old_contents: #=======================================================================
  # machine.py
  #=======================================================================
  
  #-----------------------------------------------------------------------
  # Machine
  #-----------------------------------------------------------------------
  class Machine( object ):
    def __init__( self, memory, register_file, debug, reset_addr=0x400 ):
  
      self.pc       = reset_addr
      self.rf       = register_file
      self.mem      = memory
  
      self    .debug = debug
      self.rf .debug = debug
      self.mem.debug = debug
  
      # common registers
      self.status        = 0
      self.stats_en      = 0
      self.num_insts       = 0
      self.stat_num_insts  = 0
  
      # we need a dedicated running flag bacase status could be 0 on a
      # syscall_exit
      self.running       = True
  
    def fetch_pc( self ):
      return self.pc
  
new_contents: #=======================================================================
  # machine.py
  #=======================================================================
  
  #-----------------------------------------------------------------------
  # Machine
  #-----------------------------------------------------------------------
  class Machine( object ):
    def __init__( self, memory, register_file, debug, reset_addr=0x400 ):
  
      self.pc       = reset_addr
      self.rf       = register_file
      self.mem      = memory
  
      self    .debug = debug
      self.rf .debug = debug
      self.mem.debug = debug
  
      # common registers
      self.status        = 0
      self.stats_en      = 0
      self.num_insts       = 0
      self.stat_num_insts  = 0
  
      # we need a dedicated running flag because status could be 0 on a
      # syscall_exit
      self.running       = True
  
    def fetch_pc( self ):
      return self.pc
  
subject: FIX typo.