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Optional single quotes ( ‘ ) may be inserted between the digits as a separator; they are ignored during compilation.

Escape-последовательность

Сочетания символов, состоящие из обратной косой черты (\), за которой следует буква или сочетание цифр, называются escape-последовательностями. Для представления символа новой строки, одинарной кавычки или некоторых других символов в символьной константе необходимо использовать escape-последовательности. Escape-последовательность рассматривается как один символ и, следовательно, является допустимой символьной константой.

Escape-последовательности обычно используются для указания действий, например возврата каретки или табуляции, на терминалах и принтерах. Они также используются для обозначения буквенных представлений непечатаемых символов, а также символов, которые обычно имеют специальное значение, например двойных кавычек ( “ ). В следующей таблице перечислены escape-последовательности ANSI и представляемые ими значения.

Обратите внимание, что вопросительный знак, перед которым стоит обратная косая черта (\?), обозначает литерал вопросительного знака в случаях, когда эта последовательность символов может быть ошибочно интерпретирована как триграф. Дополнительные сведения см. в разделе Триграфы.

Escape-последовательность

Escape-последовательность	Представляет
\a	Звонок (предупреждение)
\b	Backspace
\f	Перевод страницы
\n	Новая строка
\r	Возврат каретки
\t	Горизонтальная табуляция
\v	Вертикальная табуляция
\’	Одиночная кавычка
\”	Двойная кавычка
\\	Обратная косая черта
\?	Литерал вопросительного знака
\ooo	Символ ASCII в восьмеричной нотации
\xhh	Символ ASCII в шестнадцатеричной нотации
\xhhhh	Символ юникода в шестнадцатеричном формате, если эта escape-последовательность используется в многобайтовой знаковой константе или строковом литерале юникода.

Блок, относящийся только к системам Microsoft

Если обратная косая черта предшествует символу, которого нет в таблице, компилятор не обрабатывает неопределенный символ сам как символ. Например, escape-последовательность \c обрабатывается как символ c .

Завершение блока, относящегося только к системам Майкрософт

Escape-последовательности позволяют отправлять неграфические управляющие символы на устройство отображения. Например, символ ESC ( \033) часто используется в качестве первого символа команды управления для терминала или принтера. Некоторые escape-последовательности используются только на конкретных устройствах. Например, escape-последовательности вертикальной табуляции и перевода страницы ( \v и \f) не влияют на вывод данных на экране, но отвечают за соответствующие операции на принтере.

Кроме того, обратную косую черту ( \ ) можно использовать как символ продолжения. Если сразу за обратной косой чертой следует символ новой строки (эквивалентен нажатию клавиши ВОЗВРАТ), компилятор игнорирует эту последовательность и обрабатывает следующую строку как продолжение предыдущей. Эта возможность используется в основном для определений препроцессора, длина которых превышает одну строку. Пример:

#define assert(exp) \ ( (exp) ? (void) 0:_assert( #exp, __FILE__, __LINE__ ) ) 

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Integer literal

Allows values of integer type to be used in expressions directly.

Contents

[edit] Syntax

An integer literal has the form

decimal-literal integer-suffix (optional)	(1)
octal-literal integer-suffix (optional)	(2)
hex-literal integer-suffix (optional)	(3)
binary-literal integer-suffix (optional)	(4)	(since C++14)

• decimal-literal is a non-zero decimal digit ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ), followed by zero or more decimal digits ( 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 )
• octal-literal is the digit zero ( 0 ) followed by zero or more octal digits ( 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 )
• hex-literal is the character sequence 0x or the character sequence 0X followed by one or more hexadecimal digits ( 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , a , A , b , B , c , C , d , D , e , E , f , F )
• binary-literal is the character sequence 0b or the character sequence 0B followed by one or more binary digits ( 0 , 1 )
• integer-suffix , if provided, may contain one or both of the following (if both are provided, they may appear in any order:

• unsigned-suffix (the character u or the character U )
• one of

• long-suffix (the character l or the character L )

• long-long-suffix (the character sequence ll or the character sequence LL )

• size-suffix (the character z or the character Z )

Optional single quotes ( ‘ ) may be inserted between the digits as a separator; they are ignored during compilation.

An integer literal (as any literal) is a primary expression.

