diff --git a/Makefile b/Makefile
index 19a6c8037..466ce8eaa 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,7 @@ SHELL := /bin/bash
 
 all:
 	pushd src && make && popd
+	pushd runtime && make && popd
 
 install: ;
 
@@ -12,5 +13,6 @@ regression:
 
 clean:
 	pushd src && make clean && popd
+	pushd runtime && make clean && popd
 	pushd regression && make clean && popd
 
diff --git a/regression/Makefile b/regression/Makefile
index a3f16f0ae..021bea2d6 100644
--- a/regression/Makefile
+++ b/regression/Makefile
@@ -7,6 +7,7 @@ RC=../src/rc.opt
 check: $(TESTS) 
 
 $(TESTS): %: %.expr
+	$(RC) $< && cat $@.input | ./$@ > $@.log && diff $@.log orig/$@.log
 	cat $@.input | $(RC) -i $< > $@.log && diff $@.log orig/$@.log
 	cat $@.input | $(RC) -s $< > $@.log && diff $@.log orig/$@.log
 
diff --git a/regression/deep-expressions/Makefile b/regression/deep-expressions/Makefile
index 939e151d8..eb36d1702 100644
--- a/regression/deep-expressions/Makefile
+++ b/regression/deep-expressions/Makefile
@@ -7,6 +7,7 @@ RC = ../../src/rc.opt
 check: $(TESTS)
 
 $(TESTS): %: %.expr
+	RC_RUNTIME=../../runtime $(RC) $< && cat $@.input | ./$@ > $@.log && diff $@.log orig/$@.log
 	cat $@.input | $(RC) -i $< > $@.log && diff $@.log orig/$@.log
 	cat $@.input | $(RC) -s $< > $@.log && diff $@.log orig/$@.log
 
diff --git a/regression/expressions/Makefile b/regression/expressions/Makefile
index 939e151d8..eb36d1702 100644
--- a/regression/expressions/Makefile
+++ b/regression/expressions/Makefile
@@ -7,6 +7,7 @@ RC = ../../src/rc.opt
 check: $(TESTS)
 
 $(TESTS): %: %.expr
+	RC_RUNTIME=../../runtime $(RC) $< && cat $@.input | ./$@ > $@.log && diff $@.log orig/$@.log
 	cat $@.input | $(RC) -i $< > $@.log && diff $@.log orig/$@.log
 	cat $@.input | $(RC) -s $< > $@.log && diff $@.log orig/$@.log
 
diff --git a/runtime/Makefile b/runtime/Makefile
new file mode 100644
index 000000000..c4414a5c8
--- /dev/null
+++ b/runtime/Makefile
@@ -0,0 +1,6 @@
+all:
+	gcc -m32 -c runtime.c
+
+clean:
+	rm -f runtime.o *~
+
diff --git a/runtime/runtime.c b/runtime/runtime.c
new file mode 100644
index 000000000..c24283f99
--- /dev/null
+++ b/runtime/runtime.c
@@ -0,0 +1,22 @@
+/* Runtime library */
+
+# include <stdio.h>
+
+/* Lread is an implementation of the "read" construct */
+extern int Lread () {
+  int result;
+
+  printf ("> "); 
+  fflush (stdout);
+  scanf  ("%d", &result);
+
+  return result;
+}
+
+/* Lwrite is an implementation of the "write" construct */
+extern int Lwrite (int n) {
+  printf ("%d\n", n);
+  fflush (stdout);
+
+  return 0;
+}
diff --git a/src/Driver.ml b/src/Driver.ml
index 67dd012d7..f500a3774 100644
--- a/src/Driver.ml
+++ b/src/Driver.ml
@@ -19,23 +19,30 @@ let parse infile =
 let main =
   try
     let interpret  = Sys.argv.(1) = "-i"  in
-    let infile     = Sys.argv.(2) in
+    let stack      = Sys.argv.(1) = "-s"  in
+    let to_compile = not (interpret || stack) in
+    let infile     = Sys.argv.(if not to_compile then 2 else 1) in
     match parse infile with
     | `Ok prog ->
-       let rec read acc =
-         try
-	   let r = read_int () in
-	   Printf.printf "> ";
-	   read (acc @ [r]) 
-         with End_of_file -> acc
-       in
-       let input = read [] in	
-       let output = 
-	 if interpret 
-	 then Language.eval prog input 
-	 else SM.run (SM.compile prog) input
-       in
-       List.iter (fun i -> Printf.printf "%d\n" i) output
+      if to_compile
+      then 
+        let basename = Filename.chop_suffix infile ".expr" in
+        ignore @@ X86.build prog basename
+      else 
+	let rec read acc =
+	  try
+	    let r = read_int () in
+	    Printf.printf "> ";
+	    read (acc @ [r]) 
+          with End_of_file -> acc
+	in
+	let input = read [] in	
+	let output = 
+	  if interpret 
+	  then Language.eval prog input 
+	  else SM.run (SM.compile prog) input
+	in
+	List.iter (fun i -> Printf.printf "%d\n" i) output
     | `Fail er -> Printf.eprintf "Syntax error: %s\n" er
   with Invalid_argument _ ->
-    Printf.printf "Usage: rc [-i] <input file.expr>\n"
+    Printf.printf "Usage: rc [-i | -s] <input file.expr>\n"
diff --git a/src/Makefile b/src/Makefile
index 5f5d854be..8be318c26 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2,7 +2,7 @@ TOPFILE = rc
 OCAMLC = ocamlc
 OCAMLOPT = ocamlopt
 OCAMLDEP = ocamldep
-SOURCES = Language.ml SM.ml Driver.ml
+SOURCES = Language.ml SM.ml X86.ml Driver.ml
 LIBS = GT.cma unix.cma re.cma re_emacs.cma re_str.cma
 CAMLP5 = -pp "camlp5o -I `ocamlfind -query GT.syntax` -I `ocamlfind -query ostap.syntax` pa_ostap.cmo pa_gt.cmo -L `ocamlfind -query GT.syntax`"
 PXFLAGS = $(CAMLP5)
diff --git a/src/SM.ml b/src/SM.ml
index c15137de3..98b00a9ba 100644
--- a/src/SM.ml
+++ b/src/SM.ml
@@ -7,7 +7,6 @@ open Language
 (* put a constant on the stack     *) | CONST of int                 
 (* read to stack                   *) | READ
 (* write from stack                *) | WRITE
-(* put a constant of the stack     *) | CONST of int
 (* load a variable to the stack    *) | LD    of string
 (* store a variable from the stack *) | ST    of string with show