This package provides GPSS (Generalized System Simulation) graphical language which can be used to construct event-driven systems. It provides following elements:

Generate: Generate Transactions
Advance: Delay
Enter/Seize: Facility entrance with queue.
Leave/Release: Facility exit ? used with Enter/Seize
Goto: Stochastic branch
If: Conditional branch
WaitIf: Conditional Wait
Priority: Change transaction priority
Let: Free expression
Print: Print value while simulation is ruining