When you're all out of specific cases and you want to handle everything else, you literally say "default:" And here I could end the program with break, but it's kind of unnecessary because once I'm at the bottom of the curly braces, that's it.

当它不在你列出的所有情况中,为了处理其他的情况，你可以用“default：“,这里我可以用break来终止这段代码，但是它是有点,不必要的，因为我已经在这个花括号的,底部了，就这样了。

哈佛公开课 - 计算机科学课程节选

It comes with all Macs by default.

默认情况下所有的Mac电脑都装有该程序。

哈佛公开课 - 计算机科学课程节选