Simula was created by Kristen Nygaard and Ole-Johan Dahl at the Norwegian Computing Center in Oslo. It began in the early 1960s as a special-purpose simulation tool layered on Algol, and matured into the general-purpose Simula 67. In their own firsthand account, “The Development of the SIMULA Languages,” the two authors trace how the work grew out of operational-research needs and ran from 1961 to 1971.
The decisive contribution was the class and object concept. To describe systems made of many interacting parts, Nygaard and Dahl introduced the “class” as a template that bundled both data and the procedures acting on that data, and “objects” as instances generated from a class. This packaging of state and behavior together is the foundation of what later became known as object-oriented programming.
Simula also introduced subclassing (inheritance), letting one class be defined as a specialization of another. These ideas were largely invented to model real-world processes faithfully, but they turned out to be general tools for organizing any large program.
Later language designers drew directly on Simula. Bjarne Stroustrup has cited it as the inspiration for the class facilities he added to C, and Alan Kay’s Smalltalk work also acknowledged Simula among its parents, carrying the object idea forward into the languages used today.