Mod

How can you use modulo division in the VB.NET language? With the Mod operator, you can compute the remainder of a division expression.

Mod is equivalent to the modulo operator in C-like languages. With Mod we can determine whether a number is odd or even (its parity).

Example

This example shows some Mod expressions with constant Integers. When the value 90 goes into 1000 11 times, but leaves a remainder of 10. This is the result of 1000 Mod 90.

Module Module1
    Sub Main()
        ' Compute some modulo expressions with Mod.
        Console.WriteLine(5 Mod 3)
        Console.WriteLine(1000 Mod 90)
        Console.WriteLine(100 Mod 90)
        Console.WriteLine(81 Mod 80)
        Console.WriteLine(1 Mod 1)
    End Sub
End Module
2
10
10
1
0

Loop example

Using a Mod expression is appropriate in a For-loop. You can apply Mod to the variable "i". In this program, we display "i" whenever it is divisible by 10.

Module Module1
    Sub Main()
        ' Loop through integers.
        For i As Integer = 0 To 200 - 1
            ' Test i with Mod 10.
            If i Mod 10 = 0 Then
                Console.WriteLine(i)
            End If
        Next
    End Sub
End Module
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190

Odd, even numbers

The parity of a number is whether it is odd or even. We can test parity by creating 2 functions in VB.NET that return true or false.

Module Module1

    Function IsOdd(ByVal number As Integer) As Boolean
        ' Handle negative numbers by returning the opposite of IsEven.
        Return IsEven(number) = False
    End Function

    Function IsEven(ByVal number As Integer) As Boolean
        ' Handles all numbers because it tests for 0 remainder.
        ' ... This works for negative and positive numbers.
        Return number Mod 2 = 0
    End Function

    Sub Main()
        For i = -10 To 10
            Console.WriteLine(i.ToString() + " EVEN = " + IsEven(i).ToString())
            Console.WriteLine(i.ToString() + " ODD  = " + IsOdd(i).ToString())
        Next

    End Sub
End Module
-10 EVEN = True
-10 ODD  = False
-9 EVEN = False
-9 ODD  = True
-8 EVEN = True
-8 ODD  = False
-7 EVEN = False
-7 ODD  = True
-6 EVEN = True
-6 ODD  = False
-5 EVEN = False
-5 ODD  = True
-4 EVEN = True
-4 ODD  = False
-3 EVEN = False
-3 ODD  = True
-2 EVEN = True
-2 ODD  = False
-1 EVEN = False
-1 ODD  = True
0 EVEN = True
0 ODD  = False
1 EVEN = False
1 ODD  = True
2 EVEN = True
2 ODD  = False
3 EVEN = False
3 ODD  = True
4 EVEN = True
4 ODD  = False
5 EVEN = False
5 ODD  = True
6 EVEN = True
6 ODD  = False
7 EVEN = False
7 ODD  = True
8 EVEN = True
8 ODD  = False
9 EVEN = False
9 ODD  = True
10 EVEN = True
10 ODD  = False

Syntax note

In C-like languages, the "%" character expresses a modulo division. We cannot use this character in VB.NET. Instead the Mod operator is used.

Modulo division is an important concept to understand in computer programming. In .NET, modulo division is used to implement collections such as Dictionary.

The Mod operator often comes in handy whenever a mathematical procedure is needed. We can use modulo for determining parity (odd or even).