what is the problem in this code?

[garimak04]

#include<stdio.h>
#include<stdlib.h>
struct Node
{
    int data;
    struct Node *add;
};
void insert(struct Node **,int );
void main()
{
    int pos,value;
    struct Node* head=NULL; struct Node *point;
    insert(&head,10);
    insert(&head,20);
    insert(&head,30);
    insert(&head,40);
    insert(&head,50);
    insert(&head,60);
    insert(&head,70);
    insert(&head,80);
    insert(&head,90);
    insert(&head,100);
    printf("Enter the position from the last to be displayed:");
    scanf("%d",&pos);
    point=display_nth(head);
    value=point->data;
    printf("\n%dth value for nth node is %d",pos,value);
    display(head);
}
insert(struct Node** ref_head,int new_data)
{
    struct Node* temp=(struct Node*)malloc(sizeof(struct Node));
    temp->data=new_data;
    temp->add=(*ref_head);
    (*ref_head)=temp;
}
 

31 1 C:\Users\GARIMA \Documents\nth from last.c [Warning] conflicting types for 'insert' [enabled by default]
8 6 C:\Users\GARIMA \Documents\nth from last.c [Note] previous declaration of 'insert' was here
C:\Users\GARIMA \AppData\Local\ Temp\ccqujr3n.o nth from last.c:(.text+0 x116): undefined reference to `display'
C:\Users\GARIMA \Documents\coll ect2.exe [Error] ld returned 1 exit status

[weaknessforcats]

In the function prototype insert() returns void.

In the function definition insert() return int.

oops.

When the return type is not specified, it defaults to int.

BTW: main() returns int. Not void. main() is the only function that returns int and you don't need a return statement.