gpss

from The Free On-line Dictionary of Computing (8 July 2008)

GPSS

   General Purpose Systems Simulator.  Geoffrey Gordon, 1960.
   Discrete simulations.  "The Application of GPSS V to Discrete
   System Simulation", G.  Gordon, P-H 1975.  Versions include
   GPSS II (1963), GPSS III (1965), GPS/360 (1967), and GPSS V
   (1970).