VISCII

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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, but legacy VSCII and VISCII files may need conversion.

History[edit]

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 essentially three different ways to handle this problem:

  1. Use variable-width encoding
  2. Use combining diacritical marks (as do VSCII and Windows-1258)
  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 Silicon Valley, California in 1992 while they were working with the Unicode consortium to include precomposed Vietnamese characters in the Unicode standard. It is mentioned in RFC 1456, though incorrectly dubbed "VIetnamese Standard Code for Information Interchange" (the same name taken by VSCII).

Support[edit]

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.

Character set[edit]

VISCII
_0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _A _B _C _D _E _F
0_
0
NUL
0000
SOH
0001

1EB2
ETX
0003
EOT
0004

1EB4

1EAA
BEL
0007
BS
0008
HT
0009
LF
000A
VT
000B
FF
000C
CR
000D
SO
000E
SI
000F
1_
16
DLE
0010
DC1
0011
DC2
0012
DC3
0013

1EF6
NAK
0015
SYN
0016
ETB
0017
CAN
0018

1EF8
SUB
001A
ESC
001B
FS
001C
GS
001D

1EF4
US
001F
2_
32
SP
0020
!
0021
"
0022
#
0023
$
0024
%
0025
&
0026
'
0027
(
0028
)
0029
*
002A
+
002B
,
002C
-
002D
.
002E
/
002F
3_
48
0
0030
1
0031
2
0032
3
0033
4
0034
5
0035
6
0036
7
0037
8
0038
9
0039
:
003A
;
003B
<
003C
=
003D
>
003E
?
003F
4_
64
@
0040
A
0041
B
0042
C
0043
D
0044
E
0045
F
0046
G
0047
H
0048
I
0049
J
004A
K
004B
L
004C
M
004D
N
004E
O
004F
5_
80
P
0050
Q
0051
R
0052
S
0053
T
0054
U
0055
V
0056
W
0057
X
0058
Y
0059
Z
005A
[
005B
\
005C
]
005D
^
005E
_
005F
6_
96
`
0060
a
0061
b
0062
c
0063
d
0064
e
0065
f
0066
g
0067
h
0068
i
0069
j
006A
k
006B
l
006C
m
006D
n
006E
o
006F
7_
112
p
0070
q
0071
r
0072
s
0073
t
0074
u
0075
v
0076
w
0077
x
0078
y
0079
z
007A
{
007B
|
007C
}
007D
~
007E
DEL
007F
8_
128

1EA0

1EAE

1EB0

1EB6

1EA4

1EA6

1EA8

1EAC

1EBC

1EB8

1EBE

1EC0

1EC2

1EC4

1EC6

1ED0
9_
144

1ED2

1ED4

1ED6

1ED8

1EE2

1EDA

1EDC

1EDE

1ECA

1ECE

1ECC

1EC8

1EE6
Ũ
0168

1EE4

1EF2
A_
160
Õ
00D5

1EAF

1EB1

1EB7

1EA5

1EA7

1EA9

1EAD

1EBD

1EB9
ế
1EBF

1EC1

1EC3

1EC5

1EC7

1ED1
B_
176

1ED3

1ED5

1ED7

1EE0
Ơ
01A0

1ED9

1EDD

1EDF

1ECB

1EF0

1EE8

1EEA

1EEC
ơ
01A1

1EDB
Ư
01AF
C_
192
À
00C0
Á
00C1
Â
00C2
Ã
00C3

1EA2
Ă
0102

1EB3

1EB5
È
00C8
É
00C9
Ê
00CA

1EBA
Ì
00CC
Í
00CD
Ĩ
0128

1EF3
D_
208
Đ
0110

1EE9
Ò
00D2
Ó
00D3
Ô
00D4

1EA1

1EF7

1EEB

1EED
Ù
00D9
Ú
00DA

1EF9

1EF5
Ý
00DD

1EE1
ư
01B0
E_
224
à
00E0
á
00E1
â
00E2
ã
00E3

1EA3
ă
0103

1EEF

1EAB
è
00E8
é
00E9
ê
00EA

1EBB
ì
00EC
í
00ED
ĩ
0129

1EC9
F_
240
đ
0111

1EF1
ò
00F2
ó
00F3
ô
00F4
õ
00F5

1ECF

1ECD

1EE5
ù
00F9
ú
00FA
ũ
0169

1EE7
ý
00FD

1EE3

1EEE

  Letter   Number   Punctuation   Symbol   Other   undefined

See also[edit]

References[edit]

Further reading[edit]

  • Flohr, Guido (2016) [2006]. "Locale::RecodeData::VISCII - Conversion routines for VISCII". CPAN libintl-perl. Archived from the original on 2017-01-14. Retrieved 2017-01-14.
  • https://www.math.nmsu.edu/~mleisher/Software/csets/VISCII.TXT

External links[edit]