All in 1

OOP COMPLETE NOTESBY

Umer Tanvir

CSC241:Object Oriented ProgrammingSpring 2013

1. Starting OOP

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Please turn OFF your Mobile Phones!

Monday, April 10, 2023Farhan Aadil

10 April 2023 COMSATS Institute of Information Technology 3

Study Assignment

• I hope you did go through chapter 1 of both the books.• How was the experience?• What did you learn?


Procedural vs. Object-Oriented

• Procedural

Withdraw, deposit, transfer

• Object Oriented

Customer, money, account

Object-Orientation (OO)

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What is Object-Orientation?

• A technique for system modeling

• OO model consists of several interacting objects


What is a Model?

• A model is an abstraction of something

• Purpose is to understand the product before developing it


Examples – Model

• Highway maps

• Architectural models

• Mechanical models


Example – OO Model


…Example – OO Model• Objects

• Ali• House• Car• Tree

• Interactions• Ali lives in the house• Ali drives the car


Ali

Car

House

Tree

lives-in

drives

Object-Orientation - Advantages

• People think in terms of objects

• OO models map to reality

• Therefore, OO models are• easy to develop• easy to understand


What is an Object?

An object is

• Something tangible (Ali, Car)

• Something that can be apprehended intellectually (Time, Date)


… What is an Object?

An object has

• State (attributes)• Well-defined behaviour (operations)• Unique identity


Example – Ali is a Tangible Object

• State (attributes)• Name• Age

• behaviour (operations)• Walks• Eats

• Identity• His name


Example – Car is a Tangible Object

• State (attributes)- Color- Model

• behaviour (operations)- Start Car- Accelerate- Change Gear

• Identity- Its registration number


Example – Time is an Object Apprehended Intellectually

• State (attributes)- Hours - Seconds- Minutes

• behaviour (operations)- Set Hours - Set Seconds- Set Minutes

• Identity- Would have a unique ID in the model


Example – Date is an Object Apprehended Intellectually• State (attributes)

- Year - Day- Month

• behaviour (operations)- Set Year - Set Day- Set Month

• Identity- Would have a unique ID in the model



Definition

• What Is an Object? • An object is a software bundle of related variables and methods.

Software objects are often used to model real-world objects you find in everyday life.

• Objects are key to understanding object-oriented technology. You can look around you now and see many examples of real-world objects: dog, desk, television set, bicycle.


Real-world objects share two characteristics • They all have state and behavior • dogs have state (name, color, breed, hungry) and behavior (barking,

fetching, and wagging tail). • Bicycles have state (current gear, current pedal cadence, two wheels,

number of gears) and behavior (braking, accelerating, slowing down, changing gears).


Software objects are modeled after real-world objects • A software object maintains its state in one or more variables . • A software object implements its behavior with methods . A method

is a function (subroutine) associated with an object.


Can represent real-world objects by using software objects. • You might want to represent real-world dogs as software objects in an

animation program or a real-world bicycle as a software object in the program that controls an electronic exercise bike.

• You can also use software objects to model abstract concepts. For example, an event is a common object used in GUI window systems to represent the action of a user pressing a mouse button or a key on the keyboard.


Moving to new thinking …

• C is a procedural language. A procedure is a list of instructions.

• Very small programs (tens of lines) need no organization.• As they get large (hundreds of lines), they are divided into

functions.• Functions are still lists of instructions.• Dividing a program into functions gives a structure to the

program (hence structured programming).


Moving to new thinking …

• C programming cannot do the following well:• Functions have unrestricted access to global data.• Data and Functions are unrelated; they do not form a

logical group or show any form of binding.• Cannot model ‘real world’.

• In real world, we deal with objects like cars, people etc.

• Are such objects like ‘data’? Which data type describes a car, for example?

• Are such objects like ‘functions’? What will a function car() do?


Moving to new thinking …• A real world object, e.g. car:

• Is its description purely the ability to have a ‘data type’ to represent its specifications or ‘attributes’ only? For example what attributes describe a car?

• So by having all these attributes ‘only’ do you know all about a car? Would you buy a car by merely looking at these attributes and their values?

• No! What else do you wish to have?


Moving to new thinking …• A real world object, e.g. car:

• Test drive! Right?• What would you know through a test drive: how it

‘behaves’ in response to various stimulus!• How can it negotiate a speed braker, a speedy turn, full braking

etc.• Effectively, you wish to know how it ‘functions’.• Behaviour is like a function.

• So neither data nor functions, by themselves, model real-world objects effectively.


Object Oriented Approach …• Neither data nor functions, by themselves, model real-

world objects effectively.• OO languages (like C++) combine both ‘data’ and ‘functions

that operate on that data’ into a single unit, called ‘object’. Hence ‘encapsulating’ an entity.

• The objects functions are called member functions.• Typically, data can be accessed through functions only. So

data gets ‘hidden’.• Data hiding ensures the data is not accidentally altered.• Reference analogy of a growing company; 2 people vs 100

employee company.• Objects communicate with each other by calling each

other’s member functions.


Object Oriented Approach …• OOP is all about ‘organization’ and not about program

operation. Most individual statements are similar to C statements. Member functions may be very similar to C procedural functions.

• In C you used to think about functions.• In C++ you should think about objects.• Often objects in C++ are real-world analogies.• In C++ objects are ‘instances’ of ‘classes’. E.g. Honda

City is an instance of class car!• Class serves as a cookie cutter and an object a cookie.

Abstraction

• Abstraction is a way to cope with complexity.

• Principle of abstraction:

“Capture only those details about an object that are relevant to current perspective”


Example – Abstraction

• Attributes- Name - Employee ID- Student Roll No - Designation- Year of Study - Salary- CGPA - Age


Ali is a PhD student and teaches BS students


• behaviour- Study - DevelopExam- GiveExam - TakeExam- PlaySports - Eat- DeliverLecture - Walk


Ali is a PhD student and teaches BS students


Attributes• - Name - Employee ID• - Student Roll No - Designation• - Year of Study - Salary• - CGPA - Age


Student’s Perspective




Student’s Perspective


• Attributes- Name - Employee ID- Student Roll No - Designation- Year of Study - Salary- CGPA - Age


Teacher’s Perspective




Teacher’s Perspective


• Ordinary PerspectiveA pet animal with• Four Legs• A Tail• Two Ears• Sharp Teeth

• Surgeon’s PerspectiveA being with• A Skeleton• Heart• Kidney• Stomach


A cat can be viewed with different perspectives



Driver’s View

Engineer’s View

Abstraction – Advantages

• Simplifies the model by hiding irrelevant details

• Abstraction provides the freedom to defer implementation decisions by avoiding commitment to details


Classes

• In an OO model, some of the objects exhibit identical characteristics (information structure and behaviour)

