Oop lec 2

CSC 103 - Object Oriented
Programming

Spring, 2011
Lecture 2, Background

18th Feb, 2011

Instructor: M. Anwar-ul-Haq

Imperative Programming
What is Imperative Programming?
• Imperative programming is the type of
programming you do when you essentially
just have a list of commands that work
from the top down to the bottom, and then
the program is complete.
• This means that it doesn’t have any
functions or the like.
OOP, Spring 2011, Engr. Anwar, 2
Foundation University (FUIEMS),

Imperative Programming
• This type of programming is very
simplistic, which makes it very difficult,
time-consuming, and inefficient to do
complex programs.


Procedural Programming
• What is Procedural Programming?
• Procedural programming is the type of
programming you do when you make use
of procedures (yet another synonym for
functions, processes, and subroutines).


Procedural Programming
• This type of programming is higher-level
than imperative and allows you to
accomplish more complex programs.
• However, even procedural programming
isn’t very effective when it comes to very
large programs.
• FORTRAN and C are two popular
procedural programming languages.

Object Oriented Programming
• What is Object-Oriented Programming
(OOP)?
• Object-oriented programming is the type
of programming in which you make use of
objects. Objects are essentially meant to
be representative of a potentially physical
object. Objects contain their own data and
methods (another synonym for functions).


• Object-oriented programming allows for
the rapid development of larger scale
programs.
• Instead of having to have all the
commands in one location, you can break
the code down into separate objects.
• This allows for much more manageable
and readable code, which in turn allows
for more efficient programming.

• C++, Java, and PHP are popular object-
oriented programming languages. You
could consider JavaScript to be an OOP
language as well, though it doesn’t make
use of the typical “class” as others do.


Which is Best?
• OOP programs are best if they meet one
or more of these criteria:
– Are fairly large (more than a couple hundred
lines of code) and will be run on general
computers.
– Are fairly complex (more than just output
simple data).
– Will be maintained and added to over a period
of time.

What is Object Oriented
Programming?
• Identifying objects and
assigning responsibilities to
these objects.
• Objects communicate to
An object is like a
other objects by sending
black box.
messages.
The internal • Messages are received by
details are
the methods of an object
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.
• Reusability - Programs can be
assembled from pre-written software
components.
• Extensibility - New software
components can be written or
developed from existing ones.

What is an Object?
• Real world consists of objects (desk, your
television set, your bicycle).
• They share two characteristics: They all
have state and behavior.
• Bicycles have state (current gear, current
speed) and behavior (changing gear,
applying brakes).
• Hiding internal state and requiring all
interaction to be performed through an
object's methods is known as data
encapsulation.

Real-World Modeling

• Attributes/State
– Bicycle: Speed and Gear.
– People: eye color and job etc.
– Cars: horsepower and number of doors.

• Behavior: Something a real-world object
does in response to some stimulus.
– Bicycle: changeGear, speedUp, applyBrakes
and printStates.


What Is an Object?
• Grouping code into individual software
objects provides a number of benefits,
including:
– Modularity: The source code for an object
can be written and maintained
independently of the source code for other
objects. Once created, an object can be
easily passed around inside the system.
– Information-hiding: By interacting only with
an object's methods, the details of its
internal implementation remain hidden from
the outside world.

What Is an Object?
– Code re-use: If an object already exists,
you can use that object in your program.
– Pluggability and debugging ease: If a
particular object turns out to be
problematic, you can simply remove it
from your application and plug in a
different object as it is.


The two parts of an object
Object = Data (state) + Methods (behaviour)
or to say the same differently

An object has the responsibility to know and
the responsibility to do.

= +

Example
#include <iostream> void speedUp(int increment)
using namespace std; {

class Bicycle { speed = speed + increment;
private: }
int speed;
int gear; void applyBrakes(int decrement)
{
public: speed = speed - decrement;
Bicycle() }
{
speed=0; void printStates()
gear=0; {
} cout<<"Speed:"<<speed<<endl;
cout<<"Gear:"<<gear<<endl;
}
};

Example (contd..)
void main()
{
Bicycle bike1,bike2;

bike1.speedUp(10);
bike1.printStates();

bike2.speedUp(15);
bike2.changeGear(12);
bike2.applyBrakes(5);

bike2.speedUp(10);
bike2.changeGear(3);
}

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