ISO 646 is an ISO standard that specifies a 7 bit character code from which several national standards are derived, the best known of which is ASCII. Since the portion of ISO 646 shared by all countries specified only the letters used in the English alphabet, other countries using the Latin alphabet with extensions needed to create national variants of ISO 646 to be able to use their native languages. Since universal acceptance of the 8 bit byte did not exist at that time, the national characters had to be made fit within the constraints of 7 bits, meaning that some characters that appear in ASCII do not appear in other national variants of ISO 646.
The specifics of the changes for some of these variants are given in this table:
Binary
Decimal
Hex
ASCII
DE
DK/NO
GB
HU
JP
MT
SE
YU
0010 0011
35
23
#
#
#
£
#
#
#
#
#
0010 0100
36
24
$
$
$
$
¤
$
$
¤
$
0100 0000
64
40
@
§
@
@
Á
@
@
@
Ž
0101 1011
91
5B
[
Ä
Æ
[
É
[
ġ
Ä
Š
0101 1100
92
5C
Ö
Ø
Ö
¥
ż
Ö
Đ
0101 1101
93
5D
]
Ü
Å
]
Ü
]
ħ
Å
Ć
0101 1110
94
5E
^
^
^
^
^
^
^
^
Č
0110 0000
96
60
`
`
`
`
á
`
ċ
`
ž
0111 1011
123
7B
{
ä
æ
{
é
{
Ġ
ä
š
0111 1100
124
7C
|
ö
ø
|
ö
|
Ż
ö
đ
0111 1101
125
7D
}
ü
å
}
ü
}
Ħ
å
ć
0111 1110
126
7E
~
ß
~
~
˝
‾
Ċ
~
č
Later, when 8 bit characters sets gained more acceptance, ISO 8859-1, ISO 8859-2, and ISO 8859-3 became the preferred method of coding these variants.
Variants of ASCII that are not ISO 646
There are also some 7-bit character sets that are not officially part of the ISO 646 standard. Examples include:
7-bit Greek, ELOT 927. The Greek alphabet is mapped to positions 0x61-0x71 and 0x73-0x79, on top of the Latin lowercase letters. This mapping with the high bit set is ISO 8859-7.
7-bit Cyrillic, KOI-7 or Short KOI. The Cyrillic characters are mapped to positions 0x60-0x7E, on top of the Latin lowercase letters. Superseded by the KOI-8 variants.
7-bit Hebrew, SI 960. The Hebrew alphabet is mapped to positions 0x60-0x7A, on top of the lowercase Latin letters (and grave accent for aleph). This mapping with the high bit set, i.e. with the Hebrew letters in 0xE0-0xFA, is ISO 8859-8.
7-bit Arabic, ASMO 449. The Arabic alphabet is mapped to positions 0x41-0x5A and 0x60-0x6A, on top of both uppercase and lowercase Latin letters. This mapping with the high bit set is ISO 8859-6.
External links
Zeichensatz nach ISO 646 (ASCII) (http://www.soziologie.uni-halle.de/unger/scripts/workshop_internet/ref_char_646.html) (in German)
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