Doubly Link List Assignment

/*
Name: Jiban
ID: 192-15-13117
Section: C
Batch: 53rd
*/
#include<stdio.h>
#include<stdlib.h>
typedef struct Data
{
    int a;
    struct Data *next, *prev;
} Data;

Data *head=NULL;
Data *tail=NULL;

void insrt_at_fst(int n)
{
    Data *tmp=head;
    Data *new_node=(Data*) malloc(sizeof  (Data));
    new_node->a=n;
    new_node->next=NULL;
    new_node->prev=NULL;
    if(head==NULL)
    {
        head=new_node;
        tail=head;
        return;
    }
    head->prev=new_node;
    new_node->next=head;
    head=new_node;
}

void insrt_at_end(int n)
{
    Data *tmp=head;
    Data *new_node=(Data*) malloc(sizeof  (Data));
    new_node->a=n;
    new_node->next=NULL;
    new_node->prev=NULL;
    if(head==NULL)
    {
        head=new_node;
        tail=head;
        return;
    }
    new_node->prev=tail;
    tail->next=new_node;
    tail=new_node;
}

void insrt_at_xth(int x, int n)
{
    Data *tmp=head;
    Data  *new_node=(Data*) malloc(sizeof (Data));
    new_node->a=n;
    new_node->next=NULL;
    new_node->prev=NULL;

    if(head==NULL||x==1)
    {
        new_node->next=head;
        head=new_node;
        return;
    }
    x=x-2;
    while(x--&&tmp->next!=NULL)
    {
        tmp=tmp->next;
    }
    new_node->next=tmp->next;
    tmp->next->prev=new_node;
    new_node->prev=tmp;
    tmp->next=new_node;
}

void dlt_by_pstn(int x)
{
    Data *tmp=head;
    if(head==NULL)
    {
        printf("No data found!\n");
        return;
    }
    if(x==1)
    {
        head=tmp->next;
        free(tmp);
        return;
    }
    x=x-2;
    while(x-- && tmp->next!=NULL)
    {
        tmp=tmp->next;
    }
    Data *dlt=tmp->next;
    tmp->next=dlt->next;
    free(dlt);
    tmp->next->prev=tmp;
}

void dlt_by_vlu(int n)
{
    Data *tmp=head;
    if(head==NULL)
    {
        printf("No match found!\n");
    }
    if(tmp->next==NULL&&tmp->a==n)
    {
        head=tail=NULL;
        free(tmp);
        printf("Deleted integer %d\n",n);
        return;
    }
    if(tmp->a==n)
    {
        head=head->next;
        head->prev=NULL;
        free(tmp);
        printf("Deleted integer %d\n",n);
        return;
    }
    while(tmp->next->a!=n)
    {
        tmp=tmp->next;
    }
    Data *del=tmp->next;
    tmp->next=del->next;
    del->next->prev=tmp;
    free(del);
    printf("Deleted integer %d\n",n);
    return;
}

int cnt()
{
    int ct=0;
    Data *tmp=head;
    while(tmp!=NULL)
    {
        ct++;
        tmp=tmp->next;
    }
    printf("Number of integer %d\n",ct);
    return ct;

}

int add()
{
    int ttl=0;
    Data *tmp=head;
    while(tmp!=NULL)
    {

        ttl=ttl+tmp->a;
        tmp=tmp->next;
    }

    printf("Sum of inputed integers %d\n",ttl);
    return ttl;
}

void avg(float a,float b)
{
    float avg;
    avg=a/b;
    printf("Average of inputed integers %.2f\n",avg);
}

void print()
{
    Data *tmp=head;
    while(tmp!=NULL)
    {
        printf("Inputed integer %d\n",tmp->a);
        tmp=tmp->next;
    }
}

int main()
{
    float sum,ct;
    head=NULL;
    insrt_at_end(6);
    insrt_at_fst(8);
    insrt_at_end(5);
    insrt_at_fst(9);
    insrt_at_end(1);
    insrt_at_xth(5,4);
    dlt_by_pstn(3);
    sum=add();
    ct=cnt();
    avg(sum,ct);
    dlt_by_vlu(8);
   /*sarch(1);
    */
    print();
    return 0;

}