std::bitset<N>::set

bitset& set();	(1)	(noexcept since C++11) (constexpr since C++23)
bitset& set( std::size_t pos, bool value = true ) ;	(2)	(constexpr since C++23)

Sets all bits to true or sets one bit to specified value.

1) Sets all bits to true.

2) Sets the bit at position pos to the value value.

Parameters

pos	-	the position (counting from 0, i.e. from least significant to most significant) of the bit to set
value	-	the value to set the bit to

Return value

*this

Exceptions

2) Throws std::out_of_range if pos

Example

Run this code

#include <bitset>
#include <cstddef>
#include <iostream>
 
int main()
{
    std::bitset<8> b;
    std::cout << b << '\n';
    std::cout << b.set() << '\n';
    std::cout << b.reset() << '\n';
 
    for (std::size_t i = 1; i < b.size(); i += 2)
        b.set(i);
 
    std::cout << b << '\n';
}

Output:

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 186	C++98	the type of value was int	corrected to bool
LWG 2250	C++98	the behavior was undefined if pos does not correspond to a valid bit position	always throws an exception in this case

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Diagnostics library
Memory management library
Metaprogramming library (C++11)
General utilities library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library (C++17)
Concurrency support library (C++11)
Execution support library (C++26)
Technical specifications
Symbols index
External libraries

reset	sets bits to false (public member function)
flip	toggles the values of bits (public member function)