gistfile1.txt

#include <iostream>
#include <iomanip>
#include <sstream>
int main()
{
  std::string number = "111111111.2";
  std::cout << std::setprecision(20) << atof(number.c_str()) << std::endl; // double: 111111111.20000000298

  std::stringstream ss;
  ss << number;
  float val;
  ss >> val;
  std::cout  << std::setprecision(20) << val << std::endl; // float: 111111112
}