// Fig. 2.22: fig02_22.cpp
// Counting letter grades.
#include <iostream>
#include <stdio.h>

     
using std::cout;
using std::cin;
using std::endl;
     
// function main begins program execution
int main()
{
  int grade;       // one grade
  int aCount = 0;  // number of As
  int bCount = 0;  // number of Bs
  int cCount = 0;  // number of Cs
  int dCount = 0;  // number of Ds
  int fCount = 0;  // number of Fs
    
  cout << "Enter the letter grades." << endl
       << "Enter the EOF character to end input." << endl;
    
  // loop until user types end-of-file key sequence
  while ( ( grade = cin.get() ) != EOF ) {
    
    // determine which grade was input
    switch ( grade ) {  // switch structure nested in while
    
    case 'A':        // grade was uppercase A
    case 'a':        // or lowercase a
      ++aCount;     // increment aCount
      break;        // necessary to exit switch
    
    case 'B':        // grade was uppercase B
    case 'b':        // or lowercase b
      ++bCount;     // increment bCount    
      break;        // exit switch
    
    case 'C':        // grade was uppercase C
    case 'c':        // or lowercase c
      ++cCount;     // increment cCount    
      break;        // exit switch
    
    case 'D':        // grade was uppercase D
    case 'd':        // or lowercase d
      ++dCount;     // increment dCount    
      break;        // exit switch
    
    case 'F':        // grade was uppercase F
    case 'f':        // or lowercase f
      ++fCount;     // increment fCount    
      break;        // exit switch
    
    case '\n':       // ignore newlines,  
    case '\t':       // tabs, 
    case ' ':        // and spaces in input
      break;        // exit switch
    
    default:         // catch all other characters
      cout << "Incorrect letter grade entered."
	   << " Enter a new grade." << endl;
      break;        // optional; will exit switch anyway
      
    } // end switch
    
  } // end while
  
  // output summary of results
  cout << "\n\nTotals for each letter grade are:" 
       << "\nA: " << aCount   // display number of A grades
       << "\nB: " << bCount   // display number of B grades
       << "\nC: " << cCount   // display number of C grades 
       << "\nD: " << dCount   // display number of D grades
       << "\nF: " << fCount   // display number of F grades
       << endl;
    
  return 0;  // indicate successful termination
    
} // end function main