Question

Exercise 3.4.1

In P3_4_1.cpp (BELOW), right at the beginning, the program initializes choice to 1. This forces the while loop to run at least once. If you use a do ... while instead, you wouldn't need to initialize the choice. Re-write the below program, call the new program ex341.cpp, so that is uses do ... while. Do not initialize the choice to 1 this time. Compile and run the program.

Answer questions:

Does the program work the same way? Write your answer as a comment inside the code of your ex341.cpp file.  

// P3_4_1.cpp - Read and average some integers, print the result.

// This program continue asking for a new number until the user enters a 0 to terminate the program

#include <iostream>  using namespace std;  

int main(void)  

{      int x;

        int count = 0; // (1) initialize a counter to 0 to count number of values  

        int choice = 1; // This is the choice that controls the looping continuation or termination          

        double sum = 0; // initialize sum to 0 to make sure sum at the beginning is 0              

        double average;  

        while( choice == 1) // (2) read N grades and compute their sum, count ensures N entries  

       {

              // read each number and compute the sum:  

              cout << "\n Enter a grade <Enter>: ";               

              cin >> x;               

              sum = sum + x;  

             count++; // (3) update the count  

            // prompt the user:              

            cout << "Do you wish to enter another grade? (1 for yes and 0 or other key for no): "

                   << endl;  

            cin >> choice;

        }

        if(count == 0)  

              cout << "You haven't entered any number. No average will be computed. Bye!\n";            

        else{

              average = sum/count; //Notice that we have divided by count this time  

              cout << "The average of these " << count << " grades is " << average <<"." << endl;  

        }

        return 0;  

}  

Answer 1

Here is code:

#include <iostream>
using namespace std;
int main(void)
{
int x;
int count = 0;
int choice;
int N; // Number of values for which the average must be computed.
double sum = 0;
double average;
char repeat;
do
{
count = 0; // (1) initialize a counter to 0 to count number of values
choice = 1; // This is the choice that controls the looping continuation or termination
while (choice == 1) // (2) read N grades and compute their sum, count ensures N entries
{
// read each number and compute the sum:
cout << "\n Enter a grade <Enter>: ";
cin >> x;
sum = sum + x;
count++; // (3) update the count
// prompt the user:
cout << "Do you wish to enter another grade? (1 for yes and 0 or other key for no): "
<< endl;
cin >> choice;
}
if (count == 0)
cout << "You haven't entered any number. No average will be computed. Bye!\n";
else
{
average = sum / count; //Notice that we have divided by count this time
cout << "The average of these " << count << " grades is " << average << "." << endl;
}
// (4) read user input and wheather user wants to play again.
cout << "\nDo you want to run again (Y/N) : ";
cin >> repeat;
} while (repeat == 'Y');
return 0;
}

Output: