ISO 646
ISO/CEI 646 (ICS n°35.040) is a standard ISO which specifies graphic codes of natures coded on 7 bits from which several national standards are derived. Most known of them is the American alternative, commonly (but improperly) indicated “ASCII”. The ISO 646 is also indicated like the “international Alphabet of reference n°5” (AIR5), “international Alphabet n°5” (AI5) or (in English) “ International Alphabet No 5 ” (IA5).
General information
Since that the portion of ISO/CEI 646 divided by all the countries is made up only of the basic letters of the alphabet Latin sufficient for modern English, the other languages using a wider Latin alphabet needed to create extensions and national alternatives of the ISO 646 with an aim of using the letters specific to their languages.At the time, the universal recognition of a Octet of 8 bit did not exist; also, the national character sets create through this constraint of 128 characters (27 = 128) could not always include all the ASCII characters which did not appear in the national alternatives.
The ISO 646 thus standardizes the national alternatives authorized for the European plays in Latin matters, making it possible to create a set of 94 graphic characters (numbered from 33 to 126) including/understanding 80 characters invariants between all the national versions, and 12 positions usable for the characters (alphabetical or not) necessary to a language or a group of languages. It also fixes an international alphabet of reference (IRV) being used as guide (not requirement) for the placement from the 1 to 12 characters selected out of the 12 positions alternatives.
The plays incomplete ISO 646 are authorized (however the majority of the approved plays and registered voters in register ISO-IR supplement the free positions by the characters of the play of reference (similar to the play retained for the standard American, but restricted with only the 94 graphic positions of the beach of code G0 defined by the standard of coding ISO 2022 with which the standard ISO 646 is completely compatible).
Later, when the character sets made up of 8 bits became more frequent, the standard ISO 8859 was then preferred with these national alternatives of the Latin play coded on 7 bits, by imposing the choice of the alternative ISO 646/IRV (i.e. graphic set with 94 elements recorded under number ISO-IR/002) improperly called ASCII (which indicates in fact the American Latin character set coded on 7 bits, supplemented character set of controls ISO 646/C0 (ISO-IR/001) for the first 32 positions). However, the wider development of character sets (on 8 bits, and sometimes with multiple plans of codes for each block of 32,94 or 96 codes) was based on the standard ISO 2022 making it possible to make them compatible with a coding on 7 bits, thanks to a system of and certain standardized control character escape sequences.
The standards ISO 646 and ISO 8859 are in theory fixed since June 2004 (the international standardization of new handsets with 7 and 8 bits from now on is stopped, the work group of the ISO having suspended its activities) and are intended to be replaced by the new more complete and more precise standard ISO/CEI 10646 (related to Unicode) whose interpretation and interworking are much better, this last standard allowing to represent all the other existing standardized character sets and to refine final effective coding while preserving the Sémantique coded text and by improving its Typographie. ISO/CEI 10646 kept the upward compatibility with the growing old standard ISO 646.
Characters invariants
The invariant positions of the Latin graphic character sets compatible with the ISO 646 are the following ones: |valign=" top" | |- |valign=" top" | |valign=" top" | |}
National alternatives of the ISO 646
Many alternatives of the ISO 646 were standardized by official national organizations, and the majority were then declared in the international register (ISO-IR) of the character sets to 7 and 8 bits. However this register is now closed since June 2004, its members having decided to concentrate their efforts with the maintenance of the universal standard ISO/CEI 10646.Other alternatives were developed in way initially owner to meet the needs for certain languages, before being recorded publicly with the support of official organizations of standardization (in particular the ECMA in the European plan, in order to stabilize the conversion charts). There exists however of many alternatives owners not having received this support and which thus were not recorded formally by the ISO-IR (and in the immediate future, it will not undoubtedly be never, their obsolescence being very accelerated because of inaccuracy of their definition and the parallel obsolescence of the systems which supported them).
Among the national standards recorded for the alternatives of the ISO/CEI 646 one finds: |width=" 20" | |width=" 50%" valign=" top" | |}
Among the standards initially owners finally approved with the international plan for interworking thanks to the support of an organization of standardization, one finds: |width=" 20" | |width=" 50%" valign=" top" | |}
In the tables above, the column code indicates the correspondence with those used like the shortened wording of columns to locate the variable characters of the following section; these codes are not standardized (only the numbers of recording ISO-IR are it).
