diff --git a/asm/asm.rb b/asm/asm.rb
index 2a63511..4f4383d 100644
--- a/asm/asm.rb
+++ b/asm/asm.rb
@@ -6,4 +6,46 @@
 # may 2009
 
 module Assembler
+
+  # Abstract class for common functionality between different code
+  # generators.  Also defines somewhat of an interface that must be
+  # implemented to be useful.
+  class AssemblerBase
+
+    def initialize(*args)
+      @vars = {}                   # Symbol table, maps names to locations in BSS.
+      @num_labels = 0              # Used to generate unique labels.
+      @num_labels_with_suffix = Hash.new(0)
+
+      # Maps names to locations.
+      @labels = Hash.new {|h, key| raise "undefined label: #{key}"}
+      
+    end
+
+    def block(*args, &blk)
+      instance_eval(&blk)
+    end
+
+    def output
+      raise "#{self.class} is supposed to implement this method!"
+    end
+
+    def var(name)
+      @vars[name]
+    end
+    alias_method :var?, :var
+    
+    # Generate a unique label.
+    def label(suffix=nil)
+      @num_labels += 1
+      if suffix
+        @num_labels_with_suffix[suffix] += 1
+        suffix = "_#{suffix}_#{@num_labels_with_suffix[suffix]}"
+      end
+      name = "L#{sprintf "%06d", @num_labels}#{suffix}"
+      return name
+    end
+
+  end
+
 end
diff --git a/asm/binary.rb b/asm/binary.rb
index cfbdcae..154c72e 100644
--- a/asm/binary.rb
+++ b/asm/binary.rb
@@ -5,13 +5,18 @@
 # sjs
 # may 2009
 
+ROOT = __FILE__.sub(/\/asm\/binary\.rb$/, '') unless defined? ROOT
+$LOAD_PATH << ROOT unless $LOAD_PATH.include?(ROOT)
+
+require 'asm/asm'
+
 module Assembler
 
   # Define a method named `emit_byte` and one named `binary_size` and
   # include this module.  Calling the assembler methods will output
   # x86 machine code ... hopefully.  So far it's incomplete and
   # binaries just segfault.
-  class Binary
+  class Binary < AssemblerBase
 
     # This structure allows for x86 registers of all sizes.  The
     # number of the register is the index of the array in which it was
@@ -44,7 +49,72 @@ module Assembler
     MaxUnsigned = 2**MachineBits - 1
     SignedRange = MinSigned..MaxSigned
 
-    
+    X86_exit = {
+      'linux' => [0x89, 0xc3,        # mov ebx, eax (exit code)
+                 0xb8, 1, 0, 0, 0,   # mov eax, 1
+                 0xcd, 0x80          # int 0x80
+                ].pack('c*'),
+
+      'darwin' => [0x50,               # push eax (exit code)
+                   0xb8, 1, 0, 0, 0,   # mov eax, 1
+                   0xcd, 0x80          # int 0x80
+                  ].pack('c*')
+    }
+
+    def initialize(platform='linux', binformat='elf')
+      super
+      @binary = []                 # Byte array of machine code.
+      @platform = platform
+      @binformat = binformat
+      init_sections
+    end
+
+    def init_sections
+      case @platform
+
+      when 'linux'
+        raise "unsupported" unless @binformat == 'elf'
+        @header_size = 0x100                     # ELF, Linux
+        @text_offset = 0x08048000 + @header_size # Offset of text section in memory
+
+      when 'darwin'
+        raise "unsupported" unless @binformat == 'macho'
+        @header_size = 0x100                     # Mach-O, Darwin
+        @text_offset = 0x08048000 + @header_size # Offset of text section in memory
+      else
+        raise "unsupported platform: #{platform}"
+      end
+      @text_size = 0x02be00                    # Size of text section.
+      @data_offset = @text_offset + @text_size # Offset of data section.
+      @data_size = 0x4e00                      # Size of data section.
+      @bss_offset = @data_offset + @data_size  # Offset of bss section.
+      @bss_size = 0                            # Size of bss section.
+    end
+
+    def output
+      @binary.pack('c*') + X86_exit[@platform]
+    end
+
+    # Define a constant in the .data section.
+    def const(name, value)
+      raise "unimplemented!"
+    end
+
+    # Define a variable with the given name and size (in dwords).
+    def defvar(name, dwords=1)
+      unless var?(name)
+        @vars[name] = @bss_size
+        @bss_size += dwords
+      else
+        STDERR.puts "[warning] attempted to redefine #{name}"
+      end
+    end
+
+    def label(suffix=nil)
+      name = super
+      @labels[name] = bytes_written
+      return name
+    end
 
     # Count the bytes that were encoded in the given block.
     def asm
@@ -56,7 +126,18 @@ module Assembler
       # return the number of bytes written
       bytes_written - instruction_offset
     end
+    
+    def emit_byte(byte)
+      @binary << byte
+    end
 
+    def bytes_written
+      @binary.size
+    end
+
+    def emit_label(name=label)
+      @labels[name] = @binary.length
+    end
 
     def emit_dword(num)
       num_to_quad(num).each {|byte| emit_byte(byte)}
@@ -119,7 +200,7 @@ module Assembler
     end
 
     def regnum(op)
-      num = register?
+      num = register?(op)
       raise "not a register: #{op.inspect}" unless num
       num
     end
@@ -146,7 +227,7 @@ module Assembler
     #   3.  mov r/m32, reg32 (0x89, mod r/m, maybe sib)
     #   3a. mov memoffset32, eax (0xa3, disp32)
     #   4.  mov r/m32, immediate32 (0xc7, mod r/m, maybe sib, imm32)
-    def x86_mov(dest, src)
+    def mov(dest, src)
       dest = dest[6..-1] if dest.is_a?(String) && dest[0..5] == 'dword '
       src = src[6..-1] if src.is_a?(String) && src[0..5] == 'dword '
 
