Write a C program for PUSH and POP operation performed on Stack

#include<iostream.h>
#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
#define size 3
   int push();
   int pop();
   int push()
{
    int z;
    cout<<"\nEnter the value of z: ";
    cin>>z;
    return(z);
}
    int pop()
{
    return(0);
}
    void main()
{
    int ar[size],top,a,value;
    char ch='y';
clrscr();
top=-1;
while(ch=='Y'||ch=='y')
{
cout<<"\n1.push";
cout<<"\n2.pop";
cout<<"\n3.display";
cout<<"\n4.exit";
cout<<"\nEnter your choice :";
cin>>a;
switch(a)
{
case 1:if(top>=size-1)
{
cout<<"\nstack overflow";
}
else
{
top=top+1;
ar[top]=push();
}
break;
case 2:if(top==1)
       {
       cout<<"\nstack underflow";
       }
       else
       {
       value=ar[top];
       cout<<"\npopped element :"<<value;
       top=top-1;
       }
       break;
case 3:
       for(int i=0;i<=top;i++)
       {
       cout<<"\nthe stack value are :"<<ar[i];
       }
       break;
case 4:
       exit;
       break;

default:
       cout<<"\nwrong choice";
       }
       cout<<"\ndo you want to continue (press y): ";
       cin>>ch;
       getch();
      }
}