C# Variables

A variable in C# is a storage location in the computer’s memory that is used to hold data. Each variable has:

  1. A name to identify it (like a label on the storage).
  2. A data type to specify the kind of data it can hold (like numbers, text, etc.).
  3. A value which is the data the variable holds (like 10, “Hello”, true, etc.).

Syntax:


dataType variable_name = variable_value;

Example:


string a = "Hello World";

Rules for declare Naming Variables

1. It must start with a letter (a-z, A-Z) or an underscore (_).

2. Subsequent characters can include letters, digits (0-9), or underscores.

3. It can not start with a digit.

4. It can not be a C# keyword (e.g., int, class, bool).

5. Variable names are case-sensitive.

Example of Valid Variable

int age;
string name;
bool isAdmin;

Example of Invalid Variable

string 1age;
string class;

Declaring and Initializing Variables

1. Declaration: Telling the program about the variable’s type and name.

2. Initialization: Giving the variable a value

1. You can declare and initialize a variable in a single step:

Example:


int age = 35;

2. declare and initialize separately


int age;         // Declaration
age = 35;        // Initialization

Default Values of Variables

If you declare a variable without giving it a value, C# assigns a default value depending on the type.

  • int gets 0
  • bool gets false.
  • string gets null (because it’s an object type).
  • double gets 0.0.