@@ -199,35 +280,35 @@ module Assembler
     end
 
 
-    def x86_add(dest, src)
+    def add(dest, src)
     end
 
-    def x86_sub(dest, src)
+    def sub(dest, src)
     end
 
-    def x86_imul(op)
+    def imul(op)
     end
 
-    def x86_idiv(op)
+    def idiv(op)
     end
 
-    def x86_inc(op)
+    def inc(op)
       asm do
         if register?(op)
           emit_byte(0x40 + regnum(op))
         elsif rm32?(op)
           emit_byte(0xff)
-          emit_modrm(...)
+#           emit_modrm(...)
         else
           raise "unsupported op #{op}, wanted r32 or r/m32"
         end
       end
     end
 
-    def x86_push(reg)
+    def push(reg)
     end
 
-    def x86_cmp(a, b)
+    def cmp(a, b)
     end
 
 
diff --git a/asm/text.rb b/asm/text.rb
index ebb543d..cb152dc 100644
--- a/asm/text.rb
+++ b/asm/text.rb
@@ -3,123 +3,166 @@
 # sjs
 # may 2009
 
+ROOT = __FILE__.sub(/\/asm\/text\.rb$/, '') unless defined? ROOT
+$LOAD_PATH << ROOT unless $LOAD_PATH.include?(ROOT)
+
+require 'asm/asm'
+
 module Assembler
 
-    # Define a method named `emit` and include this module.  Calling
-    # the assembler methods will output nasm-friendly x86 asm code,
-    # line by line.  This is dead easy and we can trust nasm to
-    # compile correct machine code, which is tricky.
-    module Text
+    # Assembler methods output nasm-friendly x86 asm code, line by
+    # line.  This is dead easy and we can trust nasm to compile
+    # correct machine code, which isn't trivial.
+    class Text < AssemblerBase
 
-      def self.included(other)
-        im = other.instance_methods
-        unless im.include?(:emit)
-          raise "#{self.name} requires the including class define the emit method"
+      def initialize(platform='linux')
+        super
+        @data = ''
+        @bss = ''
+        @code = ''
+        @templatefile = "#{ROOT}/template.#{platform}.asm"
+        raise "unsupported platform: #{platform}" unless File.readable?(@templatefile)
+      end
+
+      # Define a constant in the .data section.
+      def const(name, value)
+        @data << "#{name}\tequ  #{value}"
+      end
+
+      # Define a variable with the given name and size (in dwords).
+      def defvar(name, dwords=1)
+        unless var?(name)
+          @bss << "#{name}: resd #{dwords}\n"
+          @vars[name] = name
+        else
+          STDERR.puts "[warning] attempted to redefine #{name}"
         end
       end
 
-
-      def x86_mov(dest, src)
-        emit("mov #{dest}, #{src.is_a?(Numeric) ? "0x#{src.to_s(16)}" : src}")
+      # Emit a line of code wrapped between a tab and a newline.
+      def emit(code, options={})
+        tab = options.has_key?(:tab) ? options[:tab] : "\t"
+        @code << "#{tab}#{code}\n"
       end
 
-      def x86_movzx(dest, src)
+      def label(suffix=nil)
+        name = super
+        @labels[name] = name
+        return name
+      end
+
+      def output
+        File.read(@templatefile).
+          sub("{data}", @data).
+          sub("{bss}", @bss).
+          sub("{code}", @code)
+      end
+
+      def emit_label(name=label)
+        emit("#{name}:", :tab => nil)
+      end
+
+      def mov(dest, src)
+        emit("mov #{dest}, #{src}#{src.is_a?(Numeric) ? " ; 0x#{src.to_s(16)}" : ''}")
+      end
+
+      def movzx(dest, src)
         emit("movzx #{dest}, #{src}")
       end
 
-      def x86_add(dest, src)
+      def add(dest, src)
         emit("add #{dest}, #{src}")
       end
 
-      def x86_sub(dest, src)
+      def sub(dest, src)
         emit("sub #{dest}, #{src}")
       end
 
-      def x86_imul(op)
+      def imul(op)
         emit("imul #{op}")
       end
 
-      def x86_idiv(op)
+      def idiv(op)
         emit("idiv #{op}")
       end
 
-      def x86_inc(op)
+      def inc(op)
         emit("inc #{op}")
       end
 
-      def x86_dec(op)
+      def dec(op)
         emit("dec #{op}")
       end
 
-      def x86_push(reg)
+      def push(reg)
         emit("push #{reg}")
       end
 
-      def x86_pop(reg)
+      def pop(reg)
         emit("pop #{reg}")
       end
 
-      def x86_call(label)
+      def call(label)
         emit("call #{label}")
       end
 
-      def x86_neg(reg)
+      def neg(reg)
         emit("neg #{reg}")
       end
 
-      def x86_not(rm32)
+      def not(rm32)
         emit("not #{rm32}")
       end
 
-      def x86_xchg(op1, op2)
+      def xchg(op1, op2)
         emit("xchg #{op1}, #{op2}")
       end
 
-      def x86_and(op1, op2)
+      def and_(op1, op2)
         emit("and #{op1}, #{op2}")
       end
 
-      def x86_or(op1, op2)
+      def or(op1, op2)
         emit("or #{op1}, #{op2}")
       end
 
-      def x86_xor(op1, op2)
+      def xor(op1, op2)
         emit("xor #{op1}, #{op2}")
       end
 
