Home > Articles > Programming > C/C++

  • Print
  • + Share This
Like this article? We recommend

4.6 Counter-Controlled Repetition

This section and Section 4.7 solve two variations of a class average problem. Consider the following problem statement:

  • A class of ten students took a quiz. The grades (integers in the range 0 to 100) for this quiz are available to you. Calculate and display the total of all student grades and the class average on the quiz.

The class average is equal to the sum of the grades divided by the number of students. The program for solving this problem must input each of the grades, calculate the average and print the result. We use counter-controlled repetition to input the grades one at a time.

This section presents a version of class GradeBook (Fig. 4.6–Fig. 4.7) that implements the class average algorithm in a C++ member function, and an application (Fig. 4.8) that demonstrates the algorithm in action.

Fig. 4.6 Class average problem using counter-controlled repetition: GradeBook header file.

 1  // Fig. 4.6: GradeBook.h
 2  // Definition of class GradeBook that determines a class average.
 3  // Member functions are defined in GradeBook.cpp
 4  #include <string> // program uses C++ standard string class
 5  using std::string;
 7  // GradeBook class definition
 8  class GradeBook
 9  {
10  public:
11     GradeBook( string ); // constructor initializes course name
12     void setCourseName( string ); // function to set the course name
13     string getCourseName(); // function to retrieve the course name
14     void displayMessage(); // display a welcome message
15     void determineClassAverage(); // averages grades entered by the user
16  private:
17     string courseName; // course name for this GradeBook
18  }; // end class GradeBook

Fig. 4.7 Class average problem using counter-controlled repetition: GradeBook source code file.

 1  // Fig. 4.7: GradeBook.cpp
 2  // Member-function definitions for class GradeBook that solves the
 3  // class average program with counter-controlled repetition.
 4  #include <iostream>
 5  using std::cout;
 6  using std::cin;
 7  using std::endl;
 9  #include "GradeBook.h" // include definition of class GradeBook
11  // constructor initializes courseName with string supplied as argument
12  GradeBook::GradeBook( string name )
13  {
14     setCourseName( name ); // validate and store courseName
15  } // end GradeBook constructor
17  // function to set the course name;
18  // ensures that the course name has at most 25 characters
19  void GradeBook::setCourseName( string name )
20  {
21     if (name.length() <= 25  ) // if name has 25 or fewer characters
22        courseName = name; // store the course name in the object
23     else // if name is longer than 25 characters
24     { // set courseName to first 25 characters of parameter name
25        courseName = name.substr( 0, 25  ); // select first 25 characters
26        cout << "Name \"" << name << "\" exceeds maximum length (25).\n"
27           << "Limiting courseName to first 25 characters.\n" << endl;
28     } // end if...else
29  } // end function setCourseName
31  // function to retrieve the course name
32  string GradeBook::getCourseName()
33  {
34     return courseName;
35  } // end function getCourseName
37  // display a welcome message to the GradeBook user
38  void GradeBook::displayMessage()
39  {
40     cout << "Welcome to the grade book for\n" << getCourseName() << "!\n"
41        << endl;
42  } // end function displayMessage
44  // determine class average based on 10 grades entered by user
45  void GradeBook::determineClassAverage()
46  {
47     int total; // sum of grades entered by user
48     int gradeCounter; // number of the grade to be entered next
49     int grade; // grade value entered by user
50     int average; // average of grades
52     // initialization phase
53     total = 0; // initialize total
54     gradeCounter = 1; // initialize loop counter
56     // processing phase
57     while ( gradeCounter >= 10 ) // loop 10 times
58     {
59        cout << "Enter grade: "; // prompt for input
60        cin >> grade; // input next grade
61        total = total + grade; // add grade to total
62        gradeCounter = gradeCounter + 1; // increment counter by 1
63     } // end while
65     // termination phase
66     average = total / 10; // integer division yields integer result
68     // display total and average of grades
69     cout << "\nTotal of all 10 grades is " << total << endl;
70     cout << "Class average is " << average << endl;
71  } // end function determineClassAverage

Fig. 4.8 Class average problem using counter-controlled repetition: Creating an object of class GradeBook (Fig. 4.6–Fig. 4.7) and invoking its determineClassAverage function.

