Variables and Data types

 Variables  and Data types

Variable:

A variable is a location in the memory.

A variable has a name and contains a value. 

A variable is associated with a data type. 

A variable refers to the memory address. When you create variable, it creates holds space in the memory that is used for storing temporary data. As you know about c# data types, each data type has predefined size.

The following figure shows the process of storing user input in the memory by using variables.

Data Types in a programming language describes that what type of data a variable can hold. 
CSharp is a strongly typed language, therefore every variable and object must have a declared type. 
The CSharp type system contains three Type categories. They are Value Types, Reference Types and Pointer Types. 
In CSharp it is possible to convert a value of one type into a value of another type.
The operation of Converting a Value Type to a Reference Type is called Boxing and the reverse operation is called Unboxing.

When we declare a variable, we have to tell the compiler about what type of the data the variable can hold or which data type the variable belongs to.

C# provides two types of data types: Value types and Reference types.

Value Types:

Directly contain data. The following figure shows the memory allocation of an int variable.

Example
int age=25;
int num=5;

float fees=1500.00;

Data Types	Size	Values
sbyte	8 bit	-128 to 127
byte	8 bit	0 to 255
short	16 bit	-32,768 to 32,767
ushort	16 bit	0 to 65,535
int	32 bit	-2,147,483,648 to 2,147,483,647
uint	32 bit	0 to 4,294,967,295
long	64 bit	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
ulong	64 bit	0 to 18,446,744,073,709,551,615
char	16 bit	0 to 65535
float	32 bit	-1.5 x 1045 to 3.4 x 1038
double	64 bit	-5 x 10324 to 1.7 x 10308
decimal	128 bit	-1028 to 7.9 x 1028
bool	---	True or false

Reference Types:

Contain the address of the memory where data is stored. The following figure shows the memory allocation of a string value HELLO in a variable named Str.

String name="Amit"
String Str="HELLO"

Data Types	Size	Values
string	Variable length	0-2 billion Unicode characters
object	---	---

C# also supports dynamic data type.

A variable declared with the dynamic data type can be used to store a value of any type.

dynamic data=10

             id = “A001”

             id=10.5

Complete Example

using System;

namespace Variable

{

    class Program

    {

        static void Main(string[] args)

        {

            //cretaing integer type variable

            int age;

            //cretaing string type variable

            string name;

            //cretaing float type variable

            float fees;

            //cretaing gender type variable

            char gender;

            //Displaying message

            Console.WriteLine("Please enter age");

            //Accepting Value in age

           // age = Convert.ToInt32(Console.ReadLine());

            //we can use also use Convert.ToInt32 instead of Int32.Parse

            age = Int32.Parse(Console.ReadLine());

          

            //Displaying message

            Console.WriteLine("Please enter name");

            //Accepting Value in name

            name = Console.ReadLine();

            //Displaying message

            Console.WriteLine("Please enter fees");

            //Accepting Value in fees

            fees =float.Parse(Console.ReadLine());

            //Displaying message

            Console.WriteLine("Enter Gender M or F");

            //Accepting Value

            gender = char.Parse(Console.ReadLine());

        

            //displaying data

            Console.WriteLine(" name: {0}\n age: {1}\n fees: {2}\n Gender: {3}", name, age, fees,gender); //Output

            Console.ReadLine();

        }

    }

}

If you want to display more than one variable values then you will have to assign place holder for each variables. In the preceding line {0} denotes to name, {1} denotes to age and {2} denotes to fees and so on.

Conversion

C# accepts string value by default. If you are using other value then you will have to convert of specific data types.

age = Int32.Parse(Console.ReadLine());

or

age = Convert.ToInt32(Console.ReadLine());

we can use the following method to convert one data type to another data type.

int -> int.Parse()

int -> Convert.ToInt32()  :-Converts the value provided by the user to int data type.

Double=Convert.ToDouble() :-Converts the value provided by the user to Double data type.

Decimal=Convert.ToDecimal() :-Converts the value provided by the user to Decimal data type.

Byte=Convert.ToByte() :-Converts the value provided by the user to Byte data type.