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The term extended ASCII (or high ASCII) describes 8-bit or larger character encodings that include the standard 7- bit ASCII characters as well as others.1 Motives for extending
Because the number of written symbols used in common natural languages far exceeds the limited range of the ASCII code, many extensions to it have been used to facilitate handling of those languages. Foreign markets for computers and communication equipment were historically open long before standards bodies had time to deliberate upon the best way to accommodate them, so there are many incompatible proprietary extensions to ASCII.
Since ASCII is a 7-bit code, and most computers manipulate data in 8-bit bytes, many extensions use the additional 128 codes available by using all 8 bits of each byte. This helps include many languages otherwise not easily representable in ASCII, but still not enough to cover all languages of countries in which computers are sold, so even these 8-bit extensions had to have local variants.
2 Proprietary extensions
Various proprietary extensions appeared on non- EBCDIC mainframe and mini-computers, especially in universities. Commodore microcomputers added many graphic symbols to their non-standard ASCII ( PETSCII, based on the original ASCII standard of 1963). IBM introduced 8-bit extended ASCII codes on the original IBM PC and later produced variations in for different languages and cultures. IBM called such character sets code pages and assigned numbers to both those they themselves invented as well as many invented and used by other manufacturers. Accordingly character sets are very often indicated by their IBM code page number. In ASCII-compatibile code pages, the lower 128 characters maintained their standard US-ASCII values, and different pages (or sets of characters) could be made available in the upper 128 characters. DOS computers built for the American market, for example, used codepage 437, which included accented characters needed for French, German, and a few other European languages, as well as some graphical line-drawing characters. The larger character set made it possible to create documents in a combination of languages such as English and French, but not, for example, in English and Greek (which required code page 737).
A set with less characters but more letter and diagritic combinations was used by the Digital VT-220 terminalA computer terminal is an electronic or electromechanical hardware device. It is used for entering data into, and displaying data from, a computer or a computing system. Historical Early terminals were Teletypes (TTYs), later ones use a Visual Display Uni based on draft versions of a ISO standard that was being developed.
3 ISO 8859 and proprietary adaptions
Eventually, ISO released this standard as ISO 8859ISO 8859 more formally ISO/IEC 8859 is a joint ISO and IEC standard for 8-bit character encodings for use by computers. The standard is divided into numbered, separately published parts, such as ISO/IEC 8859-1, ISO/IEC 8859-2, etc. each of which may be in describing its own set of 8-bit ASCII extensions. The most popular was ISO 8859-1ISO 8859-1 more formally cited as ISO/IEC 8859-1 or less formally as Latin-1 is part 1 of ISO/IEC 8859, a standard character encoding defined by ISO. It encodes what it refers to as Latin alphabet no. 1, consisting of 191 characters from the Latin script,, 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 WindowsImage use policy. Microsoft Windows is a range of commercial operating environments for personal computers. The range was first introduced by Microsoft in 1985 and eventually has come to dominate the world personal computer market. All recent versions of, including English versions.
ISO 8859-1 is the common character encoding used by the X Window SystemIn computing, the X Window System (commonly X11 or X is a windowing system for bitmap displays. It is the standard graphical interface on Unix, Unix-like operating systems and OpenVMS, and is available for most other modern operating systems. X provides t, and most InternetThis article is about the Internet the extensive, worldwide computer network available to the public. An internet is a more general term for a set of interconnected computer networks that are connected by internetworking''. WWW information network structu standards.
The Apple MacintoshMacintosh now known simply as Mac in all official capacities, is a family of personal computers manufactured by Apple Computer, Inc. of Cupertino, California, USA. Named after the McIntosh, a type of apple favoured by Jef Raskin, the Macintosh was launche, under Mac OS X, currently uses Unicode as its default encoding. Under Mac OS, it used MacRoman.
