unicodearabicnumber-systems

In Unicode, why are there two representations for the Arabic digits?

I was reading the specification of Unicode @ Wikipedia (Arabic Unicode) and I see that each of the Arabic digits has 2 Unicode code points. For example 1 is defined as U+0661 and as U+06F1.

Which one should I use?

Solution

  • According to the code charts, U+0660 .. U+0669 are ARABIC-INDIC DIGIT values 0 through 9, while U+06F0 .. U+06F9 are EXTENDED ARABIC-INDIC DIGIT values 0 through 9.

    In the Unicode 3.0 book (5.2 is the current version, but these things don't change much once set), the U+066n series of glyphs are marked 'Arabic-Indic digits' and the U+06Fn series of glyphs are marked 'Eastern Arabic-Indic digits (Persian and Urdu)'. Together, they are called Eastern Arabic numerals. It also notes:

    Here is a comparison (enlarged to see better):

    U+066n: ٠١٢٣٤٥٦٧٨٩

    U+06Fn: ۰۱۲۳۴۵۶۷۸۹

    Or:

         U+066n    U+06Fn
0      ٠         ۰
1      ١         ۱
2      ٢         ۲
3      ٣         ۳
4      ٤         ۴
5      ٥         ۵
6      ٦         ۶
7      ٧         ۷
8      ٨         ۸
9      ٩         ۹

    (Whether you can see any of those, and how clearly they are differentiated may depend on your browser and the fonts installed on your machine as much as anything else. I can see the difference on 4, 5, and 6 clearly.)

    Based on this information, if you are working with Arabic from the Middle East, use the U+066n series of digits; if you are working with Persian or Urdu, use the U+06Fn series of digits. As a Unicode application, you should accept either set of codes as valid digits (but you might look askance at a sequence that mixed the two sets of digits - or you might just leave well alone).