-      def x86_jz(label)
+      def jz(label)
         emit("jz #{label}")
       end
 
-      def x86_jnz(label)
+      def jnz(label)
         emit("jnz #{label}")
       end
 
-      def x86_jmp(label)
+      def jmp(label)
         emit("jmp #{label}")
       end
 
-      def x86_jl(label)
+      def jl(label)
         emit("jl #{label}")
       end
 
-      def x86_cmp(a, b)
+      def cmp(a, b)
         emit("cmp #{a}, #{b}")
       end
 
-      def x86_lea(a, b)
+      def lea(a, b)
         emit("lea #{a}, #{b}")
       end
 
-      def x86_shr(a, b)
+      def shr(a, b)
         emit("shr #{a}, #{b}")
       end
 
-      def x86_loop(label)
+      def loop_(label)
         emit("loop #{label}")
       end
 
-      def x86_int(num)
+      def int(num)
         emit("int 0x#{num.to_s(16)}")
       end
 
diff --git a/build.rb b/build.rb
index 810a991..c928917 100755
--- a/build.rb
+++ b/build.rb
@@ -1,14 +1,8 @@
 #!/usr/bin/env ruby
 
-ROOT = __FILE__.sub(/\/build\.rb$/, '') unless defined? ROOT
-
 require 'compiler'
-
-
-X86_exit = [0x89, 0xc3,         # mov ebx, eax (exit code)
-            0xb8, 1, 0, 0, 0,   # mov eax, 1
-            0xcd, 0x80          # int 0x80
-           ].pack('c*')
+require 'asm/text'
+require 'asm/binary'
 
 def main
   filename = ARGV[0].to_s
@@ -23,39 +17,21 @@ def base(filename)
   filename.sub(/\.[^.]*$/, '')
 end
 
-def interpolate(templatefile, data)
-  template = File.read(templatefile)
-  data.inject(template) do |template, mapping|
-    token, replacement = *mapping
-    template.sub("{#{token}}", replacement)
-  end
-end
 
 # filename: input filename
-# format:   output format, nasm or binary
+# asm:      assembler to use
 # returns:  output filename
-def compile(filename, format='asm')
+def compile(filename, asm, binformat='elf')
 
-  # compile to asm or binary
-  output = nil
   File.open(filename, 'r') do |input|
-    compiler = Compiler.new(input, format)
-    output = compiler.compile
+    compiler = Compiler.new(input, asm, binformat)
+    compiler.compile
   end
-  if format == 'asm'
-    mode = 'w'
-    data, bss, code = *output
-    output = interpolate("#{ROOT}/template.asm",
-                         :data => data, :bss => bss, :code => code)
-  else
-    mode = 'wb'
-    output += X86_exit
-  end
-  outfile = "#{base(filename)}.#{format}"
-  File.open(outfile, mode) do |out|
-    if format == 'asm'
-      out.puts(output)
-    end
+
+  ext = asm.class.name.split('::').last[0,3].downcase == 'bin' ? 'bin' : 'asm'
+  outfile = "#{base(filename)}.#{ext}"
+  File.open(outfile, 'wb') do |out|
+    out.puts(asm.output)
   end
   return outfile
 
@@ -68,33 +44,47 @@ rescue ParseError => e
 end
 
 # assemble using nasm, return resulting filename.
-def asm(filename)
+def asm(filename, binformat='elf')
   f = base(filename)
   outfile = "#{f}.o"
-  output = `nasm -f elf -g -o #{outfile} #{filename}`
+  output = `nasm -f #{binformat} -g -o #{outfile} #{filename}`
   if $?.exitstatus != 0
-    raise "nasm failed: #{$?.exitstatus}", output
+    puts output
+    raise "nasm failed: #{$?.exitstatus}"
   end
   return outfile
 end
 
 # link with ld, return resulting filename.
-def link(filename)
+def link(filename, platform='linux')
   f = base(filename)
-  output = `ld -o #{f} #{filename}`
+  cmd, args = *case platform
+               when 'darwin': ['gcc', '-arch i386']
+               when 'linux': ['ld', '']
+               else
+                 raise "unsupported platform: #{platform}"
+               end
+  output = `#{cmd} #{args} -o #{f} #{filename}`
   if $?.exitstatus != 0
-    raise "ld failed: #{$?.exitstatus}", output
+    puts output
+    raise "ld failed: #{$?.exitstatus}"
   end
   `chmod +x #{f}`
   return f
 end
 
-def build(filename, format='asm')
-  if format == 'asm'
-    link( asm( compile(filename) ) )
-  else # binary
-    link( compile(filename, format='bin') )
-  end
+# TODO Use a dependency injection framework for the assembler, and
+#      other parts as things become more modular.
+def build(filename, platform='linux', format='asm', binformat='elf')
+  bin = if format == 'asm'
+          code = compile(filename, Assembler::Text.new(platform))
+          obj = asm( code, binformat )
+          link( obj, platform )
+        else # binary
+          obj = compile(filename, Assembler::Binary.new(platform), binformat)
+          link( obj, platform )
+        end
+  return bin
 end
 
 def run(filename)
diff --git a/compiler.rb b/compiler.rb
index 88cf403..272acd8 100644
--- a/compiler.rb
+++ b/compiler.rb
@@ -12,9 +12,6 @@
 # require 'rubygems'
 # require 'unroller'
 
-require 'asm'
-require 'opcode'
-
 class ParseError < StandardError
   attr_reader :caller, :context
   def initialize(caller, context=nil)
@@ -24,43 +21,27 @@ class ParseError < StandardError
 end
 
 class Compiler
-  # This module uses our `emit_byte` method to output x86 machine code
-  # directly using the assembler library.
-  # include Assembler::Binary
 
