head                8 bidlist.c        ret->head = NULL;
head               24 bidlist.c        if(blist->head == NULL){
head               25 bidlist.c          blist->head = newnode;
head               45 bidlist.c          blist->head = next;
head               58 bidlist.c        bidnode* point = blist->head;
head               66 bidlist.c        blist->mark = blist-> head;
head               12 bidlist.h        bidnode* head;