SWI-Prolog 5.11.18 Reference Manual: Section A.5

## A.5 library(charsio): I/O on Lists of Character Codes

Compatibility
  The naming of this library is not in line with the ISO standard. We believe that the SWI-Prolog native predicates form a more elegant alternative for this library.

This module emulates the Quintus/SICStus library `charsio.pl` for reading and writing from/to lists of character codes. Most of these predicates are straight calls into similar SWI-Prolog primitives. Some can even be replaced by ISO standard predicates.

[det]format_to_chars(+Format, +Args, -Codes)
  Use format/2 to write to a list of character codes.
[det]format_to_chars(+Format, +Args, -Codes)
  Use format/2 to write to a difference list of character codes.
write_to_chars(+Term, -Codes)
  Codes is a list of character codes produced by write/1 on Term.
write_to_chars(+Term, -Codes, ?Tail)
  Codes is a difference-list of character codes produced by write/1 on Term.
[det]atom_to_chars(+Atom, -Codes)
  Convert Atom into a list of character codes.
  deprecated
    Use ISO atom_codes/2.
[det]atom_to_chars(+Atom, -Codes, ?Tail)
  Convert Atom into a difference-list of character codes.
[det]number_to_chars(+Number, -Codes)
  Convert Atom into a list of character codes.
  deprecated
    Use ISO number_codes/2.
[det]number_to_chars(+Atom, -Codes, ?Tail)
  Convert Number into a difference-list of character codes.
[det]read_from_chars(+Codes, -Term)
  Read Codes into Term.
  Compatibility
    The SWI-Prolog version does not require Codes to end in a full-stop.
[det]read_term_from_chars(+Codes, -Term, +Options)
  Read Codes into Term. Options are processed by read_term/3.
  Compatibility
    sicstus
[det]open_chars_stream(+Codes, -Stream)
  Open Codes as an input stream.
  bug
    Depends on autoloading library(memfile). As many applications do not need this predicate we do not want to make the entire library dependent on autoloading.
[det]with_output_to_chars(:Goal, Codes)
  Run Goal with as once/1. Output written to `current_output` is collected in Codes.
[det]with_output_to_chars(:Goal, -Codes, ?Tail)
  Run Goal with as once/1. Output written to `current_output` is collected in Codes`\`Tail.
[det]with_output_to_chars(:Goal, -Stream, -Codes, ?Tail)
  As with_output_to_chars/2, but Stream is unified with the temporary stream.