diff --git a/app/register_view.rb b/app/register_view.rb
index d72c389..8dbad70 100644
--- a/app/register_view.rb
+++ b/app/register_view.rb
@@ -2,10 +2,20 @@ class RegisterView
 
   include React::Component
   required_param :interpreter
+  define_state :registers
+
+  before_mount do
+    interpreter.register_event(:register_changed,  self)
+    registers! interpreter.registers
+  end
+
+  def register_changed reg , old , bl
+    registers! interpreter.registers
+  end
 
   def render
     div :class => :row  do
-      interpreter.registers.each do |r , has|
+      registers.each do |r , has|
         div :class => "col-md-1" do
           "#{r} : #{has}"
         end
diff --git a/lib/interpreter.rb b/lib/interpreter.rb
index da6f92a..9b375c2 100644
--- a/lib/interpreter.rb
+++ b/lib/interpreter.rb
@@ -12,22 +12,40 @@ class Interpreter
     @registers = Hash[(0...12).collect{|i| ["r#{i}" , "undefined"]}]
   end
 
-  def start block
-    set_block  block
+  def start bl
+    set_block  bl
   end
-  def set_block block
-    return if @block == block
+
+  def set_block bl
+    return if @block == bl
+    raise "Error, nil block" unless bl
     old = @block
-    @block = block
-     trigger(:block_changed , old , block)
-     set_instruction block.codes.first
+    @block = bl
+     trigger(:block_changed , old , bl)
+     set_instruction bl.codes.first
   end
+
   def set_instruction i
     return if @instruction == i
+    raise "Error, nil instruction" unless i
     old = @instruction
     @instruction = i
     trigger(:instruction_changed, old , i)
   end
+
+  def get_register( reg )
+    reg = reg.symbol if  reg.is_a? Register::RegisterReference
+    raise "Not a register #{reg}" unless Register::RegisterReference.look_like_reg(reg)
+    @registers[reg]
+  end
+
+  def set_register reg , val
+    old = get_register( reg ) # also ensures format
+    return if old === val
+    @registers[reg] = val
+    trigger(:register_changed, reg ,  old , val)
+  end
+
   def tick
     name = @instruction.class.name.split("::").last
     fetch = send "execute_#{name}"
@@ -40,4 +58,10 @@ class Interpreter
     set_block target
     false
   end
+  def execute_LoadConstant
+    to = @instruction.register
+    value = @instruction.constant.object_id
+    set_register( to , value )
+    true
+  end
 end