   Keywords = %w[
     if else end while until repeat for to do break
     print
   ]
   
-  attr_reader :data, :bss, :code
+  attr_reader :asm
 
-  def initialize(input, asm=Assembler::Text.new)
+  def initialize(input, asm, binformat='elf')
     # XXX for development only!
     @indent = 0                  # for pretty printing
 
+    # The only binary format our assembler knows right now is ELF.
+    unless binformat == 'elf'
+      raise "Only ELF is supported.  Unsupported binary format: #{binformat}."
+    end
+
     @look = ''                   # Next lookahead char.
     @token = nil                 # Type of last read token.
     @value = nil                 # Value of last read token.
     @input = input               # Stream to read from.
-    @data = ''                   # Data section.
-    @bss = ''                    # BSS section.
-    @code = ''                   # Code section.
-    @binary = []                 # Byte array of machine code.
-    @vars = {}                   # Symbol table, maps names to locations in BSS.
-    @num_labels = 0              # Used to generate unique labels.
-    @num_labels_with_suffix = Hash.new(0)
-
-    @header_size = 0x100                     # ELF, Linux, x86
-    @text_offset = 0x08048000 + @header_size # Offset of text section in memory (Linux, x86).
-    @text_size = 0x02be00                    # Size of text section.
-    @data_offset = @text_offset + @text_size # Offset of data section.
-    @data_size = 0x4e00                      # Size of data section.
-    @bss_offset = @data_offset + @data_size  # Offset of bss section.
-    @bss_size = 0                            # Size of bss section.
-
-    # Labels for the assembler.  Maps names to locations.
-    @labels = Hash.new {|h, key| raise "undefined label: #{key}"}
 
     @asm = asm
 
@@ -68,10 +49,6 @@ class Compiler
     get_char
   end
 
-  def asm
-    @asm
-  end
-
   def compile
     block
     expected(:'end of file') unless eof?
@@ -107,10 +84,10 @@ class Compiler
       match('(')
       # TODO arg list
       match(')')
-      x86_call(name)
+      asm.call(name)
     else
       # variable access
-      x86_mov(:eax, "dword [#{name}]")
+      asm.mov(:eax, "dword [#{name}]")
     end
   end
 
@@ -123,7 +100,7 @@ class Compiler
     elsif alpha?(@look)
       identifier                # or call
     elsif digit?(@look)
-      x86_mov(:eax, get_number.to_i)
+      asm.mov(:eax, get_number.to_i)
     else
       expected(:'integer, identifier, function call, or parenthesized expression', :got => @look)
     end
@@ -134,7 +111,7 @@ class Compiler
     sign = @look
     match(sign) if op?(:unary, sign)
     factor
-    x86_neg(:eax) if sign == '-'
+    asm.neg(:eax) if sign == '-'
   end
 
   # Parse and translate a single term (factor or mulop).  Result is in
@@ -172,7 +149,7 @@ class Compiler
   def add
     match('+')
     term                        # Result is in eax.
-    x86_add(:eax, '[esp]')         # Add a to b.
+    asm.add(:eax, '[esp]')         # Add a to b.
   end
 
   # Parse a subtraction operator and the 2nd term (b).  The result is
@@ -180,8 +157,8 @@ class Compiler
   def subtract
     match('-')
     term                      # Result, b, is in eax.
-    x86_neg(:eax)             # Fake the subtraction.  a - b == a + -b
-    x86_add(:eax, '[esp]')    # Add a and -b.
+    asm.neg(:eax)             # Fake the subtraction.  a - b == a + -b
+    asm.add(:eax, '[esp]')    # Add a and -b.
   end
 
   # Parse an addition operator and the 2nd term (b).  The result is
@@ -189,7 +166,7 @@ class Compiler
   def multiply
     match('*')
     signed_factor               # Result is in eax.
-    x86_imul('dword [esp]')     # Multiply a by b.
+    asm.imul('dword [esp]')     # Multiply a by b.
   end
 
   # Parse a division operator and the divisor (b).  The result is
@@ -197,14 +174,14 @@ class Compiler
   def divide
     match('/')
     signed_factor               # Result is in eax.
-    x86_xchg(:eax, '[esp]')     # Swap the divisor and dividend into
+    asm.xchg(:eax, '[esp]')     # Swap the divisor and dividend into
                                 # the correct places.
 
     # idiv uses edx:eax as the dividend so we need to ensure that edx
     # is correctly sign-extended w.r.t. eax.
-    emit('cdq')       # Sign-extend eax into edx (Convert Double to
-                      # Quad).
-    x86_idiv('dword [esp]')     # Divide a (eax) by b ([esp]).
+    asm.cdq              # Sign-extend eax into edx (Convert Double to
+                         # Quad).
+    asm.idiv('dword [esp]')     # Divide a (eax) by b ([esp]).
   end
 
 
@@ -215,19 +192,19 @@ class Compiler
   def bitor_expr
     match('|')
     term
-    x86_or(:eax, '[esp]')
+    asm.or(:eax, '[esp]')
   end
 
   def bitand_expr
     match('&')
     signed_factor
-    x86_and(:eax, '[esp]')
+    asm.and_(:eax, '[esp]')
   end
 
   def xor_expr
     match('^')
     term
-    x86_xor(:eax, '[esp]')
+    asm.xor(:eax, '[esp]')
   end
 
