Information Technology Reference
In-Depth Information
Although each approach demonstrates internal consistency
in the ways uppercase letters, lowercase letters, and digits are
coded, the actual bit patterns are essentially arbitrary. For ex
ample, the EBCDIC encodings for uppercase letters represent
larger integers than the EBCDIC encodings for lowercase letters
(“A” is represented by 11000001, and “a” is represented by
10000001). However, the situation is exactly opposite for ASCII
encodings (“A” is denoted by 01000001, and “a” is denoted by
01100001).
Over time, ASCII has become more common than EBCDIC,
but ASCII character encodings are still based on the Roman al
phabet—using just 7 or 8 bits (256 combinations) to represent
characters. In more recent years, especially with the expansion of
international communication and the advent of the Internet, de
mand has grown to accommodate different alphabets and charac
ters. Essentially, this is done in one of two ways. The first ap
proach continues to use a small number of bits (often 8 bits) to
store a character, but allows those bits to be interpreted accord
ing to alternative alphabets. The ISO has adopted encodings for
various character sets. Thus, standard ISO88591 specifies a
standard coding for a Western (Roman) alphabet; standard ISO
88597 provides a standard for Greek; and standard ISO2022
CN specifies Simplified Chinese.
With these various standards as options, a computer application
must be told which to use. For example, in writing materials for dis
play on the World Wide Web, Web designers are expected to spec
ify in an early part of the code for any page which alphabet the
browser should use when it displays the page. The encoding being
used for a specific Web page or application is called a character set .
Thus, when you look at the source code of a Web page displayed in
a browser, check for information beginning with the word
“META” and try to find the statement “charset= . . .” to determine
the alphabet and encoding used. (To see the code for a Web site, use
the menus on your browser to view the “source” of a page.) If the
META data are omitted, then the browser is forced to pick what en
coding to try and often defaults to a Roman alphabet. Because
browsers may make bad choices without guidance, the World Wide
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