Queue SINGLE LINK LIST

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

typedef struct node
{
    int data;
    struct node *link;
}N;

N *f;
N *r;


N *getnode()
{
    N *New;
    New=(N*)malloc(sizeof(N*));
    New->data=0;
    New->link=NULL;
    return New;
}

void Insert(int x)
{
    N *New;
    New=getnode();
    New->data=x;

    if(f==NULL)
    {
        f=New;
        r=f;
    }
    else
    {
        r->link=New;
        r=New;
    }
}
void Delete()
{
    N *x,*y;
    x=f;
    if(f==NULL)
    {
        printf("underfow\n");
    }
    else
    {
        if(f==r)
        {
            f=NULL;
            r=NULL;
        }
        else
        {
            while(1)
            {
                y=x;
                x=x->link;
                if(x==r)
                {
                    break;
                }
            }
            r=y;
            r->link=NULL;
            free(x);
        }
    }
}

void Display()
{
    N *x;
    x=f;
    if(f==NULL)
    {
        printf("underfow\n");
    }
    else
    {
        while(x!=NULL)
        {
            printf("%d\n",x->data);
            x=x->link;
        }
    }
}

int main()
{
    int n,ch;
    f=NULL;
    r=NULL;
    while(1)
    {
        printf("1>Insert\n2>Delete\n3>display\n4>exit\nenter the number :");
        scanf("%d",&ch);
        switch(ch)
        {
            case 1:
                printf("enter the data :");
                scanf("%d",&n);
                Insert(n);
                    Display();
                break;
            case 2:
                Delete();
                printf("deleted\n");
                    Display();
                break;
            case 3:
                Display();
                break;
            case 4:
                exit(0);
            default:
                printf("invaid choice");
        }
    }
    return 0;
}