**Variables** are simply places to store data like numbers, strings (text), *arrays* of numbers or strings, and other objects. Each variable can only store data of one *type*, and you must *declare* variables before attempting to set or get their values. Here is a sample program that uses variables:

class VariablesExample { public static void Main() { int number; string myText; number = 100; System.Console.WriteLine(number); myText = "Hello!"; System.Console.WriteLine(myText); number = 200; System.Console.WriteLine(number); System.Console.ReadKey(); } }

The output would be:

100 Hello! 200

You can see that variables are declared using the form `[type] [variable name];`

and are set using the

operator. You can declare multiple variables of the same type by placing commas after each variable name:**=**

int x, y, z;

If you want to set variables immediately after you declare them, you can use the form `[type] [variable name] = [value];`

:

class VariablesExample2 { public static void Main() { int number = 100; string myText = "Hello!"; System.Console.WriteLine(number); System.Console.WriteLine(myText); number = 200; System.Console.WriteLine(number); System.Console.ReadKey(); } }

The output would be exactly the same as before.

## TypesEdit

C# offers various types of variables besides `int`

and `string`

. Here is a short list of the available types:

`bool`

- stores**true**or**false**.`byte`

- stores an unsigned*byte*.`sbyte`

- stores a signed byte.`char`

- stores a single character:char theLetterA = 'a';

`int`

- stores an integer:int number = 100;

`short`

,`long`

- both store an integer.`ushort`

,`uint`

,`ulong`

- both store an*unsigned integer*`float`

- stores a*floating-point*number:float number = 3.14159;

`double`

- stores a double-precision*floating-point*number.`decimal`

- stores a quadruple-precision*floating-point*number.`string`

- stores a*string*, or a sequence of characters.

Note: a floating-point number is a number which can be fractional. For example, 3.14159 is a floating-point number while 314 is just an integer.

You may be wondering why there are so many types for storing integers and floating-point numbers. *Signed* integers can be negative as well as positive, while *unsigned* integers can only be positive. So, `byte`

, `ushort`

, `uint`

and `ulong`

can only store positive integers.

There are also different sizes for integers and floating-point numbers; a type with a bigger size has a bigger range than a type with a smaller size. Here are the sizes of the types:

`byte, sbyte`

- 8 bits, or 1 byte.`byte`

can store numbers from 0 to 255, while`sbyte`

can store numbers from -128 to 127.`short, ushort`

- 16 bits, or 2 bytes.`short`

can store numbers from -32,768 to 32,767, while`ushort`

can store numbers from 0 to 65,535.`int, uint`

- 32 bits, or 4 bytes.`int`

can store numbers from negative 2 billion to positive 2 billion, while`uint`

store numbers from 0 to 4 billion.`long, ulong`

- 64 bits, or 8 bytes.`long`

can store numbers from negative 9 million million million to positive 9 million million million, while`ulong`

can store numbers from 0 to 18 million million million.

You may also be wondering why there are small types when we could use the biggest available types (`long`

, `decimal`

). The answer is that most computers today are 32-bit, which means that they are designed to handle 32-bit numbers. 64-bit numbers are therefore slower to add, subtract, multiply, and divide.