bitmap = file-name + img ->
  if bmp IS_PM_BITMAP 
     ' bmp = char-in file-name ->
    img = bmp
  else
    img = convert bmp
  ;
_
  img : array : integer : 2^8
;

file-is bitmap -a = bytes IS_PM_BITMAP ->                                      ++- Internal (hidden) function
  [ bytes.1 = 'B' &&
    bytes.2 = 'M' &&
    bytes.3 = 'N' && bytes.4 = "\0" ]
_
  bytes : array : integer : 2^8
;