ProCoS: How It All Began - as Seen from Denmark

I reminisce over an episode at the 9–13 November 1987 IFIP WG2.3 meeting at Château du Pont d’Oye in Belgium — and at what followed. I had given, at an IFIP WG2.3 meeting, in Belgium, a half hour presentation of how we, in Denmark, had developed a compiler for the full Ada programming language. My presentation had evolved around a single slide showing boxes and arrows between these, all properly labeled. Edsger W. Dijkstra had railed during my short presentation against my using diagrams — despite my claiming that boxes denoted certain kinds of algebras and arrows certain kind of morphisms between these. After my talk there was a coffee break. Tony Hoare took me aside. Asked permission to write in my note book. And this is what he wrote: ∗ Paper read at the BCS-FACS ProCoS Workshop on Provably Correct Systems, London, UK, 9-10 March 2015.