Variables and Data Types in C#

1. What Are Variables? (Simple Definition)

A variable is like a container in memory that stores data.

Think of it like:

A water bottle (container) = variable
The water inside = value
The type of water (500ml, 1 liter) = data type

C# Definition

A variable in C# is a named storage location in memory used to store a value.
It has:

Name
Data Type
Value

Syntax

dataType variableName = value;

Example

int age = 25;
string name = "Sandhiya";
double price = 99.50;

Real-Time Example (Easy Explanation)

Imagine you are building a shopping website:

Variable Name	Data Type	Purpose
productName	string	Store the product name
productPrice	double	Store the price
stockCount	int	How many items available

string productName = "Laptop";
double productPrice = 59999.99;
int stockCount = 10;

2. What Are Data Types?

A data type tells the compiler what type of data a variable will store.

C# Data Types Categories

1. Value Types (store data directly)

int
double
float
char
bool

2. Reference Types (store memory address)

string
arrays
class objects

Common Data Types with Examples

Below are all commonly used data types with simple, real-time examples.

1. int (Integer)

Stores whole numbers (no decimal).

int age = 25;
int stock = 100;

Real-time: Number of items in cart, number of login attempts.

2. double (Decimal Number – high precision)

double salary = 20000.75;
double rating = 4.5;

Real-time: Price, ratings.

3. float (decimal but less precision)

float temperature = 32.5f;

Has ‘f’ at end.

4. decimal (Money values – very accurate)

decimal accountBalance = 10500.75m;

Used for banking, finance.

5. char (Single character)

char grade = 'A';

6. string (Sequence of characters)

string customerName = "Sandhiya";
string email = "[email protected]";

Real-time: Names, messages, emails, addresses.

7. bool (true/false)

bool isVerified = true;
bool isLoggedIn = false;

Real-time: Login success, item isActive, user subscription.

Real-Time Mini Example (All Combined)

Scenario: Online product page

string productName = "Mobile Phone";
int stock = 50;
double price = 14999.99;
bool isAvailable = true;
char category = 'A';

Code Example: Small Console App

using System;

class Program
{
    static void Main()
    {
        string name = "Sandhiya";
        int age = 24;
        double height = 5.4;
        bool isStudent = true;

        Console.WriteLine("Name: " + name);
        Console.WriteLine("Age: " + age);
        Console.WriteLine("Height: " + height);
        Console.WriteLine("Student? " + isStudent);
    }
}

Summary Table

Data Type	Example	Purpose
int	20	Whole numbers
double	20.50	Decimal values
decimal	100.50m	Money
string	"Hello"	Text
char	'A'	Single character
bool	true/false	Logical values