[edit] Explanation

1) Decimal integer literal (base 10)
2) Octal integer literal (base 8)

3) Hexadecimal integer literal (base 16, the letters ‘a’ through ‘f’ represent values (decimal) 10 through 15)

4) Binary integer literal (base 2)

The first digit of an integer literal is the most significant.

Example. The following variables are initialized to the same value:

int d = 42; int o = 052; int x = 0x2a; int X = 0X2A; int b = 0b101010; // C++14

Example. The following variables are also initialized to the same value:

unsigned long long l1 = 18446744073709550592ull; // C++11 unsigned long long l2 = 18'446'744'073'709'550'592llu; // C++14 unsigned long long l3 = 1844'6744'0737'0955'0592uLL; // C++14 unsigned long long l4 = 184467'440737'0'95505'92LLU; // C++14

[edit] The type of the literal

The type of the integer literal is the first type in which the value can fit, from the list of types which depends on which numeric base and which integer-suffix was used:

• int
• long int
• long long int (since C++11)

• int
• unsigned int
• long int
• unsigned long int
• long long int (since C++11)
• unsigned long long int (since C++11)

• unsigned int
• unsigned long int
• unsigned long long int (since C++11)

• unsigned int
• unsigned long int
• unsigned long long int (since C++11)

• long int
• unsigned long int (until C++11)
• long long int (since C++11)

• long int
• unsigned long int
• long long int (since C++11)
• unsigned long long int (since C++11)

• unsigned long int
• unsigned long long int (since C++11)

• unsigned long int
• unsigned long long int (since C++11)

• long long int (since C++11)

• long long int (since C++11)
• unsigned long long int (since C++11)

• unsigned long long int (since C++11)

• unsigned long long int (since C++11)

• the signed version of std::size_t (since C++23)

• the signed version of std::size_t (since C++23)
• std::size_t (since C++23)

• std::size_t (since C++23)

• std::size_t (since C++23)

If the value of the integer literal is too big to fit in any of the types allowed by suffix/base combination and the compiler supports extended integer types (such as __int128 ) the literal may be given the extended integer type — otherwise the program is ill-formed.

[edit] Notes

Letters in the integer literals are case-insensitive: 0xDeAdBeEfU and 0XdeadBEEFu represent the same number (one exception is the long-long-suffix , which is either ll or LL , never lL or Ll ) (since C++11)

There are no negative integer literals. Expressions such as – 1 apply the unary minus operator to the value represented by the literal, which may involve implicit type conversions.

In C prior to C99 (but not in C++), unsuffixed decimal values that do not fit in long int are allowed to have the type unsigned long int .

When used in a controlling expression of #if or #elif, all signed integer constants act as if they have type std::intmax_t and all unsigned integer constants act as if they have type std::uintmax_t .

Due to maximal munch, hexadecimal integer literals ending in e and E , when followed by the operators + or – , must be separated from the operator with whitespace or parentheses in the source:

auto x = 0xE+2.0; // error auto y = 0xa+2.0; // OK auto z = 0xE +2.0; // OK auto q = (0xE)+2.0; // OK

Otherwise, a single invalid preprocessing number token is formed, which causes further analysis to fail.

Feature-test macro	Value	Std	Comment
__cpp_binary_literals	201304L	(C++14)	Binary literals
__cpp_size_t_suffix	202011L	(C++23)	Literal suffixes for std::size_t and its signed version

[edit] Example

Run this code

#include #include #include int main() { std::cout  123  '\n'  0123  '\n'  0x123  '\n'  0b10  '\n'  12345678901234567890ull  '\n'  12345678901234567890u  '\n'; // the type is unsigned long long // even without a long long suffix // std::cout // 9223372036854775808 cannot fit in signed long long, which is the // biggest type allowed for unsuffixed decimal integer literal std::cout  -9223372036854775808u  '\n'; // unary minus applied to unsigned // value subtracts it from 2^64, this gives 9223372036854775808 std::cout  -9223372036854775807 - 1  '\n'; // correct way to calculate // the value -9223372036854775808 #if __cpp_size_t_suffix >= 202011L // C++23 static_assert(std::is_same_vdecltype(0UZ), std::size_t>); static_assert(std::is_same_vdecltype(0Z), std::make_signed_tstd::size_t>>); #endif }

123 83 291 2 12345678901234567890 12345678901234567890 9223372036854775808 -9223372036854775808