The Free On-line Dictionary of Computing (30 December 2018):

BinHex

    A Macintosh format for representing a binary
   file using only printable characters.  The file is
   converted to lines of letters, numbers and punctuation.
   Because BinHex files are simply text they can be sent through
   most electronic mail systems and stored on most computers.
   However the conversion to text makes the file larger, so it
   takes longer to transmit a file in BinHex format than if the
   file was represented some other way.

   Filename extension: .hqx.

   See also BinHex 4.0, uuencode.

   [Encoding algorithm?]

   (1994-11-30)