Character encoding
<character> (Or "character encoding scheme") A mapping of
binary values to code positions and back; generally a 1:1 (bijective) mapping.
In the case of
ASCII, this is generally a f(x)=x mapping: code point 65 maps to the byte value 65, and vice versa.
This is possible because ASCII uses only code positions representable as single bytes, i.e., values between 0 and 255, at most.
(
US-ASCII only uses values 0 to 127, in fact.)
Unicode and many
CJK coded character sets use many more than 255 positions, requiring more complex mappings: sometimes the characters are mapped onto pairs of bytes (see
DBCS). In many cases, this breaks programs that assume a one-to-one mapping of bytes to characters, and so, for example, treat any occurrance of the byte value 13 as a
carriage return.
To avoid this problem, character encodings such as
UTF-8 were devised.
