Digital Equipment Corporation developed a "Multinational Character Set", which had fewer characters but more letter and diacritic combinations, based on draft versions of ISO 8859. It was supported by the VT220 and later DEC computer terminals.
ISO 8859 and proprietary adaptions
Eventually, ISO released this standard as ISO 8859 describing its own set of eight-bit ASCII extensions. The most popular was ISO 8859-1, also called ISO Latin1, which contained characters sufficient for the most common Western European languages. Variations were standardized for other languages as well: ISO 8859-2 for Eastern European languages and ISO 8859-5 for Cyrillic languages, for example. One notable way in which ISO character sets differ from code pages is that the character positions 128 to 159, corresponding to ASCII control characters with the high-order bit set, are specifically unused and undefined in the ISO standards, though they had often been used for printable characters in proprietary code pages, a breaking of ISO standards that was almost universal. Microsoft later created code page 1252, a compatible superset of ISO 8859-1 with extra characters in the ISO unused range. Code page 1252 is the standard character encoding of western European language versions of Microsoft Windows, including English versions. ISO 8859-1 is the common character encoding used by the X Window System, and most Internet standards. The Apple Macintosh, under Mac OS X, currently uses Unicode as its default encoding. Under Mac OS, it used Mac OS Roman.
Because these ASCII extensions have so many variants, it is necessary to identify which set is being used for a particular text for it to be interpreted correctly. However, because the most-used characters (those in ASCII, the seven-bit code points) are common to all sets--even most proprietary ones--failure to correctly identify a character set often suffers no adverse consequences if the user is typing in English. Further, because many Internet standards use ISO 8859-1, and because Microsoft Windows (using the code page 1252 superset of ISO 8859-1) is the dominant operating system for personal computers today, unannounced use of ISO 8859-1 is quite commonplace, and should generally be assumed without evidence to the contrary.
In many protocols, most importantly e-mail and HTTP, the character encoding of content has to be tagged with IANA-assigned character set identifiers.
A proposal called Unicode was made in 1991 to address many of these problems, and is now widely accepted. Unicode reserves 1,114,112 code points (= 17 planes × 2^16 code points per plane), and currently assigns characters to more than 101,000 of those code points. The first 256 codes precisely match those of ISO-8859-1. The majority of the 96,000 code points are, at this time, used for Chinese, Japanese and Korean characters.
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