Cannot connect to database !!

exception 'PDOException' with message 'SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using password: NO)' in /home/ncapakis/public_html/alumni/php/Connection.simple.php:22 Stack trace: #0 /home/ncapakis/public_html/alumni/php/Connection.simple.php(22): PDO->__construct('mysql:host=loca...', 'root', '') #1 /home/ncapakis/public_html/alumni/registeredm.php(15): dbConnect() #2 {main}