Extended-A (08A0–08FF, 96 characters) Arabic Extended-B (0870–089F, 41 characters) Arabic Extended-C (10EC0–10EFF, 3 characters) Arabic Presentation Forms-A (FB50–FDFF, 631 characters) Arabic Presentation Forms-B (FE70–FEFF, 141 characters) Rumi Numeral Symbols (10E60–10E7F, 31 characters) Indic Siyaq Numbers (1EC70–1ECBF, 68 characters) Ottoman Siyaq Numbers (1ED00–1ED4F, 61 characters) Arabic Mathematical Alphabetic Symbols (1EE00—1EEFF, 143 characters) The basic Arabic range encodes the standard letters and diacritics but does not encode contextual forms (U+0621-U+0652 being directly based on ISO 8859-6). It also includes the most common diacritics and Arabic-Indic digits. U+06D6 to U+06ED encode Qur'anic annotation signs such as "end of ayah" ۝ۖ and "start of rub el hizb" ۞. The Arabic supplement range encodes letter variants mostly used for writing African (non-Arabic) languages. The Arabic Extended-A range encodes additional Qur'anic annotations and letter variants used for various non-Arabic languages. The Arabic Presentation Forms-A range encodes contextual forms and ligatures of letter variants needed for Persian, Urdu, Sindhi and Central Asian languages. The Arabic Presentation Forms-B range encodes spacing forms of Arabic diacritics, and more contextual letter forms. The Arabic Mathematical Alphabetical Symbols block encodes characters used in Arabic mathematical expressions. See also the notes of the section on modified letters. Keyboards Keyboards designed for different nations have different layouts, so proficiency in one style of keyboard, such as Iraq's, does not transfer to proficiency in another, such as Saudi Arabia's. Differences can include the location of non-alphabetic characters. All Arabic keyboards allow typing Roman characters, e.g., for the URL in a web browser. Thus, each Arabic keyboard has both Arabic and Roman characters marked on the keys. Usually, the Roman characters of an Arabic keyboard conform to the QWERTY layout, but in North Africa, where French is the most common language typed using the Roman characters, the Arabic keyboards are AZERTY. To encode a particular written form of a character, there are extra code points provided in Unicode which can be used to express the exact written form desired. The range Arabic presentation forms A (U+FB50 to U+FDFF) contain ligatures while the range Arabic presentation forms B (U+FE70 to U+FEFF) contains the positional variants. These effects are better achieved in Unicode by using the zero-width joiner and zero-width non-joiner, as these presentation forms are deprecated in Unicode and should generally only be used within the internals of text-rendering software; when using Unicode as an intermediate form for conversion between character encodings; or for backwards compatibility