Literal number suffixes in C#

Literal number suffixes in C# are used to explicitly specify the data type of numeric literals. Without suffixes, the compiler infers the type based on the value, but suffixes ensure the literal is treated as a specific numeric type.

These suffixes are particularly useful when working with method overloads, preventing ambiguous type conversions, and ensuring the correct data type is used for calculations.

Syntax

Following is the syntax for using literal number suffixes −

dataType variable = numericValue + suffix;

The suffix can be either uppercase or lowercase, but uppercase is recommended for clarity −

long val1 = 12345L;    // L for long
float val2 = 3.14F;    // F for float  
decimal val3 = 99.99M; // M for decimal

Common Literal Number Suffixes

Using Integer Suffixes

Example

using System;

public class Program {
    public static void Main() {
        // long suffix
        long val1 = 29345L;
        Console.WriteLine("Long: " + val1);
        
        // unsigned int suffix
        uint val2 = 3456U;
        Console.WriteLine("Unsigned int: " + val2);
        
        // unsigned long suffix
        ulong val3 = 987654321UL;
        Console.WriteLine("Unsigned long: " + val3);
        
        // Demonstrating the difference
        Console.WriteLine("Type of 123: " + 123.GetType());
        Console.WriteLine("Type of 123L: " + 123L.GetType());
    }
}

The output of the above code is −

Long: 29345
Unsigned int: 3456
Unsigned long: 987654321
Type of 123: System.Int32
Type of 123L: System.Int64

Using Floating-Point Suffixes

Example

using System;

public class Program {
    public static void Main() {
        // float suffix - required for float literals
        float val1 = 250.35F;
        Console.WriteLine("Float: " + val1);
        
        // double suffix - optional since double is default
        double val2 = 297.325D;
        Console.WriteLine("Double: " + val2);
        
        // decimal suffix - required for decimal literals
        decimal val3 = 3245.5678M;
        Console.WriteLine("Decimal: " + val3);
        
        // Showing precision differences
        Console.WriteLine("Float precision: " + (1.0F/3.0F));
        Console.WriteLine("Double precision: " + (1.0/3.0));
        Console.WriteLine("Decimal precision: " + (1.0M/3.0M));
    }
}

The output of the above code is −

Float: 250.35
Double: 297.325
Decimal: 3245.5678
Float precision: 0.33333334
Double precision: 0.3333333333333333
Decimal precision: 0.3333333333333333333333333333

Why Use Suffixes

Suffixes prevent compilation errors and ensure the correct data type is used, especially in method overloading scenarios −

Example

using System;

public class Calculator {
    public static void Calculate(float value) {
        Console.WriteLine("Float method called: " + value);
    }
    
    public static void Calculate(double value) {
        Console.WriteLine("Double method called: " + value);
    }
    
    public static void Main() {
        // Without suffix - calls double method (default)
        Calculate(3.14);
        
        // With F suffix - calls float method
        Calculate(3.14F);
        
        // With D suffix - explicitly calls double method
        Calculate(3.14D);
    }
}

The output of the above code is −

Double method called: 3.14
Float method called: 3.14
Double method called: 3.14

Conclusion

Literal number suffixes in C# explicitly specify the data type of numeric literals, preventing ambiguity and ensuring the correct type is used. Common suffixes include L for long, F for float, D for double, M for decimal, and U for unsigned types. Using suffixes is essential for method overloading scenarios and when precise numeric types are required.