Numbers and Math

Arithmetic operators

Module Program
    Sub Main()
        Console.WriteLine(7 + 3)
        Console.WriteLine(7 - 3)
        Console.WriteLine(7 * 3)
        Console.WriteLine(7 / 2)      ' always floating-point division
        Console.WriteLine(7 \ 2)      ' integer division
        Console.WriteLine(7 Mod 2)    ' remainder
        Console.WriteLine(2 ^ 10)     ' power (a Double)
        Console.WriteLine(-7 \ 2)
    End Sub
End Module

10
4
21
3.5
3
1
1024
-3

Unlike C-style languages, / in VB always produces a floating-point result, even for two integers. Use \ for integer division; it truncates toward zero.

The Math class

Module Program
    Sub Main()
        Console.WriteLine(Math.Sqrt(16))
        Console.WriteLine(Math.Abs(-5))
        Console.WriteLine(Math.Max(3, 9))
        Console.WriteLine(Math.Round(2.5))
        Console.WriteLine(Math.Round(2.5, MidpointRounding.AwayFromZero))
        Console.WriteLine(Math.Round(3.14159, 2))
        Console.WriteLine(Math.Floor(2.7))
        Console.WriteLine(Math.Ceiling(2.1))
        Console.WriteLine(Math.PI)
    End Sub
End Module

4
5
9
2
3
3.14
2
3
3.141592653589793

Math.Round uses banker's rounding by default (2.5 becomes 2); pass MidpointRounding.AwayFromZero for the school rule.

Overflow is checked

Module Program
    Sub Main()
        Dim big As Integer = Integer.MaxValue
        Console.WriteLine(big)
        Dim asLong As Long = CLng(big) + 1
        Console.WriteLine(asLong)
        big += 1
        Console.WriteLine("never printed")
    End Sub
End Module

2147483647
2147483648
Unhandled exception. System.OverflowException: Arithmetic operation resulted in an overflow.
   at Demo.Program.Main()

VB checks integer overflow by default and throws an OverflowException instead of silently wrapping around. Use Long (or System.Numerics.BigInteger) for bigger values.

Decimal for money

Module Program
    Sub Main()
        Console.WriteLine(0.1 + 0.2 = 0.3)
        Console.WriteLine(0.1D + 0.2D = 0.3D)
        Dim price = 19.99D
        Console.WriteLine(price * 3)
    End Sub
End Module

False
True
59.97

Random numbers

Module Program
    Sub Main()
        Dim rng As New Random(42)       ' fixed seed: same numbers every run
        Dim a = rng.Next(1, 7)
        Dim b = rng.Next(1, 7)
        Console.WriteLine(a >= 1 AndAlso a <= 6)
        Console.WriteLine(b >= 1 AndAlso b <= 6)
    End Sub
End Module

True
True

Next(1, 7) returns 1 to 6 — the upper bound is exclusive. Use Random.Shared.Next(1, 7) for everyday randomness without creating an object; a seed is useful for repeatable tests. (Older code uses VB6's Randomize and Rnd.)

Practice

Convert 100 minutes into hours and minutes using \ and Mod, and compute the area of a circle with radius 3 rounded to two decimals.

Module Program
    Sub Main()
        Dim minutes = 100
        Console.WriteLine($"{minutes \ 60} h {minutes Mod 60} min")
        Console.WriteLine(Math.Round(Math.PI * 3 ^ 2, 2))
    End Sub
End Module

1 h 40 min
28.27