Dictionary.net

(Or "character encoding scheme") A mapping ofbinary 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. Thisis possible because ASCII uses only code positionsrepresentable 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 morethan 255 positions, requiring more complex mappings: sometimesthe characters are mapped onto pairs of bytes (see DBCS).In many cases, this breaks programs that assume a one-to-onemapping of bytes to characters, and so, for example, treat anyoccurrance of the byte value 13 as a carriage return. Toavoid this problem, character encodings such as UTF-8 weredevised.