Quote:
1). What is the purpose of Inheritance? Why using Inheritance?
Code re-use.
Quote:
2). What is the purpose of Abstraction?
3). What is the purpose of Abstraction?
Are you asking about 'Abstraction' or 'Iteration'? :-)
'Abstraction' is a powerful tool in any field. You may find a nice explanation of 'abstraction' meaning in computer science in this
Wikipedia
page:
Abstraction (computer science)[
^].
Quote:
4). What is design pattern? Why using design pattern?
Again,
Wikipedia
helps:
Software design pattern[
^]. You use a design pattern because it is a ready-made, robust solution to a problem.
Please note there is also some criticism on design patterns.