So, conceptually if you've ever wondered why you get access in all of your functions to global variables that's because they're not down here, they're at the very top of RAM and any function can access that RAM way up there, but for now the interesting player in the story is this thing called the heap.

所以，如果你想知道为什么全局变量能在,所有的函数中使用,那是因为它们不在这下面，而是在内存的顶端,那样任意函数都可以在内存中使用它们，现在，这里面一个有用的角色是,叫做堆的东西。

哈佛公开课 - 计算机科学课程节选