Use numeric_limits to get max value for float, double and long double : numeric_limits « STL Algorithms Helper « C++ Tutorial

1. C++ Tutorial
2. STL Algorithms Helper
3. numeric_limits

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <limits>
#include <string>
using namespace std;

int main()
{
   // use textual representation for bool
   cout << boolalpha;

   // print maximum of floating-point types
   cout << "max(float):       "
        << numeric_limits<float>::max() << endl;
   cout << "max(double):      "
        << numeric_limits<double>::max() << endl;
   cout << "max(long double): "
        << numeric_limits<long double>::max() << endl;
   cout << endl;

}

max(float):       3.40282e+038
max(double):      1.79769e+308
max(long double): 1.#INF