insert first doubly

#include<stdio.h>
#include<stdlib.h>

typedef struct node
{

    int a;
    char ch;
    struct node*next;
    struct node*previous;
} node;
node*head;
void display()
{

    node *list=head;
    while(list !=NULL)
    {
        printf("A: %d\n",list->a);
        printf("C: %c\n",list->ch);
        printf("\n");

        list=list->next;

    }
}
void insert_at_first(int aN, char chN)
{
    node *N=(node*)malloc(sizeof(node));
    N->a=aN;
    N->ch=chN;
    N->next=NULL;
    N->previous=NULL;
    if(head==NULL)
    {
        head=N;
        return;
    }
    N->next=head;
    head->previous=N;
    head=N;
}
int main()
{
    head=NULL;
    insert_at_first(1,'A');
    insert_at_first(3,'b');
    insert_at_first(5,'c');
    insert_at_first(7,'d');
    insert_at_first(9,'e');
    display();
}