diff --git a/MagickCore/string-private.h b/MagickCore/string-private.h
index b3dd2e1..6e4308c 100644
--- a/MagickCore/string-private.h
+++ b/MagickCore/string-private.h
@@ -31,6 +31,9 @@
     scale,
     value;
 
+  /*
+    Interpret string with International System of Units (SI) unit prefix.
+  */
   value=InterpretLocaleValue(string,&q);
   scale=1000.0;
   if ((*q != '\0') && (tolower((int) ((unsigned char) *(q+1))) == 'i'))