diff --git a/libsrc/atari/diopncls.s b/libsrc/atari/diopncls.s
new file mode 100644
index 000000000..50899bfe7
--- /dev/null
+++ b/libsrc/atari/diopncls.s
@@ -0,0 +1,46 @@
+;
+; Christian Groessler, October 2000
+;
+; This file provides the __dio_open and __dio_close functions
+; Since on the Atari no real open and close is necessary, they
+; do not much. The __dio_open queries the sector size of the
+; drive which is later used by the _dio_read and _dio_write
+; functions.
+;
+; unsigned char __fastcall__ _dio_open  (_driveid_t drive_id);
+; unsigned char __fastcall__ _dio_close (_driveid_t drive_id);
+;
+
+ 	.export		__dio_open,__dio_close
+	.export		sectsizetab
+	.include	"atari.inc"
+
+.bss
+
+sectsizetab:
+	.res	NUMDRVS * 2
+
+.code
+
+
+.proc	__dio_open
+
+	asl	a	; make index from drive id
+	tax
+	lda	#128	; currently hardcoded (until I get an 815 :-)
+	sta	sectsizetab,x
+	lda	#0
+	sta	sectsizetab+1,x
+
+	; fall thru to __dio_close
+
+.endproc
+
+.proc	__dio_close
+
+	lda	#0
+	tax
+	rts		; return no error
+
+.endproc
+