Variables in C#

A variable in C# is a named memory location used to store data during program execution. The stored value can be accessed, modified, and reused throughout the program.

Each variable consists of three components:

• Name: Identifier used to reference the variable.
• Type: Specifies the type of data the variable can store (e.g., int, char, double).
• Value: The actual data stored in the variable.

using System;

class Program
{
    static void Main()
    {
        // Creating and initializing a variable
        int num = 3;

        // Accessing the variable
        Console.WriteLine(num);

        // Updating the value
        num = 7;

        // Printing updated value
        Console.WriteLine(num);
    }
}

3
7

Rules for Naming Variables

• Variable names can contain the letters ‘a-z’ or ’A-Z’ or digits 0-9 as well as the character ‘_’.
• Variable names cannot start with a digit.
• The name of the variable cannot be any C# keyword say int, float, null, string, etc.

Variable Declaration

Declaration means defining the data type and name of a variable. At this stage, the variable is created but no value is assigned.

dataType variableName;

Example:

int x;
double price;
char grade;

Here:

• int, double, and char are data types.
• x, price, and grade are variable names.

Variable Initialization

Initialization means assigning a value to a variable after it has been declared. Example:

int x;
x = 5;

In this example, the variable x is declared first and later assigned the value 5.

A variable can also be declared and initialized in a single statement.

int y = 7;

• y is declared as an integer.
• The value 7 is assigned at the same time.

There are two basic ways for initialization as mentioned below:

1. Compile Time Initialization

In compile-time initialization, the value of the variable is assigned when the program is written. The value remains fixed during execution. Example:

using System;

class Program
{
    static void Main()
    {
        int x = 32;
        int y = 0;

        Console.WriteLine("Value of x is " + x);
        Console.WriteLine("Value of y is " + y);
    }
}

Value of x is 32
Value of y is 0

Here, the values of x and y are known before the program runs.

2. Run Time Initialization

In run-time initialization, the value of the variable is assigned during program execution. The value may come from user input, function calls, or program logic. Example:

using System;

class Program
{
    static void Main()
    {
        Console.Write("Enter a number: ");
        int num = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("Value of num is " + num);
    }
}

Input:

Enter a number: 45

Output:

Value of num is 45

Explanation: Console.ReadLine() reads input from the user and the entered value is stored in the variable num.