ListItem *LinkedListNew(char *data)
{
    // allocate memory for the list
    ListItem *newlist = malloc(sizeof (ListItem));
    if (newlist == NULL) {
        return NULL;
    }
    // empty list, set data field to contain string
    // pointers to other nodes to be NULL
    newlist -> data = data;
    newlist -> previousItem = NULL;
    newlist -> nextItem = NULL;

    return newlist;
}