C# - Constants and Literals

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The constants refer to fixed values that the program may not alter during its execution. These fixed values are also called literals. Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal. There are also enumeration constants as well.

The constants are treated just like regular variables except that their values cannot be modified after their definition.

Integer Literals

An integer literal can be a decimal, or hexadecimal constant. A prefix specifies the base or radix: 0x or 0X for hexadecimal, and there is no prefix id for decimal.

An integer literal can also have a suffix that is a combination of U and L, for unsigned and long, respectively. The suffix can be uppercase or lowercase and can be in any order.

Examples

Here are some examples of integer literals −

212         /* Legal */
215u        /* Legal */
0xFeeL      /* Legal */

Following are other examples of various types of Integer literals −

85         /* decimal */
0x4b       /* hexadecimal */
30         /* int */
30u        /* unsigned int */
30l        /* long */
30ul       /* unsigned long */

Floating-point Literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent part. You can represent floating point literals either in decimal form or exponential form.

Examples

Here are some examples of floating-point literals −

3.14159       /* Legal */
314159E-5F    /* Legal */
510E          /* Illegal: incomplete exponent */
210f          /* Illegal: no decimal or exponent */
.e55          /* Illegal: missing integer or fraction */

While representing in decimal form, you must include the decimal point, the exponent, or both; and while representing using exponential form you must include the integer part, the fractional part, or both. The signed exponent is introduced by e or E.

Character Constants

Character literals are enclosed in single quotes. For example, 'x' and can be stored in a simple variable of char type. A character literal can be a plain character (such as 'x'), an escape sequence (such as '\t'), or a universal character (such as '\u02C0').

There are certain characters in C# when they are preceded by a backslash. They have special meaning and they are used to represent like newline (\n) or tab (\t). Here, is a list of some of such escape sequence codes −

Example

Following is the example to show few escape sequence characters −

using System;
namespace EscapeChar {
   class Program {
      static void Main(string[] args) {
         Console.WriteLine("Hello\tWorld\n\n");
         Console.ReadLine();
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Hello   World

String Literals

String literals or constants are enclosed in double quotes "" or with @"". A string contains characters that are similar to character literals: plain characters, escape sequences, and universal characters.

You can break a long line into multiple lines using string literals and separating the parts using whitespaces.

Example

Here are some examples of string literals. All the three forms are identical strings.

"hello, dear"
"hello, \
dear"
"hello, " "d" "ear"
@"hello dear"

Defining Constants

Constants are defined using the const keyword. Syntax for defining a constant is −

const <data_type> <constant_name> = value;

Accessing Constants

You can access a constant using its name, as long as it is within scope.

Below is the syntax to access constants in C#:

//When constant is in local scope
constant_name

//When constant is in a class
class_name.constant_name

Class Constants

Class constants are declared inside a class using the const keyword. They are implicitly static, which means they belong to the class rather than an instance.

Class constants can be accessed using the class name.

Syntax

You can define a class constant by using the following syntax:

class ClassName
{
    public const datatype ConstantName = value;
}

Example

In the following example, we are defining a class named MathConstants that contains two class constants, Pi and SpeedOfLight:

using System;

class MathConstants
{
    public const double Pi = 3.14159;
    public const int SpeedOfLight = 299792458;
}

class Program
{
    static void Main()
    {
        Console.WriteLine("Value of Pi: " + MathConstants.Pi);
        Console.WriteLine("Speed of Light: " + MathConstants.SpeedOfLight);
    }
}

When the above code is compiled and executed, it produces the following result −

Value of Pi: 3.14159
Speed of Light: 299792458

More Examples on Constant and Literal

Below are examples of how to declare and access different types of constants and literals in C#:

Example 1

The following program demonstrates defining and using a constant in c# sharp program −

using System;
namespace DeclaringConstants {
   class Program {
      static void Main(string[] args) {
         const double pi = 3.14159;   
            
         // constant declaration 
         double r;
         Console.WriteLine("Enter Radius: ");
         r = Convert.ToDouble(Console.ReadLine());
            
         double areaCircle = pi * r * r;
         Console.WriteLine("Radius: {0}, Area: {1}", r, areaCircle);
         Console.ReadLine();
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Enter Radius: 
3
Radius: 3, Area: 28.27431

Example 2

The example below demonstrates both string literal and floating-point literal in a single c# code −

using System;
class Example {
   static void Main() {
      // String Literals
      string regularString = "Hello, World!";
      string verbatimString = @"C:\Users\Admin\Documents\";
      
      Console.WriteLine("Regular String Literal: " + regularString);
      Console.WriteLine("Verbatim String Literal: " + verbatimString);
   
      // Floating Point Literals
      float floatLiteral = 3.14F;
      // Default floating-point type
      double doubleLiteral = 3.14159265359;
      // Requires 'M' suffix for high precision
      decimal decimalLiteral = 3.14159265359M;
      
      Console.WriteLine("\nFloating Point Literals:");
      Console.WriteLine("Float Literal: " + floatLiteral);
      Console.WriteLine("Double Literal: " + doubleLiteral);
      Console.WriteLine("Decimal Literal: " + decimalLiteral);
   }
}

Following is the output of the above code −

Regular String Literal: Hello, World!
Verbatim String Literal: C:\Users\Admin\Documents\

Floating Point Literals:
Float Literal: 3.14
Double Literal: 3.14159265359
Decimal Literal: 3.14159265359