LLVM  Bitcode files start with  BC  (0x42, 0x43) WAD  files start with  IWAD  or  PWAD  (for  Doom ),  WAD2  (for  Quake ) and  WAD3  (for  Half-Life ). Microsoft Office  document files start with  D0   CF   11   E0 , which is visually suggestive of the word "DOCFILE0". Headers in