all two-dot diacritics, irrespective of the actual term used for the language in question.) In addition, many more symbols may be composed using the combining character facility, , that may be used with any letter or other diacritic to create a customised symbol but this does not mean that the result has any real-world application. Both the combining character and the pre-composed codepoints may be regarded as an umlaut or a diaeresis according to context. Compound diacritics are possible, for example , used as a tonal marks for Hanyu Pinyin, which uses both a two dots diacritic with a caron diacritic. Conversely, when the letter to be accented is an , the diacritic replaces the tittle, thus: . Sometimes, there's a need to distinguish between the umlaut sign and the diaeresis sign. For instance, either may appear in a German name. ISO/IEC JTC 1/SC 2/WG 2 recommends the following for these cases: To represent the umlaut use the Combining Diaeresis (U+0308) To represent the diaeresis use Combining Grapheme Joiner (CGJ, U+034F) + Combining Diaeresis (U+0308) The same advice can be found in the official Unicode FAQ. Since version 3.2.0, Unicode also provides which can produce the older umlaut typography. Unicode provides a combining double dot below as . Finally, for use with the N'Ko script, there is . In ASCII, ISO/IEC 646 and ISO 8859 ASCII, a seven-bit code with just 95 "printable" characters, has no provision for any kind of dot diacritic. Subsequent standardisation treated ASCII as the US national variant of ISO/IEC 646: the French, German and other national variants reassigned a few code points to specific vowels with diacritics, as precomposed characters. The subsequent (eight bit) ISO 8859-1 character encoding includes the letters ä, ë, ï, ö, ü, and their respective capital forms, as well as ÿ in lower case only, with Ÿ added in the revised edition ISO 8859-15 and Windows-1252. These standards are technically obsolete, having been replaced by Unicode. Computer usage Character encoding generally treats the umlaut and the diaeresis as the same diacritic mark. Unicode refers to both as diareses without making any distinction, although the term itself has a more precise literary meaning. For example, represents both a-umlaut and a-diaeresis, while similar codes are used to represent all such cases. Keyboard input If letters with double dots are not present on the keyboard (or if they are not recognized by the operating