# C# Math - ILogB() Method

The C# ILogB() method returns the base-2 integer logarithm of a given number. In special cases it returns the following:

• If the argument is NaN, positive infinity or negative infinity, the method returns Int32.MaxValue which is 2147483647.
• If the argument is zero, the method returns Int32.MinValue which is -2147483648.

### Syntax

```public static int ILogB (double arg);
```

### Parameters

 `arg` Specify the number whose logarithm is to be found.

### Return Value

Returns the base-2 integer logarithm of a given number.

### Example:

In the example below, ILogB() method is used to calculate the base-2 integer logarithm of a given number.

```using System;

class MyProgram {
static void Main(string[] args) {
Console.WriteLine("Math.ILogB(0) = "
+ Math.ILogB(0));
Console.WriteLine("Math.ILogB(10) = "
+ Math.ILogB(10));
Console.WriteLine("Math.ILogB(50) = "
+ Math.ILogB(50));
Console.WriteLine("Math.ILogB(Double.NaN) = "
+ Math.ILogB(Double.NaN));
Console.WriteLine("Math.ILogB(Double.NegativeInfinity) = "
+ Math.ILogB(Double.NegativeInfinity));
Console.WriteLine("Math.ILogB(Double.PositiveInfinity) = "
+ Math.ILogB(Double.PositiveInfinity));
}
}
```

The output of the above code will be:

```Math.ILogB(0) = -2147483648
Math.ILogB(10) = 3
Math.ILogB(50) = 5
Math.ILogB(Double.NaN) = 2147483647
Math.ILogB(Double.NegativeInfinity) = 2147483647
Math.ILogB(Double.PositiveInfinity) = 2147483647
```

❮ C# Math Methods

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