NULL, 0, \0 and nul?

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FAQ > What's the difference between... > NULL, 0, \0 and nul?

This item was added on: 2003/03/13

NULL is a macro defined in several standard headers, 0 is an integer constant, '\0' is a character constant, and nul is the name of the character constant. All of these are *not* interchangeable:

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

0 can be used anywhere, it is the generic symbol for each type's zero value and the compiler will sort things out.

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

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'

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