 
@@ -240,6 +217,7 @@ class Compiler
     while @look == '|'
       op '||' do
         boolean_term
+        # !!! this method has moved, IMPLEMENT THIS!
         emit("<logical or>")
       end
     end
@@ -250,6 +228,7 @@ class Compiler
     while @look == '&'
       op '&&' do
         not_factor
+        # !!! this method has moved, IMPLEMENT THIS!
         emit("<logical and>")
       end
     end
@@ -258,9 +237,9 @@ class Compiler
   def boolean_factor
     if boolean?(@look)
       if get_boolean == 'true'
-        x86_mov(:eax, -1)
+        asm.mov(:eax, -1)
       else
-        x86_xor(:eax, :eax)
+        asm.xor(:eax, :eax)
       end
       scan
     else
@@ -273,7 +252,7 @@ class Compiler
       match('!')
       boolean_factor
       make_boolean(:eax)        # ensure it is -1 or 0...
-      x86_not(:eax)             # so that not is also boolean not
+      asm.not(:eax)             # so that not is also boolean not
     else
       boolean_factor
     end
@@ -282,11 +261,11 @@ class Compiler
   # Convert any identifier to a boolean (-1 or 0).  This is
   # semantically equivalent to !!reg in C or Ruby.
   def make_boolean(reg=:eax)
-    end_label = unique_label(:endmakebool)
-    x86_cmp(reg, 0)             # if false do nothing
-    x86_jz(end_label)
-    x86_mov(reg, -1)            # truthy, make it true
-    emit_label(end_label)
+    end_label = asm.label(:endmakebool)
+    asm.cmp(reg, 0)             # if false do nothing
+    asm.jz(end_label)
+    asm.mov(reg, -1)            # truthy, make it true
+    asm.emit_label(end_label)
   end
 
   def relation
@@ -314,14 +293,14 @@ class Compiler
   # and make_boolean will leave -1 (true) for us in eax.
   def neq_relation
     expression
-    x86_sub(:eax, '[esp]')
+    asm.sub(:eax, '[esp]')
     make_boolean
   end
 
   # Invert the != test for equal.
   def eq_relation
     neq_relation
-    x86_not(:eax)
+    asm.not(:eax)
   end
 
   # > and < are both implemented in terms of jl (jump if less than).
@@ -337,20 +316,20 @@ class Compiler
     # Invert the sense of the test?
     invert = options[:invert]
 
-    true_label = unique_label(:cmp)
-    end_label = unique_label(:endcmp)
-    x86_cmp(a, b)
-    x86_jl(true_label)
+    true_label = asm.label(:cmp)
+    end_label = asm.label(:endcmp)
+    asm.cmp(a, b)
+    asm.jl(true_label)
 
-    x86_xor(:eax, :eax)         # return false
-    x86_not(:eax) if invert     # (or true if inverted)
-    x86_jmp(end_label)
+    asm.xor(:eax, :eax)         # return false
+    asm.not(:eax) if invert     # (or true if inverted)
+    asm.jmp(end_label)
 
-    emit_label(true_label)
-    x86_xor(:eax, :eax)          # return true
-    x86_not(:eax) unless invert  # (or false if inverted)
+    asm.emit_label(true_label)
+    asm.xor(:eax, :eax)          # return true
+    asm.not(:eax) unless invert  # (or false if inverted)
 
-    emit_label(end_label)
+    asm.emit_label(end_label)
   end
 
   # a: [esp]
@@ -401,8 +380,8 @@ class Compiler
     name = @value
     match('=')
     boolean_expression
-    defvar(name) unless var?(name)
-    x86_mov("dword [#{name}]", :eax)
+    asm.defvar(name) unless asm.var?(name)
+    asm.mov("dword [#{name}]", :eax)
   end
 
   # Parse a code block.
@@ -439,26 +418,26 @@ class Compiler
   
   # Parse an if-else statement.
   def if_else_stmt(label)
-    else_label = unique_label(:end_or_else)
+    else_label = asm.label(:end_or_else)
     end_label = else_label      # only generated if else clause
                                 # present
     condition
     skip_any_whitespace
-    x86_jz(else_label)
+    asm.jz(else_label)
     @indent += 1
     block(label)
     @indent -= 1
     if @token == :keyword && @value == 'else'
       skip_any_whitespace
-      end_label = unique_label(:endif) # now we need the 2nd label
-      x86_jmp(end_label)
-      emit_label(else_label)
+      end_label = asm.label(:endif) # now we need the 2nd label
+      asm.jmp(end_label)
+      asm.emit_label(else_label)
       @indent += 1
       block(label)
       @indent -= 1
     end
     match_word('end')
-    emit_label(end_label)
+    asm.emit_label(end_label)
   end
 
   # Used to implement the Two-Label-Loops (while, until, repeat).
@@ -467,9 +446,9 @@ class Compiler
   # block: Code to execute at the start of each iteration. (e.g. a
   #        condition)
   def simple_loop(name)
-    start_label = unique_label(:"loop_#{name}")
-    end_label = unique_label(:"end_#{name}")
-    emit_label(start_label)
+    start_label = asm.label(:"loop_#{name}")
+    end_label = asm.label(:"end_#{name}")
+    asm.emit_label(start_label)
 
     yield(end_label)
 
@@ -477,15 +456,15 @@ class Compiler
     block(end_label)
     @indent -= 1
     match_word('end')
-    x86_jmp(start_label)
-    emit_label(end_label)
+    asm.jmp(start_label)
+    asm.emit_label(end_label)
   end
 
   def while_stmt
     simple_loop('while') do |end_label|
       condition
       skip_any_whitespace
-      x86_jz(end_label)
+      asm.jz(end_label)
     end
   end
 
@@ -493,7 +472,7 @@ class Compiler
     simple_loop('until') do |end_label|
       condition
       skip_any_whitespace
-      x86_jnz(end_label)
+      asm.jnz(end_label)
     end
   end
 
