VSCII (Vietnamese Standard Code for Information Interchange), also known asTCVN 5712,^[2]ISO-IR-180,^[3].VN,^[4]ABC^[4] or simply theTCVN encodings,^[4][5] is a set of three closely relatedVietnamese national standardcharacter encodings forusing the Vietnamese language with computers, developed by the TCVN Technical Committee on Information Technology (TCVN/TC1) and first adopted in 1993 (as TCVN 5712:1993).^[2]

It should not be confused with the similarly-named unofficialVISCII encoding, which was sometimes used by overseas Vietnamese speakers.^[4] VISCII was also intended to stand forVietnamese Standard Code for Information Interchange, but is not related to VSCII.^[6]

VSCII (TCVN) was used extensively in the north of Vietnam, whileVNI was popular in the south.^[4]Unicode and theWindows-1258 code page are now used for virtually all Vietnamese computer data,^{[citation needed]} but legacy files or archived messages may need conversion.

All three forms of VSCII keep the 95 printable characters ofASCII unmodified.

VSCII-3, also known as TCVN 5712-3, VN3 or simply TCVN3,^[7] includes the fewest assignments. It is anextended ASCII, because it keeps all 128 codes of ASCII unmodified. It does not reassign any of theC0 and C1 control codes. Compared toASCII, it adds 75 characters:

• 67 lowercase characters, allowing full lowercase support.
• 7 uppercase characters, allowing uppercase support for the29 base letters without tone marks.
• Thenon-breaking space.

Tone marks on uppercase vowels is accomplished in TCVN3 by switching to an all-capital font.^[8]

VSCII-2, also known as TCVN 5712-2 and VN2, is a superset of VSCII-3. It is anextended ASCII, because it keeps all 128 codes of ASCII unmodified. It does not reassign any of theC0 and C1 control codes, making it conformant withISO 2022 as a 96-set.^[2][3] Compared to VSCII-3, it adds (for a total of 96 non-ASCII characters):

• 16 more uppercase characters with pre-composed tone marks (for a total of 23 non-ASCII uppercase characters)
• 5combining diacritics fortone marks, allowing other combinations of uppercase letters and tone marks to be represented. Combining marks follow the base letter^[2] as inVNI (rather than preceding them as inANSEL).

VSCII-1, also known as TCVN 5712-1 and VN1, is an extension of VSCII-2, and is a modified ASCII, since it replaces 12 of the 33control characters with precomposed characters. Compared to VSCII-2, it (for a total of 140 non-ASCII characters):

• Adds 44 more pre-composed uppercase letters, bringing them to the same count as the lowercase
• Does this by replacing 12 ASCII control characters and allocating 32 graphical characters to the C1 control area, breaking ISO 2022 compatibility

Conversion from VSCII-3 to VSCII-2 or VSCII-1 and conversion from VSCII-2 to VSCII-1 are not necessary, but can result in smaller files.

Conversion from VSCII-1 to VSCII-2 or VSCII-3 and conversion from VSCII-2 to VSCII-3 require expansion of some pre-composed characters.

• tables with Unicode points and names

• Computer-related introductions in 1993
• 1993 establishments in Vietnam
• Vietnamese inventions
• Character sets
• Vietnamese writing systems

• Articles with short description
• Short description is different from Wikidata
• All articles with unsourced statements
• Articles with unsourced statements from July 2020