The simple question of who invented the digital computer has many possible answers. Several strands of development – both theoretical and practical – converged around 1950, and no single inventor can be identified.
Before that time, numerous mechanical calculating machines were devised and constructed. These greatly facilitated the preparation of mathematical tables, crucial for engineering and for navigation, but were of relatively limited power.
In the 1820s, Charles Babbage designed his Difference Engine, an automatic mechanical calculator. He never constructed a working machine but moved on to design a much more ambitious and powerful model, the Analytical Engine.
This was the first example of what might be called a general-purpose computer. However, for various reasons Babbage was unable to complete construction of his pioneering machine.
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Little happened for 80 years or so following Babbage’s work. In 1903, Percy Ludgate, an accountant in Dublin, began work on designing computing equipment. He was initially unaware of Babbage’s Analytical Engine and his design was strikingly different.
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He had, essentially produced the second-ever design of a computer. His plans were never implemented and his work was more or less forgotten for a century. However, his paper, “On a proposed analytical machine”, published in the Scientific Proceedings of the Royal Dublin Society in 1909, was to play a surprising role in the development of computing.
In 1941, German engineer and inventor Konrad Zuse built his Z3 machine. This was the first working programmable general-purpose computer; it contained an arithmetic unit, a control unit, memory, and input and output devices, a structure similar to what we now call the von Neumann architecture.
For some people, Zuse is considered as the inventor of the modern computer. Later, he built a more advanced machine in a bunker in the Harz mountains, where Wernher von Braun was developing ballistic missiles. Completed in 1945 and dubbed the Z4, it had several enhancements over the Z3 and became the first commercial digital computer.
In 1941, Zuse sought a patent for the concept of a programmable digital computer, based on his Z3 computer design. If granted, this would have become the primary patent for the design of digital computers, giving Zuse enormous commercial advantage and influence over subsequent developments. After many delays, the patent office indicated in 1959 that it intended to grant the patent to Zuse.
However, at the last moment a new objection was submitted by motorcycle manufacturer Triumph-Werke, citing that Zuse’s concepts were anticipated in the paper of Percy Ludgate. The German patent office gave its final decision in 1967, some 26 years after the original patent application had been filed, stating that a patent could not be granted “due to insufficient inventive merit”.
A recent article by Brian Coghlan, Brian Randell and Ralf Buelow, in the IEEE Annals of the History of Computing, discusses how the work of Percy Ludgate was of central importance in thwarting Zuse’s patent application. They present evidence that, while the appeal against granting of the patent was made by Triumph-Werke, assistance was provided by IBM to frustrate Zuse’s case. Indeed, Zuse had always maintained that this was the case.
Konrad Zuse never got a patent for his concept of the structure of a digital computer, which today is the basis for most modern computers. He continued his work, developing mainframe computers for academic, administrative and business use and won several prestigious awards. In 1972, he received the Order of Merit of the Federal Republic of Germany. Zuse died in 1995, 30 years ago today.
Peter Lynch is emeritus professor at the School of Mathematics and Statistics, University College Dublin. He blogs at thatsmaths.com
