VISCII

VISCII is an unofficially-defined modified ASCII character encoding for using the Vietnamese language with computers. It should not be confused with the similarly-named officially registered VSCII encoding. VISCII keeps the 95 printable characters of ASCII unmodified, but it replaces 6 of the 33 control characters with printable characters. It adds 128 precomposed characters. Unicode and the Windows-1258 code page are now used for virtually all Vietnamese computer data,^{[citation needed]} but legacy VSCII and VISCII files may need conversion.

History and naming

VISCII was designed by the Vietnamese Standardization Working Group (Viet-Std Group)^[1] led by Christopher Cuong T. Nguyen, Cuong M. Bui, and Hoc D. Ngo based in Silicon Valley, California in 1992 while they were working with the Unicode consortium to include pre-composed Vietnamese characters in the Unicode standard. VISCII, along with VIQR, was first published in a bilingual report in September 1992, in which it was dubbed the "Vietnamese Standard Code for Information Interchange".^[2] The report noted a proliferation in computer usage in Vietnam and the increasing volume of computer-based communications among Vietnamese abroad, that existing applications used vendor-specific encodings which were unable to interoperate with one another, and that standardisation between vendors was therefore necessary. The successful inclusion of composed and precomposed Vietnamese in Unicode 1.0 was the result of the lessons learned from the development of 8-bit VISCII and 7-bit VIQR.^[2]

The next year, in 1993, Vietnam adopted

A traditional extended ASCII character set consists of the ASCII set plus up to 128 characters. Vietnamese requires 134 additional letter-diacritic combinations, which is six too many. There are (short of dropping tone mark support for capital letters, as in VSCII-3) essentially four different ways to handle this problem:

1. Use variable-width encoding (as does UTF-8)
2. Include combining diacritical marks for tone marks (as do VSCII-2 and Windows-1258) or for diacritics in general (as do ANSEL and VNI)
3. Replace some ASCII punctuation, preferably punctuation which is not invariant in
   ISO 646 (as does VNI for DOS
   )
4. Replace at least six of the basic ASCII
   VPS and VSCII-1
   )

However, using up all the extended code points for accented letters left no room to add useful symbols, superscripted numbers, curved quotes, proper dashes, etc., like most other extended ASCII character sets.

Location of characters deliberately mostly follows

VISCII is partially supported by the TriChlor Software Group in California, which has released various VISCII-compliant software packages, libraries, and fonts for MS-DOS and Windows, Unix, and Macintosh. VISCII-compliant software is available at many FTP sites.

VISCII was historically offered as an encoding for outgoing email by Mozilla Thunderbird.^[8] It was also supported by the Windows Vietnamese keyboard software, WinVNKey, created by Christopher Cuong T. Nguyen and later upgraded through various Windows versions by Hoc D. Ngo and others.

VISCII was mostly used by overseas Vietnamese speakers, with VSCII (TCVN) being more popular in northern Vietnam and VNI being more popular in southern Vietnam.^[9]

Character set

See also

• ASCII
• Vietnamese Quoted-Readable (VIQR)
• Vietnamese Standard Code for Information Interchange
  (VSCII)
• Windows-1258

References