模拟实现网桥的转发功能，以从文件中读取帧模拟网桥从网络中收到一帧，即从两个文件中读入一系列帧，从第一个文件中读入一帧然后从第二个文件中再读入一帧，如此下去。对每一帧，显示网桥是否会转发。(The simulation realizes the forwarding function of the bridge. It reads the fr a me analog bridge from the file, receives a fr a me from the network, reads a series of fr a mes from two files, reads a fr a me from the first file, and reads another fr a me from second files, and goes on like this. For each fr a me, it shows whether the bridge will be forwarded.)