Konrad Zuse. Biography. Contributions. Zuse-Companies. Z3r. Tour-Zuse-Computer. Z23 Crosses Altlantic. Early Computers. Neumann vs Konrad Zuse. Impressum and Contact. Professor Dr.-Ing. habil.
Horst Zuse

Konrad Zuse’s Contributions to the modern Computer

Ambros Speiser /SPEI98/ and F.L. Bauer /ROJA98a/ say that Konrad Zuse must be credited with the following fundamental inventions in the area of computing development, where most of them were implemented in the machines Z1 (1938), Z3 (1941) and Z4 (1945), with the exception of the Plankalkül:

* The use of the binary number system for numbers and the circuits.

* The use of floating point numbers, along with the algorithms for the translation between binary and decimal and vice versa.

* An algorithm for the non-restoring calculation of the square-root. With this algorithm, the square-root can be calculated with n steps, if n is the number of digits. This fine method was not known in the US in 1949.

* The carry-look ahead circuit for the addition operation.

* Look-Ahead: The program is read two instructions in advance, and it is tested whether memory instructions can be performed ahead of time.

* Pseudo-memory: In case the look-ahead mechanism finds that a number that is to be restored is needed again within the next two instructions, the number id placed in a register of mechanical contacts where it is available with no access time. For this purpuse, the memory has two registers of reading contacts.

* Special values (Sonderwerte): If a result exceeds the capacity of the arithmetic unit, it is designed as Sonderwert. This principle guarantees that the machine always calculates correctly.

* The most unusual feature was undoubtedly the mechanical binary cells that made up the memory. The memory has 64 words with 32 bits (Z1 and Z4). These devices were completely different from mechanisms in contempory cash registers or desk-top calculators. The elements could be used not only for storage, but also for calculation, for example for address coding. A relay memory would have required about 2500 relays which would have more than doubled the size and the weight of the machine Z4.

* The Plankalkül as the first complete high-level language of the world in 1945/46 (final edition).

All these ideas were Konrad Zuses personal achievements. In one or two cases he was perhaps not the first inventor, but he certainly had no knowledge what was done elsewhere;

Until 1950 he lived in complete isolation from the world outside Germany. I think, that Giloi /GILO97/ writes very correctly: Through Brian Randell’s book /RAND73/, an English translation of Zuse’s first patent application of 1936 /ZUSE36/ has become more widely known, proving that Zuse had already developed many of the major concepts of the digital computer years before John von Neumann, Arthur Burks, and Herman Goldstine wrote their famous report /BURK46/.


/ROJA98a/ Rojas Raul (Editor): Die Rechenmaschinen von Konrad Zuse, Springer Verlag, 1998.

This is a detailed analysis of a Konrad Zuses machines Z1 and Z3 with many new details. It also contains the report of the fight of Konrad Zuse for his patents from 1938 till 1967. Konrad Zuse lost this fight in 1967.

/SPEI98/ Speiser, Ambros: The Early Years of the Institute: Aquisition and Operation of the Z4, Planning of the ERMETH. Departement of Computer Science, ETH-Zürich, 1998.

Ambros Speiser (1998)