diff --git a/Demo/sgi/cd/cdwin.py b/Demo/sgi/cd/cdwin.py
index 823866f..8834c1d 100755
--- a/Demo/sgi/cd/cdwin.py
+++ b/Demo/sgi/cd/cdwin.py
@@ -1,3 +1,5 @@
+# Window interface to (some of) the CD player's vital audio functions
+
 import cd
 import stdwin
 from stdwinevents import *
@@ -91,3 +93,5 @@
 	v1 = top + (bottom - top) / 3
 	v2 = top + (bottom - top) * 2 / 3
 	return left, top, right, bottom, v1, v2
+
+main()