C# Variable

A variable is a name of memory location. It is used to store data. Its value can be changed and it can be reused many times.

It is a way to represent memory location through symbol so that it can be easily identified.

The basic variable type available in C# can be categorized as:

Variable Type	Example
Decimal types	decimal
Boolean types	True or false value, as assigned
Integral types	int, char, byte, short, long
Floating point types	float and double
Nullable types	Nullable data types

Syntax

Let's see the syntax to declare a variable:

type variable_list;

The example of declaring variable is given below:

snippet

int i, j;
double d;    
float f;    
char ch;

Here, i, j, d, f, ch are variables and int, double, float, char are data types.

We can also provide values while declaring the variables as given below:

snippet

int i=2,j=4;  //declaring 2 variable of integer type    
float f=40.2;    
char ch='B';

Rules for defining variables

A variable can have alphabets, digits and underscore.

A variable name can start with alphabet and underscore only. It can't start with digit.

No white space is allowed within variable name.

A variable name must not be any reserved word or keyword e.g. char, float etc.

Example #1

Valid variable names:

snippet

int x;    
int _x;    
int k20;

Example #2

Invalid variable names:

snippet

int 4;    
int x y;    
int double;