drupal/modules/help.module

<?php
// $Id$

function help_system($field){
  $system["description"] = t("Manages displaying online help.");
  return $system[$field];
}

function help_link($type) {
  if ($type == "admin") {
    menu_add("help", url("admin/help"), "Help", NULL, NULL, 9);
  }
}

function help_admin() {

  foreach (module_list() as $name) {
    if (module_hook($name, "help")) {
      $links[] = l($name, "admin/help#$name");
    }
  }

  print "<small>". implode(" &middot; ", $links) ."</small><hr />";

  foreach (module_list() as $name) {
    if (module_hook($name, "help")) {
      print "<h2><a name=\"$name\">". ucfirst($name) ." module</a></h2>";
      print module_invoke($name, "help");
    }
  }
}

?>