Chapter 7, Problem 1PP

(Statistics) a. Write a C++ program that reads a list of double-precision grades from the keyboard into an array named grade. The grades are to be counted as they’re read, and entry is to be terminated when a negative value has been entered. After all grades have been input, your program should find and display the sum and average of the grades. The grades should then be listed with an asterisk (*) placed in front of each grade that’s below the average.

b. Extend the program written for Exercise 1a to display each grade and its letter equivalent, using the following scale:

$\begin{array}{l}Between90and100=A\hfill \\ Greaterthanorequalto80andlessthan90=B\hfill \\ Greaterthanorequalto70andlessthan80=C\hfill \\ Greaterthanorequalto60andlessthan70=D\hfill \\ Lessthan60=F\hfill \end{array}$

Program Plan Intro

Program Plan:

• Declaremax and count variables of int data type.
• Declare sumand average variables of double data type
• Declare an array grade[100] of double data type.
• Use for loop to read all the array elements from the user.
• Use if statementto check the negative value.
• Calculatethe sum and average of all the user entered score.
• Display the calculated results to the user.
• Use for loop to calculate grades below the average.
• Use if condition to find the grades below the average.
• Display the grades below average by using the asterisk in the front of the grade(*).
• int main() method function is used to perform all the tasks.

Program Description: The main purpose of the program is to read all scores from the user, storing the scores in the grade[] array, calculating the sum and average of all the entered elements and to display the grades below average by using the asterisk in the front of grade(*).

Explanation of Solution

Program code:

//including required header files
#include<iostream>
usingnamespacestd;
//main method
int main()
{
//declaring required variables
int max = 100, count =0;
double sum=0, average=0;
//Declaring the array to store value of grades
double grade[max];

cout<<"Enter scores and any negative number to terminate"<<endl;

//This loop will execute maximum of 100
//while loop
while(count<max){
//Reading inputs from user 
cin>>grade[count];
//if the number is negative then loop is terminated
if(grade[count]<0)

break;
//adding the entered sum
sum = sum + grade[count];
//increnting loop variable 
count++;
    }//end of while loop
//Calculating  average
average = sum/count;
//displaying Calculated results to the user
cout<<"Total of the scores: "<<sum<<endl;
cout<<"Average of the scores: "<<average<<endl;
cout<<"Scores below average: ";
//for loop to find the score below average
for(int i=0; i<count; i++)
    {
//if the score is below average
if(grade[i]<average)
        {
cout<<"\n * "<<grade[i];
        }
    }
return0;

}//end of the main method

Sample output:

Program Plan Intro

Program Plan:

• Declaremax and count variables of int data type.
• Declare sumand average variables of double data type
• Declare an array grade[100] of double data type.
• Use for loop to read all the array elements from the user.
• Use if statement to check the negative value.
• Calculate the sum and average of all the user entered score.
• Display the calculated results to the user.
• Use for loop to calculate grades below the average.
• Use if condition to find the grades below the average.
• Display the grades below average by using the asterisk in the front of grade(*).
• Use if condition to find the grade.
• int main() method function is used to perform all the task.

Program Description: The main purpose of the program is to modify the program code given in part (a) so that the code will also display the grade letters to the user.

Explanation of Solution

Program code:

//including required header files
#include<iostream>
usingnamespacestd;
//main method
int main()
{
//declaring required variables
int max = 100, count =0;
double sum=0, average=0;
//Declaring the array to store value of grades
double grade[max];

cout<<"Enter scores and any negative number to terminate"<<endl;

//This loop will execute maximum of 100
//while loop
while(count<max){
//Reading inputs from user 
cin>>grade[count];
//if the number is negative then loop is terminated
if(grade[count]<0)

break;
//adding the entered sum
sum = sum + grade[count];
//increnting loop variable 
count++;
    }//end of while loop
//Calculating  average
average = sum/count;
//displaying Calculated results to the user
cout<<"Total of the scores: "<<sum<<endl;
cout<<"Average of the scores: "<<average<<endl;
cout<<"Scores below average: ";
//for loop to find the score below average
for(int i=0; i<count; i++)
    {
//if the score is below average
if(grade[i]<average)
        {
cout<<"\n * "<<grade[i];
        }
    }
//displaying message to the user
cout<<"\n Grades and equivalent letters are: ";
//for loop
for(int i=0; i<count; i++)
    {
//if grades are between 90 and 100
if(grade[i]<=100&& grade[i]>=90){

cout<<"  \n"<<grade[i]<<": A"<<endl;

            }
/*if grades are greater than or equal to 80 and less than 90*/
elseif(grade[i]<90&& grade[i]>=80){

cout<<"  \n"<<grade[i]<<": B"<<endl;

            }
/*if grades are greater than or equal to 70 and less than 80*/
elseif(grade[i]<80&& grade[i]>=70){

cout<<"  \n"<<grade[i]<<": C"<<endl;

            }
/*if grades are greater than or equal to 60 and less than 70*/
elseif(grade[i]<70&& grade[i]>=60)
            {
cout<<"  \n"<<grade[i]<<": D"<<endl;

            }
//otherwise
else{
cout<<"  \n"<<grade[i]<<": F"<<endl;
            }
    }
return0;

}//end of the main method

Sample output: