Pseudocode Algorithm with Counter-Controlled Repetition

Let’s use pseudocode to list the actions to execute and specify the order in which they should execute. We use counter-controlled repetition to input the grades one at a time. This technique uses a variable called a counter (or control variable) to control the number of times a set of statements will execute. In this example, repetition terminates when the counter exceeds 10. This section presents a fully developed pseudocode algorithm (Fig. C.1) and a version of class GradeBook (Fig. C.2) that implements the algorithm in a Java method. We then present an application (Fig. C.3) that demonstrates the algorithm in action.

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 1   Set total to zero
 2   Set grade counter to one
 3
 4   While grade counter is less than or equal to ten
 5      Prompt the user to enter the next grade
 6      Input the next grade
 7      Add the grade into the total
 8      Add one to the grade counter
 9
10   Set the class average to the total divided by ten
11   Print the class average

Fig. C.1 | Pseudocode algorithm that uses counter-controlled repetition to solve the classaverage problem.

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 1   // Fig. C.2: GradeBook.java
 2   // GradeBook class that solves the class-average problem using
 3   // counter-controlled repetition.
 4   import java.util.Scanner; // program uses class Scanner
 5
 6   public class GradeBook
 7   {
 8      private String courseName; // name of course this GradeBook represents
 9
10      // constructor initializes courseName
11      public GradeBook( String name )
12      {
13         courseName = name; // initializes courseName
14      } // end constructor
15
16      // method to set the course name
17      public void setCourseName( String name )
18      {
19         courseName = name; // store the course name
20      } // end method setCourseName
21
22      // method to retrieve the course name
23      public String getCourseName()
24      {
25         return courseName;
26      } // end method getCourseName
27
28      // display a welcome message to the GradeBook user
29      public void displayMessage()
30      {
31         // getCourseName gets the name of the course
32         System.out.printf( "Welcome to the grade book for %s! ",
33            getCourseName() );
34      } // end method displayMessage
35
36      // determine class average based on 10 grades entered by user
37      public void determineClassAverage()
38      {
39         // create Scanner to obtain input from command window
40         Scanner input = new Scanner( System.in );
41
42         int total; // sum of grades entered by user
43         int gradeCounter; // number of the grade to be entered next
44         int grade; // grade value entered by user
45         int average; // average of grades
46
47         // initialization phase
48         total = 0; // initialize total
49         gradeCounter = 1; // initialize loop counter
50
51         // processing phase uses counter-controlled repetition
52         while ( gradeCounter <= 10 ) // loop 10 times
53         {
54            System.out.print( "Enter grade: " ); // prompt
55            grade = input.nextInt(); // input next grade
56            total = total + grade; // add grade to total
57            gradeCounter = gradeCounter + 1; // increment counter by 1
58         } // end while
59
60         // termination phase
61         average = total / 10; // integer division yields integer result
62
63         // display total and average of grades
64         System.out.printf( " Total of all 10 grades is %d ", total );
65         System.out.printf( "Class average is %d ", average );
66      } // end method determineClassAverage
67   } // end class GradeBook

Fig. C.2 | GradeBook class that solves the class-average problem using counter-controlled repetition.

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 1   // Fig. C.3: GradeBookTest.java
 2   // Create GradeBook object and invoke its determineClassAverage method.
 3
 4   public class GradeBookTest
 5   {
 6      public static void main( String[] args )
 7      {
 8         // create GradeBook object myGradeBook and
 9         // pass course name to constructor
10         GradeBook myGradeBook = new GradeBook(
11            "CS101 Introduction to Java Programming" );
12
13         myGradeBook.displayMessage(); // display welcome message
14         myGradeBook.determineClassAverage(); // find average of 10 grades
15      } // end main
16   } // end class GradeBookTest

Fig. C.3 | GradeBookTest class creates an object of class GradeBook (Fig. C.2) and invokes its determineClassAverage method.

Note the references in the algorithm of Fig. C.1 to a total and a counter. A total is a variable used to accumulate the sum of several values. A counter is a variable used to count—in this case, the grade counter indicates which of the 10 grades is about to be entered by the user. Variables used to store totals are normally initialized to zero before being used in a program.