why it is not working

Please read the following code

<?php
$a=mysql_connect(localhost,root,"");
if(!$a)
echo "Could not connect";
?>

When i run the above pgm it gives the following errors:

Notice: Use of undefined constant localhost - assumed 'localhost' in C:\Program Files\EasyPHP 3.0\www\dbase.php on line 2

Notice: Use of undefined constant root - assumed 'root' in C:\Program Files\EasyPHP 3.0\www\dbase.php on line 2

Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'root'@'localhost' (using password: NO) in C:\Program Files\EasyPHP 3.0\www\dbase.php on line 2
Could not connect



Please tell where is the problem. I am using easyphp 3.0