- Well -- and I'll fix this blue next time -- I'm first telling the compiler I need access to the standard io library because printf is declared there.

哦！--下次我把这个字体颜色改成蓝色的-,我先告诉编译器--我需要使用,标准输入输出库,因为printf在那个库里面申明的。

哈佛公开课 - 计算机科学课程节选

The standard library, that first line of code, it's not strictly necessary but any time you use a function, a tool that someone else wrote that lives in that so called library, you do need that include line as we'll see.

标准库函数--第一行代码，严格来说，不是每次都要写的，但是一旦你调用某个别人写，的函数，而这个函数又恰巧位于标准库里面,你就要像我们看到的这样，把它include进去。

哈佛公开课 - 计算机科学课程节选