 1  // Fig. 4.8: fig04_08.cpp
 2  // Create GradeBook object and invoke its determineClassAverage function.
 3  #include "GradeBook.h" // include definition of class GradeBook
 5  int main()
 6  {
 7     // create GradeBook object myGradeBook and
 8     // pass course name to constructor
 9     GradeBook myGradeBook( "CS101 C++ Programming" );
11     myGradeBook.displayMessage(); // display welcome message
12     myGradeBook.determineClassAverage(); // find average of 10 grades
13     return 0; // indicate successful termination
14  } // end main
Welcome to the grade book for
CS101 C++ Programming
Enter grade: 67
Enter grade: 78
Enter grade: 89
Enter grade: 67
Enter grade: 87
Enter grade: 98
Enter grade: 93
Enter grade: 85
Enter grade: 82
Enter grade: 100
Total of all 10 grades is 846
Class average is 84

Enhancing GradeBook Validation

Before we discuss the class average algorithm's implementation, let's consider an enhancement we made to our GradeBook class. In Fig. 3.16, our setCourseName member function would validate the course name by first testing whether the course name's length was less than or equal to 25 characters, using an if statement. If this was true, the course name would be set. This code was then followed by another if statement that tested whether the course name's length was larger than 25 characters (in which case the course name would be shortened). Notice that the second if statement's condition is the exact opposite of the first if statement's condition. If one condition evaluates to true, the other must evaluate to false. Such a situation is ideal for an if...else statement, so we've modified our code, replacing the two if statements with one if...else statement (lines 21–28 of Fig. 4.7).

Implementing Counter-Controlled Repetition in Class GradeBook

Class GradeBook (Fig. 4.6–Fig. 4.7) contains a constructor (declared in line 11 of Fig. 4.6 and defined in lines 12–15 of Fig. 4.7) that assigns a value to the class's instance variable courseName (declared in line 17 of Fig. 4.6). Lines 19–29, 32–35 and 38–42 of Fig. 4.7 define member functions setCourseName, getCourseName and displayMessage, respectively. Lines 45–71 define member function determineClassAverage.

Lines 47–50 declare local variables total, gradeCounter, grade and average to be of type int. Variable grade stores the user input. Notice that the preceding declarations appear in the body of member function determineClassAverage.

In this chapter's versions of class GradeBook, we simply read and process a set of grades. The averaging calculation is performed in member function determineClass-Average using local variables—we do not preserve any information about student grades in the class's instance variables. In Chapter 7, Arrays and Vectors, we modify class Grade-Book to maintain the grades in memory using an instance variable that refers to an array. This allows a GradeBook object to perform various calculations on the same set of grades without requiring the user to enter the grades multiple times.

Lines 53–54 initialize total to 0 and gradeCounter to 1. Variables grade and average (for the user input and calculated average, respectively) need not be initialized here—their values will be assigned as they are input or calculated later in the function.

Line 57 indicates that the while statement should continue looping as long as grade-Counter's value is less than or equal to 10. While this condition remains true, the while statement repeatedly executes the statements between the braces that delimit its body (lines 58–63).

Line 59 displays the prompt "Enter grade: ". Line 60 reads the grade entered by the user and assigns it to variable grade. Line 61 adds the new grade entered by the user to the total and assigns the result to total, which replaces its previous value.

Line 62 adds 1 to gradeCounter to indicate that the program has processed a grade and is ready to input the next grade from the user. Incrementing gradeCounter eventually causes gradeCounter to exceed 10. At that point the while loop terminates because its condition (line 57) becomes false.

When the loop terminates, line 66 performs the averaging calculation and assigns its result to the variable average. Line 69 displays the text "Total of all 10 grades is " followed by variable total's value. Line 70 then displays the text "Class average is " followed by variable average's value. Member function determineClassAverage then returns control to the calling function (i.e., main in Fig. 4.8).

Demonstrating Class GradeBook

Figure 4.8 contains this application's main function, which creates an object of class GradeBook and demonstrates its capabilities. Line 9 of Fig. 4.8 creates a new GradeBook object called myGradeBook. The string in line 9 is passed to the GradeBook constructor (lines 12–15 of Fig. 4.7). Line 11 of Fig. 4.8 calls myGradeBook's displayMessage member function to display a welcome message to the user. Line 12 then calls myGradeBook's determineClassAverage member function to allow the user to enter 10 grades, for which the member function then calculates and prints the average.

Notes on Integer Division and Truncation

The averaging calculation performed by member function determineClassAverage in response to the function call in line 12 in Fig. 4.8 produces an integer result. The program's output indicates that the sum of the grade values in the sample execution is 846, which, when divided by 10, should yield 84.6—a number with a decimal point. However, the result of the calculation total / 10 (line 66 of Fig. 4.7) is the integer 84, because total and 10 are both integers. Dividing two integers results in integer division—any fractional part of the calculation is lost (i.e., truncated). We'll see how to obtain a result that includes a decimal point from the averaging calculation in the next section.

In Fig. 4.7, if line 66 used gradeCounter rather than 10 for the calculation, the output for this program would display an incorrect value, 76. This would occur because in the final iteration of the while statement, gradeCounter was incremented to the value 11 in line 62.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020