RFC 1456

RFC 1456: Conventions for Encoding the Vietnamese Language 🌸

Okay bestie, RFC 1456 is giving Vietnamese typing glow-up 💖. The full title is Conventions for Encoding the Vietnamese Language, with two parts: VISCII (VIetnamese Standard Code for Information Interchange) and VIQR (VIetnamese Quoted-Readable Specification), and this is Revision 1.1 ✨.

• Series: Network Working Group
• Author: Vietnamese Standardization Working Group
• Date: May 1993
• Category and status: it provides information for the Internet community, and it is not an Internet standard 📚
• Obsoletes and Updates: nothing is listed in the header, so it doesn't replace or change any other RFC 🫶

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Status of this Memo 🎀

This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited 💅.

Abstract ✨

This doc tells the Internet crowd how Vietnamese characters are currently encoded in two ways: into 7-bit US ASCII, and into an 8-bit form 🌈. Overseas Vietnamese folks who are on the Internet and active on USENET use these conventions a lot. It's purely informational, so it doesn't set any level of standard 🙈.

1. Introduction 🦋

Okay so there are two conventions here. VISCII (pronounced "visky") is an 8-bit encoding that's similar to the one used with ISO-8859. VIQR (pronounced "vicker") is a mnemonic encoding that turns Vietnamese characters into US ASCII for 7-bit systems 💜. There's already a ton of freely distributable software for UNIX and personal computers that uses these, so Vietnamese users get to use the powerful tools the English-speaking world already built, with zero reinvention needed 🙌. The paper also exists so that MIME-compliant software might support Vietnamese too 🧚.

NOTE 🍓: The accented Vietnamese letters are shown here using their VIQR equivalents, wrapped in angle brackets. For example, the single letter "a acute" is written as <a'>, where the apostrophe is the mnemonic symbol for the acute.

2. LINGUISTIC OVERVIEW 💅

Vietnamese is a romanized language, so it kind of looks like it could slide right into existing English-based systems 🫠. Think about French: you could give the 8-bit space some extra code positions for accented letters like <e^> or <e'>, then let users reach them from the keyboard. For French, you'd only need a small number of extra positions (see ISO-8859/Latin-1 [1]), and since accented letters show up pretty rarely, you don't need a super efficient keyboard input scheme 🥱.

Vietnamese is a whole different story though 😭. Both the number of accented letters and how often they show up are huge. On top of the plain ASCII letters, Vietnamese needs another 134 combinations of a letter plus a diacritical symbol 🔥.

You could use a composite encoding scheme to shrink that, but then you'd be giving up integration with today's computing platforms, and most of them just don't support that kind of scheme 💀. Also, Vietnamese uses a lot of diacritical marks, so the keyboard input should not need extra keystrokes like a special "compose" key to make accented letters ⌨️. With that many combinations, the scheme also has to be easy to learn and memorize 🧠.

Finally, email systems are still limited to 7 bits, so Vietnamese text needs a representation that's easy to read in its 7-bit form 📬.

The Viet-Std group is an electronic standardization roundtable that spent a few years drafting proposals for all of this 👑. It all came together in the conventions described in the next two sections. The detailed technical considerations were reported elsewhere [2]. This memo gives a quick outline of the working standards and talks about where you can get the supporting software 🌷.

3. SPECIFICATION OF VISCII 🌈

VISCII stands for VIetnamese Standard Code for Information Interchange, and it's an 8-bit encoding specification. The main highlights are:

1. Every Vietnamese letter gets encoded as a single unit, instead of splitting base vowels and diacritical marks apart 🎀.
2. The complete ASCII graphics set is kept, so integration is easier 🦋.
3. The 6 least-often-used upper-case letters are encoded into the 6 least problematic C0 (control) characters ✨.
4. The character placement was designed with Unix/X integration and ISO-8859/Latin-1 compatibility in mind. It also plays nicely with a wide range of existing software, including spots for single- and double-line drawing characters in the IBM graphic character set 🫶.

Here's the 8-bit VISCII encoding. Because 7-bit US ASCII is limited, the table uses the mnemonic form to show Vietnamese glyphs. For how the diacritical marks get applied, check the VIQR specification below. The online PostScript version of reference [2] can also help, since it shows each character correctly 🖨️.

