lcd keypad

How do i stop the password from "sliding"
if the password is 123456 and i enter 1234567 the password is still valid?

void checkPIN()
{
  int correct=0;
  for (int q=0; q<6; q++) 
  {
    if (attempt[q]==PIN[q])
    {
      correct++;
    }
  }
  if (correct==6)
  {
    systemSet();
    //correctPIN();
  }
  else
  {
    //incorrectPIN();
    systemUnSet();
  }
  for (int zz=0; zz<16; zz++) // wipe attempt
  {
    attempt[zz]=0;

  }
}


//------------------------------------------------------------------------------------


void readKeypad()
{


  char key = keypad.getKey();
  if (key != NO_KEY)   // only be bothered to do something if a key was pressed 

  { 
    fromKeypad++; //Each time there is a character received, increment the counter:
    lcd.setCursor(fromKeypad-1, 1);
    lcd.print(key);

    switch(key)// look for the special keys to initiate an event
    {
    case '*':
      z=0;
      fromKeypad = 0;
      break;
    case '#':
      delay(100); // for extra debounce
      fromKeypad = 0;
      lcd.clear();
      checkPIN();
      break;
    default:
      attempt[z]=key;
      z++;


      KeyPadTone();// play a beep to acknowledge that key pressed


    }
  }

}