how to adjust decimal places c++ without printing in output code example

Example 1: how to print a decimal number upto 6 places of decimal in c++

#include <iostream>
#include <iomanip>

int main()
{
    double d = 122.345;

    std::cout << std::fixed;
    std::cout << std::setprecision(2);
    std::cout << d;
}

Example 2: how to format decimal palces in c++

std::cout << std::setprecision(2) << std::fixed;
// where the 2 is how many decimal places you want
// note you need to <iomanip>