diff --git a/src/os_dos.h b/src/os_dos.h
new file mode 100644
index 0000000..103cded
--- /dev/null
+++ b/src/os_dos.h
@@ -0,0 +1,125 @@
+/* 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.
+ */
+
+/*
+ * Common MS-DOS and Win32 (Windows NT and Windows 95) defines.
+ *
+ * Names for the EXRC, HELP and temporary files.
+ * Some of these may have been defined in the makefile or feature.h.
+ */
+
+#ifndef SYS_VIMRC_FILE
+# define SYS_VIMRC_FILE		"$VIM\\vimrc"
+#endif
+#ifndef USR_VIMRC_FILE
+# define USR_VIMRC_FILE		"$HOME\\_vimrc"
+#endif
+#ifndef USR_VIMRC_FILE2
+# define USR_VIMRC_FILE2	"$VIM\\_vimrc"
+#endif
+#ifndef EVIM_FILE
+# define EVIM_FILE		"$VIMRUNTIME\\evim.vim"
+#endif
+
+#ifndef USR_EXRC_FILE
+# define USR_EXRC_FILE		"$HOME\\_exrc"
+#endif
+#ifndef USR_EXRC_FILE2
+# define USR_EXRC_FILE2		"$VIM\\_exrc"
+#endif
+
+#ifdef FEAT_GUI
+# ifndef SYS_GVIMRC_FILE
+#  define SYS_GVIMRC_FILE	"$VIM\\gvimrc"
+# endif
+# ifndef USR_GVIMRC_FILE
+#  define USR_GVIMRC_FILE	"$HOME\\_gvimrc"
+# endif
+# ifndef USR_GVIMRC_FILE2
+#  define USR_GVIMRC_FILE2	"$VIM\\_gvimrc"
+# endif
+# ifndef SYS_MENU_FILE
+#  define SYS_MENU_FILE		"$VIMRUNTIME\\menu.vim"
+# endif
+#endif
+
+#ifndef SYS_OPTWIN_FILE
+# define SYS_OPTWIN_FILE	"$VIMRUNTIME\\optwin.vim"
+#endif
+
+#ifdef FEAT_VIMINFO
+# ifndef VIMINFO_FILE
+#  define VIMINFO_FILE		"$HOME\\_viminfo"
+# endif
+# ifndef VIMINFO_FILE2
+#  define VIMINFO_FILE2		"$VIM\\_viminfo"
+# endif
+#endif
+
+#ifndef VIMRC_FILE
+# define VIMRC_FILE	"_vimrc"
+#endif
+
+#ifndef EXRC_FILE
+# define EXRC_FILE	"_exrc"
+#endif
+
+#ifdef FEAT_GUI
+# ifndef GVIMRC_FILE
+#  define GVIMRC_FILE	"_gvimrc"
+# endif
+#endif
+
+#ifndef DFLT_HELPFILE
+# define DFLT_HELPFILE	"$VIMRUNTIME\\doc\\help.txt"
+#endif
+
+#ifndef FILETYPE_FILE
+# define FILETYPE_FILE	"filetype.vim"
+#endif
+#ifndef FTPLUGIN_FILE
+# define FTPLUGIN_FILE	"ftplugin.vim"
+#endif
+#ifndef INDENT_FILE
+# define INDENT_FILE	"indent.vim"
+#endif
+#ifndef FTOFF_FILE
+# define FTOFF_FILE	"ftoff.vim"
+#endif
+#ifndef FTPLUGOF_FILE
+# define FTPLUGOF_FILE	"ftplugof.vim"
+#endif
+#ifndef INDOFF_FILE
+# define INDOFF_FILE	"indoff.vim"
+#endif
+
+#ifndef SYNTAX_FNAME
+# define SYNTAX_FNAME	"$VIMRUNTIME\\syntax\\%s.vim"
+#endif
+
+#ifndef DFLT_BDIR
+# define DFLT_BDIR	".,c:\\tmp,c:\\temp"	/* default for 'backupdir' */
+#endif
+
+#ifndef DFLT_VDIR
+# define DFLT_VDIR	"$VIM/vimfiles/view"	/* default for 'viewdir' */
+#endif
+
+#ifndef DFLT_DIR
+# define DFLT_DIR	".,c:\\tmp,c:\\temp"	/* default for 'directory' */
+#endif
+
+#define DFLT_ERRORFILE		"errors.err"
+#define DFLT_RUNTIMEPATH	"$HOME/vimfiles,$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after,$HOME/vimfiles/after"
+
+#define CASE_INSENSITIVE_FILENAME   /* ignore case when comparing file names */
+#define SPACE_IN_FILENAME
+#define BACKSLASH_IN_FILENAME
+#define USE_CRNL		/* lines end in CR-NL instead of NL */
+#define HAVE_DUP		/* have dup() */
+#define HAVE_ST_MODE		/* have stat.st_mode */