The availability of special purpose simulation languages, at massive computing capabilities at a decreasing cost per operation, and of advances in simulation methodologies have made simulation most widely used and accepted tools in operations research and systems analysis. Circumstances under which simulation is the appropriate tool to use have been discussed below.

• To study the internal interaction among different components of system.

• With the help of simulation system parameters can be adjusted.

• To experiment new design prior to the implementation.

• To verify analytical solution.

• To determine the requirement of system.

• To visualize the plan through animation.

• To observe the effect of environment changes on the system.

• To improve the system through the knowledge gained in designing simulation model.

• To provide better understanding of system operation.

• To perform bottle neck analysis.

• The modern system (factory, service organization, fabrication plant, etc.) is so complex that its internal interactions can be treated only through simulation.

• Changing simulation inputs and observing the resulting outputs can produce valuable insight into which variables are the most important and into how variables interact.