Windows code page

Windows code pages are sets of characters or code pages (known as character encodings in other operating systems) used in Microsoft Windows from the 1980s and 1990s. Windows code pages were gradually superseded when Unicode was implemented in Windows, although they are still supported both within Windows and other platforms, and still apply when Alt code shortcuts are used.

There are two groups of system code pages in Windows systems: OEM and Windows-native ("ANSI") code pages. (ANSI is the American National Standards Institute.) Code pages in both of these groups are extended ASCII code pages. Additional code pages are supported by standard Windows conversion routines, but not used as either type of system code page.

ANSI code page
Windows-125x series
Alias(es)ANSI (misnomer)
StandardWHATWG Encoding Standard
ExtendsUS-ASCII
Preceded byISO 8859
Succeeded byUnicode
UTF-16 (in Win32 API)

ANSI code pages (officially called "Windows code pages" [1] after Microsoft accepted the former term being a misnomer [2]) are used for native non-Unicode (say, byte oriented) applications using a graphical user interface on Windows systems. The term "ANSI" is a misnomer because these Windows code pages do not comply with any ANSI (American National Standards Institute) standard; code page 1252 was based on an early ANSI draft that became the international standard ISO 8859-1, [2] which adds a further 32 control codes and space for 96 printable characters. Among other differences, Windows code-pages allocate printable characters to the supplementary control code space, making them at best illegible to standards-compliant operating systems.)

Most legacy "ANSI" code pages have code page numbers in the pattern 125x. However, 874 (Thai) and the East Asian multi-byte "ANSI" code pages (932, 936, 949, 950), all of which are also used as OEM code pages, are numbered to match IBM encodings, none of which are identical to the Windows encodings (although most are similar). While code page 1258 is also used as an OEM code page, it is original to Microsoft rather than an extension to an existing encoding. IBM have assigned their own, different numbers for Microsoft's variants, these are given for reference in the lists below where applicable.

All of the 125x Windows code pages, as well as 874 and 936, are labelled by Internet Assigned Numbers Authority (IANA) as "Windows-number", although "Windows-936" is treated as a synonym for "GBK". Windows code page 932 is instead labelled as "Windows-31J".[3]

ANSI Windows code pages, and especially the code page 1252, were so called since they were purportedly based on drafts submitted or intended for ANSI. However, ANSI and ISO have not standardized any of these code pages. Instead they are either:[2]

Microsoft assigned about twelve of the typography and business characters (including notably, the euro sign, €) in CP1252 to the code points 0x80–0x9F that, in ISO 8859, are assigned to C1 control codes. These assignments are also present in many other ANSI/Windows code pages at the same code-points. Windows did not use the C1 control codes, so this decision had no direct effect on Windows users. However, if included in a file transferred to a standards-compliant platform like Unix or MacOS, the information was invisible and potentially disruptive.

OEM code page

The OEM code pages (original equipment manufacturer) are used by Win32 console applications, and by virtual DOS, and can be considered a holdover from DOS and the original IBM PC architecture. A separate suite of code pages was implemented not only due to compatibility, but also because the fonts of VGA (and descendant) hardware suggest encoding of line-drawing characters to be compatible with code page 437. Most OEM code pages share many code points, particularly for non-letter characters, with the second (non-ASCII) half of CP437.

A typical OEM code page, in its second half, does not resemble any ANSI/Windows code page even roughly. Nevertheless, two single-byte, fixed-width code pages (874 for Thai and 1258 for Vietnamese) and four multibyte CJK code pages (932, 936, 949, 950) are used as both OEM and ANSI code pages. Code page 1258 uses combining diacritics, as Vietnamese requires more than 128 letter-diacritic combinations. This is in contrast to VISCII, which replaces some of the C0 (i.e. ASCII) control codes.

History

Initially, computer systems and system programming languages did not make a distinction between characters and bytes: for the segmental scripts used in most of Africa, the Americas, southern and south-east Asia, the Middle East and Europe, a character needs just one byte, but two or more bytes are needed for the ideographic sets used in the rest of the world. This subsequently led to much confusion. Microsoft software and systems prior to the Windows NT line are examples of this, because they use the OEM and ANSI code pages that do not make the distinction.

Since the late 1990s, software and systems have adopted Unicode as their preferred storage format; this trend has been improved by the widespread adoption of XML which default to UTF-8 but also provides a mechanism for labelling the encoding used.[4] All current Microsoft products and application program interfaces use Unicode internally, but some applications continue to use the default encoding of the computer's 'locale' when reading and writing text data to files or standard output. Therefore, files may still be encountered that are legible and intelligible in one part of the world but unintelligible mojibake in another.

UTF-8, UTF-16

Microsoft adopted a Unicode encoding (first the now-obsolete UCS-2, which was then Unicode's only encoding), i.e. UTF-16 for all its operating systems from Windows NT onwards, but additionally supports UTF-8 (aka CP_UTF8) since Windows 10 version 1803.[5] UTF-16 uniquely encodes all Unicode characters in the Basic Multilingual Plane (BMP) using 16 bits but the remaining Unicode (e.g. emojis) is encoded with a 32-bit (four byte) code – while the rest of the industry (Unix-like systems and the web), and now Microsoft chose UTF-8 (which uses one byte for the 7-bit ASCII character set, two or three bytes for other characters in the BMP, and four bytes for the remainder).

