Character Encodings and Internet Names

This document provides information on character encodings and the Internet. It discusses the Internet Assigned Numbers Authority (IANA) registry, Internet names used for similar character encodings that could lead to confusion, and provides a list of common Internet names for character encodings along with their availability in the Mac OS.

Identifying Character Encodings on the Internet

In many Internet protocols, a charset parameter may be used in certain contexts to specify both a character set and a character encoding scheme. The value of the charset parameter is a case-insensitive string limited to the characters A–Z, a–z, 0–9, hyphen–minus, underscore, period, and colon. The character encoding names specified for this parameter are generally expressed in US–ASCII octet values.

The character encoding name may be an experimental name beginning with x-; if it is not an experimental name, it must be a name registered with the Internet Assigned Numbers Authority (IANA) that corresponds to a character encoding that has a formal specification. Multiple names exist for most character encodings in the registry. Note that the IANA registry is updated periodically. Table A-1 identifies character encodings for various languages, gives some of their common Internet names, and tells when the character encoding was first supported for the Text Encoding Converter and the Unicode Converter. To preview the style of character set name used on the Internet, here are a few sample names:

ISO-8859-1 latin1 UNICODE-1-1-UTF-7 Shift_JIS X-EUC-CN

Many of the character encodings in use on the Internet are not registered with IANA and do not have official Internet names, although they may have names that have become de facto standards. Moreover, even when an encoding is registered, the name specified by IANA may not be the one that is actually used on the Internet. For example, EUC-JP has been registered for some time with the unwieldy name Extended_UNIX_Code_Packed_Format_for_Japanese, but the name actually used is the unofficial X-EUC-JP. Another example, Shift_JIS,is the official name, but the names commonly used in its stead are x-shift-jis and x-sjis. In many cases, mail and browser software recognizes only the unofficial names, not the official ones.

In some cases, the names for unregistered encodings follow a pattern established by other, registered encodings. For example, some IBM/Microsoft code pages are registered with names consisting of cp followed by the code page number: cp437, cp850, cp852. Code page 874 is not registered, but the name cp874 would be expected. Most Windows code pages are registered using the form used in these examples: windows-1250, windows-1251. Windows Latin-1 is, oddly enough, not registered as either windows-1252 or cp1252, although both forms are in use.

Character Encodings Masquerading as Related Encodings

Some Internet names used for similar character encodings could lead to confusion. For example, the Windows Latin-1 character encoding is commonly labeled ISO-8859-1 on the Internet because it is a superset of ISO 8859-1. Clients that actually treat it as ISO 8859-1 may be confused by the extra characters in the C1 area.

The Mac OS Roman character set used for Western European languages was created several years before ISO 8859-1. It does not have exactly the same repertoire, and many of the characters it does share with ISO 8859-1 have different code points. Many Mac OS Internet applications use an encoding developed by André Pirard in which the Mac OS Roman repertoire is assigned new code points to align as much as possible with ISO 8859-1; this character encoding is referred to as Mac Latin-1 or Mac Mail and is usually labeled as ISO-8859-1 on the Internet.

Character Encodings and Their Internet Names

Table A-1 lists character encodings for various languages, gives some of their common Internet names, and identifies the version of the Text Encoding Conversion Manager for which character encoding was first supported for use by the Text Encoding Converter and the Unicode Converter. In the last two columns of the table, “N/A” means that the encoding is not supported.

