# <bit>

**[<bit>](https://en.cppreference.com/w/cpp/header/bit)** provides bit manipulation utilities introduced in C++20: `std::popcount` (count set bits), `std::countl_zero` / `std::countr_zero` (leading/trailing zeros), `std::rotl` / `std::rotr` (rotate), and `std::byteswap`.

These are thin wrappers around intrinsics like `__builtin_popcount`, providing portable, consistent semantics without writing assembly.

## Example

This example demonstrates counting set bits, counting leading zeros, and rotating bits left, all on an integer value.

```cpp
// compile: g++ -std=c++20 -o bitexample bitexample.cpp
// run: ./bitexample
// description: bit counting and rotation

#include <bit>
#include <iostream>

int main() {
    unsigned int x = 0b11010011;
    
    std::cout << "popcount of " << x << ": " << std::popcount(x) << "\n";
    std::cout << "leading zeros: " << std::countl_zero(x) << "\n";
    std::cout << "rotl by 2: " << std::rotl(x, 2) << "\n";
    
    return 0;
}
```