include fstream include iostream include cstring int main auto myfile

#include <fstream>
#include <iostream>
#include <cstring>

int main()
{
    auto myfile = std::fstream("file.binary", std::ios::out | std::ios::binary);
    char buff[8];
    double pi = 3.1415925;
    std::memcpy(buff, &pi, 8);
    myfile.write(buff, 8);
    myfile.close();
}