第一，这是一个全局函数而不是成员函数。

First, it is a global function, not a member function.

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尽量不使用全局函数。

Use of global functions should be minimized.

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类设计器不支持全局函数和变量。

Class Designer does not support global functions and variables.

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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

So I start this program by declaring as I did before a global variable X. It is global simply because it is not inside any of my functions.

在程序的开始，我声明,一个全局变量X，它是一个全局的,因为它不在任何一个函数里面。

哈佛公开课 - 计算机科学课程节选

So pictorially, it's as though there's now some other part of the blackboard here, maybe way up here where I can put anything I want that's accessible to main, that's accessible to swap, that's accessible to increment or any other function I might implement because it is, in fact, global.

绘画般地，它是在这里黑板上的其他部分,可能在这里的上面,我在哪里可以放置这些东西,使它们可以被main函数使用，可以被swap函数使用，可以被increment函数使用,或者我所实现的其它函数,因为它实际上是一个全局变量。

哈佛公开课 - 计算机科学课程节选