When a program writes to memory, the processor only modifies the line in the cache, but does not update main memory.
当一个程序写入存储，处理器仅仅只会修改缓存线，而不会更新主要的存储内容。
2
Finally, Listing 7 shows the main function of the program, which just calls the process_directory function for every argument passed on the command line.
To see what's going on in main() we can set a breakpoint at a particular line or on a function in the program code so gdb will interrupt execution when it is reached.