User Defined Data Type

 What is meant by user defined datatype?

• Derived from one or more existing datatype.
• Used to extend the built-in data types.
• To meet programmer's requirement.

Explain why user defined datatype are necessary?

• No suitable data type is provided by the language used.
• If a programmer needs specific datatype.
• that meets programmer's requirements.

Data Types

Non-composite Datatype: A single datatype that does not refer to another data type. 

(Enumerated, Pointer, Real, String, Char, Boolean, Integer)

Composite Datatype: A data type that refers to other data types. Data type constructed from another data type.

Record: Collection of related items which may have different data types.

List: An indexed collection that can have different data types.

Set: Supports mathematical operations.

Array: Collection of items with the same data type.

Class: Gives properties and methods for an object.

Enumerated Data Type

• Non-composite
• Defined by a given list of all possible values
• In an order

Pseudocode to Declare an Enumerated Data Type

Type ____ = ( __, __)

Q. Declare a variable currentmonth of data type Months.

DECLARE Currentmonth: Months

Q. Declare a variable nextmonth and print nextmonth.

DECLARE Nextmonth: Months

Nextmonth <-- Currentmonth + 1

PRINT Nextmonth

Pointer Data Type

• Non-composite
• Used to reference a memory location.

^ : This symbol represents pointer.

@ : This symbol represents, the address is required not the value.

Pseudocode to Declare Pointer Data Type

Type ___ = ^___

Dereferencing: You have the address and you want the value on that address.

Num2 <--- myintpointer^

Records Data Type

• Composite Data type
• Group of multiple data types

Pseudocode to Create a Record Data Type

TYPE

         DECLARE ____:____

         DECLARE ____:_____

ENDTYPE

Declaring a Range

DECLARE Number: 0, 1, 2, 3 ....

DECLARE Name: ("Alizan", "Junior Tanol", "Samona")

Specific Data Type in Array

DECLARE Names: ARRAY[1:3] OF STRING

DECLARE Num: ARRAY[1:3] OF ["1", "2", "3"]

Arrays --> Multiple --> Specific Data types with Quotation Marks

Variable --> Single --> Enumerated without Quotation Marks