diff --git a/lib/risc/interpreter.rb b/lib/risc/interpreter.rb
index 58e5635c..882260aa 100644
--- a/lib/risc/interpreter.rb
+++ b/lib/risc/interpreter.rb
@@ -8,7 +8,8 @@ module Risc
   # will be executed by method execute_SlotToReg
   #
   # The Interpreter (a bit like a cpu) has a state flag, a current instruction and registers
-  # We collect the stdout (as a hack not to interpret the OS)
+  # We collect the stdout (as a hack not to interpret the OS) in a string. It can also be passed
+  # in to the init, as an IO
   #
   class Interpreter
     # fire events for changed pc and register contents
@@ -18,11 +19,13 @@ module Risc
 
     attr_reader :instruction , :clock , :pc  # current instruction and pc
     attr_reader :registers     # the registers, 16 (a hash, sym -> contents)
-    attr_reader :stdout,  :state , :flags  # somewhat like the lags on a cpu, hash  sym => bool (zero .. . )
+    attr_reader :stdout,  :state , :flags  # somewhat like the flags on a cpu, hash  sym => bool (zero .. . )
 
-    #start in state :stopped and set registers to unknown
-    def initialize( linker )
-      @stdout , @clock , @pc , @state = "", 0 , 0 , :stopped
+    # start in state :stopped and set registers to unknown
+    # Linker gives the state of the program
+    # Passing a stdout in (an IO, only << called) can be used to get output immediately.
+    def initialize( linker , stdout = "")
+      @stdout , @clock , @pc , @state = stdout, 0 , 0 , :stopped
       @registers = {}
       @flags = {  :zero => false , :plus => false ,
                   :minus => false , :overflow => false }
@@ -32,8 +35,7 @@ module Risc
       @linker = linker
     end
 
-    def start_program(linker = nil)
-      initialize(linker || @linker)
+    def start_program()
       init = @linker.cpu_init
       set_state(:running)
       set_pc( Position.get(init).at )
@@ -249,10 +251,12 @@ module Risc
       str = get_register( :r1 ) # should test length, ie r2
       case str
       when Symbol
-        @stdout += str.to_s
+        @stdout << str.to_s
+        @stdout.flush if @stdout.respond_to?(:flush)
         return str.to_s.length
       when Parfait::Word
-        @stdout += str.to_string
+        @stdout << str.to_string
+        @stdout.flush if @stdout.respond_to?(:flush)
         return str.char_length
       else
         raise "NO string for putstring #{str.class}:#{str.object_id}" unless str.is_a?(Symbol)
diff --git a/lib/rubyx/rubyxc.rb b/lib/rubyx/rubyxc.rb
index 3483e11b..93b21a0d 100644
--- a/lib/rubyx/rubyxc.rb
+++ b/lib/rubyx/rubyxc.rb
@@ -1,5 +1,6 @@
 require "thor"
 require "rubyx"
+require "risc/interpreter"
 
 class RubyXC < Thor
   desc "compile FILE" , "Compile given FILE to binary"
@@ -27,7 +28,44 @@ class RubyXC < Thor
 
     outfile = file.split("/").last.gsub(".rb" , ".o")
     writer.save outfile
+  end
+
+  desc "interpret FILE" , "Interpret given FILE "
+  long_desc <<-LONGDESC
+      Compiles the given file to an intermediate RISC format, and runs the
+      Interpreter.
+
+      RISC is the last abstract layer inside the compiler. It is in nature
+      very close to arm (without quirks and much smaller).
+
+      An interpreter was originally developed for the RISC layer for debugging purposes.
+      Running the interpreter is about 50k slower than binary, but it can be used
+      to veryfy simple programs.
+
+      No output file will be generated, the only output is generated by the
+      given program.
+
+      The program must define a main method on the Space class, which will be invoked.
+    LONGDESC
+
+  def interpret(file)
+    begin
+      ruby = File.read(file)
+    rescue
+      fail MalformattedArgumentError , "No such file #{file}"
+    end
+    options = {
+       parfait:  { factory: 3*1024, },
+       load_parfait: false ,
+     }
+    compiler = RubyX::RubyXCompiler.new(options)
+    linker = compiler.ruby_to_binary(ruby, :interpreter)
+
+    puts "interpreting #{file}"
+
+    interpreter = Risc::Interpreter.new(linker , STDOUT )
+    interpreter.start_program
+    interpreter.tick while(interpreter.instruction)
 
-    return outfile
   end
 end