Doubly-Ended Queues

#include <stdio.h>
#include <stdlib.h>
struct node{
        int data;
        struct node *next, *prev;
} *head = NULL, *tail = NULL;
void display(struct node *help){
    if(!help) printf("\nEmpty Queue.");
    else while(help){
            printf(" %d ", help->data);
            help = help->next;
        }
}
void frontInsert(struct node *newNode){
        newNode->prev = NULL;
        newNode->next = head;
        if(!head) tail = newNode;
        else head->prev = newNode;
        head = newNode;
}
void backInsert(struct node *newNode){
        newNode->next = NULL;
        newNode->prev = tail;
        if(!tail) head = newNode;
        else tail->next = newNode;
        tail = newNode;
}
void frontDelete(){
        if(!head->next) head = tail = NULL;
        else{
            struct node *target = head;
            head = head->next;
            head->prev = NULL;
            free(target);
        }
}
void backDelete(){
    if(!tail->prev) tail = head = NULL;
    else{
        struct node *target = tail;
        tail = tail->prev;
        tail->next = NULL;
        free(target);
    }
}
int main(){
    int choice, value;
    while(1){
        display(head);
        printf("\n1. Insert 2. Delete 3. Exit: ");
        scanf("%d", &choice);
        switch(choice){
            case 1:{
                printf("\nEnter the value to be inserted: ");
                scanf("%d", &value);
                printf("\nInsert at 1. Front 2. Back: ");
                scanf("%d",&choice);
                struct node *newNode = (struct node*) malloc(sizeof(struct node));
                newNode->data = value;
                if(choice == 1) frontInsert(newNode);
                else if(choice == 2) backInsert(newNode);
                else goto down;
                break;
            }
            case 2: if(!head) printf("\nCan't Delete.");
                    else{
                        printf("\nDelete from 1. Front 2. Back: ");
                        scanf("%d", &choice);
                        if(choice == 1) frontDelete();
                        else if(choice == 2) backDelete();
                        else goto down;
                    } break;
            case 3: return 0;
            default: down: printf("\nInvalid input.");
        }
    }
}