Magento: Display top level categories and subcategories of current category

In this article I’m writing code for display top level categories and sub categories of current category. If you want to have a list with the sub categories of magento of the current Parent category then you can use below code:-

<?php $_helper = Mage::helper('catalog/category') ?>
<?php $_categories = $_helper->getStoreCategories() ?>
<?php $currentCategory = Mage::registry('current_category') ?>
<?php if (count($_categories) > 0): ?>
    <ul class="category">
        <?php foreach($_categories as $_category): ?>
            <li>
                <a href="<?php echo $_helper->getCategoryUrl($_category) ?>">
                    <?php echo $_category->getName() ?>
                </a>
                <?php if ($currentCategory->getId() && $currentCategory->getId() == $_category->getId()): ?>
                    <?php $_category = Mage::getModel('catalog/category')->load($_category->getId()) ?>
                    <?php $_subcategories = $_category->getChildrenCategories() ?>
                    <?php if (count($_subcategories) > 0): ?>
                        <ul class="subcategory">
                            <?php foreach($_subcategories as $_subcategory): ?>
                                <li>
                                    <a href="<?php echo $_helper->getCategoryUrl($_subcategory) ?>">
                                        <?php echo $_subcategory->getName() ?>
                                    </a>
                                </li>
                            <?php endforeach; ?>
                        </ul>
                    <?php endif; ?>
                <?php endif; ?>
            </li>
        <?php endforeach; ?>
    </ul>
<?php endif; ?>