               Table 1.  VISCII 8-bit Encoding Table (v1.1)
*=======================================================================*
|    | 0x  1x  2x  3x  4x  5x  6x  7x | 8x  9x  Ax  Bx  Cx  Dx  Ex  Fx  |
|====|==================================================================|
| x0 | nul dle sp  0   @   P   `   p  | A.  O^` O~  o^` A`  DD  a`  dd  |
| x1 | soh dc1 !   1   A   Q   a   q  | A(' O^? a(' o^? A'  u+' a'  u+. |
| x2 | A(? dc2 "   2   B   R   b   r  | A(` O^~ a(` o^~ A^  O`  a^  o`  |
| x3 | etx dc3 #   3   C   S   c   s  | A(. O^. a(. O+~ A~  O'  a~  o'  |
| x4 | eot Y?  $   4   D   T   d   t  | A^' O+. a^' O+  A?  O^  a?  o^  |
| x5 | A(~ nak %   5   E   U   e   u  | A^` O+' a^` o^. A(  a.  a(  o~  |
| x6 | A^~ syn &   6   F   V   f   v  | A^? O+` a^? o+` a(? y?  u+~ o?  |
| x7 | bel etb '   7   G   W   g   w  | A^. O+? a^. o+? a(~ u+` a^~ o.  |
| x8 | bs  can (   8   H   X   h   x  | E~  I.  e~  i.  E`  u+? e`  u.  |
| x9 | ht  Y~  )   9   I   Y   i   y  | E.  O?  e.  U+. E'  U`  e'  u`  |
| xA | lf  sub *   :   J   Z   j   z  | E^' O.  e^' U+' E^  U'  e^  u'  |
| xB | vt  esc +   ;   K   [   k   {  | E^` I?  e^` U+` E?  y~  e?  u~  |
| xC | ff  fs  ,   <   L   \   l   |  | E^? U?  e^? U+? I`  y.  i`  u?  |
| xD | cr  gs  -   =   M   ]   m   }  | E^~ U~  e^~ o+  I'  Y'  i'  y'  |
| xE | so  Y.  .   >   N   ^   n   ~  | E^. U.  e^. o+' I~  o+~ i~  o+. |
| xF | si  us  /   ?   O   _   o   DEL| O^' Y`  o^' U+  y`  u+  i?  U+~ |
*=======================================================================*

6. MIME CONSIDERATIONS ✨

okay so this section is about making VISCII and VIQR play nicely with MIME-compliant software 💌 the authors registered "VISCII" with the Internet Assigned Numbers Authority as a charset name for the VISCII encoding we just went over, and "VIQR" got its own registration too for the mnemonic encoding 🎀 implementing support for these two MIME character set types is not required to comply with RFC-1341, so it's totally optional 🫶 BUT if you're using these encodings in MIME email or news, you SHOULD label the body-part containing that text with the matching MIME character set value 💅

7. SECURITY CONSIDERATIONS 🔐

bestie, this one is short and sweet 🙈 the memo says security issues are not discussed in it 💀 so just know that this document doesn't cover that topic at all ✨

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REFERENCES 📚

[1] International Organization for Standardization. ISO 8859/x: 8-bit International Code Sets. ISO, 1977. 🌸

[2] Viet-Std, "A Unified Framework for Vietnamese Information Processing-v1.1," published on the Internet, available for FTP from Sonygate.Sony.COM:tin/viet-std, September 1992. 🦋

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AUTHORS' ADDRESSES 💜

Cuong T. Nguyen Center for Integrated Systems CIS 062--MC 4070 Stanford, CA 94305-4070

Phone: (415) 725-3721 Email: cuong@haydn.Stanford.EDU

Hoc D. Ngo Vista Research, Inc. 100 View St, Suite 200 P.O. Box 998 Mountain View, CA 94042

Phone: (415) 966-1171 Email: uunet!vri280!hoc

Cuong M. Bui National Semiconductor Corp. 3388 Burgundy Dr. San Jose, CA 95132

Phone: (408) 721-6873 Email: bui@berlioz.nsc.com

Thanh van Nguyen Roche Image Analysis Systems 95 First Str Suite 110 Los Altos, CA 94022

Phone: 415-917-2022 Fax: 415-917-2025 Email: thanh@rias.com

For more information, please contact the authors at: viet-std@haydn.stanford.edu 🧚