Code page
Texts, words, and characters are represented in computers by numbers, so it is necessary to make an assignment of numbers and characters. This mapping is defined by a character set table that assigns the printable characters and control characters numerical values. Alternative terms for character set table code page or character map.
History
Historic character set tables are often subject to a limit of 256 characters, which in turn implies that a character set table with 256 characters can usually save just another alphabet next to the Latin alphabet. The use of these early, simple character set tables but led to problems. In some fontcharts all the characters are not well documented or specific entries in the character table are used in different ways. Further, a text often use only one character set table, which makes it difficult to integrate characters from other languages in the text. To solve these problems, Unicode has been introduced. In contrast to normal character set tables Unicode separates between the assignment of numbers (called code points ) to characters and the encoding of the characters. The various encoding schemes of Unicode can be understood as character set tables but turn. While a character set table defines the mapping of numbers to characters, fonts save the appearance of the characters. So usually both a character set table as well as a font for the display of text on a computer are necessary.
The representation of text or file name with the wrong character set table leads to the presentation of false characters. In German texts including often suffer the umlauts or the sharp s, even if the text remains essentially unreadable. Asian texts on display with the wrong character set table, however unreadable ( Mojibake ).
Examples
IBM PC ( OEM) character set tables
This character set tables should be used only for compatibility with existing documents and systems. For new systems, and texts the use of Unicode is recommended.
DBCS
These code pages allow storing Asian characters, not enough where the resulting 8-bit 256 characters. To 16- tuples are used (DBCS), which allow up to 65,536 different characters.
Important fontcharts
For efficient processing on computers character set tables are identified by numbers. However, the numbering of the character set tables is not standardized, so that different computers or operating systems may use different numbers.