@@ -511,24 +490,24 @@ class Compiler
     counter = "[#{get_name}]"
     match('=')
     boolean_expression          # initial value
-    x86_sub(:eax, 1)            # pre-decrement because of the
+    asm.sub(:eax, 1)            # pre-decrement because of the
                                 # following pre-increment
-    x86_mov(counter, :eax)      # stash the counter in memory
+    asm.mov(counter, :eax)      # stash the counter in memory
     match_word('to', :scan => true)
     boolean_expression          # final value
     skip_any_whitespace
-    x86_push(:eax)              # stash final value on stack
+    asm.push(:eax)              # stash final value on stack
     final = '[esp]'
 
     simple_loop('for') do |end_label|
-      x86_mov(:ecx, counter)      # get the counter
-      x86_add(:ecx, 1)            # increment
-      x86_mov(counter, :ecx)      # store the counter
-      x86_cmp(final, :ecx)        # check if we're done
-      x86_jz(end_label)           # if so jump to the end
+      asm.mov(:ecx, counter)      # get the counter
+      asm.add(:ecx, 1)            # increment
+      asm.mov(counter, :ecx)      # store the counter
+      asm.cmp(final, :ecx)        # check if we're done
+      asm.jz(end_label)           # if so jump to the end
     end
 
-    x86_add(:esp, 4)            # clean up the stack
+    asm.add(:esp, 4)            # clean up the stack
   end
 
   # do 5
@@ -538,39 +517,38 @@ class Compiler
 
     boolean_expression
     skip_any_whitespace
-    x86_mov(:ecx, :eax)
-    x86_push(:ecx)
+    asm.mov(:ecx, :eax)
 
-    start_label = unique_label(:do)
-    end_label = unique_label(:enddo)
-    emit_label(start_label)
+    start_label = asm.label(:do)
+    end_label = asm.label(:enddo)
+    asm.emit_label(start_label)
 
-    x86_push(:ecx)
+    asm.push(:ecx)
 
     @indent += 1
     block(end_label)
     @indent -= 1
 
-    x86_pop(:ecx)
+    asm.pop(:ecx)
 
     match_word('end')
-    x86_loop(start_label)
+    asm.loop_(start_label)
 
     # Phony push!  break needs to clean up the stack, but since we
     # don't know if there is a break at this point we fake a push and
     # always clean up the stack after.
-    x86_sub(:esp, 4)
+    asm.sub(:esp, 4)
 
-    emit_label(end_label)
+    asm.emit_label(end_label)
 
     # If there was a break we have to clean up the stack here.  If
     # there was no break we clean up the phony push above.
-    x86_add(:esp, 4)
+    asm.add(:esp, 4)
   end
 
   def break_stmt(label)
     if label
-      x86_jmp(label)
+      asm.jmp(label)
     else
       expected(:'break to be somewhere useful',
                :got => :'a break outside a loop')
@@ -581,51 +559,57 @@ class Compiler
   def condition
     boolean_expression
     skip_whitespace
-    x86_cmp(:eax, 0)            # 0 is false, anything else is true
+    asm.cmp(:eax, 0)            # 0 is false, anything else is true
   end
 
   # print eax in hex format
   def print_stmt
-    # define a lookup table of digits
-    unless var?('DIGITS')
-      defvar('DIGITS', 4)
-      x86_mov('dword [DIGITS]',    0x33323130)
-      x86_mov('dword [DIGITS+4]',  0x37363534)
-      x86_mov('dword [DIGITS+8]',  0x62613938)
-      x86_mov('dword [DIGITS+12]', 0x66656463)
+    asm.block do
+      # define a lookup table of digits
+      unless var?('DIGITS')
+        defvar('DIGITS', 4)
+        mov('dword [DIGITS]',    0x33323130)
+        mov('dword [DIGITS+4]',  0x37363534)
+        mov('dword [DIGITS+8]',  0x62613938)
+        mov('dword [DIGITS+12]', 0x66656463)
+      end
+      # 3 dwords == 12 chars
+      defvar('HEX', 3) unless var?('HEX')
+      # TODO check sign and prepend '-' if negative
+      mov('word [HEX]', 0x7830) # "0x" == [48, 120]
+      mov('word [HEX+10]', 0xa)  # newline + null terminator
     end
-    # 3 dwords == 12 chars
-    defvar('HEX', 3) unless var?('HEX')
-    # TODO check sign and prepend '-' if negative
-    x86_mov('word [HEX]', 0x7830) # "0x" == [48, 120]
-    x86_mov('word [HEX+10]', 0xa)  # newline + null terminator
     boolean_expression
-    # convert eax to a hex string
-    x86_lea(:esi, '[DIGITS]')
-    x86_lea(:edi, '[HEX+9]')
-    # build the string backwards (right to left), byte by byte
-    x86_mov(:ecx, 4)
-    emit_label(loop_label=unique_label)
-    # low nybble of nth byte
-    x86_movzx(:ebx, :al)
-    x86_and(:bl, 0x0f)        # isolate low nybble
-    x86_movzx(:edx, 'byte [esi+ebx]')
-    x86_mov('byte [edi]', :dl)
-    x86_dec(:edi)
-    # high nybble of nth byte
-    x86_movzx(:ebx, :al)
-    x86_and(:bl, 0xf0)        # isolate high nybble
-    x86_shr(:bl, 4)
-    x86_mov(:dl, 'byte [esi+ebx]')
-    x86_mov('byte [edi]', :dl)
-    x86_dec(:edi)
-    x86_shr(:eax, 8)
-    x86_loop(loop_label)
-    x86_mov(:eax, 4)            # SYS_write
-    x86_mov(:ebx, 1)            # STDOUT
-    x86_lea(:ecx, '[HEX]')
-    x86_mov(:edx, 11)           # excluding term, max # of chars to print
-    x86_int(0x80)
+    asm.block do
+      # convert eax to a hex string
+      lea(:esi, '[DIGITS]')
+      lea(:edi, '[HEX+9]')
+      # build the string backwards (right to left), byte by byte
+      mov(:ecx, 4)
+    end
+    asm.emit_label(loop_label=asm.label)
+    asm.block do
+      # low nybble of nth byte
+      movzx(:ebx, :al)
+      and_(:bl, 0x0f)        # isolate low nybble
+      movzx(:edx, 'byte [esi+ebx]')
+      mov('byte [edi]', :dl)
+      dec(:edi)
+      # high nybble of nth byte
+      movzx(:ebx, :al)
+      and_(:bl, 0xf0)        # isolate high nybble
+      shr(:bl, 4)
+      mov(:dl, 'byte [esi+ebx]')
+      mov('byte [edi]', :dl)
+      dec(:edi)
+      shr(:eax, 8)
+      loop_(loop_label)
+      mov(:eax, 4)            # SYS_write
+      mov(:ebx, 1)            # STDOUT
+      lea(:ecx, '[HEX]')
+      mov(:edx, 11)           # excluding term, max # of chars to print
+      int(0x80)
+    end
   end
 
