1. Object Oriented Theory I19
Object Oriented Theory I

2. Previously
File & Streams
Read
Write
Parsing

3. Overview Programming Methodologies Unstructured Programming
Procedural Programming
Modular Programming
Properties of Modular Programming
Object Oriented Programming
Object Oriented Languages
Objects

4. Programming Methodologies
Unstructured Programming
Procedural Programming
Modular Programming
Object Oriented Programming

5. Unstructured Programming
The main program consists of statements that directly operates on global data (i.e. data that is always available).
Program
Main Program
Data

6. Procedural Programming
Sequences of statements are combined into one place called a procedure. This can then be invoked as often as needed by the main program.
Program
Procedure
Main Program
Procedure

7. Modular Programming Program
Procedures are grouped into modules or libraries.
Program
Main Program
Module2
Procedure2 Procedure3
Module1
Procedure1

8. Properties of Modular Programming
Programs consist of several (sometimes many) interacting parts.
Libraries can be re-used.
Each module can have its own data, and can manage its own internal state.
Each module exists once in a program, and has a single state.
Management of the state of a module can become complex.

9. Object Oriented Programming
OO programs consist of a web of interacting objects - each with their own state.
Each object is responsible for initialising and destroying itself correctly.
This addresses the complexities of modular programming.
Objects have other attributes that greatly add to the power of manipulating them.

10. Object Oriented Languages
Pure OO languages
Smalltalk
Java
Impure OO languages
C++
PERL
Pascal/Delphi
Mixed paradigm languages
Visual Basic
JavaScript

11. Objects The world is full of objects.
OO programming was originally developed for the creation of simulations.
Because programs ultimately interact with the real world, many (the vast majority) of programming problems can be solved by mapping program code to “objects” that mirror real world objects.