C - pointer is not null after freeing it

Question

Does the value of pointer become NULL after freeing it?

int* p = malloc(sizeof(*p));

free(p);

if(p==NULL)
    printf("Null\n");
else
    printf("Not null\n");

Output:

 Not null

Well, I assume not;

Anyway, I have asked a question earlier today :

Check it out here: C - How can I free dynamically allocated memory?

List* head1 = NULL;

insertFront(&head1, 1);
insertFront(&head1, 2);

print(head1);

while (head1)
{

    List *temp = head1;
    head1 = head1->next;
    free(temp);
}

if(head1 == NULL)
    printf("Null\n");
else
    printf("Not null\n");

Output in this case:

Null

In this case after freeing head1 (nodes also) the head1 becomes null, does'nt it?

And finally, am I missing some concepts?

head1 is null, however p isn't.

My Question is:

Why values differs between head1 and p?

Answer 1

The condition of the loop

while (head1)
       ^^^^^^
{

    List *temp = head1;
    head1 = head1->next;
    free(temp);
}

becomes equal to false when the data member next of the next node is equal to NULL

head1 = head1->next;
^^^^^         ^^^^^

This has nothing common with the function free. The function accepts the argument by value. That is it deals with a copy of the original [pointer. So the original pointer itself will not be changed.