Alan Kay's "The Early History of Smalltalk" (1993) is long, and absolutely worth a read, and includes this memorable bit about Kay seeing Simula for the first time:<p>> <i>Finally, another graduate student and I unrolled the program listing 80 feet down the hall and crawled over it yelling discoveries to each other. The weirdest part was the storage allocator, which did not obey a stack discipline as was usual for Algol. A few days later, that provided the clue. What Simula was allocating were structures very much like the instances of Sketchpad. There were descriptions that acted like masters and they could create instances, each of which was an independent entity. What Sketchpad called masters and instances, Simula called activities and processes. Moreover, Simula was a procedural language for controlling Sketchpad-like objects, thus having considerably more flexibility than constraints (though at some cost in elegance) [Nygaard, 1966, Nygaard, 1983].</i><p><a href="https://worrydream.com/EarlyHistoryOfSmalltalk/" rel="nofollow">https://worrydream.com/EarlyHistoryOfSmalltalk/</a><p><a href="https://dl.acm.org/doi/10.1145/155360.155364" rel="nofollow">https://dl.acm.org/doi/10.1145/155360.155364</a>