Table A-1  Character encoding Internet names and availability in Mac OS

Character encoding

Common Internet names

Related information

Version of Text Encoding Conversion Manager that first offered support in:

Text Encoding Converter

Unicode Converter

Universal

Unicode 2.0 (16 bit)

UTF-16

1.2

1.2

Unicode 2.0 UTF-8

UTF-8

1.2

1.2.1

Unicode 2.0 UTF-7

UTF-7

1.2

N/A

Unicode 1.1 (16-bit)

UNICODE 1-1

1.2

1.2

Unicode 1.1 UTF-8

UNICODE-1-1-UTF-8

1.2

1.2.1

Unicode 1.1 UTF-7

UNICODE-1-1-UTF-7

1.2

N/A

Western European languages

ASCII

US-ASCII

1.2.1

1.2.1

ISO 8859-1 (Latin-1)

ISO-8859-1, latin1

1.2.1

1.2.1

ISO 8859-3 (Latin 3)

ISO-8859-3 , latin3

1.5

1.5

ISO-8859-15 (Latin 9)

ISO-8859-15, latin9

Latin-1 with EURO SIGN and CP 1252 letters

1.5

1.5

CP 1252 (Windows Latin-1)

windows-1252, cp1252

ISO 8859-1, plus additions in C1 area

1.2

1.2

CP 437 (DOS Latin-US)

cp437

1.2

1.2

CP 850 (DOS Latin-1)

cp850

1.4

1.4

Mac OS Roman

mac, macintosh, x-mac-roman

1.2

1.2

Mac OS Icelandic

x-mac-icelandic

based on Mac OS Roman

1.2

1.2

Mac OS Latin-1, Mac OS Mail

x-mac-latin1 (commonly sent as ISO-8859-1)

Mac OS Roman permuted to align with 8859-1

1.2

1.2

NextStep Latin

1.2

1.2

CP 037 (EBCDIC-US)

cp037

ISO 8859-1 repertoire, different layout

1.2.1

1.2.1

Arabic

ISO 8859-6 (Latin/Arabic)

ISO-8859-6, arabic

1.2

1.2

CP 1256 (Windows Arabic)

windows-1256, cp1256

Partly 8859-6, plus C1 additions

1.2

1.2

CP 864 (DOS Arabic)

cp864

Encodes Arabic presentation forms

1.2

1.2

Mac OS Arabic

x-mac-arabic

1.2

1.2

Mac OS Farsi

x-mac-farsi

1.2

1.2

Central European languages

ISO 8859-2 (Latin-2)

ISO-8859-2, latin2

1.2

1.2

ISO 8859-4 (Latin-4)

ISO-8859-4, latin4

1.5

1.5

CP 1250 (Windows Latin-2)

windows-1250, cp 1250

Partly 8859-2, plus C1 additions

1.2

1.2

CP 1257 (Windows BalticRim)

windows-1257,cp 1257

1.5

1.5

Mac OS Central European Roman

x-mac-centraleurroman

1.2

1.2

Mac OS Croatian

x-mac-croatian

Based on Mac OS Roman

1.2

1.2

Mac OS Romanian

x-mac-romanian

Based on Mac OS Roman

1.2

1.2

Chinese

GB 2312-80

1.2

N/A

EUC-CN

GB2312, X-EUC-CN

ASCII + GB 2312- 80 (8-bit)

1.2

1.2

CP 936 (DOS and Windows Simplified)

Similar to GBK

1.4

1.4

Mac OS Chinese Simplified

Based on EUC-CN

1.2

1.2

ISO 2022-CN ("GB")

ISO-2022-CN

ASCII + GB 2312-80 (7-bit) (see RFC1922)

1.2

N/A

HZ

HZ-GB-2312

ASCII + GB 2312-80 (7-bit) (see RFC1842);

1.2

N/A

GBK (extended GB)

EUC-CN + Unihan repertoire (8-bit)

1.2

1.2

CNS 11643 plane 1

x-cns11643-1

N/A

N/A

CNS 11643 plane 2

x-cns11643-2

N/A

N/A

EUC-TW

X-EUC-TW

ASCII + CNS 11643-1992 (8-bit)

1.2

1.2

Big-5

Big5

(8-bit)

1.2

1.2

CP 950 (DOS and Windows Traditional)

Based on Big-5

1.4

1.4

Mac OS Chinese Traditional

Based on Big-5

1.2

1.2

CCCII

N/A

N/A

EACC

N/A

N/A

Cyrillic

ISO 8859-5 (Latin/Cyrillic)

