Only the operating system has controlling of byte zero NULL in the computer's RAM and so if a function ever returns null, aka zero, well, something must have gone wrong because that can't possibly belong to me that memory because by human convention zero is owned by the operating system; not by a program I wrote.

只用操作系统在内存中能够控制,字节0，并且如果一个函数返回，或者说0，好的，可能出错了,因为那可能是不属于我的内存,因为惯例上，0是由操作系统拥有的,而不是由我的程序拥有的。

哈佛公开课 - 计算机科学课程节选