[lex.char]
5 Lexical conventions [lex]
5.3 Characters [lex.char]
5.3.1 Character sets [lex.charset]
5.3.2 Universal character names [lex.universal.char]
5.3.1 Character sets [lex.charset]
The translation character set consists of the following elements:
- each abstract character assigned a code point in the Unicode codespace as specified in the Unicode Standard, and
- a distinct character for each Unicode scalar value not assigned to an abstract character.
The basic character set is a subset of the translation character set, consisting of 99 characters as specified in Table 1.
In this document, glyphs are often used to identify elements of the basic character set.
Table 1 — Basic character set [tab:lex.charset.basic]
character | glyph | |
U+0009 | character tabulation | |
U+000b | line tabulation | |
U+000c | form feed | |
U+0020 | space | |
U+000a | line feed | new-line |
U+0021 | exclamation mark | ! |
U+0022 | quotation mark | " |
U+0023 | number sign | # |
U+0024 | dollar sign | $ |
U+0025 | percent sign | % |
U+0026 | ampersand | & |
U+0027 | apostrophe | ' |
U+0028 | left parenthesis | ( |
U+0029 | right parenthesis | ) |
U+002a | asterisk | * |
U+002b | plus sign | + |
U+002c | comma | , |
U+002d | hyphen-minus | - |
U+002e | full stop | . |
U+002f | solidus | / |
U+0030 .. U+0039 | digit zero .. nine | 0 1 2 3 4 5 6 7 8 9 |
U+003a | colon | : |
U+003b | semicolon | ; |
U+003c | less-than sign | < |
U+003d | equals sign | = |
U+003e | greater-than sign | > |
U+003f | question mark | ? |
U+0040 | commercial at | @ |
U+0041 .. U+005a | latin capital letter a .. z | A B C D E F G H I J K L M |
N O P Q R S T U V W X Y Z | ||
U+005b | left square bracket | [ |
U+005c | reverse solidus | \ |
U+005d | right square bracket | ] |
U+005e | circumflex accent | ^ |
U+005f | low line | _ |
U+0060 | grave accent | ` |
U+0061 .. U+007a | latin small letter a .. z | a b c d e f g h i j k l m |
n o p q r s t u v w x y z | ||
U+007b | left curly bracket | { |
U+007c | vertical line | | |
U+007d | right curly bracket | } |
U+007e | tilde | ~ |
The basic literal character set consists of all characters of the basic character set, plus the control characters specified in Table 2.
Table 2 — Additional control characters in the basic literal character set [tab:lex.charset.literal]
U+0000 | null |
U+0007 | alert |
U+0008 | backspace |
U+000d | carriage return |
The ordinary literal encoding is the encoding applied to an ordinary character or string literal.
The wide literal encoding is the encoding applied to a wide character or string literal.
A literal encoding or a locale-specific encoding of one of the execution character sets ([character.seq]) encodes each element of the basic literal character set as a single code unit with non-negative value, distinct from the code unit for any other such element.
[Note 3:
A character not in the basic literal character set can be encoded with more than one code unit; the value of such a code unit can be the same as that of a code unit for an element of the basic literal character set.
— end note]
The U+0000 null character is encoded as the value 0.
No other element of the translation character set is encoded with a code unit of value 0.
The code unit value of each decimal digit character after the digit 0 (U+0030) is one greater than the value of the previous.
The ordinary and wide literal encodings are otherwise implementation-defined.
For a UTF-8, UTF-16, or UTF-32 literal, the implementation shall encode the Unicode scalar value corresponding to each character of the translation character set as specified in the Unicode Standard for the respective Unicode encoding form.
5.3.2 Universal character names [lex.universal.char]
n-char:
any member of the translation character set except the U+007d right curly bracket or new-line character
The universal-character-name construct provides a way to name any element in the translation character set using just the basic character set.
A universal-character-name of the form \u hex-quad, \U hex-quad hex-quad, or \u{simple-hexadecimal-digit-sequence} designates the character in the translation character set whose Unicode scalar value is the hexadecimal number represented by the sequence of hexadecimal-digits in the universal-character-name.
The program is ill-formed if that number is not a Unicode scalar value.
A universal-character-name that is a named-universal-character designates the corresponding character in the Unicode Standard (chapter 4.8 Name) if the n-char-sequence is equal to its character name or to one of its character name aliases of type “control”, “correction”, or “alternate”; otherwise, the program is ill-formed.