So it's not defined. But in fact, what this did was it threw an exception.

这是未定义，但实际上，这里做的就是抛出一个异常。

麻省理工公开课 - 计算机科学及编程导论课程节选

Undefined reference, what was the solution last time?

未定义的引用，上次我们是怎么解决的呢？

哈佛公开课 - 计算机科学课程节选

And what I want to point out that we just figured out for molecular orbital theory, is that o 2 is a biradical, because remember, the definition of a radical is when we have an unpaired electron.

我要指出的是,我们刚利用分子轨道理论，指导了O2是二价自由基，因为记住，自由基的定义是,有个未配对的电子。

麻省理工公开课 - 化学原理课程节选

But the take away for now is that if you don't clue -lcs50, -- you get some mention -- some error message -- about "undefined symbol," and that should be your clue that, "Oh it's undefined in that I haven't told the compiler that I want to link in these zeros and ones."

但现在如果你删除“-lcs50“,你们会得到一些提示--一些错误信息-,像“未定义的符号“，这可以为你提过线索，“这个没有被定义，我没有告诉编译器,把想把这个与“1“和“0“建立连接，“

哈佛公开课 - 计算机科学课程节选