If you are having trouble getting HTML code like <script> or <code> working correctly in Drupal articles using Full HTML or Display Suite code there are two things to check. Go to /admin/structure/types/manage/article/display/full and /admin/structure/types/manage/article/display/default check under the content type that you are having issues with and ensure that it is set to Default and not Plain Text. Then, under ‘Layout for article’ select any layout in order for Display Suite code to work.