A hexadecimal literal (a HP extension to nonnumeric literals) is
  a character string of 2 to 256 hexadecimal digits.  It is delimited on
  the left by the separator 'X' (or 'x') immediately followed by a
  quotation mark (") or apostrophe ('); on the right it is delimited by a
  matching quotation mark or apostrophe.  The character string consists
  only of pairs of hexadecimal digits representing a value ranging from
  00 to FF; hence, only the characters '0' through '9', 'A' through 'F',
  and 'a' through 'f' are valid.

  The value of a hexadecimal literal is the composite value of the paired
  hexadecimal representations.  The compiler truncates hexadecimal
  literals to a maximum of 128 hexadecimal representations (pairs of
  hexadecimal digits).

  A hexadecimal literal can be used interchangeably wherever a nonnumeric
  literal can appear in VSI COBOL syntax.  (Note that hexadecimal
  literals cannot be used as operands in arithmetic statements.)