0, \0, NULL的區別

這個都知道在哪裡用，但是道理不清楚。然後google 了一下，一個比較好的解釋雖然是英文，但是很經典。

1.0 is an integer constant

2.'\0' is a character constant

3.NULL is a macro（宏）
defined in several standard headers（標準標頭檔）

4.nul is the name of the character constant. （這個貌似一般很少見把。。反正我沒見過 = = ）

All of these are *not* interchangeable（不可交換使用）


各自的用法如下：
1.0 can be used anywhere, it is the generic symbol for each type's zero value and the compiler will sort things out.

2.'\0' should be used only in a character context.

3.NULL is to be used for pointers only since it may be defined as ((void *)0), this would cause problems with anything
but pointers.

4.nul is not defined in C or C++, it shouldn't be used unless you define it yourself in a suitable manner, like:#define
nul '\0'