Internal level

Conceptual level

External level

Domain level

Abstract class

Final class

Concrete class

Parent class

is downloaded to the client upon request

is shared by both the client and server

resides on the server side

resides on the client side

Presentation

Transport

Network

Data Link

There is no difference

We can define functions within union but not within a structure

We can define functions within union but not within a structure

The way memory is allocated