Static simulation is adopted for representing systems in which time does not play a role or describing a system at a particular time, whereas dynamic simulation is used to evaluate a system that evolves. Time-driven simulations advance time with fixed time steps, then afterward the state variables are updated. This chapter presents an overview of discrete event simulation (DES) and describes its essential functions. A discrete event model could be coded and simulated using programming languages, and the metrics of interest could also be evaluated using such languages. Transitions with age memory should be considered distinct situations. Accuracy, speed, memory use, and simplicity are aspects to be considered when selecting an appropriate generator. As the ”random number” generation strategy is intrinsically based on some procedure, these methods could not generate true randomness.