List

The following Windows code pages exist:

Windows-125x series

These nine code pages are all extended ASCII 8-bit SBCS encodings, and were designed by Microsoft for use as ANSI codepages on Windows. They are commonly known by their IANA-registered[6] names as windows-<number>, but are also sometimes called cp<number>, "cp" for "code page". They are all used as ANSI code pages; Windows-1258 is also used as an OEM code page.

The Windows-125x series includes nine of the ANSI code pages, and mostly covers scripts from Europe and West Asia with the addition of Vietnam. System encodings for Thai and for East Asian languages were numbered to match similar IBM code pages and are used as both ANSI and OEM code pages; these are covered in following sections.

IDDescriptionRelationship to ISO 8859 or other established encodings
1250[7][8]Latin 2 / Central EuropeanSimilar to ISO-8859-2 but moves several characters, including multiple letters.
1251[9][10]CyrillicIncompatible with both ISO-8859-5 and KOI-8.
1252[11][12]Latin 1 / Western EuropeanSuperset of ISO-8859-1 (without C1 controls). Letter repertoire accordingly similar to CP850.
1253[13][14]GreekSimilar to ISO 8859-7 but moves several characters, including a letter.
1254[15][16]TurkishSuperset of ISO 8859-9 (without C1 controls).
1255[17][18]HebrewAlmost a superset of ISO 8859-8, but with two incompatible punctuation changes.
1256[19][20]ArabicNot compatible with ISO 8859-6; rather, OEM Code page 708 is an ISO 8859-6 (ASMO 708) superset.
1257[21][22]BalticNot ISO 8859-4; the later ISO 8859-13 is closely related, but with some differences in available punctuation.
1258[23][24]Vietnamese (also OEM)Not related to VSCII or VISCII, uses fewer base characters with combining diacritics.

DOS code pages

These are also ASCII-based. Most of these are included for use as OEM code pages; code page 874 is also used as an ANSI code page.

  • 437 – IBM PC US, 8-bit SBCS extended ASCII.[25] Known as OEM-US, the encoding of the primary built-in font of VGA graphics cards.
  • 708 – Arabic, extended ISO 8859-6 (ASMO 708)
  • 720 – Arabic, retaining box drawing characters in their usual locations
  • 737 – "MS-DOS Greek". Retains all box drawing characters. More popular than 869.
  • 775 – "MS-DOS Baltic Rim"
  • 850 – "MS-DOS Latin 1". Full (re-arranged) repertoire of ISO 8859-1.
  • 852 – "MS-DOS Latin 2"
  • 855 – "MS-DOS Cyrillic". Mainly used for South Slavic languages. Includes (re-arranged) repertoire of ISO-8859-5. Not to be confused with cp866.
  • 857 – "MS-DOS Turkish"
  • 858 – Western European with euro sign
  • 860 – "MS-DOS Portuguese"
  • 861 – "MS-DOS Icelandic"
  • 862 – "MS-DOS Hebrew"
  • 863 – "MS-DOS French Canada"
  • 864 – Arabic
  • 865 – "MS-DOS Nordic"
  • 866 – "MS-DOS Cyrillic Russian", cp866. Sole purely OEM code page (rather than ANSI or both) included as a legacy encoding in WHATWG Encoding Standard for HTML5.
  • 869 – "MS-DOS Greek 2", IBM869. Full (re-arranged) repertoire of ISO 8859-7.
  • 874 – Thai, also used as the ANSI code page, extends ISO 8859-11 (and therefore TIS-620) with a few additional characters from Windows-1252. Corresponds to IBM code page 1162 (IBM-874 is similar but has different extensions).

East Asian multi-byte code pages

These often differ from the IBM code pages of the same number: code pages 932, 949 and 950 only partly match the IBM code pages of the same number, while the number 936 was used by IBM for another Simplified Chinese encoding which is now deprecated and Windows-951, as part of a kludge, is unrelated to IBM-951. IBM equivalent code pages are given in the second column. Code pages 932, 936, 949 and 950/951 are used as both ANSI and OEM code pages on the locales in question.

