Mapping of Unicode characters
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Unicode reserves 1,114,112 (= 220 + 216 or 17 × 216, hexadecimal 110000) code points.
As of Unicode 5.0.0, 101,063 (9.1%) of these codepoints are assigned, with another 137,468 (12.3%) reserved for private use, leaving 875,441 (78.6%) unassigned. The number of assigned code points is made up as follows:
- 98,884 graphemes
- 140 formatting characters
- 65 control characters
- 2,048 supplementary characters
The first 256 codes correspond with those of ISO 8859-1, the most popular 8-bit character encoding in the Western world. As a result, the first 128 characters are also identical to ASCII.
The Unicode code space for characters is divided into 17 planes, each with 65,536 (= 216) code points, although currently only a few planes are used:
- Plane 0 (0000–FFFF): Basic Multilingual Plane (BMP)
- Plane 1 (10000–1FFFF): Supplementary Multilingual Plane (SMP)
- Plane 2 (20000–2FFFF): Supplementary Ideographic Plane (SIP)
- Planes 3 to 13 (30000–DFFFF) are unassigned
- Plane 14 (E0000–EFFFF): Supplementary Special-purpose Plane (SSP)
- Plane 15 (F0000–FFFFF) reserved for the Private Use Area (PUA)
- Plane 16 (100000–10FFFF), reserved for the Private Use Area (PUA)
The cap of 220 code points (excluding Plane 16) exists in order to maintain compatibility with the UTF-16 encoding, which addresses only that range (see below). Currently, about ten percent of the Unicode code space is used. Furthermore, ranges of characters have been tentatively blocked out for every known unencoded script (see [1]), and while Unicode may need another plane for ideographic characters, there are ten planes available if previously unknown scripts with tens of thousands of characters are discovered. This 20 bit limit is unlikely to be reached in the near future.
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[edit] Basic Multilingual Plane
The first plane (plane 0), the Basic Multilingual Plane (BMP), is where most characters have been assigned so far. The BMP contains characters for almost all modern languages, and a large number of special characters. Most of the allocated code points in the BMP are used to encode Chinese, Japanese, and Korean (CJK) characters.
The graphic on the right is a visual roadmap to the Basic Multilingual Plane. The colours in use are:
- Black = Latin scripts and symbols
- Light Blue = Linguistic scripts
- Blue = Other European scripts
- Orange = Middle Eastern and SW Asian scripts
- Light Orange = African scripts
- Green = South Asian scripts
- Purple = Southeast Asian scripts
- Red = East Asian scripts
- Light Red = Unified CJK Han
- Yellow = Canadian Aboriginal scripts
- Magenta = Symbols
- Dark Grey = Diacritics
- Light Grey = UTF-16 surrogates and private use
- Cyan = Miscellaneous characters
- White = Unused
As of Unicode 5.0, The BMP includes the following scripts:
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[edit] Future additions
Several scripts are expected to be included in the BMP in the next revision of Unicode. These scripts, and their proposed code point ranges, are the following:
- Cham (18B0–18FF)
- Lanna (Old Tai Lue) (1A80–1AEF)
- Santali (Ol Cemet' / Ol Chiki) (2DE0–2DFF)
- Vai (A500–A61F)
- Saurashtra (AB00–AB5F)
Several other scripts are proposed for inclusion in the BMP, including:
- Avestan (0800–083F)
- Pahlavi (0840–087F)
- Batak (1A20–1A5F)
- Meitei Mayek / Meitei (1C80–1CDF)
- Varang Kshiti (AA00–AA3F)
- Sorang Sompeng (AA40–AA6F)
[edit] Supplementary Multilingual Plane
Plane 1, the Supplementary Multilingual Plane (SMP), is mostly used for historic scripts such as Linear B, but is also used for musical and mathematical symbols.
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As of Unicode 5.0, Plane One includes the following scripts:
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Many other scripts are proposed for inclusion in Plane One, including: |
[edit] Private Use Area
A Private Use Area (PUA) is one of several ranges which are reserved for private use. For this range, the Unicode standard does not specify any characters.
The Basic Multilingual Plane includes a PUA in the range from U+E000 to U+F8FF (57344–63743). Plane Fifteen (U+F0000 to U+FFFFF), and Plane Sixteen (U+100000 to 10FFFF) are completely reserved for private use as well.
The use of the PUA was a concept inherited from certain Asian encoding systems. These systems had private use areas to encode Japanese Gaiji (rare personal name characters) in application-specific ways. Similarly the ConScript Unicode Registry aims to coordinate the mapping of scripts not yet encoded in or rejected by Unicode in the PUAs. The Medieval Unicode Font Initiative uses the PUA to encode various ligatures, precomposed characters, and symbols found in medieval texts.
One example of usage of the Private Use Area is Apple Computer's usage of U+F8FF for the Apple logo.
[edit] Other planes
Plane 2, the Supplementary Ideographic Plane (SIP), is used for about 40,000 rare Chinese characters that are mostly historic, although there are some modern ones. Plane 14 (E in hexadecimal), the Supplementary Special-purpose Plane (SSP), currently contains some non-recommended language tag characters and some variation selection characters.
