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The Sixties

Descriptions of concepts


Dahl’s breakthroughs – the development of Simula and the foundations of object-orientation

At an early stage it was decided that the language should be based on a well-known one. ALGOL 60 was chosen principally for the following reasons: block structure, good programming safety and European patriotism. (Dahl, 2002)
The most important aspect of these four stages was the transition between stages two and three. One problem was ALGOL’s strict dynamic stack regime of procedure calls and storage allocation that was incompatible with an adequate implementation of Simula’s sophisticated simulation facilities. ALGOL’s 60 procedure calls and storage allocation mechanisms operated strictly according to a stack principle whereas objects in a simulation model tended to behave according to a queue principle. So in the course of 1963 Dahl designed a storage allocation package based on a two-dimensional free list area (Dahl, 1963) .
This new scheme released them from the restrictions imposed by ALGOL 60 and they decided to drop the pre-processor idea and implement Simula by modifying and extending UNIVAC’s ALGOL 60 compiler. Based on this solution the search space for useful dynamic structures was drastically increased and in 1964 the Simula process concept was born. A process was understood as a generalized ALGOL procedure with quasi-parallel properties.
The first important publication open to a wider audience was published in 1966(Dahl, 1966). This paper gave an introduction to Simula, described the relationship to ALGOL 60 and described the concept of quasi-parallel processing aa an important new feature.

Descriptions of concepts


Class concept






Virtual methods


Dynamic Binding


Automatic memory management including garbage collection






Object-Orientation concepts


Storage Allocation

Programming languages:

Simula 1


Simula 67




Topics for stage: The Sixties of Dahl

Topics Documents
Programming Languages Simula - an ALGOL based Simulation-Language (application/pdf)
Simula Simula - an ALGOL based Simulation-Language (application/pdf)

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