void insert(int key, int data)
{
    struct item *new, **p;

    /* create the new item */
    new = (struct item *)malloc(sizeof(struct item));
    /* (should check for NULL return, but omit for this example) */
    new->key = key;
    new->data = data;

    /* find the (struct item *) to place it at */
    for (p = &head; *p && (*p)->key < key; p = &(*p)->next)
        ;

    /* link it in */
    new->next = *p;
    *p = new;
}


void delete(int key)
{
    struct item **p;

    /* find the (struct item *) which points to it */
    for (p = &head; *p && (*p)->key < key; p = &(*p)->next)
        ;

    if (*p && (*p)->key == key) {
        struct item *old = *p;
        *p = (*p)->next;
        free((char *)old);
    } else {
        printf("error: %d not found\n", key);
    }
}