Enqueue ,Dequeue ,Display with linked list

enqueDequeueWithLinkedList.cpp

#include<iostream>
using namespace std;

struct node
{
    int data;
    node *next;
}*front = NULL,*rear = NULL,*p = NULL,*np = NULL;

void enqueue( int value)
{
    np=new node;
    np->data=value;
    np->next=NULL;
    if(front==NULL)
    {
        front = rear = np;
        rear->next = NULL;
    }
    else
    {
        rear->next = np;
        rear = np;
        rear->next = NULL;
    }
}
int dequeue(int value)
{
    if(front==NULL)
    {
        cout<<"empty queue";
    }
    else
    {
        p = front;
        value = p->data;
        front = front->next;
        delete(p);
        return(value);
    }
}
void display(){
    if(front == NULL){

        cout<<"\nNothing to Display\n";

    }else{
        np=front;
        while(np!=NULL){


            cout<<endl<<np->data;

            np = np->next;




        }

    }

}
int main()
{
    int value, choice;
    do{
        cout<<"\n 1.enqueue \n 2.dequeue \n 3.display \n 4.exit\n \n input choice:  ";
        cin>>choice;

        if(choice==1)
        {
            cout<<"\n enter a value";
            cin>> value;
            enqueue(value);
        }
        if(choice==2)
        {
            dequeue(value);
        }
        if(choice==3)
        {
            display();
        }
    }
    while(choice!=4);
    cout<<"\n\n\n Existing......\n";
    return 0;
}