Wordpress Post Type without a plugin

It is the code for book post type.

add_action( 'init', 'codex_book_init' );

/**

 * Register a book post type.

 * @link http://apnagarage.blogspot.in

 */

function codex_book_init() {

            $labels = array(

                 'name'               => _x( 'Books', 'post type general name', 'your-plugin-textdomain' ),

                 'singular_name'      => _x( 'Book', 'post type singular name', 'your-plugin-textdomain' ),

                 'menu_name'          => _x( 'Books', 'admin menu', 'your-plugin-textdomain' ),

                 'name_admin_bar'     => _x( 'Book', 'add new on admin bar', 'your-plugin-textdomain' ),

                 'add_new'            => _x( 'Add New', 'book', 'your-plugin-textdomain' ),

                 'add_new_item'       => __( 'Add New Book', 'your-plugin-textdomain' ),

                 'new_item'           => __( 'New Book', 'your-plugin-textdomain' ),

                 'edit_item'          => __( 'Edit Book', 'your-plugin-textdomain' ),

                 'view_item'          => __( 'View Book', 'your-plugin-textdomain' ),

                 'all_items'          => __( 'All Books', 'your-plugin-textdomain' ),

                 'search_items'       => __( 'Search Books', 'your-plugin-textdomain' ),

                 'parent_item_colon'  => __( 'Parent Books:', 'your-plugin-textdomain' ),

                 'not_found'          => __( 'No books found.', 'your-plugin-textdomain' ),

                 'not_found_in_trash' => __( 'No books found in Trash.', 'your-plugin-textdomain' )

            );

            $args = array(

                        'labels'                       => $labels,

                        'public'                       => true,

                        'publicly_queryable'  => true,

                        'show_ui'                  => true,

                        'show_in_menu'       => true,

                        'query_var'              => true,

                        'rewrite'                   => array( 'slug' => 'career' ),

                        'capability_type'     => 'post',

                        'has_archive'           => true,

                        'hierarchical'           => false,

                        'menu_position'      => null,

                        'supports'           => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments' )

            );

             register_post_type( 'book', $args );

}