wordpress post types with thumbnail code example

Example: wordpress post types supports thumbnail

<?php 
$args = array(
  /* ... */
  'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments' )
 ); 
  register_post_type('book',$args);
}
add_action( 'init', 'custom_post_init' );