fig02_22.cpp

《c＋＋大学教程》源码

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

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



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