Publication:    FSP-1013
Revision:       1
Title:          Character set definition in Fidonet messages
Author:         Peter Karlsson
Revision Date:  04 September 1999
Expiry Date:    04 September 2199
                1. Introduction
                2. Format of the identifier
                3. Supported levels
                4. Supported character sets
                5. Obsolete identifiers
                6. Notes

Status of this document

  This document suggests a proposed protocol for the FidoNet(r)
  community, and requests discussion and suggestions for improvements.
  Distribution of this document is unlimited.


  This document defines the identifiers that are used to indicate the
  character set used within messages that are distributed in Fidonet.

  There has been many attempts on defining a common standard on what
  character set is used in Fidonet distributed messages. The only one
  that has gained widespread is the "CHRS" standard, described in
  FSC-0054. This document tries to describe the current usage, as
  well as standardizing the parts of it that was ambigously defined.

1. Introduction

  As Fidonet is an international network, one has to consider that
  not all people speak English. Many languages also have alphabets
  that are either bigger than the standard English alphabet, or
  completely different. To keep track of which character set is used
  for a particular message, this documents describes a way to identify
  this to the reader.

2. Format of identifier

  The CHRS control line is formatted as follows:

        ^ACHRS: <identifier> <level>

  Where <identifier> is a character string of no more than eight (8)
  characters identifying the character set to use, and level is a
  numeric value describing what level of CHRS this message is written

  For backward compatibility, the use of "CHARSET" instead of "CHRS"
  should be supported when reading messages.

  Some current implementations do not add the required <level> field.
  Implemetations of this document should allow for this usage, but
  never write such control lines themselves.

  Incoming messages without "CHRS" control lines should be considered
  as being written in the area's default character set (normally
  ASCII, IBM codepage 437, LATIN-1 or similar).

3. Supported levels

  These levels are the one that are implemented in current software:

 Level 0

  This level is for messages containing of pure seven-bit ASCII only.
  Outgoing messages in pure ASCII need not be identified by a "CHRS"
  control line, but if they are, they should be indicated as
  "ASCII 1" (not "ASCII 0").

 Level 1

  First level of internationalization, using seven bit character sets.
  Most of these are based on US ASCII, with minor internationalization

 Level 2

  Second level of internationalization, using eight bit character

  This level adds support for character sets that use "extended
  ASCII", i.e codes with the most significant bit set. The character
  sets in level two are all based on ASCII (the codes 0-127 coincides
  with ASCII).

 Level 3 and above

  Level 3 or higher as specified by FSC-54 has no known current
  implementation, because of which this document are considered
  reserved for future use.

  Level 3 would be suited for a Unicode (ISO 10646) implementation.
  Because of limitations of currently available Fidonet packet
  standards, it is not at the time of writing viable to specify how
  this should work.

4. Supported character sets

  These character sets are defined at the moment:

  Identifier  Character set
  ----------  -------------

    Level 1 character sets (seven-bit)

  ASCII       ISO 646-1 (US ASCII)
  DUTCH       ISO 646 Dutch
  FINNISH     ISO 646-10 (Swedish/Finnish)
  FRENCH      ISO 646 French
  CANADIAN    ISO 646 Canadian
  GERMAN      ISO 646 German
  ITALIAN     ISO 646 Italian
  NORWEIG     ISO 646 Norweigian
  PORTU       ISO 646 Protuguese
  SPANISH     ISO 646 Spanish
  SWEDISH     ISO 646-10 (Swedish/Finnish)
  SWISS       ISO 646 Swiss
  UK          ISO 646 UK

    Level 1 known depreciated character set identifiers

  ISO-10      ISO 646-10 (Swedish/Finnish)

    Level 2 character sets (eight-bit, ASCII based)

  CP437       IBM codepage 437 (Western European)
  CP850       IBM codepage 850 (Latin-1)
  CP865       IBM codepage 865 (Nordic)
  CP866       IBM codepage 866 (Russian)

  LATIN-1     ISO 8859-1 (Western European)
  LATIN-2     ISO 8859-2 (Eastern European)
  LATIN-5     ISO 8859-9 (Turkish)

  MAC         MacIntosh character set

    Level 2 obsolete character set identifiers (see note)

  IBMPC       IBM PC character set
  +7_FIDO     IBM codepage 866

5. Obsolete indentifiers

  Since the "IBMPC" identifier, initially used to indicate IBM
  codepage 437, eventually evolved into identifying "any IBM
  codepage", there exists in some implementations an additional
  control line, "CODEPAGE", identifying the messages codepage:

        ^ACODEPAGE: xxx

  This use is depreciated in favour of the "CPxxx" identifiers
  defined above. If found in incoming messages, however, it should be
  used as an override of the "CHRS: IBMPC" identifier.

  The character set "+7_FIDO" is currently in use as an identifier for
  CP866. This use is depreciated, and "CP866" is recommended instead.
  Implementations should treat "+7_FIDO" as a synonym for "CP866".

  FSC-54 also defined control lines for style changes, "CHRC". These
  are not implemented in any software known to the author, and are

  Levels 3 and 4, as defined by FSC-54, are also considered "obsolete"
  since there currently are no known implementations of them. All
  levels not documented here are considered reserved for future use.

6. Notes

  The character set identifier applies to all parts of the message,
  including the header information, and the tear and Origin lines.

  FSC-54 documents file formats for mapping files that could be used
  for storing character translation data. These are not documented

A. Author contact data

  Peter Karlsson
  Fidonet: 2:206/221
  E-mail: pk@abc.se

B. Acknowledgements

  Duncan McNutt (original FSC-0054 author).

C. History

  Rev.1, 19990904: Based on FSC-0054, by Peter Karlsson