Technical Terms and Definitions

Konrad Zuse - People

Konrad Zuse is popularly recognized in Germany as the "father of the computer" and his Z1, a programmable automaton built from 1936 to 1938, has been called the "first computer" in the world. Other nations reserve this privilege for one of their own scientists and there has been a long and often acrimonious debate on the issue of the 'true' inventor of the computer. Sometimes the discussion is preempted by specifying in full detail the technological features of a specific machine. The ENIAC, for example, has been called the first large scale general purpose electronic computer in the world. The ENIAC (acronym for Electronic Numerical Integrator and Computer) was built at the Moore School of Electrical Engineering of the University of Pennsylvania from May 1943 to 1945. It solved its first problem in December 1945 and was officially presented in February 1946. Another contender for the title of first computer is the Mark I built by Howard Aiken at Harvard University between 1939 to 1944. The Mark I was an electro mechanical machine, a kind of hybrid between the totally mechanical nature of previous computing devices and the electronics available at the time (Aiken, Hopper 46). The machine built by John Atanasoff (later called the ABC) at Iowa State College from 1938 to 1942 used vacuum tubes, but was restricted to the addition and subtraction of vectors and had an structure inappropriate for universal computation [Burks, Burks 88]. In direct contrast to these three machines, the Z1 was far more flexible and was designed to execute a long and modifiable sequence of instructions contained on a punched tape. Zuse's machines were not purely electronic and were of reduced size. Since the Z1 was completed prior to the Mark I, it has been called the first programmable calculating machine in the world. Of course the old debate will not be closed with this paper, but we want to show here just how advanced the machines built by Zuse were when considered from the viewpoint of modern computer architecture and compared with other early designs of the time.

The university student Konrad Zuse started thinking about computing machines in the 1930s. He realized that he could construct an automaton capable of executing a sequence of arithmetical operations like those needed to compute mathematical tables. Coming from a civil engineering background, he had no formal training in electronics and was not acquainted with the technology used in conventional mechanical calculators. This nominal deficit worked to his advantage, however, because he had to rethink the whole problem of arithmetic computation and thus hit on new and original solutions.

Zuse decided to build his first experimental calculating machine exploiting two main ideas:

  1. The machine would work with binary numbers
  2. The computing and control unit would be separated from the storage
Years before John von Neumann explained the advantages of a computer architecture in which the processor is separated from the memory, Zuse had already arrived at the same conclusions. In 1936 the memory of the planned machine was completed. It was a mechanical device but not of the usual type. Instead of using gears (as done by Babbage in the previous century), Zuse implemented logical and arithmetical operations using sliding metallic rods. The rods could move only in one of two directions (forward or backward) and were therefore appropriate for a binary machine [Zuse 70]. The processor of the Z1 was completed a few months after the storage unit, using the same kind of technology. It worked in concert with the memory but was never very reliable. The main problem was the precise synchronization that was needed in order to avoid applying excessive mechanical stress on the moving parts. It is interesting to point out that in the same year as the memory of the Z1 was completed, Alan Turing wrote his ground-breaking paper on computable numbers in which he formalized the intuitive concept of computability.

The Z1, although unreliable, showed that the architectural design was sound and compelled Zuse to start investigating other kinds of technology. Following the advice of his friend Helmut Schreyer, he considered using vacuum tubes, but gave up the idea in favor of electro mechanical relays which were easier to obtain before and during the war. An "intermediate" simpler model (the Z2) was built using a hybrid approach (a processor built out of relays and a mechanical memory). Immediately afterwards Zuse started building the Z3, a machine consisting purely of relays but with the same logical structure as the Z1. It was ready and operational in 1941 four years before the ENIAC.