< cpp‎ | utility
Utilities library
Language support
Type support (basic types, RTTI)
Library feature-test macros (C++20)
Dynamic memory management
Program utilities
Coroutine support (C++20)
Variadic functions
Debugging support
Three-way comparison
General utilities
Date and time
Function objects
Formatting library (C++20)
Relational operators (deprecated in C++20)
Integer comparison functions
Swap and type operations
Common vocabulary types
Elementary string conversions

Defined in header <bitset>
template< std::size_t N >
class bitset;

The class template bitset represents a fixed-size sequence of N bits. Bitsets can be manipulated by standard logic operators and converted to and from strings and integers. For the purpose of the string representation and of naming directions for shift operations, the sequence is thought of as having its lowest indexed elements at the right, as in the binary representation of integers.

bitset meets the requirements of CopyConstructible and CopyAssignable.

All member functions of std::bitset are constexpr: it is possible to create and use std::bitset objects in the evaluation of a constant expression.

(since C++23)


[edit] Template parameters

N - the number of bits to allocate storage for

[edit] Member types

proxy class representing a reference to a bit

[edit] Member functions

constructs the bitset
(public member function) [edit]
(removed in C++20)
compares the contents
(public member function) [edit]
Element access
accesses specific bit
(public member function) [edit]
accesses specific bit
(public member function) [edit]
checks if all, any or none of the bits are set to true
(public member function) [edit]
returns the number of bits set to true
(public member function) [edit]
returns the number of bits that the bitset holds
(public member function) [edit]
performs binary AND, OR, XOR and NOT
(public member function) [edit]
performs binary shift left and shift right
(public member function) [edit]
sets bits to true or given value
(public member function) [edit]
sets bits to false
(public member function) [edit]
toggles the values of bits
(public member function) [edit]
returns a string representation of the data
(public member function) [edit]
returns an unsigned long integer representation of the data
(public member function) [edit]
returns an unsigned long long integer representation of the data
(public member function) [edit]

[edit] Non-member functions

performs binary logic operations on bitsets
(function template) [edit]
performs stream input and output of bitsets
(function template) [edit]

[edit] Helper classes

hash support for std::bitset
(class template specialization) [edit]

[edit] Notes

If the size of a bit-set is not known at compile time, or it is necessary to change its size at run-time, the dynamic types such as std::vector<bool> or boost::dynamic_bitset<> may be used instead.

Feature-test macro Value Std Feature
__cpp_lib_constexpr_bitset 202207L (C++23) A more constexpr std::bitset
__cpp_lib_bitset 202306L (C++26) Interfacing std::bitset with std::string_view

[edit] Example

#include <bitset>
#include <cassert>
#include <cstddef>
#include <iostream>
int main()
    typedef std::size_t length_t, position_t; // the hints
    // constructors:
    constexpr std::bitset<4> b1;
    constexpr std::bitset<4> b2{0xA}; // == 0B1010
    std::bitset<4> b3{"0011"}; // can also be constexpr since C++23
    std::bitset<8> b4{"ABBA", length_t(4), /*0:*/'A', /*1:*/'B'}; // == 0B0000'0110
    // bitsets can be printed out to a stream:
    std::cout << "b1:" << b1 << "; b2:" << b2 << "; b3:" << b3 << "; b4:" << b4 << '\n';
    // bitset supports bitwise operations:
    b3 |= 0b0100; assert(b3 == 0b0111);
    b3 &= 0b0011; assert(b3 == 0b0011);
    b3 ^= std::bitset<4>{0b1100}; assert(b3 == 0b1111);
    // operations on the whole set:
    b3.reset(); assert(b3 == 0);
    b3.set(); assert(b3 == 0b1111);
    assert(b3.all() && b3.any() && !b3.none());
    b3.flip(); assert(b3 == 0);
    // operations on individual bits:
    b3.set(position_t(1), true); assert(b3 == 0b0010);
    b3.set(position_t(1), false); assert(b3 == 0);
    b3.flip(position_t(2)); assert(b3 == 0b0100);
    b3.reset(position_t(2)); assert(b3 == 0);
    // subscript operator[] is supported:
    b3[2] = true; assert(true == b3[2]);
    // other operations:
    assert(b3.count() == 1);
    assert(b3.size() == 4);
    assert(b3.to_ullong() == 0b0100ULL);
    assert(b3.to_string() == "0100");


b1:0000; b2:1010; b3:0011; b4:00000110

[edit] See also

space-efficient dynamic bitset
(class template specialization) [edit]
Bit manipulation (C++20) utilities to access, manipulate, and process individual bits and bit sequences