问题
Just read pointer on C book by Kenneth Reek. It says that a NUL byte is one whose bits are all 0, written like this '\0' and NULL has a value 0 which refers to a pointer whose value is zero.
Both are integers and have the same value, so they could be used interchangeably.
and this code also:
char const *keyword[] = { "do", "for", "if", "register",
"return", "switch", "while", NULL };
In this code, the NULL lets functions that search the table detect the end of the table. So, can we interchange NULL and NUL macros?
回答1:
NUL is the notation for an ASCII character code 0.
NULL is a macro defined in stddef for the null pointer.
So, no, they are not to be used interchangeably.
回答2:
There is no standardized NUL macro, at least not in C.
Also, NULL has the advantage over a plain 0 literal that it signals to the reader that "hey, we're dealing with a pointer" which might be considered an advantage.
In C++, the idiom was for a long while to just write 0, but then they seem to have reversed that and introduced a new literal, nullptr for some reason(s).
In C, I recommend writing NULL for pointers and '\0' for characters.
来源：https://stackoverflow.com/questions/15479335/are-nul-and-null-interchangeable-in-c