• We say that they belong to the same class


Example – Class

• Ali studies mathematics• Anam studies physics• Sohail studies chemistry

• Each one is a Student• We say these objects are instances of the Student class


Example – Class

• Ahsan teaches mathematics• Aamir teaches computer science• Atif teaches physics

• Each one is a teacher• We say these objects are instances of the Teacher class


Graphical Representation of Classes


(Class Name)

(attributes)

(operations)

(Class Name)

Normal Form

Suppressed Form

Example – Graphical Representation of Classes


CirclecenterradiusdrawcomputeArea

Normal Form

Suppressed Form

Circle

Example – Graphical Representation of Classes


Personnameagegendereatwalk

Normal Form

Suppressed Form

Person

Inheritance

• A child inherits characteristics of its parents

• Besides inherited characteristics, a child may have its own unique characteristics


Inheritance in Classes

• If a class B inherits from class A then it contains all the characteristics (information structure and behaviour) of class A

• The parent class is called base class and the child class is called derived class

• Besides inherited characteristics, derived class may have its own unique characteristics


Example – Inheritance


Person

TeacherDoctorStudent

Example – Inheritance


Shape

CircleTriangleLine

Inheritance – “IS A” or“IS A KIND OF” Relationship

• Each derived class is a special kind of its base class


Example – “IS A” Relationship



TeacherdesignationsalaryteachtakeExam

StudentprogramstudyYearstudyheldExam

DoctordesignationsalarycheckUpprescribe

Example – “IS A” Relationship


ShapecolorcoorddrawrotatesetColor

CircleradiusdrawcomputeArea

Linelengthdraw

TriangleangledrawcomputeArea

Inheritance – Advantages

• Reuse

• Less redundancy

• Increased maintainability


Reuse with Inheritance

• Main purpose of inheritance is reuse• We can easily add new classes by inheriting from existing classes

• Select an existing class closer to the desired functionality• Create a new class and inherit it from the selected class• Add to and/or modify the inherited functionality


Example Reuse




Linelengthdraw


Example Reuse






Example Reuse






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References

• “Object Oriented Programming in C++”, by “Robert Lafore”, published by Sams Publishing (The Waite Group). 4th ed. available in soft form.

• “Object Oriented Programming Using C++” by “Joyce Farrell” , published by Course Technology, Cengage Learning. 4th ed. available in soft form

• National University of Computer & Emerging Sciences [www.nu.edu.pk]

• Virtual University of Pakistan [ocw.vu.edu.pk]• Open Courseware Consortium

[http://www.ocwconsortium.org/en/courses]

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1. Inheritance & Generalization

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Recap – Inheritance

• Derived class inherits all the characteristics of the base class


• Major benefit of inheritance is reuse


Concepts Related with Inheritance

• Generalization

• Subtyping (extension)

• Specialization (restriction)


Generalization

• In OO models, some classes may have common characteristics

• We extract these features into a new class and inherit original classes from this new class

• This concept is known as Generalization


Example – Generalization


CirclecolorverticesradiusmovesetColorcomputeArea

LinecolorverticeslengthmovesetColorgetLength

TrianglecolorverticesanglemovesetColorcomputeArea



ShapecolorverticesmovesetColor

CircleradiuscomputeArea

LinelengthgetLength

TriangleanglecomputeArea



TeachernameagegenderdesignationsalaryteachtakeExameatwalk

StudentnameagegenderprogramstudyYearstudyheldExameatwalk

DoctornameagegenderdesignationsalarycheckUpprescribeeatwalk







Sub-typing & Specialization

• We want to add a new class to an existing model

• Find an existing class that already implements some of the desired state and behaviour

• Inherit the new class from this class and add unique behaviour to the new class


Sub-typing (Extension)

• Sub-typing means that derived class is behaviourally compatible with the base class

• Behaviourally compatible means that base class can be replaced by the derived class


Example –Sub-typing (Extension)


Personnameagegendereatswalks

StudentprogramstudyYearstudytakeExam

Example – Sub-typing (Extension)


ShapecolorverticessetColormove

CircleradiuscomputeCFcomputeArea

Specialization (Restriction)

• Specialization means that derived class is behaviourally incompatible with the base class

• Behaviourally incompatible means that base class can’t always be replaced by the derived class


Example – Specialization (Restriction)


Personage : [0..100]…

Adultage : [18..100]…

setAge( a )…

setAge( a )…

age = a

If age < 18 then errorelse age = a



IntegerSet…

NaturalSet…

add( elem )…

add( elem )…

add element to the set

If elem < 1 then errorelse

add element to the set

Overriding

• A class may need to override the default behaviour provided by its base class

• Reasons for overriding• Provide behaviour specific to a derived class• Extend the default behaviour• Restrict the default behaviour• Improve performance


Example – Specific Behaviour


ShapecolorverticesdrawmovesetColor


Linelengthdraw


Example – Extension


Windowwidthheightopenclosedraw

DialogBoxcontrolsenabledraw

1- Invoke Window’s draw2- draw the dialog box

Example – Restriction


IntegerSet…

NaturalSet…

add( elem )…

add( elem )…

Add element to the set

If elem < 1 then give errorelse

Add element to the set


Example – Improve Performance

• Class Circle overrides rotate operation of class Shape with a Null operation.


Circleradiusdrawrotate

Abstract Classes

• An abstract class implements an abstract concept• Main purpose is to be inherited by other classes• Can’t be instantiated• Promotes reuse


Example – Abstract Classes

• Here, Person is an abstract classApril 10, 2023 COMSATS Institute of Information Technology 79



Example – Abstract Classes

• Here, Vehicle is an abstract classApril 10, 2023 COMSATS Institute of Information Technology 80

BusTruckCar

VehiclecolormodelaccelerateapplyBrakes

Concrete Classes

• A concrete class implements a concrete concept

• Main purpose is to be instantiated

• Provides implementation details specific to the domain context


Example – Concrete Classes

• Here, Student, Teacher and Doctor are concrete classesApril 10, 2023 COMSATS Institute of Information Technology 82


programstudyYearstudyheldExam

Person

Example – Concrete Classes


• Here, Car, Bus and Truck are concrete classes

BusCar

Vehicle

Truckcapacityloadunload

Multiple Inheritance

• We may want to reuse characteristics of more than one parent class


Example – Multiple Inheritance

April 10, 2023 COMSATS Institute of Information Technology 85Mermaid



Mermaid

Woman Fish



Amphibious Vehicle



Amphibious Vehicle

Land Vehicle Water Vehicle

Vehicle

Car Boat

Problems with Multiple Inheritance

• Increased complexity

• Reduced understanding

• Duplicate features


Problem – Duplicate Features

• Which eat operation Mermaid inherits?


