std::bitset(3)

NAME
std::bitset - std::bitset

Synopsis
   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 (since C++23)
   expression.

Template parameters
   N - the number of bits to allocate storage for

Member types
   reference proxy class representing a reference to a bit
             (class)

Member functions
   constructor constructs the bitset
                      (public member function)
   operator== compares the contents
   operator!= (public member function)
   (removed in C++20)

Element access
   operator[] accesses specific bit
                      (public member function)
   test accesses specific bit
                      (public member function)
   all checks if all, any or none of the bits are set to true
   any (public member function)
   none
   count returns the number of bits set to true
                      (public member function)

Capacity
   size returns the number of bits that the bitset holds
                      (public member function)

Modifiers
   operator&=
   operator|= performs binary AND, OR, XOR and NOT
   operator^= (public member function)
   operator~
   operator<<=
   operator>>= performs binary shift left and shift right
   operator<< (public member function)
   operator>>
   set sets bits to true or given value
                      (public member function)
   reset sets bits to false
                      (public member function)
   flip toggles the values of bits
                      (public member function)

Conversions
   to_string returns a string representation of the data
                      (public member function)
   to_ulong returns an unsigned long integer representation of the data
                      (public member function)
   to_ullong returns an unsigned long long integer representation of the data
   (C++11) (public member function)

Non-member functions
   operator& performs binary logic operations on bitsets
   operator| (function template)
   operator^
   operator<< performs stream input and output of bitsets
   operator>> (function template)

Helper classes
   std::hash<std::bitset> hash support for std::bitset
   (C++11) (class template specialization)

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

Example
// Run this code
 #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");
 }

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

See also
   vector<bool> space-efficient dynamic bitset
                        (class template specialization)
   Bit manipulation (C++20) utilities to access, manipulate, and process individual
                        bits and bit sequences