NULLl Mean -1?

Your questions is quite ambiguous but the SPECIFIC value of NULL is 0 on a Microsoft Windows system.  But note that to assume that NULL always is 0 is not wise as the C and C++ language specifications do not require this.

If u want the definition of NULL, place the text cursor above it and press F12.

always refer to null as 'NULL' and not 0 or -1 etc this way it dont matter what the headers define it as.

Yes - eventhough NULL will usually be 0 in C and C++, in C# there is a keyword 'null' and in Visual Basic Scripting there is one called Null

eg the definition for null

The null keyword represents a special value that indicates a variable does not refer to any object. The value null may be assigned to any class or interface variable to aid garbage collection. (Assigning the value null to any of the items above indicates to the garbage collection system that the object or variable is no longer in use.) It cannot be cast to any other type, and should not be considered to have a known numeric value.

While you are here - also remember that BOOL is not the same as bool and is not the same as VARIANT_BOOL
which I like to right like this
BOOL != bool != VARIANT_BOOL

eek for 'right' read 'write' :)

jhance: null pointers are always denoted by the constant 0 in C and C++, even when the underlying machine uses another representation (which is not uncommon). The conversion from "x bits 0" to the internal null pointer representation must be done by the compiler - that's why the compiler needs to know when a 0 is meant as pointer, hence the ((void *)0)

Peter

oh, johngodzbi, just another comment:

where do you know HANDLE means integer?
wtypes.h says
typedef void __RPC_FAR *HANDLE;

Hi,

Actually NULL is the null-pointer value used with many pointer operations and functions. A null character is defined as ASCII character 0, Chr$(0), so u can make use of NULL in comparison statement. By this statement we can say NULL == 0.

From

MRN Murthy

Well, there is a difference in the meaning of NULL in C and C++. In C it is defined as a pointer that does not reference any object. In C++ it is an expression that evaluates to 0 (zero). In other words:

void* p = TRUE ? NULL : NULL;

should compile on any compliant ANSI-C-compiler; on any compliant C++-compiler an error should be issued since there is no implicit conversion from 0 to a void*. ShaunWild's post includes the #define's that you might want to check out. I deliberately used 'should' instead of 'do' as the real world is not perfect. VC++6.0 will compile the above line of code, even though it is erroneous.

Btw. the only constant you can be sure of in the C/C++ is sizeof( char ) == 1, even if it uses more than one byte in memory like some Alpha-chips.

-- .:fl0yd:.

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