Mermaid

Woman Fisheat…

eat…

Solution – Override the Common Feature


Mermaid

Woman Fisheat…

eat…

eat…

Invoke eat operation of desired class

Problem – Duplicate Features (Diamond Problem)

• Which changeGear operation Amphibious Vehicle inherits?


Amphibious Vehicle


Vehicle

Car Boat

changeGear

Solution to Diamond Problem

• Some languages disallow diamond hierarchy

• Others provide mechanism to ignore characteristics from one side


Association

• Objects in an object model interact with each other

• Usually an object provides services to several other objects

• An object keeps associations with other objects to delegate tasks


Kinds of Association

• Class Association• Inheritance

• Object Association• Simple Association• Composition• Aggregation


Simple Association

• Is the weakest link between objects

• Is a reference by which one object can interact with some other object

• Is simply called as “association”


Kinds of Simple Association

• w.r.t navigation• One-way Association• Two-way Association

• w.r.t number of objects• Binary Association• Ternary Association• N-ary Association


One-way Association

• We can navigate along a single direction only

• Denoted by an arrow towards the server object


Example – Association

• Ali lives in a House


Ali Houselives-in11


• Ali drives his Car


Ali Cardrives*1

Two-way Association

• We can navigate in both directions

• Denoted by a line between the associated objects


Example – Two-way Association

• Employee works for company• Company employs employees


Employee Companyworks-for1*


• Yasir is a friend of Ali• Ali is a friend of Yasir


Yasir Alifriend11

Binary Association

• Associates objects of exactly two classes

• Denoted by a line, or an arrow between the associated objects


Example – Binary Association

• Association “works-for” associates objects of exactly two classes




• Association “drives” associates objects of exactly two classes


Ali Cardrives*1

Ternary Association

• Associates objects of exactly three classes

• Denoted by a diamond with lines connected to associated objects


Example – Ternary Association

• Objects of exactly three classes are associated


Student Teacher

Course

1

*

*




Project Language

Person

*

1

*

N-ary Association

• An association between 3 or more classes

• Practical examples are very rare


Composition

• An object may be composed of other smaller objects• The relationship between the “part” objects and the “whole” object is

known as Composition• Composition is represented by a line with a filled-diamond head

towards the composer object


Example – Composition of Ali


Ali

Body

Arm

Head

Leg

1

1

2 2

Example – Composition of Chair


Chair

SeatArm

Back

Leg

1

12 4

Composition is Stronger

• Composition is a stronger relationship, because• Composed object becomes a part of the composer• Composed object can’t exist independently


Example – Composition is Stronger

• Ali is made up of different body parts

• They can’t exist independent of Ali



• Chair’s body is made up of different parts

• They can’t exist independently


Aggregation

• An object may contain a collection (aggregate) of other objects• The relationship between the container and the contained object is

called aggregation• Aggregation is represented by a line with unfilled-diamond head

towards the container


Example – Aggregation


Room

Cupboard

Bed

Chair Table*

1

1

1



Garden Plant*

Aggregation is Weaker

• Aggregation is weaker relationship, because• Aggregate object is not a part of the container• Aggregate object can exist independently


Example – Aggregation is Weaker

• Furniture is not an intrinsic part of room

• Furniture can be shifted to another room, and so can exist independent of a particular room



• A plant is not an intrinsic part of a garden

• It can be planted in some other garden, and so can exist independent of a particular garden


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References






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1. Inheritance Concepts2. Polymorphism

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Class diagram showing inheritance


Inheritance among classes is shown as open triangular arrowhead in UML Class Diagram.

Arrow be read as “derived from”.

Association

• Objects in an object model interact with each other

• Usually an object provides services to several other objects

• An object keeps associations with other objects to delegate tasks

April 10, 2023 COMSATS Intitute of Information Technology 127

Kinds of Association

• Class Association• Inheritance

• Object Association• Simple Association• Composition• Aggregation


Simple Association

• Is the weakest link between objects

• Is a reference by which one object can interact with some other object

• Is simply called as “association”


Kinds of Simple Association

• w.r.t navigation• One-way Association• Two-way Association

• w.r.t number of objects• Binary Association• Ternary Association• N-ary Association


One-way Association

• We can navigate along a single direction only

• Denoted by an arrow towards the server object



• Ali lives in a House


Ali Houselives-in11


• Ali drives his Car


Ali Cardrives*1

Two-way Association

• We can navigate in both directions

• Denoted by a line between the associated objects



• Employee works for company• Company employs employees




• Yasir is a friend of Ali• Ali is a friend of Yasir


Yasir Alifriend11

Binary Association

• Associates objects of exactly two classes

• Denoted by a line, or an arrow between the associated objects



• Association “works-for” associates objects of exactly two classes




• Association “drives” associates objects of exactly two classes


Ali Cardrives*1

Ternary Association

• Associates objects of exactly three classes

• Denoted by a diamond with lines connected to associated objects





Student Teacher

Course

1

*

*




Project Language

Person

*

1

*

N-ary Association

• An association between 3 or more classes

• Practical examples are very rare


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Class diagram showing association

• Association among classes is shown as a simple arrow (ray) in UML (Unified Modeling Language) Class Diagram.

• The direction of arrow shows ‘navigability’.• time12 calls time24.• This is unidirectional association.• If both classes call operation of the other, navigability is both sided (bidirectional

association).


Composition

• An object may be composed of other smaller objects• The relationship between the “part” objects and the “whole” object is

known as Composition• Composition is represented by a line with a filled-diamond head

towards the composer object


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Class diagram showing composition


Composition among classes is shown as solid diamond arrowhead in UML Class Diagram.

Example – Composition of Ali


Ali

Body

Arm

Head

Leg

1

1

2 2

Example – Composition of Chair


Chair

SeatArm

Back

Leg

1

12 4

Composition is Stronger

• Composition is a stronger relationship, because• Composed object becomes a part of the composer• Composed object can’t exist independently



• Ali is made up of different body parts

• They can’t exist independent of Ali



• Chair’s body is made up of different parts

• They can’t exist independently


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Composition

• Composition is a ‘consists of’ relationship.• COURSE_DATA consists of STUDENT_DATA (besides other things).• STUDENT_DATA lifetime is the same as COURSE_DATA.

• Part may belong to only one whole.• The lifetime of the part is the same as the lifetime of the whole.

Aggregation

• An object may contain a collection (aggregate) of other objects• The relationship between the container and the contained object is

called aggregation• Aggregation is represented by a line with unfilled-diamond head

towards the container


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Class diagram showing aggregation


Aggregation among classes is shown as open diamond arrowhead in UML Class Diagram.



