General C program

General C program

The following code;
typedef struct chainCell{
int data;
struct chainCell* next;
} chainCell;
bool sameValues (chainCell *x, chainCell *y)
{
if ((x == NULL) & (y == NULL)) return true;
if ((x == NULL) | (y == NULL)) return false;
bool same = true;
chainCell *xp = x, *yp = y; // scan pointers
while ((xp != NULL) & (same == true)) // point A
{
if (xp->data != yp->data) same = false;
xp = xp->next;
yp = yp->next;
if (((xp == NULL) & (yp != NULL)) // point B
| ((xp != NULL) & (yp == NULL)))
same = false;
};
return same;
};
I am very confused as to why the loop control contains (same == true) ?
Also what is the purpose of the if statement at Point B? I'm unsure of
what the Boolean expression is checking for?
Any help for further understanding would be appreciated!