diff --git a/includes/form.inc b/includes/form.inc
index 9c2a9c1..e5e309f 100644
--- a/includes/form.inc
+++ b/includes/form.inc
@@ -3644,8 +3644,49 @@ function theme_hidden($variables) {
  * @param $variables
  *   An associative array containing:
  *   - element: An associative array containing the properties of the element.
- *     Properties used: #title, #value, #description, #size, #maxlength,
- *     #required, #attributes, #autocomplete_path.
+ *     Properties used:
+ *      - #access,
+ *      - #after_build,
+ *      - #ajax,
+ *      - #attributes,
+ *      - #autocomplete_path,
+ *      - #default_value,
+ *      - #description,
+ *      - #disabled,
+ *      - #element_validate,
+ *      - #field_prefix,
+ *      - #field_suffix,
+ *      - #maxlength,
+ *      - #parents,
+ *      - #post_render,
+ *      - #prefix,
+ *      - #pre_render,
+ *      - #process,
+ *      - #required,
+ *      - #size,
+ *      - #states,
+ *      - #suffix,
+ *      - #text_format,
+ *      - #theme,
+ *      - #theme_wrappers,
+ *      - #title,
+ *      - #title_display,
+ *      - #tree,
+ *      - #type,
+ *      - #weight
+ *
+ * @example
+ *  From forum_function()
+ *  <code>
+ *   $form['title'] = array(
+ *     '#type' => 'textfield',
+ *     '#title' => t('Subject'),
+ *     '#default_value' => $node->title,
+ *     '#size' => 60,
+ *     '#maxlength' => 128,
+ *     '#required' => TRUE,
+ *   );
+ * </code>
  *
  * @ingroup themeable
  */
diff --git a/modules/system/system.module b/modules/system/system.module
index 3ebc657..8b33ca0 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -346,6 +346,7 @@ function system_element_info() {
     '#src' => NULL,
     '#theme_wrappers' => array('image_button'),
   );
+  // Format a single-line text field.
   $types['textfield'] = array(
     '#input' => TRUE,
     '#size' => 60,