/* This program illustrates the definition and use of a very simple
   function to convert Fahrenheit temperatures into Celsius
   */

#include <iostream.h>

/* The following line is the prototype for the Fahr2Cel function. It basically
   "declares" the existance of the function, telling C what types the
    function takes as parameters and returns. */

float Fahr2Cel(float); 

/* The main function will prompt the user for the Fahrenheit temperature,
   and get the corresponding Celsius temperature by calling the function */

main() {
   float f,  /* Fahrenheit temperature entered by user */
         c;  /* Celsius temperature printed to screen */

   cout << "Enter a Fahrenheit temperature: ";
   cin >> f;

   /* The function call. We pass the Fahrenheit temperature entered by 
      the user to the function, and store the value returned by the
      function in c. */

   c = Fahr2Cel(f);

   cout << "The corresponding Celsius temperature is " 
        << c << "\n";

   } /* end of main function */


/* The Fahr2Cel function takes a float value as a parameter, and stores it in
   the variable fahr_temp. It then uses that variable to compute
   cel_temp, which it then returns to the caller */

float Fahr2Cel(float fahr_temp) {

   /* cel_temp is a local variable of Fahr2Cel (as is fahr_temp) */

   float cel_temp;

   /* use the parameter to compute cel_temp */

   cel_temp = 5 * (fahr_temp - 32)/9;

   /* return the value of cel_temp to the caller */

   return cel_temp;

   } /* end of Fahr2Cel function