diff --git a/DOS.ASM b/DOS.ASM
index 646ac7a..ed5d2e9 100644
--- a/DOS.ASM
+++ b/DOS.ASM
@@ -32,3 +32,29 @@
 
 	%DEFINE ASCII_RETURN 0Dh
 	%DEFINE ASCII_NEWLINE 0Ah
+
+	%DEFINE F_READ 0
+	%DEFINE F_WRITE 1
+	%DEFINE F_READ_WRITE 2
+
+	;; DX - null-terminated file name
+	;; AL - flags
+	%MACRO OPENF 0
+	MOV AH, 3Dh
+	INT 21h
+	%ENDMACRO
+
+	%MACRO WRITEF 0
+	MOV AH, 40h
+	INT 21h
+	%ENDMACRO
+
+	%MACRO CLOSEF 0
+	MOV AH, 3Eh
+	INT 21h
+	%ENDMACRO
+
+	%MACRO CREATF 0
+	MOV AH, 3Ch
+	INT 21h
+	%ENDMACRO