Adding Data.php Helper in Magento got error

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">
开发者_如何学编程                <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.

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)}