diff --git a/calculator.asm b/calculator.asm
index 6e0c31e..3f38680 100644
--- a/calculator.asm
+++ b/calculator.asm
@@ -78,6 +78,26 @@ stEmit:
 	store ffff, r1
 	ret
 
+; ------------------------------------------------------------------
+; Stack manipulation
+; ------------------------------------------------------------------
+
+; a - a a
+stDup:
+	cleq r0, r0, peekWord
+	breq r0, r0, pushWord
+
+; a b -- a b a
+stOver:
+	cleq r0, r0, popWord
+	cleq r0, r0, tmpStoreWord01
+	cleq r0, r0, peekWord
+	cleq r0, r0, tmp2StoreWord01
+	cleq r0, r0, tmpLoadWord01
+	cleq r0, r0, pushWord
+	cleq r0, r0, tmp2LoadWord01
+	breq r0, r0, pushWord
+
 ; ==================================================================
 ; Low-level functions
 ; ==================================================================