diff --git a/Source/builtin/builtin.ml b/Source/builtin/builtin.ml
index e45a167..226fe51 100644
--- a/Source/builtin/builtin.ml
+++ b/Source/builtin/builtin.ml
@@ -9,7 +9,8 @@ primitives to suit maths conventions.
 (** Sign function
     @param x integer
 *)
-let sign x = 0
+let sign x =
+  if x >= 0 then 1 else -1;;
 
 (* Integer quotient implementation ; main use is in case of quotient
    of an integer by a natural number.
@@ -20,7 +21,10 @@ let sign x = 0
     @param a dividend
     @param b natural number you divide by.
  *)
-let quot a b = 0
+let quot a b =
+  match sign a = -1 && a mod b <> 0 with
+      true -> a/b - 1
+    | _    -> (a/b);;
 
 (* Integer modulo implementations. Negative case need be taken into
    account ; representant is expected non-negative. This is not OCAML
@@ -35,7 +39,10 @@ let quot a b = 0
     @param a input integer
     @param b moduli a natural number.
  *)
-let modulo a b = 0
+let modulo a b =
+  match sign a = -1 && a mod b != 0 with
+      true -> a mod b + b
+    | _  -> a mod b;;
 
 (* Integer modulo implementations. Negative case need be taken into
    account ; representant is expected non-negative. This is not OCAML
@@ -48,4 +55,5 @@ let modulo a b = 0
     @param a dividend
     @param b integer you divide by.
 *)
-let div a b = (0, 0)
+
+let div a b = (quot a b, modulo a b);;