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# Data Types and Variables in DART

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Data in layman's terms is the information that is stored in a computer. Data Type is the type of data that can be stored in a particular variable.

Data Types define the operations that can be performed on a variable and the amount of memory allocated for a variable.

Dart Programming Language is a type inferred language which means the compiler automatically gets to know the data type based on the values we assign.

Here are the Data Types which are built-in Dart

• Numbers (Integer and Double)
• Boolean
• String
• Maps
• Lists
• Symbols

Now we will discuss in detail about each Data Type present in Dart

# 1. Numbers

Number Data type can hold the numeric values. Dart supports both Integer and Double numeric values.

## Integer Data Type

Integer Data Type is used when whole numbers need to be stored in a variable. It can store either unsigned value(only positive numbers) or signed(both positive and negative numbers).

The value range that Integer data type can hold is from -2^63 to 2^63

Integers in Dart can be declared using the int keyword.

Example

``````int age = 18 ;
``````

Here ,
int is the data type.
age is the variable name used to store the integer value.
18 is the integer value that is stored in the variable age.

## Double Data Type

Double is used to store double precision(numbers with large decimal points) also called as floating point numbers.
The keyword used to declare double is double

Example

``````double weight = 72.56 ;
``````

Here , double is the data type .
weight is the variable name used to store the value.
72.56 is the value of the double stored in variable weight.

# 2. Boolean

Boolean Data Type is used to store or represnt boolean values(0 and 1). 1 indicates True and 0 indicates False. Boolean Data type is widely used in decision making statements.
The keyword used to declare Boolean values is bool

Example

``````bool value = false ;
``````

Here , bool is the data type.
value is the variable name.
false is the boolean value(0)

# 3. Strings

A String can be defined as sequence of characters,numbers,special characters. It can be represented by using either single quotes or double quotes in Dart.
String data type can hold sequence of characters, special characters and numbers.
String data type can be declared in Dart using the string keyword.

Example

``````string name = "OpenGenus Foundation";
``````

Here , string is the data type.
name is the variable name.
OpenGenus Foundation is the string name.

# 4. Maps

Map is used to hold a set of values as key or value pairs which can be of any type. But each key can occur only once but the value of that key can be used multiple times.
Maps can be declared using {} and the values can be accessed using []

Example:

``````void main()
{
var record = {'Name':'Sughosh' , 'Age':'18'} ;
record['number'] = 's002' ;
print(record) ;
}
``````

The Code will output the following

``````{Name : Sughosh , Age : 18 , number: s002}
``````

# 5. Lists

Dart represents arrays in form of list objects. A List is a data type used to store ordered collection of objects.
A list can be declared by using [] brackets in which values must be seperated by commas , .

Example

``````var numbers = [2,4,6,8];
``````

Here , numbers is the list name.
2,4,6,8 are list objects.

# 6. Symbols

Symbols are used to refer to an identifier declared in a Dart program. Symbols are commonly used in API's that refer to the identifers by name.
Symbol can be declared by using # and the identifer name.

Example

``````#name
``````

here name is the identifer

# Variables in DART

Variables are identifiers that are used to refer to the computer memory that holds the variable value.
The value of the variable is not constant. They can be changed during the execution.

There are some rules which have to be followed before we name a variable in Dart.

• Special characters are not allowed(@,&,#). There is an exception for dollar sign(\$) and underscore (_)
• A keyword cannot be used as a variable name for example int , double cannot be used as a variable name.
• Variables are case sensitive
• First character of a variable should not be a digit and must always be an alphabet.
• Blank spaces cannot be used
• A combination of numbers and alphabet can be used to name a variable for example , name123 can be used as a variable name.

## Declaring a variable

Variables must be declared before they are assigned a value or used. Variables can be declared using the keyword var

Syntax

``````var variable_name ;
``````

Example

``````var age ;
``````

## Multiple Variable Declaration

Multiple variables can be declared in a single statement. But they should be seperated by commas.

Syntax

``````var variable1, variable2, variable3 ;
``````

Example

``````var name,age,date_of_birth ;
``````

## Variable initialization

In Dart, a variable can be decalred and a value can be assigned to the variable.

Syntax

``````var variablename = value ;
``````

Example

``````var age = 18;
``````

## Variable Assignment Operation

Values can be assigned to variables using the assignment operator (=).

Syntax

``````var variable name ;
variable name = value ;
``````

Example

``````var name ;
name = Sughosh ;
``````

Here , name is the variable name and Sughosh is the value assigned to the variable name using the assignment operator (=)