1. Object orientation concepts
Building blocks of modern software practice
9/18/2018
S P Pal

2. Classes and Objects Physical entities User interface components Rules
Controllers
Protocols
Schedulers
9/18/2018
S P Pal

3. Classes Similar objects constitute a class ADTs (Abstract Data Types)
Operating functions or behavior
Object-based languages like SIMULA67 and ADA offer classes or ADTs
9/18/2018
S P Pal

4. Inheritance Reuse of data and behavior specifications
If C2 is a subclass, its instances inherit data and behavior of instances of C1
Collection C2 is a subset if C1
Java supports inheritance and is therefore an object oriented language
C++ supports inheritance from multiple classes
Inheritance provides flexibility in design
Languages like C++ and Java provide inheritance and are called object-oriented
9/18/2018
S P Pal

5. Repeated inheritance Suppose C1 and C2 inherit from B
C3 in turn inherits from both C1 and C2
C3 may clash on some data item or behavior revealing inconsistencies
Java avoids this facility and C++ circumvents these problems rather clumsily !
9/18/2018
S P Pal

6. Inheritance hierarchy
Multiple levels in the inheritance hierarchy provide ease and flexibility in design
Define several levels of specialized classes as required in the problem domain
e.g., students, PG students, research scholars
Create very complex classes that have too many behaviors and data items
9/18/2018
S P Pal

7. Multilevel inheritance
Base C1 C2 C5 C3 C4
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S P Pal

8. Polymorphism
Use same name for invoking similar operations irrespective of the types of objects
Draw(x1,y1) : draw a point
Draw(x1,y1,x2,y2): draw a segment
Draw(X1,y1,x2): draw a circle with center at (x1,y1) and radius x2
Graphical-object.draw(…)
Simplified code writing
Code need not be rewritten: extendible
9/18/2018
S P Pal

9. Parameter passing Pass primitive data types by value
No side effects
Functional approach, recursive, stack-based
Pass objects by reference
Big sized objects may cause stack overflow
Objects are persistent entities with global references, not to be copied or
destroyed
9/18/2018
S P Pal