/* This program uses a running total and count to compute the average
   of a set of grades entered by the user. Each time a new grade is
   entered, its value is added to the current total, and 1 is added
   to the current count. At the end, the final total and count are used
   to compute the average. 

   This program also uses a sentinel to allow the user to execute at
   any time. That sentinel is -1 (hopefully, not a legal grade). */

#include <iostream.h>
main() {

   int grade,     /* current grade entered by user */
       total,     /* running total of grades entered so far */
       count;     /* running count of how many grades ented so far */

   /* Initialize total and count to 0, which is the total and number
      of grades before any are entered. */

   total = 0;
   count = 0;

   /* Initialize grade to first value entered by user */

   cout << "Enter first grade (-1 to quit): ";
   cin >> grade;

   /* Continue looping as long as the user does not enter the sentinel
      -1 for grade */

   while (grade != -1) {
      
      /* Increment the current total by the new grade */

      total = total + grade;

      /* Increment the total number of grades */

      count = count + 1;

      /* Prompt user for next grade */

      cout << "Enter next grade (-1 to quit): ";
      cin >> grade;

      } /* End of loop */

   /* Print out the final average, based on current total and count.
      Make sure that number of grades is more than zero first 
      (otherwise, will get division by zero) */

   if (count > 0) 
      cout << "The average is " << (float)total/count << "\n";
   else
      cout << "No grades were entered\n";

   }