Willem van der Poel

PTERA with Kosten and Van der Poel

Leen Kosten and Van der Poel (seated) at the PTERA.

Willem van der Poel (2 December 1926, The Hague, The Netherlands) took his final examination of his secondary education in 1944, during the German occupation. Afterwards he registered at an intermediate level technical college, but because of the war it was too dangerous to go there. After the war he studied physics at the Technische Hogeschool Delft (now Delft University of Technology) and worked at the PTT Labs before returning to Delft again, this time as professor. Internationally, Van der Poel also played an important role in the development of the ALGOL programming language.

"I was very bad at mental arithmetic, so even in my elementary school days, from 8 to 12, say, I had an old cash register for doing my sums, and I had the Napier's rods to do the multiplications. From that time on I have always been fascinated by the mechanics of computation." [1]

Willem van der Poel

Early Interest

During the war Van der Poel was already interested in computers. He had searched every nearby library for literature about mechanical desk calculators, integrators and slide rulers for example. Because of the war he knew nothing about American, British or even German progress on the subject, but he was aware of the work Torres Quevedo and of the binary system[2].

In 1944 he made his first design for a calculator. It used telephone stepping switches so it worked in base 10. The machine was not programmable, but it did have programming levels built into it so it could not only add and subtract, but also multiply, divide and calculate sine functions. This machine was never actually built. Considering his age and lack of guidance - he had to work all by himself - it was quite a complex machine.

In 1947, when he was a student at the TH Delft, he built a computer for the optics department. He had already made a design for a programmable, digital relay computer. Resources were scarce at the time, but he managed to get a supply of 600 discarded relays through Kosten, for free. The relays all had to be rewound manually before use though, and Van Der Poel did this himself using a lathe. He also encountered the same problems as Scholten and Loopstra with the relays. He initially thought 30 milliseconds would be an ample estimate for the relays switching time, but sometimes they would bounce and switching could take up to 900 milliseconds. In 1950 Van der Poel left the TH Delft and others students finished the computer, which was nicknamed the Testudo.

The magnetic drum for the PTERA had to be coated with magnetic material. It was sent to another company to have it coated with nickel. When they got the drum back it didn't seem to work. Using an oscilloscope they found out there didn't seem to be any charge on the drum. After contacting the company that coated the drum they discovered they used chromium instead. It looked so much better.

PTT labs

In 1950 Van der Poel took a degree in Physics Engineering under A.C.S. van Heel. He started to work at the PTT Labs. There he started on the PTERA. While building the PTERA the ZERO was also developed to serve as a testing project. The PTERA was a fast but unreliable machine: it worked only about 50% of the time, the rest of the time it was undergoing maintenance. The vacuum tubes had to be tested regularly as well, because their performance degraded over time[3].

Another machine, the ZEBRA, was developed by Van der Poel and Kosten at the PTT labs. It was based on the ZERO. This machine was developed at around the same time as the ARMAC at the Mathematical Center, but the ZEBRA was slightly faster. This was cause for a little friendly competition between the Mathematical Center and the PTT labs. They wanted to have a commercial machine and first Philips was contacted to ask if they wanted to produce the machine. Philips refused the offer. Eventually the English company Standard Telephones and Cables Ltd was willing to produce the machine and in the end around 60 were sold.

Van der Poel wrote a thesis on the ZEBRA called "The Logical Principles of Some Simple Computers" with which he got a degree of Doctor of Mathematics and Physics under Van Wijngaarden. Note that during his working period he worked together with Gerrit van der Mey.

Van der Poel at ZEBRA

Van der Poel posing with ZEBRA.

Back to Delft

In 1962 Van der Poel was nominated for an extraordinary chair in the theory and construction of computer at the University of Technology in Delft. In 1967 he left the PTT labs for an ordinary chair there. Van der Mey came with him to work in Delft.

Around the same time the IFIP Working Group 2.1 on ALGOL was formed. Van der Poel was chairman of the group from 1962 to 1969 and a member after that period.

During his time in Delft he worked on many projects. Most of these projects concerned implementations of various new programming languages on different machines, like LISP implementations for the PDP-8 and PDP-9. Especially in the last 10 years of teaching at the University of Technology in Delft his interest shifted from hardware towards software.

One of Van der Poels hobbies was collecting and designing mechanical puzzles. This also reflects his view on programming. His programming style was nicknamed trickology.

In 1971 he was appointed a member of the Koninklijke Nederlandse Akademie van Wetenschappen (Royal Academy of Sciences). In the same year he was given the honorary degree of Doctor of Technology from the University of Bradford, England. Thirdly, also in 1971, he received the Computer Pioneer Award from the IEEE (Institute of Electrical and Electronic Engineers).

He retired from full professorship in May 1988. He served for 2 years on a part time chair on the Theoretical Aspects of Programming Languages and retired fully in May 1991. At his retirement he was promoted to the order of "Ridder in the Orde van de Nederlandse Leeuw" (Knight in the Order of the Netherlands Lion).


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