 
@@ -802,67 +786,7 @@ class Compiler
     get_char while any_whitespace?(@look)
   end
 
-
-  # Define a constant in the .data section.
-  def equ(name, value)
-    @data << "#{name}\tequ  #{value}"
-  end
-
-  # Define a variable with the given name and size (in dwords).
-  def defvar(name, dwords=1)
-    unless var?(name)
-      @bss << "#{name}: resd #{dwords}\n"
-      @vars[name] = @bss_size
-      @bss_size += dwords
-    else
-      STDERR.puts "[warning] attempted to redefine #{name}"
-    end
-  end
-
-  def var?(name)
-    @vars[name]
-  end
-
-  def var(name)
-    @vars[name]
-  end
-
-  # Emit a line of code wrapped between a tab and a newline.  Required
-  # by Assembler::Text.
-  def emit(code, options={})
-    tab = options.has_key?(:tab) ? options[:tab] : "\t"
-    @code << "#{tab}#{code}\n"
-  end
-
-  # emit_byte and bytes_written are required by Assembler::Binary.
-  def emit_byte(byte)
-    @binary << byte
-  end
-  def bytes_written
-    @binary.size
-  end
-
-
-  def emit_label(name=unique_label)
-    emit("#{name}:", :tab => nil)
-
-    @labels[name] = @binary.length
-  end
-
-  def resolve_label(label)
-    @labels[label]
-  end
-
-  # Generate a unique label.
-  def unique_label(suffix=nil)
-    @num_labels += 1
-    if suffix
-      @num_labels_with_suffix[suffix] += 1
-      suffix = "_#{suffix}_#{@num_labels_with_suffix[suffix]}"
-    end
-    "L#{sprintf "%06d", @num_labels}#{suffix}"
-  end
-
+  
   def indent
     real_indent = if @value == 'else' || @value == 'end'
                     @indent - 1
@@ -872,16 +796,10 @@ class Compiler
     ' ' * (real_indent * 4)
   end
 
-  # Pack the array into a byte string.
-  def binary
-    @binary.pack('c*')
-  end
-
-
   def pushing(reg)
-    x86_push(reg)
+    asm.push(reg)
     yield
-    x86_add(:esp, 4)
+    asm.add(:esp, 4)
   end
 
