Now that I've written sqrt, I can just use it anywhere I want in the code. You've got to rely on the fact that I wrote it correctly, but you can basically suppress the details of how it's used.

就是忽略细节,既然我已经编写了sqrt函数,我可以在代码的任何地方使用它，你完全可以依靠,我已经编写的这个函数。

麻省理工公开课 - 计算机科学及编程导论课程节选

Well, for a thing called main which itself is a function but a function I wrote, a tool I am writing at the moment not like printf which someone else wrote long ago, I have to say where does main start, where does main end, and I do that by using these curly braces.

至于这个名曰main的函数,由我们自己写的函数，也是一个工具,只不过由我们自己编写，而不是像printf那样已经由前人写好了,我们必须要说明main在哪开始，在哪结束，这样我们就要用到大括号了。

哈佛公开课 - 计算机科学课程节选