Object Oriented Programming Development

What are we doing today? Introduction of: the lecturer Objects Basic Terminology C++ the module

PROGRAMMING PARADIGMS A Programming Paradigms defines the Methodology of designing and implementing programs using the key feature and building blocks of a Programming Language . Types 1. Procedural Programming 2. Object Based Programming 3. Object Oriented Programming

Procedural Programming A Program in a procedural language is a list of instruction where each statements tells the computer to do something. The focus is on the Processing, the Algorithm needed to perform the desired computation.

Object Based Programming In this programming data and its associated meaningful function as enclosed in one single entity a class. Classes enforce information hiding and abstraction thereby separating the implementation details & uses the interface.

Object Oriented Programming This programming paradigm is support of object based programming. It offers all the features of object based programming and overcomes its limitations by implementing inheritance so that real world relations among objects can be represented programmatically.

What is Object Oriented Programming? Identifying objects and assigning responsibilities to these objects. Objects communicate to other objects by sending messages. Messages are received by the methods of an object An object is like a black box. The internal details are hidden.

What is an object? Tangible Things as a car, printer, ... Roles as employee, boss, ... Incidents as flight, overflow, ... Interactions as contract, sale, ... Specifications as colour, shape, …

So, what are objects? an object represents an individual, identifiable item, unit, or entity, either real or abstract, with a well-defined role in the problem domain. Or An "object" is anything to which a concept applies. Etc.

Why do we care about objects? Modularity - large software projects can be split up in smaller pieces. Reuseability - Programs can be assembled from pre-written software components. Extensibility - New software components can be written or developed from existing ones.

Example: The Person class #include<string> #include<iostream> class Person{ char name[20]; int yearOfBirth; public: void displayDetails() { cout << name << " born in " << yearOfBirth << endl; } //... }; private data public processes

The two parts of an object Object = Data + Methods or to say the same differently: An object has the responsibility to know and the responsibility to do. = +

Basic Terminology Abstraction is the representation of the essential features of an object. These are ‘encapsulated’ into an abstract data type. Encapsulation is the practice of including in an object everything it needs hidden from other objects. The internal state is usually not accessible by other objects.

Basic Terminology: Inheritance Inheritance means that one class inherits the characteristics of another class. This is also called a “is a” relationship: A car is a vehicle A dog is an animal A teacher is a person

2. Inheritance Concepts Derive a new class (subclass) from an existing class (base class or superclass). Inheritance creates a hierarchy of related classes (types) which share code and interface. 15

Inheritance Examples

Types of Inheritance Single Multiple Multilevel Hierarchical Hybrid

Basic Terminology: Polymorphism Polymorphism means “having many forms”. It allows different objects to respond to the same message in different ways, the response specific to the type of the object. E.g. the message displayDetails() of the Person class should give different results when send to a Student object (e.g. the enrolment number).

Types of Polymorphism Compile time/ Static Polymorphism Function Overloading Run time/ Dynamic Polymorphism Virtual Function Operator Overloading

Basic Terminology: Modularity Modularity is the property of a system that has been decomposed into a set of cohesive and loosely coupled modules For example the computer system comprises CPU, Monitor, Keyboard , Mouse & Speakers etc. Now these parts are complete unit in themselves, yet they are a subpart of computer. This is Modularity .

Basic Terminology: Behaviour and Messages The most important aspect of an object is its behaviour (the things it can do). A behaviour is initiated by sending a message to the object (usually by calling a method).

The two steps of Object Oriented Programming Making Classes: Creating, extending or reusing abstract data types. Making Objects interact: Creating objects from abstract data types and defining their relationships.

Historical Notes C++ owes most to C. Other ancestors are Simula67 and Algol68. First versions of C++ in 1980 under the name “C with classes”. Since 1983 the name C++ is used. 1990: ANSI/ISO 9899 defines a standard for C 1998: ISO/IEC 14882 specifies the standard for C++ C++ 1987

C++ and C C is a subset of C++. Advantages: Existing C libraries can be used, efficient code can be generated. But: C++ has the same caveats and problems as C (e.g. pointer arithmetic,…). C++ can be used both as a low level and as a high level language. We focus on the high level aspects.

C++ and Java Java is a full object oriented language, all code has to go into classes. C++ - in contrast - is a hybrid language, capable both of functional and object oriented programming. So, C++ is more powerful but also more difficult to handle than Java.

Advantages of OOPs Re use of Code It model real world well Program are easy to understand Easy redesign & Extension

Disadvantages of OOPs The relations among classes become artificial as times The OOPs Program’s design is tricky. To program with OOP, Programmer proper Skil.

Module Outline Introduction The non object oriented basics Classes Design Approaches Testing Inheritance Aggregation Polymorphism Multifile Development

Thank You