Simula

Ole-Johan Dahl and Kristen Nygaard worked at the Norwegian Computing Center in Oslo on queueing theory and operations research, and needed to describe systems of interacting parts: ships, harbours, customers in a queue. The answer was to let each part be an object with its own data and its own behaviour. Simula I (1965) was an extension of ALGOL 60; Simula 67 formalised classes, subclasses with inheritance, virtual methods, coroutines and garbage collection.

The language never gained a large user base, but its readers were influential. Alan Kay saw it and built Smalltalk; Bjarne Stroustrup used it for his thesis, missed its expressive power in C, and wrote "C with Classes" which became C++. Dahl and Nygaard received the Turing Award in 2001, a year before both died.