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Character encoding
- ASCII characters (in the range 0-127) are encoded as a single byte.
- Greek, Hebrew, Arabic and most accented European characters are encoded as two bytes;
- Other characters are encoded as three bytes;
- The individual characters are encoded according to the following rules.
Single byte encoding
Characters in the range 'u+0000' to 'u+007f' are encoded as a single byte.
| Caption label | ||||
|---|---|---|---|---|
| ||||
UTF-8 Single Byte Encoding |
byte 0 | |
|---|---|
0 | bits 0-6 |
Two byte encoding
Characters in the range 'u+0080' to 'u+07ff' are encoded as two bytes.
| Caption label | ||||
|---|---|---|---|---|
| ||||
Two byte encoding |
byte 0 | byte 1 | |||||
|---|---|---|---|---|---|---|
1 | 1 | 0 | bits 6-10 | 1 | 0 | bits 0-5 |
Three byte encoding
Characters in the range 'u+0800' to 'u+ffff' are encoded as three bytes:
| Caption label | ||||
|---|---|---|---|---|
| ||||
UTF-8 Three Byte Encoding |
byte 0 | byte 1 | byte 2 | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | 1 | 1 | 0 | bits 12-15 | 1 | 0 | bits 6-11 | 1 | 0 | bits 0-5 |
Notes on encoding rules
The first bits of each byte indicate the role of the byte. A zero bit terminates this role information. Thus possible byte values are:
| Caption label | ||||
|---|---|---|---|---|
| ||||
UTF-8 Encoding Rules |
Bits | Byte value |
| ||||
|---|---|---|---|---|---|---|
0??????? | 000-127 | Single byte encoding of a character | ||||
10?????? | 128-191 | Continuation of a multi-byte encoding | ||||
110????? | 192-223 | First byte of a two byte character encoding | ||||
1110???? | 224-239 | First byte of a three byte character encoding | ||||
1111??? | 240-255 | Invalid |
Example encoding
| Caption label | ||||
|---|---|---|---|---|
| ||||
UTF-8 Encoding Example |
Character | S | C | T | | | |||
Unicode | 0053 | 0043 | 0054 | 00AE | 2462 | |||
Bytes | 01010011 | 01000011 | 01010100 | 11000010 | 10101110 | 11101111 | 10111111 | 10111111 |
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