Linker error in my c program. The program is of insertion and deletion in doubly linked list.

The linker gives the following errors:

[...] undefined reference to `create_list'
[...] undefined reference to `delete_pos'
[...] undefined reference to `traverse'

Because you are calling such functions but they aren't defined (they have no body).

Please note the errors to be rectified:

1. you have misspelled the header file as alloc.h please change it to malloc.h
2.You have declared the function as void create(); but called the function as
create_list();
3. declaration and definition does not match void traverse(); and void display()
4.In the definition part of del_pos the variables gt and lt is not declared please declare it.

Quote:

solution(errors rectified):

C#

#include<malloc.h>
#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
struct node {
    struct node *prev;
    int n;
    struct node *next;
}   *h, *temp, *temp1, *temp2, *temp4;

void create_list();
void insert_beg();
void insert_end();
void delete_pos();
void traverse();

int count = 0;

void main()
{
    int ch;
    system("cls");
    printf("\n1.Create list\n2.Insert at beginning\n3.Insert at end\n4.Delete from given position\n5.Display");
    while (1)
    {
        printf("\n Enter your choice: ");
        scanf("%d", &ch);
        switch (ch)
        {
            case 1:
                create_list();
                break;

            case 2:
                insert_beg();
                break;

            case 3:
                insert_end();
                break;

            case 4:
                delete_pos();
                break;

            case 5:
                traverse();
                break;

            default:
                printf("\n Wong choice entered");
        }
        getch();
    }
}

void create_list()
{
    int data;
    temp = (struct node *)malloc(1 * sizeof(struct node));
    temp->prev = NULL;
    temp->next = NULL;
    printf("\n Enter the data: ");
    scanf("%d", &data);
    temp->n = data;
    count++;
}
void insert_beg()
{
    if (h == NULL)
    {
        create_list();
        h = temp;
        temp1 = h;
    }
    else
    {
        create_list();
        temp->next = h;
        h->prev = temp;
        h = temp;
    }
}

void insert_end()
{
    if (h == NULL)
    {
        create_list();
        temp->next = temp;
        temp->prev = temp1;
        temp1 = temp;
    }
}

void delete_pos()
{
    int i = 1, pos, gt,lt;
    printf("\n Enterposition to be deleted: ");
    scanf("%d", &pos);
    temp2 = h;

    if (h == NULL)
    {
        printf("\n Error: Empty iist");
        return;
    }
    else
    {
        while (i & lt, pos)
        {
            temp2 = temp2->next;
            i++;
        }
        if (i == 1)
        {
            if (temp2->next == NULL)
            {
                printf("Node deleted from list");
                free(temp2);
                temp2 = h = NULL;
                return;
            }
        }
        if (temp->next == NULL)
        {
            temp2->prev->next = NULL;
            free(temp2);
            printf("Node deleted from list");
            return;
        }
        temp2->next->prev = temp2->prev;
        if (i != 1)
            temp2->prev->next = temp2->next;
        if (i == 1)
            h = temp2->next;
        printf("\n Node deleted");
        free(temp);
    }
    count--;
}
void traverse()
{
    temp2 = h;
    if (temp2 == NULL)
    {
        printf("List empty to traverse\n");
        return;
    }
    printf("\n Lined list is:\n ");
    while (temp2->next != NULL)
    {
        printf("%d", temp2->n);
        temp2 = temp2->next;
    }
    printf("%d", temp2->n);

    getch();
}

Note:
you have used undeclared variables in the if part of the function del_pos.Since it is just an error message I have deleted it.If you want it kindly declare the variables gt & lt and use it.The deleted part is given below for your identification.

if ((pos & lt; 1) || (pos & gt; = count + 1))
    {
        printf("\n Error: Position out of range to delete");
        return;
    }