In 1941 he completed the Z1, the world's first fully operational automatic digital computer: a mechanical device of limited capacity and speed. Zuse then developed an electric model based on telephone relay technology, and planned a much faster machine to be built with electronic tubes. This had only reached the stage of a small prototype when, in 1942, the project was axed by the German Army Command. As one historian later wrote, Zuse "cracked open the door to an awesome and strange new world, but that door slammed shut before he could pass through".
Zuse was born in 1910 in Berlin, the son of a post office official. As a boy he was gifted in both the arts and sciences: an accomplished artist and an enthusiastic amateur actor, he also delighted in constructor sets and decided to make his living as an engineer. In 1927 he enrolled at the Technical University of Berlin-Charlottenburg, where he studied civil engineering. On graduating in 1935 he became a stress analyst for the Henschel Aircraft Company, where he worked on problems of aircraft vibration. Stress analysis involved formidable calculations, which could then only be performed with great difficulty using teams of human "computers" equipped with desk calculating machines.
Zuse was seduced by the calculating problem. Working in his own time in the evenings and at weekends, he began to design and build a mechanical computer in the living room of his parents' house. He called the computer the "V1" for Versuchsmodel 1 - Experimental Model 1. (After the war he renamed his machines Z1, Z2 etc, to avoid confusion with Wernher von Braun's flying bombs.) As a computer builder, Zuse worked as an amateur, completely outside the mathematical community, although he obtained some financial assistance from a local calculating machine manufacturer. He also persuaded a former university classmate, Helmut Schreyer, to work with him.
When it was completed in 1938 the Z1 was too small and crude for realistic calculations, so plans were laid for a full-scale machine. In 1939 war broke out, however, and Zuse was drafted into the infantry to serve in the front line. It took months of pleading for the German Army Command to accept the military significance of Zuse's computing work and allow him to return to his computer building. He now joined the Third Reich's Aerodynamics Research Institute which funded the building of a full-scale computer, the Z3. The Z3 became operational in December 1941, and was by two years the world's first practical automatic computer. A second machine, the Z4, was quickly commissioned.
Up to this time, Zuse's machines had been based on relay technology, which limited computing speeds to a few arithmetic operations a second. Schreyer proposed that their next machine should be based on electronic tubes, which would be potentially a thousand times faster. Only a 150- tube prototype had been completed when the project was discontinued as the German military authorities believed the end of the war was in sight.
In 1943, when the tide turned against Germany, the Z3 was destroyed by the Allied air raids on Berlin. With the intervention of Wernher von Braun the Z4 was taken to safety in the underground Harz mountain chambers where the V1 and V2 flying bombs were being developed. With extreme material shortages of every kind, Zuse and Schreyer had to abandon computer building. As the war came to its end, Schreyer, a Nazi Party member, fled to South America, while Zuse, who was neither a party member nor a dissident, retreated to an Alpine village, Hinterstein, for the next few years; there he first rescued and then preserved the precious Z4 computer in a stable.
He began to look at an aspect of computing that did not require physical resources - computer programming. He devised a remarkable system, the Plankalkul, which anticipated many programming concepts that only surfaced in the United States and Britain in the early 1950s. Like his earlier computer work, the Plankalkul was a kind of desert-island computing - entirely born of Zuse's mind, neither influenced by, nor influencing, the work of others.
In 1949, when the first electronic computers in America and Britain were becoming operational, the Federal Polytechnic Institute in Zurich acquired the carefully preserved Z4. Refurbished, it was pressed into service in 1950, helping to establish the institute as a leading centre of computing research in continental Europe.
In 1950, as German industry re-established itself, Zuse, still only 40, set up a successful computer manufacturing business, Zuse KG. The firm produced a number of slow but inexpensive relay-based computers, before making in 1958 the Z22, a full-scale electronic computer of which some 50 were sold. The 1960s were a difficult period for the European industry, with the onslaught of IBM and the American giants. In 1967, Zuse KG was acquired by Siemens. Zuse remained active as a consultant and researcher for several years. In his retirement he devoted his time to sketching and painting. He was an accomplished and natural draughtsman.
Outside Germany, Konrad Zuse was almost unknown until the 1960s, and his computer research had no discernible impact on the mainstream of computer development. Even his Plankalkul was not published in English until 1972, when software had advanced so far beyond his work of 1945 that it was little more than an academic curiosity. But a new generation of computer scientists and engineers recognised the enormity of Zuse's accomplishments, which were even more impressive for having been undertaken in almost total isolation. In the 1970s and 1980s Zuse was showered with honorary degrees, and awards and medals from the computer and electrical engineering institutions.
Konrad Zuse, computer scientist: born Berlin 22 June 1910; married (two sons, two daughters, and one son deceased); died Hunfeld, Germany 19 December 1995.