Adding Data.php Helper in Magento got error - configuration

Question

Following Alan Storm Tutorial in Custom Magento System Configuration, When i tried adding
the Data.php in the helper folder i still get this error:
Fatal error: Class 'Mage_Helloworld_Helper_Data' not found in E:\xampp\htdocs\magento
\app\Mage.php on line 520
**Alanstormdotcom\Helloworld\Helper\Data.php**
<?php
class Alanstormdotcom_Helloworld_Helper_Data extends Mage_Core_Helper_Abstract
{
}
**Alanstormdotcom\Helloworld\etc\system.xml**
<?xml version="1.0"?>
<config>
<tabs>
<helloconfig translate="label" module="helloworld">
<label>Hello Config</label>
<sort_order>99999</sort_order>
</helloconfig>
</tabs>
</config>
**Alanstormdotcom\Helloworld\etc\config.xml**
<?xml version="1.0"?>
<config>
<modules>
<Alanstormdotcom_Helloworld>
<version>0.1.0</version>
</Alanstormdotcom_Helloworld>
</modules>
<frontend>
<routers>
<helloworld>
<use>standard</use>
<args>
<module>Alanstormdotcom_Helloworld</module>
<frontName>helloworld</frontName>
</args>
</helloworld>
</routers>
</frontend>
<global>
<helpers>
<class>Alanstormdotcom_Helloworld_Helper</class>
</helpers>
</global>
</config>
I just wanted to learn.. I know this works in you but still help me find why.. i might miss
something.. Thank you.

Answer 1

This bit is wrong:
<global>
<helpers>
<class>Alanstormdotcom_Helloworld_Helper</class>
</helpers>
</global>
It should be:
<global>
<helpers>
<helloworld>
<class>Alanstormdotcom_Helloworld_Helper</class>
</helloworld>
</helpers>
</global>
(The <helloworld> tag corresponds to module="helloworld" above)