Inside simulation software: how it works and why it matters

This paper provides beginning and intermediate simulation practitioners and interested simulation consumers with a grounding in how discrete-event simulation software works. This is done by describing alternative entity states, the use of lists to organize entities in the various states and the use of algorithms to manage these lists and manipulate entities during a simulation. This general treatment, which should benefit all simulation practitioners, is then discussed in terms of GPSS/H, ProModel and SIMAN. The focus is on understanding the underlying mechanisms of simulation. Such understanding will help practitioners build models more confidently, use model verification tools more thoroughly, and model complex system logic precisely as intended.