Room

Cupboard

Bed

Chair Table*

1

1

1



Garden Plant*

Aggregation is Weaker

• Aggregation is weaker relationship, because• Aggregate object is not a part of the container• Aggregate object can exist independently



• Furniture is not an intrinsic part of room

• Furniture can be shifted to another room, and so can exist independent of a particular room



• A plant is not an intrinsic part of a garden

• It can be planted in some other garden, and so can exist independent of a particular garden



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More about ‘struct’• More on data hiding• By default all the data members of struct are

accessible (through the struct variable/object)• This behaviour is known as data being ‘public’.• We can hide them by explicitly marking them as

‘private’.• public: data or functions, can be accessed from

anywhere, outside or inside.• private: data or functions, cannot be accessed from

outside.


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More about ‘struct’ … struct TEST{

int x;}

TEST var;var.x = 10;

struct TEST{public:

int x;}

TEST var;var.x = 10;

struct TEST{private:

int x;}

TEST var;var.x = 10; //error

More about ‘struct’ … struct stack { int data[100]; int top;} S;///////////////////////////////////

void push(stack S, int a){ assert(top<100);

S.data[top]=a; S.top++; }



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More about ‘struct’ …struct TEST{

private:

int x;

public:

void Setx(int val) { x = val; };

int Getx() { return x; };

}

TEST var;

var.Setx(10);

int y = var.Getx();

struct TEST{private:

int x;}

TEST var;var.x = 10; //eint y = var.x; //e

So even legitimate access of data goes through an interface! We have secured the data further!!!


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Member functions definitionstruct TEST {private:

int x;public:

void Setx(int val);int Getx();

}void TEST::Setx(int val) {

x = val;}int TEST::Getx() {

return x;}main() {

TEST var;var.Setx(10);int y = var.Getx();

}

• We can declare member functions inside the struct and define them outside as well using the name of struct to resolve ambiguity.

• V. IMP: Note that this allows us to separate header and implementation files!

Class Compatibility

• A class is behaviorally compatible with another if it supports all the operations of the other class

• Such a class is called subtype

• A class can be replaced by its subtype


…Class Compatibility

• Derived class is usually a subtype of the base class

• It can handle all the legal messages (operations) of the base class

• Therefore, base class can always be replaced by the derived class


Example – Class Compatibility


ShapecolorverticesmovesetColordraw


Linelength

drawgetLength

Triangleangle

drawcomputeArea

Example – Class Compatibility


Filesize…openprint…

ASCII File…print…

PDF File…

print…

PS File…

print…

Polymorphism

• In general, polymorphism refers to existence of different forms of a single entity

• For example, both Diamond and Coal are different forms of Carbon


Polymorphism in OO Model

• In OO model, polymorphism means that different objects can behave in different ways for the same message (stimulus)

• Consequently, sender of a message does not need to know exact class of the receiver


Example – Polymorphism


Shape

Line Circle Triangledraw

draw

draw draw

drawView

Example – Polymorphism


File

ASCII File PDF File PS Fileprint

print

print print

printEditor

Polymorphism – Advantages• Messages can be interpreted in different ways

depending upon the receiver class


Shape


draw

draw draw

drawView

Polymorphism – Advantages• New classes can be added without changing the existing

model


Squaredraw

Shape


draw

draw draw

drawView

Polymorphism – Advantages

• In general, polymorphism is a powerful tool to develop flexible and reusable systems


Object-Oriented ModelingAn Example


Problem Statement

• Develop a graphic editor that can draw different geometric shapes such as line, circle and triangle. User can select, move or rotate a shape. To do so, editor provides user with a menu listing different commands. Individual shapes can be grouped together and can behave as a single shape.


Identify Classes

Extract nouns in the problem statement



…Identify Classes

Eliminate irrelevant classes

• Editor – Very broad scope

• User – Out of system boundary


…Identify Classes

Add classes by analyzing requirements

• Group – required to behave as a shape• “Individual shapes can be grouped together and can behave as a single

shape”

• View – editor must have a display area


…Identify Classes

• Shape• Line• Circle• Triangle• Menu


• Group• View

Following classes have been identified:

Object Model – Graphic Editor


Line

Circle

Triangle

GroupShape

View

Menu

Identify Associations

Extract verbs connecting objects

• “Individual shapes can be grouped together”• Group consists of lines, circles, triangles• Group can also consists of other groups(Composition)


… Identify Associations

Verify access paths

• View contains shapes• View contains lines• View contains circles• View contains triangles• View contains groups(Aggregation)


… Identify Associations

Verify access paths

• Menu sends message to View(Simple One-Way Association)




TriangleCircleLine

ShapeView

nnnnnn

nnMenu

Groupnn

nnnn

nn

nn

Identify Attributes

Extract properties of the object• From the problem statement

• Properties are not mentioned


…Identify Attributes

Extract properties of the object• From the domain knowledge


• Line– Color– Vertices– Length

• Circle– Color– Vertices– Radius

• Triangle– Color– Vertices– Angle

• Shape– Color– Vertices

…Identify Attributes

Extract properties of the object• From the domain knowledge


• Group– noOfObjects

• View– noOfObjects– selected

• Menu– Name– isOpen



MenunameisOpen

ViewnoOfObjectsselected

Shapecolorvertices

Linelength

Circleradius

GroupnoOfObjects

Triangleangle

nn

n

nn

n

nn

n

n

nn

nn

nn

n

Identify Operations

Extract verbs connected with an object



… Identify Operations

Eliminate irrelevant operations

• Develop – out of system boundary

• Behave – have broad semantics


…Identify Operations

Following are selected operations:


• Line– Draw– Select– Move– Rotate

• Circle– Draw– Select– Move– Rotate




• Triangle– Draw– Select– Move– Rotate

• Shape– Draw– Select– Move– Rotate




• Group– Draw– Select– Move– Rotate

• Menu– Open– Select– Move– Rotate


Extract operations using domain knowledge


• View– Add– Remove– Group– Show

– Select– Move– Rotate

GroupnoOfObjects

draw()

Triangleangle

draw()nn

Circleradius

draw()nn

Linelength

draw()

nn

Shapecolorvertices

draw()select()move()rotate()

nn


add()remove()group()show()select()move()rotate()

nn

nnnn

nn

MenunameisOpen

open()select()move()rotate()

n


Identify Inheritance

Search “is a kind of” by looking at keywords like “such as”, “for example”, etc

• “…shapes such as line, circle and triangle…”– Line, Circle and Triangle inherits from Shape


…Identify Inheritance

By analyzing requirements

• “Individual shapes can be grouped together and can behave as a single shape”

• Group inherits from Shape


Refining the Object Model

• Application of inheritance demands an iteration over the whole object model

• In the inheritance hierarchy,• All attributes are shared• All associations are shared• Some operations are shared• Others are overridden


