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Extended ASCII
Extended ASCII (or high ASCII) is eight-bit or larger character encodings that include the standard seven-bit ASCII characters as well as others. The use of the term is sometimes criticized,〔(【引用サイトリンク】title=Re: Cygwin Termcap information involving extended ascii charicters )〕〔(【引用サイトリンク】title=Thread: Print Extended ASCII Codes in sql
*plus )〕 because it can be mistakenly interpreted that the ASCII standard has been updated to include more than 128 characters or that the term unambiguously identifies a single encoding, both of which are untrue.
==Motives for extending==
Because the number of symbols (or glyphs) used in common natural languages as well as in mathematics (· × ÷ ≠ ≥ ≈ π etc.) and many programming languages and technical applications far exceeds the 96 (128-32) printable ASCII codes, many extensions to it have been used. Markets for computers and communication equipment outside English-speaking countries 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 seven-bit code and most computers manipulate data in eight-bit bytes, many extensions use the additional 128 codes available by using all eight bits of each byte. This helps include many languages otherwise not easily representable in ASCII, but is still not enough to cover all languages of countries in which computers are sold, so even these eight-bit extensions had to have local variants.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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