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

Let's see the syntax to declare a variable:

type variable_list;

The example of declaring variable is given below:

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:

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:

int x;    
int _x;    
int k20;
Example #2

Invalid variable names:

int 4;    
int x y;    
int double;
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