1. An extension of c with rendezvous-based concurrency. Versions for most unix systems are available commercially from at&t.

["Concurrent C", N.H. Gehani et al, Soft Prac & Exp 16(9):821-844 (1986)].

["The Concurrent C Programming Language", N. Gehani et al, Silicon Press 1989].

2. An extension of c with asynchronous message passing.

["Concurrent C: A Language for Distributed Systems", Y. Tsujino et al, Soft Prac & Exp 14(11):1061-1078 (Nov 1984)].