ISO-8859-5, cyrillic

1.2

1.2

KOI8-R

KOI8-R

See Rfc 1489

1.2

1.2

CP 1251 (Windows Cyrillic)

windows-1251, cp1251

Not based on ISO 8859-5

1.2

1.2

CP 866 (DOS Russian)

cp866

N/A

N/A

Mac OS Cyrillic

x-mac-cyrillic

1.2

1.2

Mac OS Ukrainian

x-mac-ukrainian

Mac OS Cyrillic with two replacements

1.2

1.2

Greek

ISO 8859-7

ISO-8859-7, greek

1.2

1.2

ISO 5428

ISO_5428:1980

N/A

N/A

CP 1253 (Windows Greek)

windows-1253, cp1253

Nearly 8859-7, plus C1 additions

1.2

1.2

Mac OS Greek

x-mac-greek

1.2

1.2

Greek CCITT

greek-ccitt

N/A

N/A

Hebrew

ISO 8859-8 (Latin/Hebrew)

ISO-8859-8, hebrew

1.2

1.2

CP 1255 (Windows Hebrew)

windows-1255,cp1255

Mostly 8859-8, plus C1 additions

1.2

1.2

Mac OS Hebrew (2 variants)

x-mac-hebrew

1.2

1.2

Indic

ISCII-91

Parallel encodings for all Indic scripts

N/A

N/A

Mac OS Gujarati

1.2

1.2

Mac OS Devanagari

1.2

1.2

Mac OS Gurmukhi

1.2

1.2

Japanese

JIS X0208

1.2

N/A

JIS X0212

N/A

N/A

EUC-JP

EUC-JP, X-EUC-JP

JIS 201 + JIS 208 + JIS 212 (8-bit)

1.2

1.4

ISO 2022-JP ("JIS")

ISO-2022-JP

JIS 201 + JIS 208 + JIS 212 (7-bit); Rfc 1468

1.2

N/A

Shift-JIS

Shift_JIS, x-sjis, x-shift-jis

JIS 201 + JIS 208 (8-bit)

1.2

1.2

CP 932 (DOS + Windows)

Based on Shift-JIS

1.4

1.4

Mac OS Japanese

Based on Shift-JIS

1.2

1.2

Korean

KSC 5601-1987

1.2

N/A

EUC-KR

EUC-KR

ASCII + KSC 5601-87 (8-bit); Rfc 1557

1.2

1.2

CP 949 (DOS + Windows)

Unified Hangul Code: EUC-KR + Johab

N/A

N/A

Mac OS Korean

Based on EUC-KR

1.2

1.2

ISO 2022-KR ("KSC")

ISO-2022-KR

ASCII + KSC 5601-87 (7-bit): Rfc 1557

1.2

N/A

KSC 5700

N/A

N/A

Symbols encoding

Adobe Symbol

Adobe-Symbol-Encoding

N/A

N/A

Mac OS Symbol

x-mac-symbol

Based on Adobe Symbol

1.2

1.2

Mac OS dingbats

x-mac-dingbats

Based on Adobe Zapf Dingbats

1.2

1.2

Thai

TIS 620-2533

N/A

N/A

CP 874 (DOS + Windows)

cp874

Based on TIS 620-2533

1.4

1.4

Mac OS Thai

x-mac-thai

Based on TIS 620-2533

1.2

1.2

Turkish

ISO 8859-9 (Latin-5)

ISO-8859, latin5

1.2

1.2

ISO 8859-3 (Latin-3)

ISO-8859-3

N/A

N/A

CP 1254 (Windows Latin-5)

windows-1254, cp1254

1.2

1.2

Mac OS Turkish

x-mac-turkish

Based on Mac OS Roman

1.2

1.2

Vietnamese

VISCII

VISCII

Rfc 1456

N/A

N/A

TCVN-n

N/A

N/A

CP 1258 (Windows Vietnamese)

windows-1258, cp1258

1.5

1.5



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