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Software Design Using C++

Review of Functions and Parameters

Answering the Question

First, we repeat the description of the problem: Write a reasonable test program for the C++ function shown below.


/* Given:  NumGrade   A numeric grade (whole number).
   Task:   To find the corresponding letter grade.
   Return: This letter grade in the function name.
*/
char LetterGrade(int NumGrade)
   {
   if (NumGrade > 100)
      return 'I';
   else if (NumGrade >= 90)
      return 'A';
   else if (NumGrade >= 80)
      return 'B';
   else if (NumGrade >= 70)
      return 'C';
   else if (NumGrade >= 60)
      return 'D';
   else if (NumGrade >= 0)
      return 'F';
   else
      return 'I';
   }

We began with an outline that contained no code for the main function. The following shows one possible way to write some of the code, but may not be the best answer. See the link at the bottom for a better method.


/* Filename:  decision.cpp

   Author:  Br. David Carlson

   Date:  December 20,2003

   This is a test program that takes several numeric grades and converts
   them into letter grades.  The numeric grades are hard-coded into the
   program.  The numeric grades and corresponding letter grades are displayed
   on the screen.
*/

#include <iostream>
using namespace std;


// Function prototypes:
char LetterGrade(int NumGrade);


int main(void)
   {
   cout << "Numeric grade " << 88 << " corresponds to the letter grade "
      << LetterGrade(88) << endl << endl;

   cout << "Numeric grade " << 65 << " corresponds to the letter grade "
      << LetterGrade(65) << endl << endl;

   cout << "Numeric grade " << 96 << " corresponds to the letter grade "
      << LetterGrade(96) << endl << endl;

   return 0;
   }


/* Given:  NumGrade   A numeric grade (whole number).
   Task:   To find the corresponding letter grade.
   Return: This letter grade in the function name.
*/
char LetterGrade(int NumGrade)
   {
   if (NumGrade > 100)
      return 'I';
   else if (NumGrade >= 90)
      return 'A';
   else if (NumGrade >= 80)
      return 'B';
   else if (NumGrade >= 70)
      return 'C';
   else if (NumGrade >= 60)
      return 'D';
   else if (NumGrade >= 0)
      return 'F';
   else
      return 'I';
   }

Note that the above method of coding the main function is awkward, especially if we want to test a longer list of numeric grades. We could package up the code that does one test as a function and just call this new function repeatedly. Try this yourself. Also think about what numbers should be tested to get a reasonable test program (sometimes called a driver program).

Click on NEXT to see one possible answer.

You can go back to the overall review listing: Review of Introductory Topics.

Back to the main page for Software Design Using C++

Author: Br. David Carlson with contributions by Br. Isidore Minerd
Last updated: January 15, 2013
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