…Refining the Object Model

Share associations

• View contains all kind of shapes

• Group consists of all kind of shapes



Share attributes

• Shape – Line, Circle, Triangle and Group• Color, vertices



Share operations

• Shape – Line, Circle, Triangle and Group• Select• Move• Rotate



Share the interface and override implementation

• Shape – Line, Circle, Triangle and Group• Draw


Linelength

draw()

Circleradius

draw()

Triangleangle

draw()

GroupnoOfObjects

draw()

Shapecolorvertices


n



nn

MenunameisOpen


n


GroupnoOfObjects

draw()

Triangleangle

draw()nn

Circleradius

draw()nn

Linelength

draw()

nn

Shapecolorvertices


nn



nn

nnnn

nn

MenunameisOpen


n


Class

• Class is a tool to realize objects• Class is a tool for defining a new type


Example

• Lion is an object• Student is an object• Both has some attributes and some behaviors


Uses

• The problem becomes easy to understand• Interactions can be easily modeled


Type in C++

• Mechanism for user defined types are• Structures• Classes

• Built-in types are like int, float and double• User defined type can be

• Student in student management system• Circle in a drawing software


Abstraction

• Only include details in the system that are required for making a functional system

• Student• Name• Address• Sibling• Father Business


Relevant to our problem

Not relevant to our problem

Defining a New User Defined Type

class ClassName

{

…

DataType MemberVariable;

ReturnType MemberFunction();

…

};


Syntax

Syntax

Example

class Student{int rollNo;char *name;float CGPA;char *address;

…void setName(char *newName);void setRollNo(int newRollNo);

…};April 10, 2023 COMSATS Intitute of Information Technology 214

Member variablesM

emb

er Fu

nction

s

Why Member Function

• They model the behaviors of an object• Objects can make their data invisible• Object remains in consistent state


Example

Student aStudent;

aStudent.rollNo = 514;

aStudent.rollNo = -514; //Error


Object and Class

• Object is an instantiation of a user defined type or a class


Declaring class variables

• Variables of classes (objects) are declared just like variables of structures and built-in data types

TypeName VaraibaleName;int var;Student aStudent;


Accessing members

• Members of an object can be accessed using • dot operator (.) to access via the variable name• arrow operator (->) to access via a pointer to an object

• Member variables and member functions are accessed in a similar fashion


Exampleclass Student{

int rollNo;

void setRollNo(int aNo);

};

Student aStudent;

aStudent.rollNo;


Error


221

struct -> class transition!class TEST {

private:

int x;

public:



}

main() {TEST var;var.Setx(10);int y = var.Getx();

}

struct TEST {private:

int x;public:


int Getx() { return x; };}main() {

TEST var;var.Setx(10);int y = var.Getx();

}• Replacing struct with class, does not have any affect!• This is the keyword that OOL (C++) provide for OOP!


222

Diff. between struct & classclass TEST {

int x;



}

main() {TEST var;var.x = 10; //errorvar.Setx(10); //errorint y = var.Getx(); //error

}

struct TEST {int x;



TEST var;var.x = 10; //possiblevar.Setx(10);int y = var.Getx();

}

• By default struct (C++) members are public, whereas class members are private.


223

Diff. between struct & classclass TEST {

int x;

public:



}

main() {TEST var;var.x = 10; //errorvar.Setx(10);int y = var.Getx();

}

struct TEST {private:

int x;public:



TEST var;var.x = 10; //errorvar.Setx(10);int y = var.Getx();

}• By default struct (C++) members are public, whereas class members are private.

Access specifiers


Access specifiers

• There are three access specifiers• ‘public’ is used to tell that member can be accessed whenever you have

access to the object• ‘private’ is used to tell that member can only be accessed from a member

function• ‘protected’ to be discussed when we cover inheritance


Example

class Student{

private:

char * name;

int rollNo;

public:

void setName(char *);

void setRollNo(int);

...

};April 10, 2023 COMSATS Intitute of Information Technology 226

Cannot be accessed outside class

Can be accessed outside class

Example

class Student{...int rollNo;

public:void setRollNo(int aNo);

};int main(){Student aStudent;aStudent.SetRollNo(1);

}April 10, 2023 COMSATS Intitute of Information Technology 227

Default access specifiers

• When no access specifier is mentioned then by default the member is considered private member


Exampleclass Student

{

char * name;

int RollNo;

};

class Student

{

private:

char * name;

int RollNo;

};


Exampleclass Student{char * name;int RollNo;void SetName(char *);};Student aStudent;aStudent.SetName(Ali);


Error

Exampleclass Student{char * name;int RollNo;public:void setName(char *);};Student aStudent;aStudent.SetName(“Ali”);



Unified Modeling Language (UML) class diagram

232 of 21

10..*

abstractstatic

private

association(“using”)

inheritance(“is a”)

233

Assignment (CP)

• Install IBM Rational Rose or any other UML tool and draw the diagrams used in this lecture and take a print out of those diagrams to show me what you have done.

• Deadline: next class


234

References







235

Thanks



1. Inheritance Concepts2. Polymorphism


236



Review

• Class• Concept• Definition

• Data members• Member Functions• Access specifier

Member Functions

• Member functions are the functions that operate on the data encapsulated in the class

• Public member functions are the interface to the class

Member Functions (contd.)

• Define member function inside the class definitionOR

• Define member function outside the class definition• But they must be declared inside class definition

Function Inside Class Body

class ClassName {…public:ReturnType FunctionName() {

…}};

Example•Define a class of student that has a roll number. This class should have a function that can be used to set the roll number

Example

class Student{

int rollNo;

public:

void setRollNo(int aRollNo){

rollNo = aRollNo;

}

};

Function Outside Class Body

class ClassName{

…

public:

ReturnType FunctionName();

};

ReturnType ClassName::FunctionName()

{

…

}

Scope resolution operator

Example

class Student{

…

int rollNo;

public:

void setRollNo(int aRollNo);

};

void Student::setRollNo(int aRollNo){

…

rollNo = aRollNo;

}

Inline Functions

• Instead of calling an inline function compiler replaces the code at the function call point

• Keyword ‘inline’ is used to request compiler to make a function inline• It is a request and not a command

Example

inline int Area(int len, int hi)

{

return len * hi;

}

int main()

{

cout << Area(10,20);

}

Inline Functions

• If we define the function inside the class body then the function is by default an inline function

• In case function is defined outside the class body then we must use the keyword ‘inline’ to make a function inline

Example

class Student{

int rollNo;

public:

void setRollNo(int aRollNo){

…

rollNo = aRollNo;

}

};

Example

class Student{

…

public:

inline void setRollNo(int aRollNo);

};

void Student::setRollNo(int aRollNo){

…

rollNo = aRollNo;

}

Example

class Student{

…

public:


};

inline void Student::setRollNo(int aRollNo){

…

rollNo = aRollNo;

}

Example

class Student{

…

public:

inline void setRollNo(int aRollNo);

};

inline void Student::setRollNo(int aRollNo){

…

rollNo = aRollNo;

}

Constructor

Constructor

• Constructor is used to initialize the objects of a class• Constructor is used to ensure that object is in well defined state at the

time of creation• Constructor is automatically called when the object is created• Constructor are not usually called explicitly

Constructor (contd.)

