The Free On-line Dictionary of Computing (30 December 2018):

ConC

    A concurrent extension of C based on decomposed
   Petri nets.  It uses the 'handshake' and 'unit' constructs.

   ["ConC: A Language for Distributed Real-Time Programming",
   V.K. Garg et al, Computer Langs 16(1):5-18 (1991)].

   (1995-03-02)