NULL and nil

• The null pointer is a special kind of pointer that doesn’t point to anything.
• Pointer can be “emptied” using the null pointer.
• A good rule of thumb is to use nil for variables that hold Objective-C objects and NULL when working with C pointers.

NSString *anObject;    // An Objective-C object
anObject = NULL;       // This will work
anObject = nil;        // But this is preferred
int *aPointer;         // A plain old C pointer
aPointer = nil;        // Don't do this
aPointer = NULL;       // Do this instead