show all posts without tags

Can I show all posts without tags using /tag/…something… without a plugin?

I am aware that I can use code like:

global $wp_query;
			$wp_query->set('tag__not_in',$tagarray);
			$wp_query->get_posts();
			include ($includedirectory . "loop.php");

on the main page

I am aware that there are plugins to achieve this.

I want however a seperate page showing only the postings that have no tag yet.