If first 127 characters are same then why are we still using ASCII and is there backward compatibility issue when using Unicode instead of ASCII


ASCII, later called ANSI, has 1:1 relation between byte and character. Multibyte character systems, including Unicode, have the advantage of displaying additional character at the expense of requiring additional storage. In addition, there are many implementations of multibyte character systems; in some, the byte order is specified by the BOM. The interpretation of UTF-8, UTF-16 and UTF-32 produces different values for the same byte string. Further, there are different ISO standards for differing alphabets, such as the Scandinavian implementation with A-minuscule-o, as in "Åland Islands".

So, for simple database purposes, or for use with very limited storage, for example, ANSI has space advantages, and is not subject to misinterpretation. If one needs to display the full character set of many alphabets, though, multibyte sets are useful.

  • I understand that there are different storage in ASCII and Unicode but say character "a" will have – Stribor Nov 23 '15 at 0:13
  • Same encoding only different padding? Is that accurate? – Stribor Nov 23 '15 at 0:14
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    ISO/IEC 8859-x are single-byte character sets. I've seen no knowledgeable source referring to US-ASCII as "ANSI". – Thomas Dickey Nov 23 '15 at 1:20
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    @ThomasDickey In the Windows world "ANSI" was used to denote the 8-bit default GUI codepage. Whether appropriate or (rather) not but it's still widely used. See for example msdn.microsoft.com/en-us/library/windows/desktop/dd317752.aspx Windows code pages, commonly called "ANSI code pages" . – dxiv Nov 23 '15 at 2:05
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    And in correct contexts (other than Windows) ANSI means the organization ansi.org which has developed or adopted standards for many thousands of things other than ASCII, from magtapes to encryption to photographic film to machine tools to eyeguards and workboots. – dave_thompson_085 Nov 23 '15 at 4:59

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