 1955. This also made the Z4 the first commercial computer in operation. In 1948, the American company IBM picked up rumours about the new computers in Germany and instructed its local representative, Hollerith GmbH, to investigate. This resulted in IBM-USA buying options on some of Zuse’s patents, however there never was a final contract signed between IBM and Zuse as IBM didn’t want to allow Zuse to work any further on computing machines.

Zuse continued development of his machines, each version receiving an appropriate higher number – in 1961 the Z23 was born. In 1964 Zuse KG was taken over by Brown Boveri & Co which would later become part of the Siemens concern – Zuse decided to stay on as a consultant engineer. In 1969 Siemens scrapped the Zuse logo and Zuse decided to retire. However, he continued to develop replicas of the machines destroyed during the war, and he rebuilt the famous Z1 and Z3. During his retirement he also spent time on his second love – painting. In 1993 he published his autobiography The Computer – My Life. Konrad Zuse died on December 18, 1995, in Hünfeld, Germany.

Zuse honored

In 1967 Zuse received Germany’s highest ranking award for technical sciences, the Werner von Siemens Ring.
In 1965 the IEEE (Institute of Electrical and Electronics Engineers) Computer Society awarded him the Harry H. Goode Memorial Award ”For his contributions to, and pioneering efforts in, automatic computing; for independently proposing the use of the binary system and floating-point arithmetic; and for designing the first program-controlled computer in Germany - one of the earliest in the world.”
In 1972 he received Germany’s Large Cross of Merit.
In 1999 he was awarded posthumously Silicon Valley’s Computer History Museum Fellow Award “For his invention of the first program controlled electromechanical, digital computer and the first high-level programming language “Plankalkül”.”
In addition Zuse received numerous honorary doctorates, while in Germany several schools, streets and even an hotel in Hünfeld have been named after him. In 1995 Hoyerswerda, the town where he spent his youth, opened the Konrad Zuse Computer Museum.

Until 2009, the only stamp portraying Konrad Zuse was issued by Guinea-Bissau, but in 2010 Germany commemorated the centenary of his birth with a stamp. The portrait-side of the stamp is made up of binary ones and zeroes – an appropriate tribute to this computer pioneer.

It is amazing to realize that this man, hardly known beyond the borders of Germany, who didn’t have the equipment and support of a large university like the ENIAC developers in the U.S., or a large support group like the Bletchley Colossus developers in the U.K, with just a small group of friends and minimal financial support from outside sponsors, while a full-scale war was raging around him, managed to develop the first digital computer in virtual isolation. A most remarkable achievement.

© Wobbe Vegter, 2008

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