为学生预约、排队上机实习所作的程序
需要实现功能：
1，查询，根据输入时间，输出机位信息。
2，即为预定，根据输入的日期和时间段查询是否有空机位，若有则预约，若无则提供最近空机时间段。另：若用户要求在非空时间上机，则将用户信息插入该时间段的等待列表.
3,退出预定，根据输入的时间，撤销该时间的预定。
4，查询是否有等待的信息，若有则按顺序显示联系方式，若无则显示提示信息。(Program for student appointment and queuing
Functions need to be implemented:
1, query, according to the input time, output the information of the machine.
2, is a reservation, according to the input date and time to query whether there is an empty space, if there is an appointment, if there is no time to provide the nearest flight time. Also: if the user requests the machine on non empty time, the user information is inserted into the waiting list of the time period.
3, withdrawing from the reservation and revoking the scheduled time according to the time of the input.
4, query whether there is waiting information, if there is the order to display the contact in order, if there is no display of prompt information.)