1)Change the directory to the root of magento installation

2)  vi app/etc/modules/Pcode_Attribute.xml and paste the below given content
<config>
<modules>
<Pcode_Attribute>
<active>true</active>
<codePool>local</codePool>
</Pcode_Attribute>
</modules>
</config>

3) mkdir app//code/local/
4) mkdir app//code/local/Pcode
5 )mkdir app//code/local/Pcode/Attribute
6) mkdir app//code/local/Pcode/Attribute/etc
7) mkdir app//code/local/Pcode/Attribute/sql
8) mkdir app/code/local/Pcode/Attribute/sql/categoryattribute_setup
9) vi app/code/local/Pcode/Attribute/sql/categoryattribute_setup/mysql4-install-0.1.0.php and paste the below given code

<?php
$this->startSetup();
$this->addAttribute(‘catalog_category’, ‘new_attribute’, array(
‘group’         => ‘General’,
‘input’         => ‘text’,
‘type’          => ‘varchar’,
‘label’         => ‘New attribute’,
‘backend’       => ”,
‘visible’       => 1,
‘required’      => 0,
‘user_defined’ => 1,
‘global’        => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL,
));
$this->endSetup();
?>

10) vi app//code/local/Pcode/Attribute/etc/config.xm and paste the below code
<?xml version=”1.0″?>
<config>
<modules>
<Pcode_Attribute>
<version>0.1.0</version>
</Pcode_Attribute>
</modules>
<global>
<resources>
<categoryattribute_setup>
<setup>
<module>Pcode_Attribute</module>
<class>Mage_Eav_Model_Entity_Setup</class>
</setup>
<connection>
<use>default_setup</use>
</connection>
</categoryattribute_setup>
</resources>
</global>
</config>