用系统调用signal()让父进程捕捉键盘上来的中断信号（按Ctrl-C键）；当捕捉到中断信号后，父进程用系统调用kill()向两个子进程发出信号，子进程捕捉到信号后分别输出下列信息后终止： 　Child Process 1 is Killed by Parent! 　Child Process 2 is Killed by Parent! 父进程等待两个子进程终止后，输出如下的信息后终止： Parent Process is Killed!-with system call signal ()