Adding Concurrency to a Programming Language.

A programming language that lacks facilities for concurrent programming can gain those facilities in two ways: the language can be extended with additional constructs, which will reflect a particular model of concurrency, or libraries of types and routines can be written with different libraries implementing different models. This paper examines the two approaches, for object-oriented and non-object-oriented languages. Examples show that concurrency interacts extensively with traditional programming language constructs, and that general elementary facilities for concurrency must be implemented at extremely low levels—the assembly language level, in some cases—and hence that safe support for concurrency requires language extension.