• Constructor is a special function having same name as the class name• Constructor does not have return type• Constructors are commonly public members

Example

class Student{

…

public:

Student(){

rollNo = 0;

…

}

};

Example

int main()

{

Student aStudent;

/*constructor is implicitly called at this point*/

}

Default Constructor

• Constructor without any argument is called default constructor• If we do not define a default constructor the compiler will generate a

default constructor• This compiler generated default constructor initialize the data

members to their default values

Example

class Student

{

int rollNo;

char *name;

float GPA;

public:

… //no constructors

};

Example

Compiler generated default constructor{rollNo = 0;GPA = 0.0;name = NULL;}

Constructor Overloading

• Constructors can have parameters• These parameters are used to initialize the data members with user

supplied data

Example

class Student{

…

public:

Student();

Student(char * aName);

Student(char * aName, int aRollNo);

Student(int aRollNo, int aRollNo, float aGPA);

};

Example

Student::Student(int aRollNo,

char * aName){

if(aRollNo < 0){

rollNo = 0;

}

else {

rollNo = aRollNo;

}

…

}

Example

int main()

{

Student student1;

Student student2(“Name”);

Student student3(”Name”, 1);

Student student4(”Name”,1,4.0);

}


• Use default parameter value to reduce the writing effort

Example

Student::Student( char * aName = NULL,

int aRollNo= 0,

float aGPA = 0.0){

…

}

Is equivalent toStudent();



Student(char * Name, int aRollNo, float aGPA);

266

References







How to correctly Search for a software @ google• When we need a software, the first place where we go is at

Google Search. If you don't know the software name, then we use some keywords at Google Search (for e.g. Note Taking software, Video Editing software, Photo Editing software etc). Once Google show us the results, we click the links after reading its title and some description. Following such practice often wastes our time by clicking useless links. What most of the people don't know is that, you can easily search for the software / applications at Google Search using its filtering options. Let's see how we can do that

• Consult the file uploaded


268

Thanks



1. Functions



Revision

• Chapter 5 of book


Functions


A function groups a number of program statements into a unit and gives it a name.

This unit can then be invoked from other parts of the program.

The most important reason to use functions is to aid in the conceptual organization of a program

Another reason to use functions is to reduce program size. Any sequence of instructions that appears in a program more than once is a candidate for being made into a function.

The function’s code is stored in only one place in memory, even though the function is executed many times in the course of the program.

Return type

Input argumentsApril 10, 2023 COMSATS Intitute of Information Technology 272

Functions


//demonstrates a simple function#include <iostream>using namespace std;int cube(int x); // function derationint main(){ // tests the cube() function: int n = 1;

while (n != 0){cin >> n;cout << "\tcube(" << n << ") = “

<< cube(n) << endl; // Calling a function} // end of while loopsystem("PAUSE"); return 0;

}//end of mainint cube( int x ){ // function definition

return x*x*x; // returns cube of x:} // { function body }

Input Arguments

Return type

Functions


Each integer read is passed to the cube() function by the call cube(n). The value returned by the function replaces the expression cube(n) and then is passed to the output object cout

The main() function passes the value 5 to the cube() function, and the cube() function returns the value 125 to the main() function.

The argument n is passed by value to the formal parameter x. This simply means that x is assigned the value of n when the function is called.

Default Arguments


#include <iostream>using namespace std;//declaration with default argumentsvoid repchar(char='*', int=45);int main(){ repchar(); //prints 45 asterisks repchar('='); //prints 45 equal signs repchar('+', 30); //prints 30 plus signs system("PAUSE"); return 0;}// displays line of charactersvoid repchar(char ch, int n){

// defaults supplied if necessary for(int j=0; j<n; j++) // loops n times cout << ch; // prints ch cout << endl;}

Inline Function


A function call involves substantial overhead. Extra time and space have to be used to invoke the function, pass parameters to it, allocate storage for its local variables, store the current variables and the location of execution in the main program, etc.

In some cases, it is better to avoid all this by specifying the function to be inline. This tells the compiler to replace each call to the function with explicit code for the function.

To the programmer, an inline function appears the same as an ordinary function, except for the use of the inline specifier.

Inline Function


// demonstrates inline functions#include <iostream>using namespace std;inline float lbstokg(float pounds){ // converts pounds to kilograms return 0.453592 * pounds;}

int main(){ float lbs; cout << "\nEnter your weight in pounds: "; cin >> lbs; cout << "Your weight in kilograms is " << lbstokg(lbs) << endl;return 0;}

Recursion


The existence of functions makes possible a programming technique called recursion.

Recursion involves a function calling itself. This sounds rather improbable, and indeed a function calling itself is often a bug. However, when used correctly this technique can be surprisingly powerful.

Recursion is much easier to understand with an example than with lengthy explanations, so let’s apply it to a program:

The next program, uses recursion instead of a loop to calculate factorial.

Recursion


#include <iostream>using namespace std;// calls itself to calculate factorialsunsigned long fct(unsigned long n){ static int I = 0; I++; cout << "You Called Me " << I << " times" << endl; if(n > 1) return n * fct(n-1); //self call else return 1;}int main(){ int n; cout << "Enter an integer: "; cin >> n; cout << "Factorial of " << n << " is " << fct(n) << "\n"; system("PAUSE"); return 0;}

Recursion


281

References



282

Thanks



1. Constructors


283



Constructor

Constructor

• Constructor is used to initialize the objects of a class• Constructor is used to ensure that object is in well defined state at the

time of creation (Lion 4 legs, Roll No +ve int)• Constructor is automatically called when the object is created• Constructor are not usually called explicitly

Constructor (contd.)

