说明：  模拟以太网上CSMA/CD协议.在字符界面下，你可以任意规定你要测试的竞争的次数，程序会按照你给的数据进行测试。在该程序中，站的总数为4个，所以每一次竞争结束之后，都会输出一个结果，告诉你在该次竞争中是1、2、3、4站中的哪个站，赢得了本次传输的机会。
(simulation Ethernet CSMA/CD agreement. Characters in the interface, You can arbitrarily requiring that you have to test competition in the number of procedures you have to be in accordance with the test data. In the process, the total number of stations to four, so every time after the end of competition will output a result, tell you that the competition is 1, 2, 3, 4 points in the station which won the transmission of this opportunity.)