Unicode Explained

applicable syntax. For example, the rules of a programming language might restrict the

character repertoire in identifier names to letters, digits, and one or two other charac-

ters. On the other hand, the underscore (low line) character _ is often usable in names,

and it normally works reliably.

The Misnomer “8-bit ASCII”

The phrase “8-bit ASCII” is used surprisingly often. It follows from the discussion in

the previous section that in reality ASCII is strictly and unambiguously a 7-bit code in

the sense that all code positions are in the range 0–127. It can be, and it usually is,

represented using 8-bit bytes, but with the first bit always zero, or used for other pur-

poses so that it is not part of the encoded form of a character.

The misnomer “8-bit ASCII” most often denotes windows-1252, the 8-bit code defined

by Microsoft for use in the Western world. More generally, 8-bit ASCII is used to refer

to various character codes, which are extensions of ASCII and mutually more or less

incompatible. The character repertoire in such a code contains ASCII as a subset, the

code numbers are in the range 0–256, and the code numbers of ASCII characters equal

their ASCII codes.

ISO 8859 Codes

ISO 8859—or more formally, ISO/IEC 8859—is a family of character code standards.

They were largely developed by Ecma, which distributes ECMA standards that are

equivalent to ISO 8859 standards. ISO 8859 standards