• Constructor is a special function having same name as the class name• Constructor does not have return type• Constructors are commonly public members

Example

class Student{

…

public:

Student(){

rollNo = 0;

…

}

};

Example

int main()

{

Student aStudent;

/*constructor is implicitly called at this point*/

}

Default Constructor

• Constructor without any argument is called default constructor• If we do not define a default constructor the compiler will generate a

default constructor• This compiler generated default constructor initialize the data

members to their default values

Example

class Student

{

int rollNo;

char *name;

float GPA;

public:

… //no constructors

};

Example

Compiler generated default constructor{rollNo = 0;GPA = 0.0;name = NULL;}


• Constructors can have parameters• These parameters are used to initialize the data members with user

supplied data

Example

class Student{

…

public:

Student();



Student(char * aName, int aRollNo, float aGPA);

};

Example

Student::Student(int aRollNo,

char * aName){

if(aRollNo < 0){

rollNo = 0;

}

else {

rollNo = aRollNo;

}

…

}

Example

int main()

{

Student student1;

Student student2(“Name”);

Student student3(”Name”, 1);

Student student4(”Name”,1,4.0);

}


• Use default parameter value to reduce the writing effort

Example

Student::Student( char * aName = NULL,

int aRollNo= 0,

float aGPA = 0.0){

…

}

Is equivalent toStudent();



Student(char * Name, int aRollNo, float aGPA);

Copy Constructor

• Copy constructor are used when:• Initializing an object at the time of creation• When an object is passed by value to a function

Example

void func1(Student student){

…

}

int main(){

Student studentA;

Student studentB = studentA;

func1(studentA);

}

Copy Constructor (Syntax)

Student::Student(const Student &obj){

rollNo = obj.rollNo;name = obj.name;GPA = obj.GPA;

}

Shallow Copy

• When we initialize one object with another then the compiler copies state of one object to the other

• This kind of copying is called shallow copying

Example

Student studentA;Student studentB = studentA;

Name

GPARollNo

studentA

Name

GPARollNo

studentBAHMAD…

Memory

Assignment

• Lab Assignment No 3


304

References







305

Thanks



1. Destructor



Review

•Copy constructors•Destructor•this Pointer•Separation of interface and implementation

Destructor• You might guess that another function is called

automatically when an object is destroyed. This is indeed the case. Such a function is called a destructor.

• A destructor also has the same name as the class name but is preceded by a tilde (~) sign:

• Like constructors, destructors do not have a return value. They also take no arguments.

• The most common use of destructors is to de-allocate memory that was allocated for the object by the constructor.


Using Destructor


// foo.cpp demonstrates destructor#include <iostream>using namespace std;class Foo{ private:

int data; public:

Foo() : data(0) // constructor (same name as class)

{cout<< "Wakeup \n" ; }~Foo() // destructor (same name with tilde)

{cout<< "ByeBye \n" ; }};int main(){

Foo s1, s2; // define two objects of class Foosystem( "PAUSE" ); // Foo *s3; s3 = new Foo; delete s3;return 0;

}

this Pointer•There are situations where designer wants to return reference to current object from a function

•In such cases reference is taken from this pointer like (*this)

Example

Student Student::setRollNo(int aNo)

{

…

return *this;

}

Student Student::setName(char *aName)

{

…

return *this;

}

Example

int main()

{

Student aStudent;

Student bStudent;

bStudent = aStudent.setName(“Ahmad”);

…

bStudent = aStudent.setName(“Ali”).setRollNo(2);

return 0;

}

Separation of interface and implementation

• Public member function exposed by a class is called interface

• Separation of implementation from the interface is good software engineering

Complex Number

•There are two representations of complex number• Euler form

• z = x + i y• Phasor form

• z = |z| (cos - + i sin -)• z is known as the complex modulus and - is known as

the complex argument or phase

Example

float getX()float getY()void setNumber (float i, float j)…

float x float y

Complex

Old implementation

float getX()float getY()void setNumber (float i, float j)…

float z float theta

Complex

New implementation

Exampleclass Complex{ //old

float x;

float y;

public:

void setNumber(float i, float j){

x = i;

y = j;

}

…

};

Exampleclass Complex{ //new

float z;

float theta;

public:

void setNumber(float i, float j){

theta = arctan(j/i);

…

}

…

};

Advantages

•User is only concerned about ways of accessing data (interface)

•User has no concern about the internal representation and implementation of the class

Separation of interface and implementation•Usually functions are defined in implementation files (.cpp) while the class definition is given in header file (.h)

•Some authors also consider this as separation of interface and implementation

Student.h

class Student{

int rollNo;

public:


int getRollNo();

…

};

Student.cpp

#include “student.h”

void Student::setRollNo(int aNo){

…

}

int Student::getRollNo(){

…

}

Driver.cpp

#include “student.h”

int main(){

Student aStudent;

}

Classes, Objects and Memory• you might have the impression that each object created

from a class contains separate copies of that class’s data and member functions.

• It’s true that each object has its own separate data items• But all the objects in a given class use the same member

functions. • The member functions are created and placed in memory

only once—when they are defined in the class definition.• Since the functions for each object are identical. The data

items, however, will hold different values.



325

References







326

Thanks



1. Static class member2. Const member function



10 April 2023 COMSATS Intitute of Information Technology 328

static class member

• What is a static variable? What is its scope (local, file) and storage class (automatic, static).

• What if a data member is static?• A member variable defined as static has characteristics

similar to a normal static variable: It is visible only within the class, but its lifetime is the entire program.

• It continues to exist even if there are no objects of the class.

• Why would we need a static member data?


static class member dataclass foo {

private:

static int count; //note: “declaration” only!

public:

foo() //incr count when object created

{ count++;

}

int getcount() //returns count

{ return count;

}

};

int foo::count = 0; //*definition* of count

int main(){foo f1, f2, f3; //create three objectscout << “count is “ << f1.getcount()

<< endl; //each objectcout << “count is “ << f2.getcount()

<< endl; //sees thecout << “count is “ << f3.getcount()

<< endl; //same valuereturn 0;}


static class member

• For multiple objects of the same class, new memory is allocated for data members and shared memory for all the functions.

• This shared memory is also used for static data members.

• Static data member requires two separate statements for:

• Declaration (compiler is told about type and name)• Definition (compiler sets aside memory)


static class member

• Why this two-part approach?• If static member data were defined inside the class (as it actually was in early versions of C++), it would violate the idea

that a class definition is only a blueprint and does not set aside any memory.

• Putting the definition of static member data outside the class also serves to emphasize that the memory space for such data is allocated only once, before the program starts to execute,

• and that one static member variable is accessed by an entire class; each object does not have its own version of the variable, as it would with ordinary member data.

• In this way a static member variable is more like a global variable.


static class member

• Be careful:• It’s easy to handle static data incorrectly, and the compiler is

not helpful about such errors.• If you include the declaration of a static variable but forget its

definition, there will be no warning from the compiler.• Everything looks fine until you get to the linker, which will tell

you that you’re trying to reference an undeclared global variable.

• This happens even if you include the definition but forget the class name (the foo:: in the example above).


Variable packing in memory• If you do a ‘sizeof(class_obj_or_name)’ for an object of

a class/struct or class/struct name, you get the size of the memory allocated for data members.

