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elisp: General Escape Syntax

 
 2.3.3.2 General Escape Syntax
 .............................
 
 In addition to the specific escape sequences for special important
 control characters, Emacs provides several types of escape syntax that
 you can use to specify non-ASCII text characters.
 
    Firstly, you can specify characters by their Unicode values.
 ‘?\uNNNN’ represents a character with Unicode code point ‘U+NNNN’, where
 NNNN is (by convention) a hexadecimal number with exactly four digits.
 The backslash indicates that the subsequent characters form an escape
 sequence, and the ‘u’ specifies a Unicode escape sequence.
 
    There is a slightly different syntax for specifying Unicode
 characters with code points higher than ‘U+FFFF’: ‘?\U00NNNNNN’
 represents the character with code point ‘U+NNNNNN’, where NNNNNN is a
 six-digit hexadecimal number.  The Unicode Standard only defines code
 points up to ‘U+10FFFF’, so if you specify a code point higher than
 that, Emacs signals an error.
 
    Secondly, you can specify characters by their hexadecimal character
 codes.  A hexadecimal escape sequence consists of a backslash, ‘x’, and
 the hexadecimal character code.  Thus, ‘?\x41’ is the character ‘A’,
 ‘?\x1’ is the character ‘C-a’, and ‘?\xe0’ is the character ‘à’ (‘a’
 with grave accent).  You can use any number of hex digits, so you can
 represent any character code in this way.
 
    Thirdly, you can specify characters by their character code in octal.
 An octal escape sequence consists of a backslash followed by up to three
 octal digits; thus, ‘?\101’ for the character ‘A’, ‘?\001’ for the
 character ‘C-a’, and ‘?\002’ for the character ‘C-b’.  Only characters
 up to octal code 777 can be specified this way.
 
    These escape sequences may also be used in strings.  Non-ASCII
 in Strings.
 

Info Catalog elisp: Basic Char Syntax elisp: Character Type elisp: Ctl-Char Syntax