diff --git a/src/os_win16.h b/src/os_win16.h
new file mode 100644
index 0000000..93b5891
--- /dev/null
+++ b/src/os_win16.h
@@ -0,0 +1,142 @@
+/* vi:set ts=8 sts=4 sw=4:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ */
+
+/*
+ * Win16 (Windows 3.1x) machine-dependent things.
+ */
+
+#include "os_dos.h"		/* common MS-DOS and Windows stuff */
+
+#define BINARY_FILE_IO
+#define USE_EXE_NAME		/* use argv[0] for $VIM */
+#define NO_COOKED_INPUT		/* mch_inchar() doesn't return whole lines */
+#define SYNC_DUP_CLOSE		/* sync() a file with dup() and close() */
+#define USE_TERM_CONSOLE
+#define HAVE_STRING_H
+#define HAVE_STRCSPN
+#define HAVE_STRICMP
+#define HAVE_STRNICMP
+#define HAVE_STRFTIME		/* guessed */
+#define HAVE_MEMSET
+#define USE_TMPNAM		/* use tmpnam() instead of mktemp() */
+#define HAVE_LOCALE_H
+#define HAVE_FCNTL_H
+#define HAVE_QSORT
+#define HAVE_ST_MODE		/* have stat.st_mode */
+//#define USE_FNAME_CASE	/* adjust case of file names */
+#ifndef FEAT_CLIPBOARD
+# define FEAT_CLIPBOARD		/* include clipboard support */
+#endif
+#if defined(__DATE__) && defined(__TIME__)
+# define HAVE_DATE_TIME
+#endif
+#define HAVE_AVAIL_MEM
+
+#define SHORT_FNAME		/* always 8.3 file name */
+
+#define SMALL_MALLOC		/* 16 bit storage allocation */
+
+#ifdef __BORLANDC__
+# define HAVE_PUTENV		/* at least Bcc 5.2 has it */
+#endif
+
+#ifdef FEAT_GUI_W16
+# define NO_CONSOLE		/* don't included console-only code */
+#endif
+
+/* toupper() is not really broken, but it's very slow.	Probably because of
+ * using unicde characters on Windows NT */
+#define BROKEN_TOUPPER
+
+#define FNAME_ILLEGAL "\"*?><|" /* illegal characters in a file name */
+
+#ifndef SIZEOF_INT
+# define SIZEOF_INT 2
+#endif
+
+typedef long off_t;
+
+#include <stdlib.h>
+#include <time.h>
+#include <dos.h>
+#include <dir.h>
+
+#ifndef STRICT
+# define STRICT
+#endif
+#ifndef COBJMACROS
+# define COBJMACROS	/* For OLE: Enable "friendlier" access to objects */
+#endif
+#include <windows.h>
+
+/*
+ *  plenty of memory, use large buffers
+ */
+#define CMDBUFFSIZE 1024	/* size of the command processing buffer */
+
+
+#define BASENAMELEN	(MAXPATHL-5)	/* length of base of file name */
+
+#ifndef DFLT_MAXMEM
+# define DFLT_MAXMEM	(256)    /* use up to 256K for a buffer*/
+#endif
+
+#ifndef DFLT_MAXMEMTOT
+# define DFLT_MAXMEMTOT	(5*1024)    /* use up to 5 Mbyte for Vim */
+#endif
+
+/*
+ * Some simple debugging macros that look and behave a lot like their
+ * namesakes in MFC.
+ */
+
+#ifdef _DEBUG
+
+# if defined(_MSC_VER)	&&  (_MSC_VER >= 1000)
+   /* Use the new debugging tools in Visual C++ 4.x */
+#  include <crtdbg.h>
+#  define ASSERT(f) _ASSERT(f)
+# else
+#  include <assert.h>
+#  define ASSERT(f) assert(f)
+# endif
+
+# define VERIFY(f)		ASSERT(f)
+# define DEBUG_ONLY(f)		(f)
+# define TRACE			Trace
+# define TRACE0(sz)		Trace(_T("%s"), _T(sz))
+# define TRACE1(sz, p1)		Trace(_T(sz), p1)
+# define TRACE2(sz, p1, p2)	Trace(_T(sz), p1, p2)
+# define TRACE3(sz, p1, p2, p3) Trace(_T(sz), p1, p2, p3)
+
+/* In debug version, writes trace messages to debug stream */
+void __cdecl
+Trace(char *pszFormat, ...);
+
+#else /* !_DEBUG */
+
+  /* These macros should all compile away to nothing */
+# define ASSERT(f)		((void)0)
+# define VERIFY(f)		((void)f)
+# define DEBUG_ONLY(f)		((void)0)
+# define TRACE			1 ? (void)0 : printf
+# define TRACE0(sz)
+# define TRACE1(sz, p1)
+# define TRACE2(sz, p1, p2)
+# define TRACE3(sz, p1, p2, p3)
+
+#endif /* !_DEBUG */
+
+
+#define ASSERT_POINTER(p, type) \
+    ASSERT(((p) != NULL)  &&  IsValidAddress((p), sizeof(type), FALSE))
+
+#define ASSERT_NULL_OR_POINTER(p, type) \
+    ASSERT(((p) == NULL)  ||  IsValidAddress((p), sizeof(type), FALSE))
+
+#define mch_setenv(name, val, x) setenv(name, val, x)