Dotted and dotless I in computing

Dotted İ i and dotless I ı are distinct letters in the Latin alphabets of a number of Turkic languages including Turkish, Azerbaijani, and Kazakh, unlike English and most languages using the Latin script, where the capital letter I is dotless (I) while the lowercase letter I has a dot on it (i). They are also used by the common Turkic Alphabet:

• Dotless I, I ı, usually denotes the close back unrounded vowel sound (/ɯ/). Neither the upper nor the lower case version has a dot.
• Dotted İ, İ i, usually denotes the close front unrounded vowel sound (/i/). Both the upper and lower case versions have a dot.

Examples:

• İstanbul /isˈtanbuɫ/ is the Turkish spelling for Istanbul. It starts with an i sound in standard dialect of Turkish, not an ı.
• Diyarbakır /diˈjaɾbakɯɾ/ is the Turkish spelling for Diyarbakir. In Turkish the first and last vowels are spelled and pronounced differently.
• Bakı /bɑˈcɯ/ is the Azerbaijani spelling for Baku.

In contrast, the letter j never has this distinction in these languages, sometimes with a dot in the lower case character: J j, but the dotless j does exist in Unicode: ȷ. That letter is sometimes used in mathematics with a combining hat to indicate a unit vector.