RFC 1456 (rfc1456) - Page 2 of 7

Conventions for Encoding the Vietnamese Language VISCII: VIetnamese Standard Code for Information Interchange VIQR: VIetnamese Quoted-Readable Specification

RFC 1456          Conventions for Encoding Vietnamese           May 1993


   example, consider implementing support for French in such systems.
   One can allocate code positions in the 8-bit space necessary for
   accented letters such as  or , then provide a means for users
   to access these codes through the keyboard.  The required number of
   "extra" code positions is small (see, e.g., ISO-8859/Latin-1 [1]),
   and the relatively low frequency of occurrence of accented letters
   does not place heavy demand on efficient keyboard input schemes.  The
   same things cannot be said for Vietnamese, where both the number and
   occurrence frequency of accented letters are large.  Apart from the
   alphabetics already available in ASCII, Vietnamese requires an
   additional 134 combinations of a letter and diacritical symbols.

   Note that one can resort to a composite encoding scheme to reduce
   this requirement, but that would mean giving up on integration into
   today's computing platforms which for the most part do not support
   such schemes.  In addition, the heavy use of diacritical marks in
   Vietnamese text calls for a keyboard input scheme that does not
   require extra keystrokes such as a special "compose" key to generate
   accented letters.  Because of the large number of possible
   combinations, the scheme should also be easily learned and memorized.

   Finally, to integrate Vietnamese into current electronic mail systems
   which are still limited to 7 bits, there should be a representation
   for Vietnamese text that is readily readable in its 7-bit form.

   The Viet-Std group, an electronic standardization roundtable, has
   worked over the past few years to draft proposals addressing these
   issues.  This has culminated in the conventions to be described
   briefly in the next two sections.  The detailed technical
   considerations have been reported elsewhere [2].  In this memo we
   give a brief outline of the working standards and describe supporting
   software availability.

3. SPECIFICATION OF VISCII

   VISCII stands for VIetnamese Standard Code for Information
   Interchange, an 8-bit encoding specification.  Its salient features
   are:

    1.  Encoding of all Vietnamese letters as single units
        rather than separating base vowels and diacritical
        marks.

    2.  Retention of the complete ASCII graphics repertoire
        in order to facilitate integration.

    3.  Encoding the 6 least-often-used upper-case letters into
        6 least problematic C0 (control) characters.



Vietnamese Standardization Working Group