//abstraction is process of Hiding  implementation and just showing essential details to the end user..

using System;

​

abstract class Bank{

    public abstract void CheckBal();          //abstract methods does not have body

    public abstract void Deposit(int amt);

    public abstract void WithDraw(int amt);

}

​

class Atm : Bank {

    int bal=10000;

    public override void CheckBal(){

        Console.WriteLine("bal is "+bal);

    }

    public override void Deposit(int amt){

        bal+=amt;

        Console.WriteLine("deposited ,Total Bal is :"+bal);

    }

    public override void WithDraw(int amt){

        if(amt<bal){

            bal-=amt;

        Console.WriteLine("withDrawn Success,remaining Bal is :"+bal);

        } else

         Console.WriteLine("Insufficiant Balance"); 

    }

}

public class User

{

    public static void Main()

    {

        Bank b= new Atm();   //upcasting

        Console.WriteLine("enter option :- \n\n1: Check balance \n2: Deposit\n3: WithDraw");

        int option=int.Parse(Console.ReadLine());

        if(option==1)

            b.CheckBal();

        else if(option==2){

            Console.WriteLine("enter  amout to Deposit :");

            b.Deposit(int.Parse(Console.ReadLine()));

        }

        else if(option==3){

            Console.WriteLine("enter  amout to WithDraw :");

            b.WithDraw(int.Parse(Console.ReadLine()));

        }

    }

}