Question

Please explain following things in regard of C or C++:

• The null pointer

• The internal representation of a null pointer

• The null pointer constant – 0

• The NULL macro

• The ASCII null character (NUL)

• The null string (“”).

Answer 1

The null pointer is a pointer that doesn’t point to any object.

The internal representation is not specified, and specifically doesn’t have to be all bits zero.

The value 0 can be converted to a null pointer.

The NULL macro is defined as a value that can be converted to a null pointer, in C++ it is often just 0 and in C often (void*)0, but can be other values as well if the implementation decides so.

The NUL character is a character that has the value 0 or '\0'.

The string "" is just an empty string.