what needs to be in the index.php of a wordpress theme code example

Example 1: wordpress theme development

You can use this as start theme or as boilerplate for theme
this has all the start up files 

https://github.com/d4rkvent/understrap

Example 2: wordpress theme devalopement

<?php
 
get_header();
 
if ( have_posts() ) :
	while ( have_posts() ) : the_post(); ?>
 
        <article class="post">
            <h2><a href="<?php the_permalink() ?>"><?php the_title() ?></a></h2>
			<?php the_content() ?>
        </article>
	
	<?php endwhile;
 
else :
	echo '<p>There are no posts!</p>';
 
endif;
 
get_footer();
 
?>