[info]Unicode & UTF-8

Unicode defines a codespace of 1,114,112 code points in the range 0_hex to 10FFFF_hex.
The Unicode codespace is divided into seventeen planes, each comprising 65,536 code points or 256 rows of 256 code points:

Plane	Range	Description	Abbreviation
0	0000–FFFF	Basic Multilingual Plane	BMP
1	10000–1FFFF	Supplementary Multilingual Plane	SMP
2	20000–2FFFF	Supplementary Ideographic Plane	SIP
3 to 13	30000–DFFFF	currently unassigned
14	E0000–EFFFF	Supplementary Special-purpose Plane	SSP
15	F0000–FFFFF	Supplementary Private Use Area-A
16	100000–10FFFF	Supplementary Private Use Area-B

The bits of a Unicode character are distributed into the lower bit positions inside the UTF-8 bytes, with the lowest bit going into the last bit of the last byte. In this table x represent the lowest 8 bits of the Unicode value, y represent the next higher 8 bits, and z represent the bits higher than that:

Unicode	Byte1	Byte2	Byte3	Byte4	example
U+0000-U+007F	0xxxxxxx				'$' U+0024 → 00100100 → 0x24
U+0080-U+07FF	110yyyxx	10xxxxxx			'¢' U+00A2 → 11000010,10100010 → 0xC2,0xA2
U+0800-U+FFFF	1110yyyy	10yyyyxx	10xxxxxx		'€' U+20AC → 11100010,10000010,10101100 → 0xE2,0x82,0xAC
U+10000-U+10FFFF	11110zzz	10zzyyyy	10yyyyxx	10xxxxxx	U+10ABCD → 11110100,10001010,10101111,10001101 → 0xF4,0x8A,0xAF,0x8D

binary	hex	decimal	notes
00000000-01111111	00-7F	0-127	US-ASCII (single byte)
10000000-10111111	80-BF	128-191	Second, third, or fourth byte of a multi-byte sequence
11000000-11000001	C0-C1	192-193	Overlong encoding: start of a 2-byte sequence, but code point <= 127
11000010-11011111	C2-DF	194-223	Start of 2-byte sequence
11100000-11101111	E0-EF	224-239	Start of 3-byte sequence
11110000-11110100	F0-F4	240-244	Start of 4-byte sequence
11110101-11110111	F5-F7	245-247	Restricted by RFC 3629: start of 4-byte sequence for codepoint above 10FFFF
11111000-11111011	F8-FB	248-251	Restricted by RFC 3629: start of 5-byte sequence
11111100-11111101	FC-FD	252-253	Restricted by RFC 3629: start of 6-byte sequence
11111110-11111111	FE-FF	254-255	Invalid: not defined by original UTF-8 specification