How To: Convert Text To Numbers In C++

This example shows how to convert a character string of digits and an optional decimal point into a number. The number can be an integer or a floating point value.

#include <iostream>
using std::cout;
using std::endl;

#include <cstdlib>

int main()
{
  char* token[] = {"100.23", "4", "one"};
    
  double a = atof(token[0]); // a floating point
  int b = atoi(token[1]);    // an integer
  double c = atof(token[2]); // non-numerics returns as zero

  cout << "atof(token[0]) = " << a << endl;
  cout << "atoi(token[1]) = " << b << endl;
  cout << "atof(token[2]) = " << c << endl;

  return 0;
}