which is visually suggestive of the word "DOCFILE0". WAD  files start with  IWAD  or  PWAD  (for  Doom ),  WAD2  (for  Quake ) and  WAD3  (for  Half-Life ). LLVM  Bitcode files start with  BC  (0x42, 0x43) Unicode  text files encoded in  UTF-16  often start with the  Byte Order Mark  to detect  endianness