hi,
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello, world!");
}
I think you should also change,
lcd.begin(16, 2);
to
lcd.begin(20, 4);
Tom..... 
hi,
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello, world!");
}
I think you should also change,
lcd.begin(16, 2);
to
lcd.begin(20, 4);
Tom.....