Editing Ole-Johan Dahl (section)

== Career ==
Dahl was born in [[Mandal, Norway]]. He was the son of Finn Dahl (1898–1962) and Ingrid Othilie Kathinka Pedersen (1905–80). When he was seven, his family moved to [[Drammen]]. When he was thirteen, the whole family fled to Sweden during the [[German occupation of Norway]] in [[World War II]]. After the war's end, Dahl studied numerical [[mathematics]] at the University of Oslo.<ref name="BioLexicon"/>

Dahl became a full [[professor]] at the [[University of Oslo]] in 1968 and was a gifted teacher as well as researcher. Here he worked on ''Hierarchical Program Structures'', probably his most influential publication, which appeared co-authored with [[C.A.R. Hoare]] in the influential book ''Structured Programming'' of 1972 by Dahl, [[Edsger Dijkstra]], and Hoare, perhaps the best-known academic book concerning software in the 1970s. As his career advanced, Dahl grew increasingly interested in the use of [[formal methods]], to rigorously reason about object-orientation for example. His expertise ranged from the practical application of ideas to their formal mathematical underpinning to ensure the validity of the approach.<ref>{{cite web |url=https://www.mn.uio.no/ifi/english/about/ole-johan-dahl/ |title=Tribute to Ole-Johan Dahl |author=<!-- Unstated --> |date=2002 |publisher=University of Oslo |access-date=14 November 2020}}</ref>

Dahl is widely accepted as Norway's foremost computer scientist. With Kristen Nygaard, he produced the initial ideas for object-oriented (OO) programming in the 1960s at the [[Norwegian Computing Center]] (Norsk Regnesentral (NR)) as part of the [[Simula]] I (1961–1965) and Simula 67 (1965–1968) [[simulation]] [[programming language]]s, which began as an extended variant and [[Subset|superset]] of [[ALGOL 60]].<ref name="CommonBase">{{cite report |last1=Dahl |first1=Ole-Johan |author-link=Ole-Johan Dahl |last2=Myhrhaug |first2=Bjørn |last3=Nygaard |first3=Kristen |author3-link=Kristen Nygaard |date=1970 |url=http://www.edelweb.fr/Simula/#7 |title=Common Base Language |publisher=Norwegian Computing Center |page=1.3.1 |access-date=14 November 2020 |url-status=usurped |archive-url=https://web.archive.org/web/20131225084408/http://www.edelweb.fr/Simula/scb-1.pdf |archive-date=2013-12-25}}</ref> Dahl and Nygaard were the first to develop the concepts of [[Class (computer science)|class]], [[Subclass (computer science)|subclass]] (allowing implicit [[information hiding]]), [[Inheritance (object-oriented programming)|inheritance]], [[dynamic object creation]], etc., all important aspects of the OO paradigm. An ''object'' is a self-contained component (with a data structure and associated procedures or ''methods'') in a software system. These are combined to form a complete system. The object-oriented approach is now pervasive in modern [[software development]], including widely used imperative programming languages such as [[C++]] and [[Java (programming language)|Java]].

He received the [[Turing Award]] for his work in 2001 (with [[Kristen Nygaard]]). He received the 2002 [[Institute of Electrical and Electronics Engineers]] (IEEE) [[John von Neumann Medal]] (with Kristen Nygaard)<ref>{{cite web |url=http://www.ieee.org/portal/pages/about/awards/pr/vonneupr.html |archive-url=https://web.archive.org/web/20060720182319/http://www.ieee.org/portal/pages/about/awards/pr/vonneupr.html |url-status=dead |archive-date=20 July 2006 |title=Recipients IEEE John von Neumann Medal|website=[[Institute of Electrical and Electronics Engineers]] (IEEE) }}</ref> and was named Commander of the [[Royal Norwegian Order of St. Olav]] in 2000.<ref>
{{cite web |url=https://amturing.acm.org/award_winners/dahl_6917600.cfm |title=Ole-Johan Dahl |last=Black |first=Andrew P. |date=2001 |website=ACM Awards |publisher=Association for Computing Machinery |access-date=14 November 2020}}</ref>

The [[Association Internationale pour les Technologies Objets]] named the [[Dahl-Nygaard Prize]] after Dahl.<ref>{{cite web |title=Dahl-Nygaard Prize |url=https://sites.google.com/aito.org/home/aito-dahl-nygaard?pli=1&authuser=1#h.mghfbijfburs |access-date=7 December 2022}}</ref>