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Code page

Code page is the traditional IBM term used for a specific variant of character coding for computers. Although the basis of many character sets is ASCII, ASCII was a seven bit code, with the 8-bit representation of ASCII either setting the top bit to zero or using it as a parity bit. Using this bit for data doubled the size of the possible character set, allowing another 128 characters to be added. No standard the existed for these "extended character sets", and IBM referred to the variants as code pages.

Although IBM maintained a myriad of code pages, the term has in general use taken on the meaning character coding for the IBM PC. Since the original IBM PC code page was not really designed for international use, several incompatible variants emerged:

The IBM PC code pages have now been rendered obsolete by international standards, specifically ISO 8859-1 and Unicode.

Other code pages of note are:

Microsoft code pages

Microsoft defined a number of proprietary code page extensions which were subtly incompatible with those by other vendors.

The most notable of these is the windows-1252 code page, which contains a range of typographical punctuation characters in character positions which were reserved for control characters in the ISO 8859-1 "latin-1" code page.

Many Microsoft products produce characters in these ranges automatically, notably with "smartquotes". This means that other software has to choose between

These code pages are often viewed as part of Microsoft's embrace, extend and extinguish strategy towards open standards. Fortunately, the transition to full Unicode support now offers standards-based applications the possibility of full interoperability with the character repertoire of these documents without giving up standards compliance on output.

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