diary80s

During Dijkstra's career at Eindhoven programming had developed from an art to a science. But, by 1982 there was still insufficient official recognition for this development. From Dijkstra's perspective, computer programmers had yet to be taken seriously in the world at large. This observation helps explain why, a year prior, he had warmly welcomed the new journal called Science of Computer Programming. In his words:

“I still remember it well, the day my future husband entered my life”, Ria Debets-Dijkstra recalls. “He was a good-looking man, 20 years of age. He entered our Computing Department with a cane!” [1]. The Computing Department was part of the newly founded Mathematical Centre in Amsterdam. Ria Debets-Dijkstra had already been working there for two years before she saw Edsger Dijkstra on that eventful day in 1951. Dijkstra officially joined the Computing Department in March of the following year.

In their joint report `An introductory essay on three algorithms for sorting in situ', Van Gasteren and Dijkstra explain what Insertion Sort, Heap Sort, and Smooth Sort have in common and how one can derive one sorting algorithm from the other.

On Tuesday 12 January 1982, Dijkstra wrote a letter to Dr. A. Caplin explaining why he had his reservations about the language APL (A Programming Language). Dijkstra did this in response to an earlier letter that he had received from Caplin, a letter in which Caplin asked whether Dijkstra favored APL and, if not, why not. In Caplin's words:

In 1963 Dijkstra explained why he wanted to avoid using case distinctions in the design of a programming language. 18 years later, Dijkstra explained why case distinctions are preferably also avoided when reasoning mathematically.

During the early 1960s, Dijkstra and Naur were much in sync with each other's research aspirations. They were, after all, both involved in implementing and promoting the ALGOL60 programming language. Dijkstra's 1970 `Notes on Structured Programming' was a pivotal point in their relationship, as described in my interview with Naur. From that point onwards, their research agendas diverged.

In 1961, Dijkstra made an analogy between mathematical proofs and computer programs. After noting the analogy, he took aspects from the field of mathematics and projected them onto his own profession of programming.

Twenty years later, Dijkstra still stood by the analogy. This time, however, he projected the lessons he had learned from programming methodology back onto mathematics. Dijkstra was thus, in 1981, keen on defining a mathematical methodology. In Dijkstra's words:

Dijkstra attended the four-day “International Symposium on Algorithmic Languages” in honor of Aad van Wijngaarden who was retiring as director of Amsterdam's `Mathematical Centre'. The symposium was held from Monday 26 October until Thursday 29 October 1981. Ershov and Turski also attended after having spent the weekend with Dijkstra at his home in Nuenen.

In the late summer of 1981, Dijkstra gave several talks in Scotland and Newcastle. Here is an overview of his trip:

+ The Marine Hotel in North Berwick. The host was Mr. Hannah of Burroughs. The audience consisted of 10 men from various Burroughs plants in Europe. Dijkstra lectured for five successive days, between 6 and 7 hours per day. The "standard surprise" from the audience was that the universal quantification over the empty set yields true.

The theme of the International Summer School in Marktoberdorf was "Theoretical Foundations of Programming Methodology". The general pattern of the day was: two lectures — a break — two lectures — lunch — two lectures — break — discussion.

In his trip report, Dijkstra listed several speakers from that summer school: