Vietnamese Standard Code for Information Interchange

The Vietnamese Standard Code for Information Interchange (VISCII) is a character set comprising the Vietnamese alphabet, punctuation, and other graphemes.

A traditional extended ASCII character set adds up-to 128 characters to the ASCII set. Vietnamese requires 134 additional letter-diacritic combinations, which is six too many. There are essentially three different ways to handle this problem:

1. Use variable-width encoding
2. Use combining diacritical marks, as Windows-1258 does
3. Replace six of the basic ASCII control characters

VISCII went for the last option, replacing six of the least problematic (e.g., least likely to be recognised by an application and acted on specially) (C0 control codes STX, ENQ, ACK, DC4, EM, and RS) with six of the least-used uppercase letter-diacritic combinations. While this option may cause programs that use those control codes to malfunction when handling VISCII text, it creates fewer complications than the other two options. 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.

VISCII was designed by the Vietnamese Standardization Working Group (Viet-Std Group) based in the Silicon Valley in California in 1992 while they were working with the Unicode consortium to include precomposed Vietnamese characters in the Unicode standard.

VISCII was fully supported by the TriChlor Software Group in California, which released a lot of software packages, libraries, and fonts for MS-DOS and Windows, Unix, and Macintosh. However, it, along with other Vietnamese-specific character sets, fell out of usage after the adoption of Unicode. VISCII-compliant software is still available at many ftp sites.

Code page layout

VISCII

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_	NUL 0000 0	SOH 0001 1	Ẳ 1EB2 2	ETX 0003 3	EOT 0004 4	Ẵ 1EB4 5	Ẫ 1EAA 6	BEL 0007 7	BS 0008 8	HT 0009 9	LF 000A 10	VT 000B 11	FF 000C 12	CR 000D 13	SO 000E 14	SI 000F 15
1_	DLE 0010 16	DC1 0011 17	DC2 0012 18	DC3 0013 19	Ỷ 1EF6 20	NAK 0015 21	SYN 0016 22	ETB 0017 23	CAN 0018 24	Ỹ 1EF8 25	SUB 001A 26	ESC 001B 27	FS 001C 28	GS 001D 29	Ỵ 1EF4 30	US 001F 31
2_	SP 0020 32	! 0021 33	" 0022 34	# 0023 35	$ 0024 36	% 0025 37	& 0026 38	' 0027 39	( 0028 40	) 0029 41	* 002A 42	+ 002B 43	, 002C 44	- 002D 45	. 002E 46	/ 002F 47
3_	0 0030 48	1 0031 49	2 0032 50	3 0033 51	4 0034 52	5 0035 53	6 0036 54	7 0037 55	8 0038 56	9 0039 57	: 003A 58	; 003B 59	< 003C 60	= 003D 61	> 003E 62	? 003F 63
4_	@ 0040 64	A 0041 65	B 0042 66	C 0043 67	D 0044 68	E 0045 69	F 0046 70	G 0047 71	H 0048 72	I 0049 73	J 004A 74	K 004B 75	L 004C 76	M 004D 77	N 004E 78	O 004F 79
5_	P 0050 80	Q 0051 81	R 0052 82	S 0053 83	T 0054 84	U 0055 85	V 0056 86	W 0057 87	X 0058 88	Y 0059 89	Z 005A 90	[ 005B 91	\ 005C 92	] 005D 93	^ 005E 94	_ 005F 95
6_	` 0060 96	a 0061 97	b 0062 98	c 0063 99	d 0064 100	e 0065 101	f 0066 102	g 0067 103	h 0068 104	i 0069 105	j 006A 106	k 006B 107	l 006C 108	m 006D 109	n 006E 110	o 006F 111
7_	p 0070 112	q 0071 113	r 0072 114	s 0073 115	t 0074 116	u 0075 117	v 0076 118	w 0077 119	x 0078 120	y 0079 121	z 007A 122	{ 007B 123	| 007C 124	} 007D 125	~ 007E 126	DEL 007F 127
8_	Ạ 1EA0 128	Ắ 1EAE 129	Ằ 1EB0 130	Ặ 1EB6 131	Ấ 1EA4 132	Ầ 1EA6 133	Ẩ 1EA8 134	Ậ 1EAC 135	Ẽ 1EBC 136	Ẹ 1EB8 137	Ế 1EBE 138	Ề 1EC0 139	Ể 1EC2 140	Ễ 1EC4 141	Ệ 1EC6 142	Ố 1ED0 143
9_	Ồ 1ED2 144	Ổ 1ED4 145	Ỗ 1ED6 146	Ộ 1ED8 147	Ợ 1EE2 148	Ớ 1EDA 149	Ờ 1EDC 150	Ở 1EDE 151	Ị 1ECA 152	Ỏ 1ECE 153	Ọ 1ECC 154	Ỉ 1EC8 155	Ủ 1EE6 156	Ũ 0168 157	Ụ 1EE4 158	Ỳ 1EF2 159
A_	Õ 00D5 160	ắ 1EAF 161	ằ 1EB1 162	ặ 1EB7 163	ấ 1EA5 164	ầ 1EA7 165	ẩ 1EA9 166	ậ 1EAD 167	ẽ 1EBD 168	ẹ 1EB9 169	ế 1EBF 170	ề 1EC1 171	ể 1EC3 172	ễ 1EC5 173	ệ 1EC7 174	ố 1ED1 175
B_	ồ 1ED3 176	ổ 1ED5 177	ỗ 1ED7 178	Ỡ 1EE0 179	Ơ 01A0 180	ộ 1ED9 181	ờ 1EDD 182	ở 1EDF 183	ị 1ECB 184	Ự 1EF0 185	Ứ 1EE8 186	Ừ 1EEA 187	Ử 1EEC 188	ơ 01A1 189	ớ 1EDB 190	Ư 01AF 191
C_	À 00C0 192	Á 00C1 193	Â 00C2 194	Ã 00C3 195	Ả 1EA2 196	Ă 0102 197	ẳ 1EB3 198	ẵ 1EB5 199	È 00C8 200	É 00C9 201	Ê 00CA 202	Ẻ 1EBA 203	Ì 00CC 204	Í 00CD 205	Ĩ 0128 206	ỳ 1EF3 207
D_	Đ 0110 208	ứ 1EE9 209	Ò 00D2 210	Ó 00D3 211	Ô 00D4 212	ạ 1EA1 213	ỷ 1EF7 214	ừ 1EEB 215	ử 1EED 216	Ù 00D9 217	Ú 00DA 218	ỹ 1EF9 219	ỵ 1EF5 220	Ý 00DD 221	ỡ 1EE1 222	ư 01B0 223
E_	à 00E0 224	á 00E1 225	â 00E2 226	ã 00E3 227	ả 1EA3 228	ă 0103 229	ữ 1EEF 230	ẫ 1EAB 231	è 00E8 232	é 00E9 233	ê 00EA 234	ẻ 1EBB 235	ì 00EC 236	í 00ED 237	ĩ 0129 238	ỉ 1EC9 239
F_	đ 0111 240	ự 1EF1 241	ò 00F2 242	ó 00F3 243	ô 00F4 244	õ 00F5 245	ỏ 1ECF 246	ọ 1ECD 247	ụ 1EE5 248	ù 00F9 249	ú 00FA 250	ũ 0169 251	ủ 1EE7 252	ý 00FD 253	ợ 1EE3 254	Ữ 1EEE 255
	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F

See also

• Vietnamese Quoted-Readable (VIQR)
• ASCII
• Windows-1258

External links

• RFC 1456 - Conventions for Encoding the Vietnamese Language
• Vietnamese-Standardization Working Group based in California
• Viet-Std Report 1992
• AnGiang Software
• VISCII-compliant software and fonts for MS-DOS and Windows
• VISCII-compliant software, libraries, and fonts for Unix
• WinVNKey, Vietnamese keyboard driver for Windows supporting multinational character sets, including VISCII
• MacVNKey, VISCII-compliant keyboard driver for Macintosh classic