problem while adding Custom Libraries to CI3

HI,
I have a working application in previous version of CI and is working well, i am trying to create a new application with somewhat reuse of previous code, (but it's a new application, not an upgrade),

I downloaded the latest zip of CI from website.
I setup CI and it worked well, i was able to see the welcome controller,
I copied some of my previous helping libraries into libraries directory and included them
as

Code:

$this->load->library('directoryinfo');

and couple of other libraries also the same way in a function loads(), which is called in the constructor of the controller,
but this give me the following error

PHP Code:

A PHP Error was encountered

Severity: Error

Message: Class 'CI_Directoryinfo' not found

Filename: core/Common.php

Line Number: 192 


I am not able to understand , why i am receiving this error, because, in my class there is no "CI_ " in the name.

So i need help in this regard

Thanks