C# Variables

What Is a Variable?

A variable is a named piece of memory that holds a value you can read and change while your program runs. Think of it as a labelled box: the label is the variable name and the contents are the value. Because C# is a strongly typed language, you must tell the compiler what kind of value the box will hold when you create it.

To create a variable you write the type, then a name, and then optionally assign a value with the equals sign. The pattern looks like this: type variableName = value;

string greeting = "Hello";
int age = 25;

Console.WriteLine(greeting);   // Outputs: Hello
Console.WriteLine(age);        // Outputs: 25

Common Variable Types

You will use a handful of types constantly. Each one is designed for a specific kind of data, and picking the right one makes your code clearer and safer.

Declaring, Assigning, and Changing

You can declare a variable first and assign a value later. You can also change the value of a variable as many times as you like, as long as the new value matches the variable's type. The most recent value is the one that is used.

int score = 10;
Console.WriteLine(score);   // Outputs: 10

score = 42;                 // change the value
Console.WriteLine(score);   // Outputs: 42

Naming Rules and the var Keyword

Variable names can contain letters, digits, and underscores, but they cannot start with a digit and cannot be a reserved C# keyword. By convention, C# developers use camelCase for local variables, such as firstName or totalPrice. C# also lets you use the var keyword, which asks the compiler to figure out the type from the value on the right side.

var city = "Bengaluru";   // compiler infers string
var year = 2026;          // compiler infers int

Console.WriteLine(city);
Console.WriteLine(year);