What are binary literals and digit separators in C# 7.0?

C# 7.0 introduced two important enhancements to numeric literals that improve code readability and provide new ways to represent numbers: binary literals and digit separators. These features make it easier to work with binary values and large numbers in your code.

Binary Literals

Before C# 7.0, you could only assign decimal and hexadecimal values to variables. Binary literals allow you to directly assign binary values using the 0b or 0B prefix, making it easier to work with bit flags, masks, and other binary operations.

Syntax

var binaryNumber = 0b10101010;  // Binary literal
var binaryNumber2 = 0B11110000; // Alternative prefix

Example

using System;

class Program {
    public static void Main() {
        var bn = 0b1000001;  // Binary for 65
        Console.WriteLine("Type: " + bn.GetType());
        Console.WriteLine("Value: " + bn);
        Console.WriteLine("Character: " + Convert.ToChar(bn));
        
        // More binary examples
        var flags = 0b11110000;  // 240 in decimal
        Console.WriteLine("Flags value: " + flags);
    }
}

The output of the above code is −

Type: System.Int32
Value: 65
Character: A
Flags value: 240

Digit Separators

Digit separators use the underscore character (_) to improve readability of numeric literals. They can be used with any numeric type including decimal, hexadecimal, and binary literals. The separators are ignored by the compiler and serve purely for visual clarity.

Syntax

long salary = 1_000_000;        // Decimal with separators
int hex = 0xFF_EC_DE_5E;        // Hexadecimal with separators  
var binary = 0b1010_0001_1000_0101;  // Binary with separators

Example

using System;

class Program {
    public static void Main() {
        // Using digit separators with different numeric types
        long salary = 1_00_00_00_00_000;  // 1 trillion
        Console.WriteLine("Salary type: " + salary.GetType());
        Console.WriteLine("Salary value: " + salary);
        
        // Binary with separators for better readability
        var permissions = 0b1111_0000_1010_0101;
        Console.WriteLine("Permissions: " + permissions);
        
        // Hexadecimal with separators
        int color = 0xFF_A5_00;  // Orange color
        Console.WriteLine("Color value: " + color);
    }
}

The output of the above code is −

Salary type: System.Int64
Salary value: 100000000000
Permissions: 61605
Color value: 16754944

Combining Binary Literals and Digit Separators

Example

using System;

class Program {
    public static void Main() {
        // Binary literals with digit separators for bit manipulation
        byte readWrite = 0b1100_0000;  // First two bits set
        byte execute = 0b0010_0000;    // Third bit set
        byte combined = (byte)(readWrite | execute);
        
        Console.WriteLine("Read/Write: " + Convert.ToString(readWrite, 2).PadLeft(8, '0'));
        Console.WriteLine("Execute: " + Convert.ToString(execute, 2).PadLeft(8, '0'));
        Console.WriteLine("Combined: " + Convert.ToString(combined, 2).PadLeft(8, '0'));
        Console.WriteLine("Combined decimal: " + combined);
    }
}

The output of the above code is −

Read/Write: 11000000
Execute: 00100000
Combined: 11100000
Combined decimal: 224

Comparison

Conclusion

Binary literals and digit separators in C# 7.0 significantly improve code readability when working with numeric values. Binary literals provide a direct way to represent binary values, while digit separators make large numbers and bit patterns more readable without affecting the actual numeric value.