Visual Basic 2008 9.0 .NET Examples and Ebook

Following example gives us all numbers from one to three.

Module Example1
    Sub Main()
        Console.WriteLine(1)
        Console.WriteLine(2)
        Console.WriteLine(3)
        '
        Console.ReadLine()
    End Sub
End Module

Output :

 1
 2
 3

The above example is very statically defined. Suppose we need all numbers from one to hundred, then 97 instructors need to be added.

A more dynamic solution can be defined when using the iteration technique.

Module Example2
    Sub Main()
        Dim value As Integer
        '
        value = value + 1
        Console.WriteLine(value)
        '
        value = value + 1
        Console.WriteLine(value)
        '
        value = value + 1
        Console.WriteLine(value)
        '
        Console.ReadLine()
    End Sub
End Module

Output :

 1
 2
 3

As you can see in the above solution the same instructions are repeated three times.

In stead of repeating the same instructions, we can code them between a Do While and Loop of an iteration.

Do While is followed by a condition, expression how long the instructions ( between Do While and Loop ) should be repeated.
As long as the condition evaluates as true the instructions are repeated. From the moment the condition evaluates as false the iteration is ended, and the instructions following the iteration are executed.

Module Example3
    Sub Main()
        Dim value As Integer
        '
        Do While value < 3
            value = value + 1
            Console.WriteLine(value)
        Loop
        '
        Console.ReadLine()
    End Sub
End Module

Output :

 1
 2
 3

The algorithm can be coded even more dynamical by adding a start- and endvalue.

Module Example4
    Sub Main()
        Dim startValue As Integer = 10
        Dim endValue As Integer = 15
        '
        Dim value As Integer = startValue - 1
        Do While value < endValue
            value = value + 1
            Console.WriteLine(value)
        Loop
        '
        Console.ReadLine()
    End Sub
End Module

Output :

 10
 11
 12
 13
 14
 15

Task :

Make a program that brings all numbers from 20 to 10 on the console.

Output :

 20
 19
 18
 17
 16
 15
 14
 13
 12
 11
 10

Solution :

Module Exercise1Solution
    Sub Main()
        Dim value As Integer = 21
        '
        Do While value > 10
            value = value - 1
            Console.WriteLine(value)
        Loop
        '
        Console.ReadLine()
    End Sub
End Module

Task :

Make a program that brings all powers of 2 smaller ( starting with exponent 1 ) than 1000 on the console.

Output :

 base : 2, exponent : 1, result : 2
 base : 2, exponent : 2, result : 4
 base : 2, exponent : 3, result : 8
 base : 2, exponent : 4, result : 16
 base : 2, exponent : 5, result : 32
 base : 2, exponent : 6, result : 64
 base : 2, exponent : 7, result : 128
 base : 2, exponent : 8, result : 256
 base : 2, exponent : 9, result : 512

Solution :

Module Exercise2Solution
    Sub Main()
        Dim base As Integer = 2
        Dim exponent As Integer = 1
        Dim result As Integer = base ^ exponent
        '
        Do While result < 1000
            Console.WriteLine("base : " & base & _
                              ", exponent : " & exponent & _
                              ", result : " & result)
            exponent = exponent + 1
            result = base ^ exponent
        Loop
        '
        Console.ReadLine()
    End Sub
End Module