diff --git a/lib/arm/arm_machine.rb b/lib/arm/arm_machine.rb
index fd76f532..7daa20df 100644
--- a/lib/arm/arm_machine.rb
+++ b/lib/arm/arm_machine.rb
@@ -31,15 +31,14 @@ module Arm
     end
     
     def word_load value , reg
-      e = Vm::Block.new("load_#{value}")
-      e.add_code( MoveInstruction.new( :left => reg , :right => value ) )
+      mov( :left => reg , :right => value )
     end
     def function_call call
       raise "Not FunctionCall #{call.inspect}" unless call.is_a? Vm::FunctionCall
       bl( :left => call.function )
     end
 
-    def main_entry
+    def main_start
       entry = Vm::Block.new("main_entry")
       entry.add_code  mov( :left => :fp , :right => 0 )
     end
@@ -47,6 +46,14 @@ module Arm
       entry = Vm::Block.new("main_exit")
       entry.add_code syscall(0)
     end
+    def function_entry f_name
+      entry = Vm::Block.new("#{f_name}_entry")
+      entry.add_code  push( :left => :lr )
+    end
+    def function_exit f_name
+      entry = Vm::Block.new("#{f_name}_exit")
+      entry.add_code  pop( :left => :pc )
+    end
     def syscall num
       [mov( :left => :r7 , :right => num ) ,  swi( :left => 0 )]
     end
diff --git a/lib/arm/logic_instruction.rb b/lib/arm/logic_instruction.rb
index b6c0884d..a815889f 100644
--- a/lib/arm/logic_instruction.rb
+++ b/lib/arm/logic_instruction.rb
@@ -71,7 +71,6 @@ module Arm
     def assemble(io)
       build
       instuction_class = 0b00 # OPC_DATA_PROCESSING
-      puts inspect
       val = @operand.is_a?(Symbol) ? reg_code(@operand) : @operand 
       val |= (reg_code(@rd) <<            12)     
       val |= (reg_code(@rn) <<            12+4)   
diff --git a/lib/arm/stack_instruction.rb b/lib/arm/stack_instruction.rb
index 2441a85e..e2730c01 100644
--- a/lib/arm/stack_instruction.rb
+++ b/lib/arm/stack_instruction.rb
@@ -19,7 +19,7 @@ module Arm
       @operand = 0
 
       @update_status_flag= 0
-      @rn = reg "r0" # register zero = zero bit pattern
+      @rn = :r0 # register zero = zero bit pattern
       # downward growing, decrement before memory access
       # official ARM style stack as used by gas
       @write_base = 1
@@ -40,10 +40,10 @@ module Arm
       build
       instuction_class = 0b10 # OPC_STACK
       cond = @condition_code.is_a?(Symbol) ?  COND_CODES[@condition_code]   : @condition_code
-      rn = reg "sp" # sp register
+      @rn = :sp # sp register
       #assemble of old
-      val = operand
-      val |= (rn.bits <<             16)
+      val = @operand
+      val |= (reg_code(@rn) <<             16)
       val |= (is_pop <<              16+4) #20
       val |= (write_base <<          16+4+ 1) 
       val |= (update_status_flag <<  16+4+ 1+1) 
@@ -57,13 +57,14 @@ module Arm
     private 
     # Build representation for source value
     def build
-      if (args.is_a?(Array))
+      if (@args.is_a?(Array))
         @operand = 0
-        args.each do |reg |
-          @operand |= (1 << reg.bits)
+        @args.each do |reg |
+          next unless reg
+          @operand |= (1 << reg_code(reg))
         end
       else
-        raise "invalid operand argument  #{args.inspect}"
+        raise "invalid operand argument  #{@args.inspect} #{inspect}"
       end
     end
   end
diff --git a/lib/vm/function.rb b/lib/vm/function.rb
index 506ae359..dbf78919 100644
--- a/lib/vm/function.rb
+++ b/lib/vm/function.rb
@@ -15,8 +15,8 @@ module Vm
     def initialize(name , args = [])
       super(name)
       @args = args
-      @entry = Block.new("entry_#{name}")
-      @exit = Block.new("exit_#{name}")
+      @entry = Kernel::function_entry( name )
+      @exit = Kernel::function_exit( name )
     end
     attr_reader :args , :entry , :exit
     
diff --git a/lib/vm/kernel.rb b/lib/vm/kernel.rb
index 30587e74..4c3e9ad9 100644
--- a/lib/vm/kernel.rb
+++ b/lib/vm/kernel.rb
@@ -1,16 +1,29 @@
 module Vm
-  module Kernel
-    def self.start
-      #TODO extract args into array of strings
-      Machine.instance.main_entry
-    end
-    def self.exit
-      # Machine.exit mov r7 , 0  + swi 0 
-      Machine.instance.main_exit
-    end
-    def self.puts string
-      # should unwrap from string to char*
-      Machine.instance.puts string
+  class Kernel
+    
+    #there are no Kernel instances, only class methods.
+    # We use this module syntax to avoid the (ugly) self.
+    module ClassMethods
+      def main_start
+        #TODO extract args into array of strings
+        Machine.instance.main_start
+      end
+      def main_exit
+        # Machine.exit mov r7 , 0  + swi 0 
+        Machine.instance.main_exit
+      end
+      def function_entry f_name
+        Machine.instance.function_entry f_name
+      end
+      def function_exit f_name
+        Machine.instance.function_exit f_name
+      end
+      def self.puts string
+        # should unwrap from string to char*
+        Machine.instance.puts string
+      end
     end
+    
+    extend ClassMethods
   end
 end
\ No newline at end of file
diff --git a/lib/vm/program.rb b/lib/vm/program.rb
index 46cb01d9..32907173 100644
--- a/lib/vm/program.rb
+++ b/lib/vm/program.rb
@@ -28,10 +28,10 @@ module Vm
       @objects = []
       # global functions
       @functions = []
-      @entry = Vm::Kernel::start
+      @entry = Vm::Kernel::main_start
       #main gets executed between entry and exit
       @main = nil
-      @exit = Vm::Kernel::exit
+      @exit = Vm::Kernel::main_exit
     end
     attr_reader :context , :main , :functions