  Object-oriented programming is inextricably linked to the pioneering work of
Ole-Johan Dahl and Kristen Nygaard on the design of the Simula language, which
started at the Norwegian Computing Centre in the Spring of 1961. However,
object-orientation, as we think of it today---fifty years later---is the result
of a complex interplay of ideas, constraints and people. Dahl and Nygaard would
certainly recognise it as their progeny, but might also be amazed at how much
it has grown up.
  This article is based on a lecture given on 22nd August 2011, on the occasion
of the scientific opening of the Ole-Johan Dahl hus at the University of Oslo.
It looks at the foundational ideas from Simula that stand behind
object-orientation, how those ideas have evolved to become the dominant
programming paradigm, and what they have to offer as we approach the challenges
of the next fifty years of informatics.
