Example 1:   convert.cpp

#include<iostream>
using namespace std;

#define CONVERSION_FACTOR  (5.0/9.0)

int main(void)
{
  double fahrenheit,   // temperature in Fahrenheit
         celsius;      // temperature in Celsius

  // Get temperature in Fahrenheit
  cout << "Enter the temperature in Fahrenheit: ";
  cin  >> fahrenheit;

  // Convert to Celsius
  celsius = (fahrenheit-32)*CONVERSION_FACTOR;

  // Print temperature in Celsius
  cout << fahrenheit << " degrees Fahrenheit is equivalent to "
       << celsius  << " degrees Celsius.\n";

  return(0);
}