diff --git a/lib/irb/ext/save-history.rb b/lib/irb/ext/save-history.rb
new file mode 100644
index 0000000000..95ef71b5c1
--- /dev/null
+++ b/lib/irb/ext/save-history.rb
@@ -0,0 +1,83 @@
+#!/usr/local/bin/ruby
+#
+#   save-history.rb - 
+#   	$Release Version: 0.9.5$
+#   	$Revision$
+#   	$Date$
+#   	by Keiju ISHITSUKAkeiju@ruby-lang.org)
+#
+# --
+#
+#   
+#
+
+@RCS_ID='-$Id$-'
+
+require "readline"
+
+module IRB
+  class Context
+    def init_save_history
+      unless (class<<@io;self;end).include?(HistorySavingAbility)
+	@io.extend(HistorySavingAbility)
+      end
+    end
+
+    def save_history
+      IRB.conf[:SAVE_HISTORY]
+    end
+
+    def save_history=(val)
+      IRB.conf[:SAVE_HISTORY] = val
+      if val
+	main_context = IRB.conf[:MAIN_CONTEXT]
+	main_context = self unless main_context
+	main_context.init_save_history
+      end
+    end
+
+    def history_file
+      IRB.conf[:HISTORY_FILE]
+    end
+
+    def history_file=(hist)
+      IRB.conf[:HISTORY_FILE] = hist
+    end
+  end
+
+  module HistorySavingAbility
+    include Readline
+
+    def HistorySavingAbility.create_finalizer
+      proc do
+	if num = IRB.conf[:SAVE_HISTORY] and (num = num.to_i) > 0
+	  if hf = IRB.conf[:HISTORY_FILE]
+	    file = File.expand_path(hf)
+	  end
+	  file = IRB.rc_file("_history") unless file
+	  open(file, 'w' ) do |f|
+	    hist = HISTORY.to_a
+	    f.puts(hist[-num..-1] || hist)
+	  end
+	end
+      end
+    end
+
+    def HistorySavingAbility.extended(obj)
+      ObjectSpace.define_finalizer(obj, HistorySavingAbility.create_finalizer)
+      obj.load_history
+      obj
+    end
+
+    def load_history
+      hist = IRB.conf[:HISTORY_FILE]
+      hist = IRB.rc_file("_history") unless hist
+      if File.exist?(hist)
+	open(hist) do |f|
+	  f.each {|l| HISTORY << l.chomp}
+	end
+      end
+    end
+  end
+end
+
diff --git a/lib/irb/notifier.rb b/lib/irb/notifier.rb
new file mode 100644
index 0000000000..22752bf894
--- /dev/null
+++ b/lib/irb/notifier.rb
@@ -0,0 +1,145 @@
+#
+#   notifier.rb - optput methods used by irb 
+#   	$Release Version: 0.9.5$
+#   	$Revision$
+#   	$Date$
+#   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
+#
+# --
+#
+#   
+#
+
+require "e2mmap"
+require "irb/output-method"
+
+module IRB
+  module Notifier
+    extend Exception2MessageMapper
+    def_exception :ErrUndefinedNotifier, 
+      "undefined notifier level: %d is specified"
+    def_exception :ErrUnrecognizedLevel, 
+      "unrecognized notifier level: %s is specified"
+
+    def def_notifier(prefix = "", output_method = StdioOutputMethod.new)
+      CompositeNotifier.new(prefix, output_method)
+    end
+    module_function :def_notifier
+  
+    class AbstructNotifier
+      def initialize(prefix, base_notifier)
+	@prefix = prefix
+	@base_notifier = base_notifier
+      end
+
+      attr_reader :prefix
+
+      def notify?
+	true
+      end
+
+      def print(*opts)
+	@base_notifier.print prefix, *opts if notify?
+      end
+
+      def printn(*opts)
+	@base_notifier.printn prefix, *opts if notify?
+      end
+
+      def printf(format, *opts)
+	@base_notifier.printf(prefix + format, *opts) if notify?
+      end
+
+      def puts(*objs)
+	if notify?
+	  @base_notifier.puts *objs.collect{|obj| prefix + obj.to_s}
+	end
+      end
+
+      def pp(*objs)
+	if notify?
+	  @base_notifier.ppx @prefix, *objs
+	end
+      end
+
+      def ppx(prefix, *objs)
+	if notify?
+	  @base_notifier.ppx @prefix+prefix, *objs
+	end
+      end
+
+      def exec_if
+	yield(@base_notifier) if notify?
