Furthermore, you can see how and where a higher-level process activity sends a feedbackmessage to a lower-level activity, or vice versa.
而且,还可以看到较高级别的流程活动如何以及从何处向较低级别的活动发送反馈消息,反之亦然。
2
A real program would have a usage message and provide some sort of feedback if the user didn't specify at least one argument, but I've left that as an exercise for the reader.