CODEWITHSUNDEEP
cpointers
user3818219
user3818219

Reputation: 43

What does char pointer zero mean?

Literally, does (char *) 0 mean a pointer to some location that contains a zero? Does the system create such an address with value 0 for each such declaration?

Upvotes: 0

Views: 977

Answers (3)

Vlad from Moscow
Vlad from Moscow

Reputation: 311048

It is null pointer value of type char *.

From the C++ Standard

A null pointer constant can be converted to a pointer type; the result is the null pointer value of that type

And from the C Standard

3 An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant.66) If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function.

4 Conversion of a null pointer to another pointer type yields a null pointer of that type. Any two null pointers shall compare equal.

It is not a pointer that points to a locarion that contains 0. So the system creates nothing. As it is written in the C Standard the null pointer "is guaranteed to compare unequal to a pointer to any object or function". So it is used to determine whether a pointer points to some object or function.

Upvotes: 3

Carl Norum
Carl Norum

Reputation: 225032

No, it's a cast of 0 to type char *. That is, a null pointer. A 0 in any pointer context refers to the null pointer constant.

What exactly it points to doesn't matter - dereferencing it would cause undefined behaviour.

For more, check out the C FAQ Part 5: Null Pointers.

Upvotes: 5

DTSCode
DTSCode

Reputation: 1090

its an explicit cast to a null pointer. i believe there is a #define macro for it allowing you to just write NULL

Upvotes: 0

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