clear; clc; % so that we start fresh

disp('A very simplified ATM program with too many assumptions');
balance = 100; % assume my account (with card 1 and pin 123456) has initial balance 100$

while 1 % this is a famous statement for looping forever 'while true'
  % 1. loop until user enters a card (number 1)
  while 1
    cardID = input('Enter card (press 1) or exit (press -1): ');
    if cardID == 1 | cardID == -1 % only stop when the card is entered or user wants to exit
      break;
    end
  end

  if cardID == -1 % one more check to stop the entire program
    break;
  end
    
  disp('Card inserted.');

  % 2. loop until user enters the correct pin (123456)
  while 1
    PIN = input('Enter PIN (6 digits): ');
    if PIN == 123456 % our simple ATM has this universal PIN
      break;
    end
    disp('PIN incorrect, try again until correct!');
  end

  disp('PIN correct!');

  % 3. the 'transaction' :D
  disp(sprintf('Current balance = %d$', balance));
  amount = input('Withdraw how much money?: ');
  if amount <= balance % for protection
    disp(sprintf('ATM dispense %d$!',amount));
    balance = balance - amount;
  else
    disp(sprintf('Cannot dispense %d$!',amount));
  end
  disp(sprintf('Current balance = %d$', balance));
  % this simple ATM directly go back to check card mode after one transaction
  disp('Have a nice day =)'); 
  disp('------------------'); % separator for each transaction
end

% Ah, just some exit note
disp('Thank you for using this not so useful ATM.');