An experience in implementing abstract data types

The abstract data type concept appears to be a useful software structuring tool. A project, called ‘Système d'Objets Conservés’, which was developed at the University of Rennes, (France), gave some experience in implementing this concept. The possibility of including abstract data type into a pre-existing compiler is demonstrated, and desirable properties of the host language are exhibited. Provision of external procedures and data makes some type checking extensions necessary: these features increase software reliability.