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4.3.1 What is so special about special characters?

In order to be able to exchange text between computers, it was necessary to agree on a scheme on how to encode letters into numbers, the so called character set. The standard character set for transferring text between a huge variety of computer systems is the ASCII character set. Unfortunately, the ASCII character set is only 7 bit wide and does not leave room for national special characters.

In order to be able to transfer special characters like accents and umlauts, it was therefore necessary to use eight bit wide extended character sets that defines how special characters are encoded.

In contrast to the standard 7 bit ASCII character set, which is a single character set used by nearly all computer systems, there exist several pseudo-standard character sets that are 8 bits wide. All of them contain ASCII as an subset, but they all differ in how they encode special characters. DOS and OS/2 computers typically use the IBM PC character set, but even there, dependent on what country you live in, there are several different code pages of the IBM PC character set. Unix computers and the Amiga in the western world typically use the ISO8859-1 character set, also known as Latin-1. Windows uses IBM PC for console applications, but ISO8859 for graphical applications. The Macintosh uses the Macintosh character set. In Russia, there is a similiar problems: There exist four ways of encoding cyrillics, namedly the KOI8-R fonts, the ISO 8859-5 fonts, the codepage 866 of the IBM PC character set, and Windows Codepage 1251.

The consequence of this is clear: If you write a text on a Unix or Windows computer using special characters like accented letters or umlauts, you cannot expect it to be properly displayed on a DOS or OS/2 computer, and vice versa, unless special measures are taken.


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