about UTF- 8

UTF-8 compaction mode is principally designed to support data systems with 8-bit communications paths.

Annex B UTF- 8

UTF-8 compaction mode is principally designed to support data systems with 8-bit communications paths. It has the clear advantage that the character addresses U+0000_hex to U+007F_hex, corresponding ASCII (and ISO 646:1991) values 00_hex to 7F_hex are represented by single octets of the same value. It is straightforward both to generate and parse and produces reasonable compaction.

Input and output of up to 21-bit Unicode 3 character addresses for all 1 114 112 characters on the 17 Code Planes 0 through 16 can be cumbersome in normal byte-oriented data systems. In Table B.1, the length of the binary data representation of characters to be encoded (ignoring leading zero bits) determines how many UTF-8 bytes are required.

Table B.1: UTF- 8 byte sequences for Unicode character addresses

During decoding, the number of bytes in each UTF-8 byte sequence can be immediately determined from the first byte of each sequence.

Legal UTF-8 byte sequences shall conform to Unicode Technical Report 27 as summarized in Table B.2.

Table B.2 – Unicode address ranges for legal UTF-8 byte sequences