IDLanguageEncodingIBM EquivalentDifference from IBM CCSID of same numberUse
932JapaneseShift JIS (Microsoft variant)943[26]IBM-932 is also Shift JIS, has fewer extensions (but those extensions it has are in common), and swaps some variant Chinese characters (itaiji) for interoperability with earlier editions of JIS C 6226.ANSI/OEM (Japan)
936Chinese (simplified)GBK1386IBM-936 is a different Simplified Chinese encoding with a different encoding method, which has been deprecated since 1993.ANSI/OEM (PRC, Singapore)
949KoreanUnified Hangul Code1363IBM-949 is also an EUC-KR superset, but with different (colliding) extensions.ANSI/OEM (Republic of Korea)
950Chinese (traditional)Big5 (Microsoft variant)1373[27]IBM-950 is also Big5, but includes a different subset of the ETEN extensions, adds further extensions with an expanded trail byte range, and lacks the Euro.ANSI/OEM (Taiwan, Hong Kong)
951Chinese (traditional) including CantoneseBig5-HKSCS (2001 ed.)5471[28]IBM-951 is the double-byte plane from IBM-949 (see above), and unrelated to Microsoft's internal use of the number 951.ANSI/OEM (Hong Kong, 98/NT4/2000/XP with HKSCS patch)

A few further multiple-byte code pages are supported for decoding or encoding using operating system libraries, but not used as either sort of system encoding in any locale.

IDIBM EquivalentLanguageEncodingUse
1361-KoreanJohab (KS C 5601-1992 annex 3)Conversion
20000-Chinese (traditional)An encoding of CNS 11643Conversion
20001-Chinese (traditional)TCAConversion
20002-Chinese (traditional)Big5 (ETEN variant)Conversion
20003938Chinese (traditional)IBM 5550Conversion
20004-Chinese (traditional)TeletextConversion
20005-Chinese (traditional)WangConversion
20932954 (roughly)JapaneseEUC-JPConversion
209365479Chinese (simplified)GB 2312Conversion
20949, 51949970KoreanWansung (8-bit with ASCII, i.e. EUC-KR)[29]Conversion

EBCDIC code pages
  • 37 – IBM EBCDIC US-Canada, 8-bit SBCS[30]
  • 500 – Latin 1
  • 870 – IBM870
  • 875 – cp875
  • 1026 – EBCDIC Turkish
  • 1047 – IBM01047 – Latin 1
  • 1140 – IBM01141
  • 1141 – IBM01141
  • 1142 – IBM01142
  • 1143 – IBM01143
  • 1144 – IBM01144
  • 1145 – IBM01145
  • 1146 – IBM01146
  • 1147 – IBM01147
  • 1148 – IBM01148
  • 1149 – IBM01149
  • 20273 – EBCDIC Germany
  • 20277 – EBCDIC Denmark/Norway
  • 20278 – EBCDIC Finland/Sweden
  • 20280 – EBCDIC Italy
  • 20284 – EBCDIC Latin America/Spain
  • 20285 – EBCDIC United Kingdom
  • 20290 – EBCDIC Japanese
  • 20297 – EBCDIC France
  • 20420 – EBCDIC Arabic
  • 20423 – EBCDIC Greek
  • 20424 – x-EBCDIC-KoreanExtended
  • 20833 – Korean
  • 20838 – EBCDIC Thai
  • 20924 – IBM00924 – IBM EBCDIC Latin 1/Open System (1047 + Euro symbol)
  • 20871 – EBCDIC Icelandic
  • 20880 – EBCDIC Cyrillic
  • 20905 – EBCDIC Turkish
  • 21025 – EBCDIC Cyrillic
  • 21027 – Japanese EBCDIC (incomplete,[31] deprecated)[32]

Macintosh compatibility code pages
  • 10000 – Apple Macintosh Roman
  • 10001 – Apple Macintosh Japanese
  • 10002 – Apple Macintosh Chinese (traditional) (BIG-5)
  • 10003 – Apple Macintosh Korean
  • 10004 – Apple Macintosh Arabic
  • 10005 – Apple Macintosh Hebrew
  • 10006 – Apple Macintosh Greek
  • 10007 – Apple Macintosh Cyrillic
  • 10008 – Apple Macintosh Chinese (simplified) (GB 2312)
  • 10010 – Apple Macintosh Romanian
  • 10017 – Apple Macintosh Ukrainian
  • 10021 – Apple Macintosh Thai
  • 10029 – Apple Macintosh Roman II / Central Europe
  • 10079 – Apple Macintosh Icelandic
  • 10081 – Apple Macintosh Turkish
  • 10082 – Apple Macintosh Croatian

ISO 8859 code pages

ITU-T code pages

KOI8 code pages

Problems arising from the use of code pages

Microsoft strongly recommends using Unicode in modern applications, but many applications or data files still depend on the legacy code pages.

  • Programs need to know what code page to use in order to display the contents of (pre-Unicode) files correctly. If a program uses the wrong code page it may show text as mojibake.
  • The code page in use may differ between machines, so (pre-Unicode) files created on one machine may be unreadable on another.
  • Data is often improperly tagged with the code page, or not tagged at all, making determination of the correct code page to read the data difficult.
  • These Microsoft code pages differ to various degrees from some of the standards and other vendors' implementations. This isn't a Microsoft issue per se, as it happens to all vendors, but the lack of consistency makes interoperability with other systems unreliable in some cases.
  • The use of code pages limits the set of characters that may be used.
  • Characters expressed in an unsupported code page may be converted to question marks (?) or other replacement characters, or to a simpler version (such as removing accents from a letter). In either case, the original character may be lost.

See also
  • AppLocale – a utility to run non-Unicode (code page-based) applications in a locale of the user's choice.

References
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