diff --git a/extern/btyacc/makefile.dos b/extern/btyacc/makefile.dos
deleted file mode 100644
index 656469b5bc..0000000000
--- a/extern/btyacc/makefile.dos
+++ /dev/null
@@ -1,71 +0,0 @@
-# Makefile for MS-DOS using Borland C (by P. Foggia)
-#
-DEST          = .
-
-HDRS          = defs.h mstring.h
-
-CFLAGS        = -ml -c
-
-LDFLAGS       =   /c
-
-# Change LIBDIR to your compiler's library path
-LIBDIR        = L:\bc\lib
-C0            = $(LIBDIR)\c0l.obj
-CLIB          = $(LIBDIR)\cl.lib
-
-LIBS          =
-
-LINKER        = tlink
-CC        = bcc
-
-MAKEFILE      = Makefile.dos
-
-OBJS1  = closure.obj error.obj lalr.obj lr0.obj main.obj mkpar.obj output.obj
-OBJS2  = mstring.obj reader.obj skeleton.obj symtab.obj verbose.obj warshall.obj
-OBJS   = $(OBJS1) $(OBJS2)
-
-
-PROGRAM       = btyacc.exe
-
-SRCS          = closure.c error.c lalr.c lr0.c main.c mkpar.c output.c  \
-                mstring.c reader.c skeleton.c symtab.c verbose.c warshall.c
-
-OTHERS        = README README.BYACC \
-                Makefile btyaccpa.ske empty.y skel2c manpage
-
-all:            $(PROGRAM)
-
-$(PROGRAM):     $(OBJS) $(LIBS)
-        @echo Linking $(PROGRAM) ...
-        @echo $(LDFLAGS) $(C0) + > link.lst
-        @echo $(OBJS1) + >> link.lst
-        @echo $(OBJS2)  >> link.lst
-        @echo $(PROGRAM) >>link.lst
-        @echo nul >> link.lst
-        @echo $(CLIB) >> link.lst
-        @$(LINKER) @link.lst
-        @echo ... done
-
-
-
-
-program:        $(PROGRAM)
-
-
-skeleton.c: btyaccpa.ske
-        awk -f skel2c btyaccpa.ske >skeleton.c
-
-###
-closure.o: defs.h
-error.o: defs.h
-lalr.o: defs.h
-lr0.o: defs.h
-main.o: defs.h
-mkpar.o: defs.h
-mstring.o: mstring.h
-output.o: defs.h
-reader.o: defs.h mstring.h
-skeleton.o: defs.h
-symtab.o: defs.h
-verbose.o: defs.h
-warshall.o: defs.h