• Simulation is an indispensable problem-solving methodology for the solution of many real-world problems.

• Simulation is the imitation of the operation of a real-world process or system over time

List Processing
Entities are managed by assigning them to resources that provide a service, attaching them to event notices, which suspends their activity in the future, or placing them in an ordered list. Queues are represented by lists.:

Resources

A resource is a dynamic entity that provides services to other entities. At the same time, the resource could indeed serve one or more dynamic entities.

Discrete-Event Simulation Model

Activities and Delays
-An activity is a period of time whose length is known before the activity begins. As a result, the duration's start and end dates can be scheduled. The duration can be a constant, a random value from a statistical distribution, the result of an equation, file input, or computed based on the event state.
-A delay is an indefinite period of time caused by a combination of system conditions. When an entity joins a queue for a resource, the time it will remain in the queue is initially unknown because it depends on other events that may occur.

Entities and Attributes

An entity is a type of object that needs to be defined explicitly. An entity can be dynamic in the sense that it moves through the system, or static in the sense that it serves other entities. An entity may have attributes that are unique to that entity. As a result,attributes should be regarded as local values