elisp: Character Codes
32.5 Character Codes
====================
The unibyte and multibyte text representations use different character
codes. The valid character codes for unibyte representation range from
0 to ‘#xFF’ (255)—the values that can fit in one byte. The valid
character codes for multibyte representation range from 0 to ‘#x3FFFFF’.
In this code space, values 0 through ‘#x7F’ (127) are for ASCII
characters, and values ‘#x80’ (128) through ‘#x3FFF7F’ (4194175) are for
non-ASCII characters.
Emacs character codes are a superset of the Unicode standard. Values
0 through ‘#x10FFFF’ (1114111) correspond to Unicode characters of the
same codepoint; values ‘#x110000’ (1114112) through ‘#x3FFF7F’ (4194175)
represent characters that are not unified with Unicode; and values
‘#x3FFF80’ (4194176) through ‘#x3FFFFF’ (4194303) represent eight-bit
raw bytes.
-- Function: characterp charcode
This returns ‘t’ if CHARCODE is a valid character, and ‘nil’
otherwise.
(characterp 65)
⇒ t
(characterp 4194303)
⇒ t
(characterp 4194304)
⇒ nil
-- Function: max-char
This function returns the largest value that a valid character
codepoint can have.
(characterp (max-char))
⇒ t
(characterp (1+ (max-char)))
⇒ nil
-- Function: get-byte &optional pos string
This function returns the byte at character position POS in the
current buffer. If the current buffer is unibyte, this is
literally the byte at that position. If the buffer is multibyte,
byte values of ASCII characters are the same as character
codepoints, whereas eight-bit raw bytes are converted to their
8-bit codes. The function signals an error if the character at POS
is non-ASCII.
The optional argument STRING means to get a byte value from that
string instead of the current buffer.
Info Catalog
elisp: Selecting a Representation
elisp: Non-ASCII Characters
elisp: Character Properties