设计一个电梯模拟系统。这是一个离散的模拟程序，因为电梯系统是乘客和电梯等

“活动体”构成的集合，虽然他们彼此交互作用，但他们的行为是基本独立的。在离散的模拟中，以模拟时钟决定每个活动体的动作发生的时刻和顺序．系统在某个模拟瞬间处理有待完成的各种事情，然后把模拟时钟推进到某个动作预定要发生的下一个时刻。

-The design of a simulation system for the lift. This is a discrete simulation program, because the elevator system and elevator passengers and other " physical activities"　constitute a collection, although they interact with each other, but their behavior is a fundamental independent. In discrete simulation, to simulate the activities of body clock each time the action took place and order. Moment in a simulation system to deal with a variety of things to be done, and then the simulation clock advanced to an action scheduled to take place the next time.