   def op(name)
diff --git a/epilogue.asm b/epilogue.asm
deleted file mode 100644
index 15fa155..0000000
--- a/epilogue.asm
+++ /dev/null
@@ -1,3 +0,0 @@
-	mov ebx, eax
-	mov eax, 1
-	int 0x80
diff --git a/min.darwin.asm b/min.darwin.asm
new file mode 100644
index 0000000..4556521
--- /dev/null
+++ b/min.darwin.asm
@@ -0,0 +1,6 @@
+BITS 32
+SECTION .text
+GLOBAL _main
+_main:
+	mov eax, 0
+	ret
diff --git a/min.asm b/min.linux.asm
similarity index 100%
rename from min.asm
rename to min.linux.asm
diff --git a/min2.asm b/min2.asm
deleted file mode 100644
index 8238ae5..0000000
--- a/min2.asm
+++ /dev/null
@@ -1,4 +0,0 @@
-BITS 32
-mov ebx,eax
-mov eax,1
-int 0x80
diff --git a/opcode.rb b/opcode.rb
deleted file mode 100644
index 772bd47..0000000
--- a/opcode.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-class OpCode
-  Attrs = [:prefix, :op, :modrm, :sib, :extra]
-  attr_accessor *Attrs
-
-  def initialize(attrs)
-    Attrs.each do |attr|
-      send("#{attr}=", attrs[attr])
-    end
-  end
-
-  def size
-    Attrs.inject(0) {|sum, attr|
-      iv = instance_variable_get("@#{attr}")
-      if iv.is_a?(Enumerable)
-        sum + iv.size
-      else
-        sum + 1
-      end
-    }
-  end
-
-  def binary
-    Attrs.map {|attr| send(attr)}.flatten.pack('c*')
-  end
-end
diff --git a/prologue.asm b/prologue.asm
deleted file mode 100644
index 6f69371..0000000
--- a/prologue.asm
+++ /dev/null
@@ -1,4 +0,0 @@
-BITS 32
-GLOBAL _start
-SECTION .text
-_start:
diff --git a/template.darwin.asm b/template.darwin.asm
new file mode 100644
index 0000000..673f104
--- /dev/null
+++ b/template.darwin.asm
@@ -0,0 +1,11 @@
+BITS 32
+GLOBAL _main
+SECTION .data
+{data}
+SECTION .bss
+{bss}
+SECTION .text
+_main:
+{code}
+	;; The result in eax is the exit code, just return.
+	ret
diff --git a/template.asm b/template.linux.asm
similarity index 100%
rename from template.asm
rename to template.linux.asm
diff --git a/test.rb b/test.rb
deleted file mode 100644
index a004c9a..0000000
--- a/test.rb
+++ /dev/null
@@ -1,47 +0,0 @@
-require 'compiler'
-require 'stringio'
-
-X86_exit = [0x89, 0xc3,         # mov ebx, eax (exit code)
-            0xb8, 1, 0, 0, 0,   # mov eax, 1
-            0xcd, 0x80          # int 0x80
-           ].pack('c*')
-
-def error(msg) STDERR.puts(msg) end
-
-def parse(input)
-  compiler = Compiler.new(input)
-  compiler.parse                # tuple of [data, bss, code, binary]
-
-rescue ParseError => e
-  error("[error] #{e.message}")
-  error("[context] #{e.context}")
-  # error("Aborting!")
-  error(e.caller)
-  exit(1)
-end
-
-def interpolate(template, data)
-  data.inject(template) do |template, mapping|
-    token, replacement = *mapping
-    template.sub("{#{token}}", replacement)
-  end
-end
-
-def main(arg)
-  input = if File.readable?(arg)
-            File.open(arg)
-          else
-            # StringIO.new("5*(3-5)*2+2-9/3-8/2-4*(5+5+5)\n")
-            StringIO.new("abc=999\nabc-888\n")
-          end
-  data, bss, code, binary = *parse(input)
-  template = File.read("template.asm")
-  asm = interpolate(template, :data => data, :bss => bss, :code => code)
-  File.open("test.asm", "w") { |f| f.puts(asm) }
-  File.open("test.bin", "wb") { |f|
-    f.write(binary)
-    f.write(X86_exit)
-  }
-end
-
-main(ARGV[0].to_s)
diff --git a/test/Makefile b/test/Makefile
index 4bbf149..bff7a29 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,50 +1,63 @@
+PLATFORM=$(shell uname -s)
+BINFORMAT="bin"
+ifeq ($(PLATFORM), Darwin)
+	BINFORMAT="macho"
+endif
+ifeq ($(PLATFORM), Linux)
+	BINFORMAT="elf"
+endif
+ifeq ($(BINFORMAT), bin)
+	@echo "WARNING: binary format is 'bin', this is probably not what you want!"
+	@echo "         Your platform, " $(PLATFORM) ", is unsupported."
+endif
+
 all: lt gt ge le eq neq if while until repeat for do break print
-	@echo -n
+	@true
 
 lt: test.rb test_lt.code
-	@./test.rb lt
+	@./test.rb lt $(BINFORMAT)
 
 gt: test.rb test_gt.code
-	@./test.rb gt
+	@./test.rb gt $(BINFORMAT)
 
 ge: test.rb test_ge.code
-	@./test.rb ge
+	@./test.rb ge $(BINFORMAT)
 
 le: test.rb test_le.code
-	@./test.rb le
+	@./test.rb le $(BINFORMAT)
 
 eq: test.rb test_eq.code
-	@./test.rb eq
+	@./test.rb eq $(BINFORMAT)
 
 neq: test.rb test_neq.code
-	@./test.rb neq
+	@./test.rb neq $(BINFORMAT)
 
 if: test.rb test_if.code
-	@./test.rb if
+	@./test.rb if $(BINFORMAT)
 
 while: test.rb test_while.code
-	@./test.rb while
+	@./test.rb while $(BINFORMAT)
 
 until: test.rb test_until.code
-	@./test.rb until
+	@./test.rb until $(BINFORMAT)
 
 repeat: test.rb test_repeat.code
-	@./test.rb repeat
+	@./test.rb repeat $(BINFORMAT)
 
 for: test.rb test_for.code
-	@./test.rb for
+	@./test.rb for $(BINFORMAT)
 
 do: test.rb test_do.code
-	@./test.rb do
+	@./test.rb do $(BINFORMAT)
 
 break: test.rb test_break.code
-	@./test.rb break
+	@./test.rb break $(BINFORMAT)
 
 print: test.rb test_print.code
-	@./test.rb print
+	@./test.rb print $(BINFORMAT)
 
 big_test: test.rb big_test.code
-	@./test.rb big
+	@./test.rb big $(BINFORMAT)
 
 clean:
 	@rm -f test*.asm test*.o
diff --git a/test/test.rb b/test/test.rb
index 16cf0ef..6227086 100755
--- a/test/test.rb
+++ b/test/test.rb
@@ -5,12 +5,21 @@ $LOAD_PATH << ROOT
 
 require 'build'
 
+# usage: build.rb <func> [binformat]
+#
+# ([format] will go before [binformat])
+
 def main
   func = ARGV[0].to_s
+  format = 'asm'                # 'bin' only assembles one or two
+                                # instructions right now, but support
+                                # is in place
+  binformat = (ARGV[1] ? ARGV[1] : 'elf').downcase
+  platform = `uname -s`.chomp.downcase
   print "testing #{func} ... "
-  success = run( build("test_#{func}.code") )
+  success = run( build("test_#{func}.code", platform, format, binformat) )
   puts success == 0 ? "pass" : "FAIL! (#{success})"
-  exit(success)
+  exit(success.to_i)
 end
 
 main if $0 == __FILE__