diff --git a/libsrc/atari/fd.inc b/libsrc/atari/fd.inc
index e59fca562..31175b3ca 100644
--- a/libsrc/atari/fd.inc
+++ b/libsrc/atari/fd.inc
@@ -4,7 +4,7 @@
 ; offsets and defines for fdtable (internal use only)
 ;
 
-MAX_FD_INDEX	=	12
+MAX_FD_INDEX	=	12	; max. # of open fds
 MAX_FD_VAL	=	8	; we have 8 IOCBs
 
 ft_entrylen = 4	; length of table entry (it's not sufficient to change here!
@@ -16,4 +16,6 @@ ft_iocb	= 1	; iocb index (0,$10,$20,etc.), $ff for empty entry
 ft_dev  = 2	; device of open iocb (0 - device not remembered, eg. filename specified)
 ft_flag = 3	; flags
 		; lower 3 bits: device number (for R: and D:)
-
+		; bit 3 - seeking supported by DOS/disk combination
+		; bit 4 - indicates a fd opened by the program as apposed to the
+		;	  inherited ones from program start (fd 0 to fd 2)