Creating "Hello World" Magento Module

To start with a new Magento module, you have to create a module code folder under an appropriate code pool.
Lets create "Hello World" module module.

Step 1:

- Please create ".xml" file for module as below:
\app\etc\modules\Demomodule_Helloworld.xml

<?xml version="1.0"?>
<config>
<modules>
<Demomodule_Helloworld>
<active>true</active>
<codePool>local</codePool>
</Demomodule_Helloworld>
</modules>
</config>


Step 2:

Now, you have to create config file for module setup as below:

\app\code\local\Demomodule\Helloworld\etc\config.xml

<?xml version="1.0"?>
<config>
<modules>
<Demomodule_Helloworld>
<version>1.0.0</version>
</Demomodule_Helloworld>
</modules>
<frontend>
        <routers>
            <helloworld>
                <use>standard</use>
                <args>
                    <module>Demomodule_Helloworld</module>
                    <frontName>helloworld</frontName>
                </args>
            </helloworld>
        </routers>
        <layout>
            <updates>
                <helloworld>
                    <file>helloworld.xml</file>
                </helloworld>
            </updates>
        </layout>
    </frontend>
</config>


Step 3: 

Please create controller file with below information.

\app\code\local\Demomodule\Helloworld\controllers\IndexController.php

<?php
class Demomodule_Helloworld_IndexController extends Mage_Core_Controller_Front_Action
{
    public function indexAction()
    {
$this->loadLayout();     
$this->renderLayout();
    }
}

Step 4:

Please create ".xml" file for plugin "Block" setup as below:

\app\design\frontend\default\default\layout\helloworld.xml

<?xml version="1.0"?>
    <layout version="0.1.0">
<helloworld_index_index>
<reference name="content">
<block type="core/template" name="helloworldpage" template="helloworld/content.phtml"/>
</reference>
</helloworld_index_index>

</layout>


Step 5:

Now, you have to create new ".phtml" file for your content as below:

\app\design\frontend\default\default\template\helloworld\content.phtml

<div class="banner-left box">
<?php echo $this->__('This is the demo "Hello World" module.');?>
</div>