Copy data of Email in registration to the username not showing in the registration page I want to copy the value of email to the username, which is not showing in the registration page, but it is showing in the /user/edit page as Display Name, which is randomly generated such that my username is my email, giving more flexibility to the user.
The Email Registration module will allow for using the email address as the username.

The LoginToboggan module will allow the user to create a username, and allow them to login with either the username OR email address.

Email Registration also provides a hook which will allow a custom module to set the account name to whatever you want it to be.  That does require writing a module, however, it doesn't have to be very complicated.

The only thing you would need to include in your module file is the hook.
Example adapted from http://www.grasmash.com/article/using-your-email-address-your-drupal-username#sthash.uZkOo6j6.dpuf

&lt;?php
/* 
* Implements hook_email_registration_name().
*/
function grasmash_email_registration_name($edit, $account) {
  return $account-&gt;mail;
}