 Early 1975 a Simula 67 compiler was released free of charge for the DECsystem-10 mainframe family.By August the same year the DECsystem-10 Simula 67 compiler had been installed at 28 sites, 22 of them in North America.The object-oriented Simula programming language was used mainly by researchers involved with physical modelling, such as models to study and improve the movement of ships and their content through cargo ports.