Concurrent Euclid (ConEuc) is a concurrent descendant of the Euclid programming language designed by James Cordy and Ric Holt, then at the University of Toronto, in 1980. ConEuc was designed for concurrent, high performance, highly reliable system software, such as operating systems, compilers and embedded microprocessor systems. The TUNIS operating system, a Unix variant, was implemented entirely in Concurrent Euclid. ConEuc extends a core subset of Euclid with  processes and monitors (as specified by C.A.R. Hoare) as well as language constructs needed for systems programming including separate compilation, variables at absolute addresses, type converters, long integers and other features.