C# - Constants and Literals

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

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

Integer Literals

An integer pteral 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 pteral 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.

Here are some examples of integer pterals −

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

Following are other examples of various types of Integer pterals −

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

Floating-point Literals

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

Here are some examples of floating-point pterals −

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 pterals are enclosed in single quotes. For example, x and can be stored in a simple variable of char type. A character pteral can be a plain character (such as x ), an escape sequence (such as ), 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 pke newpne ( ) or tab ( ). Here, is a pst of some of such escape sequence codes −

Following is the example to show few escape sequence characters −

using System;

namespace EscapeChar {
   class Program {
      static void Main(string[] args) {
         Console.WriteLine("Hello	World

");
         Console.ReadLine();
      }
   }
}

Hello   World

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

const <data_type> <constant_name> = value;

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();
      }
   }
}

Enter Radius: 
3
Radius: 3, Area: 28.27431