说明：  本程序是用VC实现的模拟某校九层教学楼的电梯系统，电梯能在每层停留，电梯“空闲”时，将来到第一层候命，乘客可随机地进出于任何层，每个人有一个能容忍的最长等待时间，一旦等候电梯时间过长，他将放弃。程序将会按时序显示系统状态的变化过程，即发生的全部人和电梯的动作序列。
(This program is a simulation of a nine-story classroom building s elevator system, elevator to stay at each floor.When the elevator is "free",it will come to the first layer to wait for command.Passengers can come in and go out of every floor, each passengers have a maximum wait time, once the waiting elevator takes too long, he will give up. The program will display the diversification of the system according the sequence in time.)