diff --git a/sys/msdos/portio.h b/sys/msdos/portio.h
new file mode 100644
index 000000000..543565617
--- /dev/null
+++ b/sys/msdos/portio.h
@@ -0,0 +1,71 @@
+/*   SCCS Id: @(#)portio.h   3.3     95/08/05                       */
+/*   Copyright (c) NetHack PC Development Team 1995                 */
+/*   NetHack may be freely redistributed.  See license for details. */
+/*                                                                  */
+/*
+ * portio.h - PC port I/O Hardware support definitions and other
+ *            low-level definitions.
+ *                                                  
+ */
+
+#ifndef PORTIO_H
+#define PORTIO_H
+
+# if defined(__GO32__) || defined(__DJGPP__)
+#define __far
+#include <go32.h>
+#include <dpmi.h>
+#include <sys/farptr.h>
+#endif
+
+# if defined(_MSC_VER)
+#define outportb _outp
+#define outportw _outpw
+#define inportb _inp
+# endif
+# if defined(__BORLANDC__)
+#define outportw outport
+/* #define inportb inport */
+# endif
+
+# ifndef MK_PTR
+/*
+ * Depending on environment, this is a macro to construct either:
+ *
+ *     -  a djgpp long 32 bit pointer from segment & offset values
+ *     -  a far pointer from segment and offset values
+ *
+ */
+#  if defined(_MSC_VER) || defined(__BORLANDC__)
+#define MK_PTR(seg, offset) (void __far *)(((unsigned long)seg << 16) \
+     + (unsigned long)(unsigned)offset)
+#define READ_ABSOLUTE(x) *(x)
+#define READ_ABSOLUTE_WORD(x) *(x)
+#define WRITE_ABSOLUTE(x,y) *(x) = (y)
+#define WRITE_ABSOLUTE_WORD(x,y) *(x) = (y)
+#  endif
+
+#  if defined(__GO32__) || defined(__DJGPP__)
+#define MK_PTR(seg, offset) (void *)(((unsigned)seg << 4) + (unsigned)offset)
+#define READ_ABSOLUTE(x) \
+	(_farpeekb(_go32_conventional_mem_selector(), (unsigned)x))
+#define READ_ABSOLUTE_WORD(x) \
+	(_farpeekw(_go32_conventional_mem_selector(), (unsigned)x))
+#define WRITE_ABSOLUTE(x,y) \
+	_farpokeb(_go32_conventional_mem_selector(), (unsigned)x, (y))
+#define WRITE_ABSOLUTE_WORD(x,y) \
+	_farpokew(_go32_conventional_mem_selector(), (unsigned)x, (y))
+#  endif
+
+#  ifdef OBSOLETE   /* old djgpp V1.x way of mapping 1st MB */
+#define MK_PTR(seg, offset) (void *)(0xE0000000+((((unsigned)seg << 4) \
+     + (unsigned)offset)))
+#define READ_ABSOLUTE(x) *(x)
+#define READ_ABSOLUTE_WORD(x) *(x)
+#define WRITE_ABSOLUTE(x,y) *(x) = (y)
+#define WRITE_ABSOLUTE_WORD(x,y) *(x) = (y)
+#  endif
+# endif /* MK_PTR */
+
+#endif /* PORTIO_H  */
+/* portio.h */