Add some comments

1 files changed, 6 insertions, 0 deletions

diff --git a/src/data.c b/src/data.c
index ad5ee663d1d..f7602c2d602 100644
--- a/src/data.c
+++ b/src/data.c
@@ -907,8 +907,12 @@ Value, if non-nil, is a list (interactive SPEC).  */)
         {
           Lisp_Object form = AREF (fun, COMPILED_INTERACTIVE);
           if (VECTORP (form))
+            /* The vector form is the new form, where the first
+               element is the interactive spec, and the second is the
+               command modes. */
             return list2 (Qinteractive, AREF (form, 0));
           else
+            /* Old form -- just the interactive spec. */
             return list2 (Qinteractive, form);
         }
     }
@@ -966,8 +970,10 @@ The value, if non-nil, is a list of mode name symbols.  */)
     {
       Lisp_Object form = AREF (fun, COMPILED_INTERACTIVE);
       if (VECTORP (form))
+        /* New form -- the second element is the command modes. */
         return AREF (form, 1);
       else
+        /* Old .elc file -- no command modes. */
         return Qnil;
     }
 #ifdef HAVE_MODULES