There are two different types of simulation:

• One-shot deterministic simulations;
• Statistical simulations.

In a deterministic simulation, a system is simulated under well determined conditions. This kind of simulation is useful to observe the behavior of system in certain particular cases, to discover errors in the design or in the implementations, to build examples, etc. In this kind of simulations, only one run is needed and there is no truly random variable involved. To see the behavior of the system we need to "trace" the output on a file and later to see and analyze it in a textual or in a graphical form. In a statistical simulation, we measure the system performance. This is useful to see if the system has good response time under average conditions, to compare different implementations of the same system, or totally different systems that have the same output.