Codes of variable natures
The characters posted on blue or red bottom in the table below are those recommended, but the alternative ASCII (posted on white zone in the same line, in particular in the US column) is often used in the place (when they are used separately). It is the case particularly for the characters known as invariants of the ISO 646, i.e. the 26 Latin letters basic (in capitals or small), the 10 following figures arabo-Europeans and the 20 symbols or punctuations: ! " % &
Also, among the 94 graphic positions of the ISO 646 (coded from 33 to 126 into decimal), only 12 positions are known as alternatives and correspond to the following graphic characters of the American alternative of the ISO 646 ( alias ASCII):
The changes specific to some of these alternatives are indicated in the following table with a red coloured bottom or blue when the character assigned with the code is different from that assigned in the ASCII (US); the blank cells on gray bottom indicate invalid positions not used in the character set standardized corresponding:
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|align=" center" bgcolor=" #CCCCFF" |å
|align=" center" bgcolor=" #CCCCFF" |å
|align=" center" bgcolor=" #CCCCFF" |å
|align=" center" bgcolor=" #CCCCFF" |å
|align=" center" bgcolor=" #CCCCFF" |å
|align=" center" bgcolor=" #CCCCFF" |U
|align=" center" bgcolor=" #CCCCFF" |U
|align=" center" bgcolor=" #CCCCFF" |E
|align=" center" bgcolor=" #CCCCFF" |E
|align=" center" bgcolor=" #CCCCFF" |E
|align=" center" bgcolor=" #CCCCFF" |E
|align=" center" bgcolor=" #CCCCFF" |ú
|align=" center" bgcolor=" #CCCCFF" |E
|align=" center" bgcolor=" #CCCCFF" |õ
|align=" center" bgcolor=" #CCCCFF" |õ
|align=" center" bgcolor=" #CCCCFF" |C
|align=" center" bgcolor=" #CCCCFF" |C
|align=" center" bgcolor=" #CCCCFF" |
|align=" center" bgcolor=" #CCCCFF" |Ħ
|align=" center" bgcolor=" #CCCCFF" |ć
|-
|bgcolor=" #EEEEEE" align=" right" |111 1110
|bgcolor=" #EEEEEE" align=" right" |126
|bgcolor=" #EEEEEE" align=" right" |7th
|align=" center" bgcolor=" #666666" |
|align=" center" |~
|align=" center" bgcolor=" #666666" |
|align=" center" |~
|align=" center" bgcolor=" #666666" |
|align=" center" |~
|align=" center" bgcolor=" #FFCCCC" |˜
|align=" center" bgcolor=" #FFCCCC" |˜
|align=" center" bgcolor=" #FFCCCC" |˜
|align=" center" bgcolor=" #FFCCCC" |¯
|align=" center" bgcolor=" #CCCCFF" |
The characters posted below on red bottom must be interpreted as of diacritic combining when they are preceded or followed by a control character return postpones (BS, code 8). These diacritic applies preceding character then if these reinterpreted characters are preceded by control return postpones , if not they apply to the following character as if they were seized like dead keys (and in this case transcribing towards Unicode will require an inversion of the caracère according to and of the diacritic one, if there does not exist precombined Unicode character corresponding). In this case, the punctuations, symbols and modifying letters following are reinterpreted as follows:
- English quotation mark → diacritic dieresis;
- apostrophizes → diacritic acute accent;
- acute accent → diacritic acute accent;
- comma → diacritic cedilla;
- indent-less → diacritic bar;
- bars oblique → diacritic bar oblique;
- → degree diacritic round as a chief;
- low indent → diacritic macron subscribes;
- symbol circumflex accent → diacritic circumflex accent;
- grave accent → diacritic grave accent;
- small tilde → diacritic tilde;
- diacritic symbol macron → macron;
- double acute accent → diacritic double acute accent.
See too
- ASCII
- ISO 2022
- ISO/CEI 10646
- Unicode
External bonds
- Register ISO-IR of the character sets on 7 or 8 bits
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