How To Display Category Name and Titles of all Posts: WordPress Codex

Are you looking for a WordPress code to display category name and titles of all posts like bellow pattern?

Category Name 1
post title 1
post title 2
post title 3
Category Name 2
Post title 1

Here is the pice of PHP code which echo the above pattern.Copy and paste it in your template.

<?php
//for each category, show all posts
$cat_args=array(
  'orderby' => 'name',
  'order' => 'ASC'
   );
$categories=get_categories($cat_args);
  foreach($categories as $category) {
    $args=array(
      'showposts' => -1,
      'category__in' => array($category->term_id),
      'caller_get_posts'=>1
    );
    $posts=get_posts($args);
      if ($posts) {
        echo '<p>Category: <a href="' . get_category_link( $category->term_id ) . '" title="' . sprintf( __( "View all posts in %s" ), $category->name ) . '" ' . '>' . $category->name.'</a> </p> ';
        foreach($posts as $post) {
          setup_postdata($post); ?>
          <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
          <?php
        } // foreach($posts
      } // if ($posts
    } // foreach($categories
?>

Refference