Doubly linked list (all 8 operations)

#include<stdio.h>

#include<conio.h>

#include<malloc.h>

struct node

{

int info;

struct node *prev;

struct node *next;

};

struct node *head=NULL;

struct node *tail=NULL;

void insert_begin(int item)

{

struct node *p;

p=(struct node *)malloc(sizeof(struct node));

p->info=item;

if (head==NULL)

{

p->prev=NULL;

p->next=NULL;

head=p;

tail=p;

}

else

{

p->prev=NULL;

head->prev=p;

p->next=head;

head=p;

}}

void insert_end(int item)

{

struct node *p;

p=(struct node *)malloc(sizeof(struct node));

p->info=item;

if (head==NULL)

{

p->prev=NULL;

p->next=NULL;

head=p;

tail=p;

}

else

{

p->next=NULL;

tail->next=p;

p->prev=tail;

tail=p;

}}

void delete_begin()

{

struct node *p;

if (head==NULL)

printf("list is empty");

else

{

 if(head==tail)

  {

  p=head;

  head=NULL;

  tail=NULL;

  }

  else

  {

  p=head;

  head=head->next;

  head->prev=NULL;

  }

  printf("\ndeleted element is %d",p->info);

  free(p);

 }}

void delete_end()

{

struct node *p;

if (head==NULL)

printf("list is empty");

else

{

 if(head==tail)

  {

  p=head;

  head=NULL;

  tail=NULL;

  }

  else

  {

   p=tail;

   tail=tail->prev;

   tail->next=NULL;

  }

  printf("\ndeleted element is %d",p->info);

  free(p);

 }}

void display()

{

int i;

struct node *p;

p=head;

if(head==NULL)

printf("empty list");

else

{

 while(p!=NULL)

 {

  printf("%d",p->info);

  p=p->next;

 }}}

void main()

{

int ch,item;

clrscr();

printf("\n1.insert begin\n2.insert end\n3.delete begin\n4.delete end\n5.display\n6.exit");

do

{

 printf("\nenter your choice");

 scanf("%d",&ch);

 switch(ch)

 {

 case 1:printf("eneter value ");

                scanf("%d",&item);

                insert_begin(item);

                break;

 case 2:printf("eneter value ");

                scanf("%d",&item);

                insert_end(item);

                break;

 case 3:delete_begin();

                break;

 case 4:delete_end();

                break;

 case 5:display();

                break;

 case 6:exit(0);

 default:printf("invalid option");

 }}while(ch!=6);

getch();

}