diff --git a/io.c b/io.c
index 169158b..6a272c0 100644
--- a/io.c
+++ b/io.c
@@ -7343,9 +7343,38 @@ select_end(VALUE arg)
  *               [, error_array
  *               [, timeout]]] )-> array  or  nil
  *
- *  See <code>Kernel#select</code>.
+ *  Calls select(2) system call.
+ *  It returns an array that contains arrays of IO objects that are ready
+ *  for *  reading, are ready for writing, and have pending exceptions
+ *  respectably. It returns nil on timeout.
+ *
+ *      rp, wp = IO.pipe
+ *      mesg = "ping "
+ *      100.times {
+ *        rs, ws, = IO.select([rp], [wp])
+ *        if r = rs[0]
+ *          ret = r.read(5)
+ *          print ret
+ *          case ret
+ *          when /ping/
+ *            mesg = "pong\n"
+ *          when /pong/
+ *            mesg = "ping "
+ *          end
+ *        end
+ *        if w = ws[0]
+ *          w.write(mesg)
+ *        end
+ *      }
+ *
+ *  <em>produces:</em>
+ *
+ *      ping pong
+ *      ping pong
+ *      ping pong
+ *      (snipped)
+ *      ping
  */
-
 static VALUE
 rb_f_select(int argc, VALUE *argv, VALUE obj)
 {