+      end
+    end
+
+    class CompositeNotifier<AbstructNotifier
+      def initialize(prefix, base_notifier)
+	super
+
+	@notifiers = [D_NOMSG]
+	@level_notifier = D_NOMSG
+      end
+
+      attr_reader :notifiers
+
+      def def_notifier(level, prefix = "")
+	notifier = LeveledNotifier.new(self, level, prefix)
+	@notifiers[level] = notifier
+	notifier
+      end
+
+      attr_reader :level_notifier
+      alias level level_notifier
+
+      def level_notifier=(value)
+	case value
+	when AbstructNotifier
+	  @level_notifier = value
+	when Integer
+	  l = @notifiers[value]
+	  Notifier.Raise ErrUndefinedNotifer, value unless l
+	  @level_notifier = l
+	else
+	  Notifier.Raise ErrUnrecognizedLevel, value unless l
+	end
+      end
+
+      alias level= level_notifier=
+    end
+
+    class LeveledNotifier<AbstructNotifier
+      include Comparable
+
+      def initialize(base, level, prefix)
+	super(prefix, base)
+	
+	@level = level
+      end
+
+      attr_reader :level
+
+      def <=>(other)
+	@level <=> other.level
+      end
+      
+      def notify?
+	@base_notifier.level >= self
+      end
+    end
+
+    class NoMsgNotifier<LeveledNotifier
+      def initialize
+	@base_notifier = nil
+	@level = 0
+	@prefix = ""
+      end
+
+      def notify?
+	false
+      end
+    end
+
+    D_NOMSG = NoMsgNotifier.new
+  end
+end
diff --git a/lib/irb/output-method.rb b/lib/irb/output-method.rb
new file mode 100644
index 0000000000..93db767de4
--- /dev/null
+++ b/lib/irb/output-method.rb
@@ -0,0 +1,85 @@
+#
+#   output-method.rb - optput methods used by irb 
+#   	$Release Version: 0.9.5$
+#   	$Revision$
+#   	$Date$
+#   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
+#
+# --
+#
+#   
+#
+
+require "e2mmap"
+
+module IRB
+  # OutputMethod
+  #   StdioOutputMethod
+
+  class OutputMethod
+    @RCS_ID='-$Id$-'
+
+    def print(*opts)
+      IRB.fail NotImplementError, "print"
+    end
+
+    def printn(*opts)
+      print opts.join(" "), "\n"
+    end
+
+    # extend printf
+    def printf(format, *opts)
+      if /(%*)%I/ =~ format
+	format, opts = parse_printf_format(format, opts)
+      end
+      print sprintf(format, *opts)
+    end
+
+    # %
+    # <フラグ>  [#0- +]
+    # <最小フィールド幅> (\*|\*[1-9][0-9]*\$|[1-9][0-9]*)
+    # <精度>.(\*|\*[1-9][0-9]*\$|[1-9][0-9]*|)?
+    # #<長さ修正文字>(hh|h|l|ll|L|q|j|z|t)
+    # <変換修正文字>[diouxXeEfgGcsb%] 
+    def parse_printf_format(format, opts)
+      return format, opts if $1.size % 2 == 1
+    end
+
+    def foo(format)
+      pos = 0
+      inspects = []
+      format.scan(/%[#0\-+ ]?(\*(?=[^0-9])|\*[1-9][0-9]*\$|[1-9][0-9]*(?=[^0-9]))?(\.(\*(?=[^0-9])|\*[1-9][0-9]*\$|[1-9][0-9]*(?=[^0-9])))?(([1-9][0-9]*\$)*)([diouxXeEfgGcsb%])/) {|f, p, pp, pos, new_pos, c|
+	puts [f, p, pp, pos, new_pos, c].join("!")
+	pos = new_pos if new_pos
+	if c == "I"
+	  inspects.push pos.to_i 
+	  (f||"")+(p||"")+(pp||"")+(pos||"")+"s"
+	else
+	  $&
+	end
+      }
+    end
+
+    def puts(*objs)
+      for obj in objs
+	print(*obj)
+	print "\n"
+      end
+    end
+
+    def pp(*objs)
+      puts *objs.collect{|obj| obj.inspect}
+    end
+
+    def ppx(prefix, *objs)
+      puts *objs.collect{|obj| prefix+obj.inspect}
+    end
+
+  end
+
+  class StdioOutputMethod<OutputMethod
+    def print(*opts)
+      STDOUT.print *opts
+    end
+  end
+end