你可以假设该值是一个非零值。

You may assume that the value for a is nonzero. Your program should be able to duplicate the following sample run.

youdao

其中一个返回0；另一个返回一个非零值。

One of them returns 0; the other, a non-zero value.

youdao

规定的唯一约定是返回0应该表示成功而返回非零值表示失败。

The only convention prescribed is that 0 should be returned for success and a nonzero value for failure.

youdao

So even though we think of conditions as being Boolean values true or false, really underneath the hood true means anything other than zero.

即使我们考虑,布尔值的真假条件，在底层“真“表示非零。

哈佛公开课 - 计算机科学课程节选