# File lib/file_systems/AppleCPM.rb, line 32
  def self.get_block(file_system_image,block_no)
    track_no= ((block_no/4)+3)%file_system_image.track_count
    s=""
    SECTORS_IN_BLOCK[block_no%4].each {|sector_no| s+=file_system_image.get_sector(track_no,sector_no)}
    s
  end