V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

BTOA
       Binary TO ASCII (ASCII)


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

btoa

    /B too A/ A binary
   to ASCII conversion utility.

   btoa is a uuencode or base 64 equivalent which addresses
   some of the problems with the uuencode standard but not as
   many as the base 64 standard.  It avoids problems that some
   hosts have with spaces (e.g. conversion of groups of spaces
   to tabs) by not including them in its character set, but may
   still have problems on non-ASCII systems (e.g. EBCDIC).

   btoa is primarily used to transfer binary files between
   systems across connections which are not eight-bit clean,
   e.g. electronic mail.

   btoa takes adjacent sets of four binary octets and encodes
   them as five ASCII octets using ASCII characters '!' through
   to 'u'.  Special characters are also used: 'x' marks the
   beginning or end of the archive; 'z' marks four consecutive
   zeros and 'y' (version 5.2) four consecutive spaces.

   Each group of four octets is processed as a 32-bit integer.
   Call this 'I'.  Let 'D' = 85^4.  Divide I by D.  Call this
   result 'R'.  Make I = I - (R * D) to avoid overflow on the
   next step.  Repeat, for values of D = 85^3, 85^2, 85 and 1.
   At each step, to convert R to the output character add decimal
   33 (output octet = R + ASCII value for '!').  Five output
   octets are produced.

   btoa provides some integrity checking in the form of a line
   checksum, and facilities for patching corrupted downloads.

   The algorithm used by btoa is more efficient than uuencode
   or base 64.  ASCII files are encoded to about 120% the size of
   their binary sources.  This compares with 135% for uuencode or
   base 64.

   C source (ftp://hpux.csc.liv.ac.uk/hpux/Misc/btoa-5.2/).
   (version 5.2 - ~1994).

   Pre-compiled MS-DOS versions are also available.

   (1997-08-08)