GCSE AQA Computer Science Defensive Design & Testing: Figure 8 shows a VB.Net program

Question

Figure 8 shows a VB.Net program that is being developed.

It is supposed to calculate and display the highest common factor of two numbers entered by the user.

The highest common factor of two numbers is the largest number that both numbers can be divided by without leaving a remainder.

Examples:

- the highest common factor of the numbers 6 and 9 is 3
- the highest common factor of 2 and 5 is 1

Line numbers are shown but are not part of the program code.

Figure 8

Dim num1 As Integer = Console.ReadLine()
    Dim num2 As Integer = Console.ReadLine()
    Dim hcf As Integer = 1
    Dim count As Integer = 1
    While count < num1
        If num1 Mod count = 0 And num2 Mod count = 0 Then
            hcf = count
        End If
        count = count + 1
    End While
    Console.WriteLine(hcf)

The program in Figure 8 works correctly sometimes but not always. When the user enters the numbers 4 and 6 it correctly outputs 2, but when the user enters the numbers 4 and 4 it should output 4 but it does not.

17.1 State the output from the program in Figure 8 when the user enters the numbers 4 and 4.

17.2 State the line number from the program in Figure 8 which contains the error that stops the program from sometimes working correctly.

17.3 Describe how the line of code identified in your answer to 17.2 should be changed so that the program in Figure 8 will work correctly.

Figure 8 shows a VB.Net program that is being developed - AQA - GCSE Computer Science - Question 17 - 2021 - Paper 1

Worked Solution & Example Answer:Figure 8 shows a VB.Net program that is being developed - AQA - GCSE Computer Science - Question 17 - 2021 - Paper 1

State the output from the program in Figure 8 when the user enters the numbers 4 and 4.

State the line number from the program in Figure 8 which contains the error that stops the program from sometimes working correctly.

Describe how the line of code identified in your answer to 17.2 should be changed so that the program in Figure 8 will work correctly.

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