＃定义VS变量 [英] #Define VS Variable

问题描述

我不明白它们之间的区别是什么

I cannot understand what is the difference between:

#define WIDTH 10 

和

int width = 10;

使用第一个或第二个有什么好处？

What are the benefits of using the first or the second?

推荐答案

嗯，有很大的不同。您可以更改 width 的值，可以获取其地址，可以要求其大小，依此类推。使用 WIDTH ，它将随处都被常量 10 代替，因此表达式 + + WIDTH 没有任何意义。在另一边，您可以声明带有 WIDTH 个项目的数组，而不能声明带有 width 个项目的数组。

Well, there is a great difference. You can change the value of width, you can take its address, you can ask for its size and so on. With WIDTH, it will be just replaced with a constant 10 everywhere, so the expression ++WIDTH doesn't make any sense. Ono the other side, you can declare an array with WIDTH items, whereas you cannot declare an array with width items.

总结一下： WIDTH 的值在编译时是已知的，不能更改。编译器不会为<$​​ c $ c> WIDTH 分配内存。相反， width 是一个 initial 值为10的变量，其进一步的值在编译时未知；该变量从编译器获取其内存。

Summing it up: the value of WIDTH is known at compile time and cannot be changed. The compiler doesn't allocate memory for WIDTH. On the contrary, width is a variable with initial value 10, its further values are not known at compile time; the variable gets its memory from the compiler.

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