in southern Bavaria, where Konrad Zuse met Wernher von Braun. By 1947 it was possible for constants to be entered by the punched tape. Use after World War II In 1949, the Swiss mathematician Eduard Stiefel, after coming back from a stay in the US where he inspected American computers, visited Zuse and the Z4. When he formulated a differential equation as a test, Zuse immediately programmed the Z4 to solve it, Stiefel decided to acquire the computer for his newly founded Institute for Applied Mathematics at the ETH Zurich. It was delivered to ETH Zurich in 1950. In 1954, Wolfgang Haack tried to obtain the Z4 for the Technical University of Berlin, but it was instead transferred to the (ISL, Franco-German Institute of Research) in France, where it was in use until 1959, under its technical head Hubert Schardin. Today, the Z4 is on display in the Deutsches Museum in Munich. The Z4 inspired the ETH to build its own computer (mainly by Ambros Speiser and Eduard Stiefel), which was called ERMETH, an acronym for ("Electronic Computing Machine ETH"). In 1950/1951, the Z4 was the only working digital computer in Germany, and the second digital computer in the world to be sold, beating the Ferranti Mark 1 by five months and the UNIVAC I by ten months, but in turn being beaten by the BINAC (although that never worked at the customer's site). Other computers, all numbered with a leading Z, were built by Zuse and his company. Notable are the Z11, which was sold to the optics industry and to universities, and the Z22. In 1955 the Z4 was sold to the French-German Research Institute of Saint-Louis (Institut franco-allemand de recherches de Saint-Louis) in Saint-Louis, close to Basel, and in 1960 transferred to the German Museum in Munich. The Z4 was used for calculations for work on the Grande Dixence Dam. Specifications Frequency: (about) 40 Hz Average calculation speed: 400 ms for an addition, 3 seconds for a multiplication. Approximately 1000 floating point arithmetic operations on average an hour. Programming: holes in 35 mm film stock, punched on a programming machine Input: Decimal floating point numbers, punch tape Output: Decimal floating point numbers, punch tape or Mercedes typewriter Word length: 32 bits floating point Elements: (about) 2,500 relays, 21 step-wise relays Memory: Mechanical memory from the Z1 and Z2 (64 words, 32 bit) Power consumption: (about) 4 kW