• Memory alignment in class/struct is a bit different.


Data member packing in class/struct

class Counter

{

private:

unsigned char count;

unsigned char temp2;

short temp1;

int temp;

static int obj;

public:

Counter() : count(0)

{

}

}

int sz = sizeof(Counter);

OR

Counter c1;int sz = sizeof(c1);

Gives sz = 8

If there was no temp2, sz will still be 8.If there was no temp1, sz will still be 8.If rearranged, sz will change.Experiment at home and make concepts.

const Member Functions

•There are functions that are meant to be read only

•There must exist a mechanism to detect error if such functions accidentally change the data member


Example

bool Student::isRollNo(int aNo){

if(rollNo = = aNo){

return true;

}

return false;

}


Example

bool Student::isRollNo(int aNo){

/*undetected typing mistake*/

if(rollNo = aNo){

return true;

}

return false;

}


Example

bool Student::isRollNo

(int aNo)const{

/*compiler error*/

if(rollNo = aNo){

return true;

}

return false;

}



•Keyword const is placed at the end of the parameter list



Declaration:class ClassName{

ReturnVal Function() const;

};

Definition:ReturnVal ClassName::Function() const{

…

}


Example

class Student{

public:

int getRollNo() const {

return rollNo;

}

};


const Functions

•Constant member functions cannot modify the state of any object

•They are just “read-only”•Errors due to typing are also caught at compile time


const Functions

•Constructors and Destructors cannot be const•Constructor and destructor are used to modify the object to a well defined state


Example

class Time{public:Time() const {} //error…~Time() const {} //error…};


const Function

•Constant member function cannot change data member

•Constant member function cannot access non-constant member functions


Example

class Student{char * name;

public:char *getName();void setName(char * aName);int ConstFunc() const{

name = getName();//errorsetName(“Ahmad”);//error

}};



348

References







349

Thanks



1. Arrays & String (Chapter 7)



Arrays In everyday life we commonly group similar

objects into units. We buy eggs by the carton. In computer languages we also need to group

together data items of the same type. The most basic mechanism that accomplishes this in C++ is the array.

Arrays can hold a few data items or tens of thousands. The data items grouped in an array can be simple types such as int or float, or they can be user-defined types such as structures and objects.

An array groups items of the same type. The items in a in an array are accessed by an index number. Using an index number to specify an item allows easy access to a large number of items.

Defining, Reading and Writing Array// gets four ages from user, displays them#include <iostream>using namespace std;int main(){ int age[4], j; //array 'age' of 4 ints for(j=0; j<4; j++){ //get 4 ages cout << "Enter an age: "; cin >> age[j]; //access array element } for(j=0; j<4; j++){ //display 4 ages cout << "age[" << j << "] = " << age[j] << endl; cout <<"Address " << &age[j] << " = " << age[j] <<

endl; } system("PAUSE"); return 0;}

Calculating Average#include <iostream>using namespace std;int main(){

double avg, sum = 0 ; int i ; int marks[10] ; /* array declaration */for ( i = 0 ; i <= 9 ; i++ ){

cout << "\nEnter marks "; cin >> marks[i]; /* store data in array */

}for ( i = 0 ; i <= 9 ; i++ )

sum = sum + marks[i] ; /* read data from array*/avg = sum / 10 ;cout << "\n Average marks = " << avg <<endl;

system("PAUSE"); return 0;}

Using Direct Access on an Array// Using Direct Access on Array#include <iostream>using namespace std;int main(){ int mem[]={50,60,70} ; // Initialize the array cout << "mem[0] = " << mem[0] << endl; cout << "mem[1] = " << mem[1] << endl; cout << "mem[2] = " << mem[2] << endl; mem[0] = 80; mem[1] = 90; mem[2] = 100; cout << endl; cout << "mem[0] = " << mem[0] << endl; cout << "mem[1] = " << mem[1] << endl; cout << "mem[2] = " << mem[2] << endl; system("PAUSE"); return 0;}

Printing in Reverse Order

#include <iostream>using namespace std;int main(){ const int SIZE=5; // defines the size N for 5 elements double a[SIZE]; // declares the array’s elements as

type double cout << "Enter " << SIZE << " numbers:\t"; for (int i=0; i<SIZE; i++) cin >> a[i]; cout << "In reverse order: "; for (int i=SIZE-1; i>=0; i--) cout << " " << a[i]; system("PAUSE"); return 0;}

Out of Bounds#include <iostream>using namespace std;int main(){

float a[] = { 22.2,44.4, 66.6 }; float x=11.1; cout << "I m going to Crash " << endl; cin >> x; a[3333] = 88.8; // ERROR: index is out of bounds!

return 0;}

Passing Array to Function#include <iostream>using namespace std;int sum(int[],int); // declarationint main(){ int a[] = { 11,33, 55,77 }; int size = sizeof(a)/sizeof(int); cout << "sum(a,size) = " << sum(a,size) << endl; cout << endl << a[0] << endl; system("PAUSE"); return 0;}int sum(int a[],int n){ int sum=0; for (int i=0; i<n; i++) sum += a[i]; a[0] = 100; return sum;}

n Dimensional Arrays#include <iostream>using namespace std;int main(){ const int row=2, col=3; int i,j; int ary[row][col] = { {11,12,13}, {21,22,23} }; for(i=0 ; i< row ; i++){ for(j=0 ; j<col; j++){ cout << ary[i][j] << " ";} cout << endl; } for(i=0 ; i< row ; i++){

for(j=0 ; j<col; j++){ cout << &ary[i][j] << "="<<ary[i][j]<<"\t";}

cout << endl;}return 0;

}

n Dimensional Arrays

0x22ff40 = 11

0x22ff44 = 12

0x22ff48 = 13

0x22ff4C = 21

0x22ff50 = 22

0x22ff54 = 23

ary[0][0]=

ary[0][1]=

ary[0][2]=

ary[1][0]=

ary[1][1]=

ary[1][2]=

232221

131211

2-Dimensional Arrays#include <iostream>using namespace std;int main(){ const int row=3, col=3; int i,j; int ary[row][col] = { {11,12,13}, {21,22,23}, {31,32,33} }; for(i=0 ; i< row ; i++){ for(j=0 ; j<col; j++){ cout << ary[i][j] << " ";} cout << endl; } for(i=0 ; i< row ; i++){

for(j=0 ; j<col; j++){ cout << &ary[i][j] << "="<<ary[i][j]<<"\t";}

cout << endl;} system("PAUSE"); return 0;}

3-Dimensional Arrays0x22ff30 = 11

0x22ff34 = 12

0x22ff38 = 13

0x22ff3C = 21

0x22ff40 = 22

0x22ff44 = 23

ary[0][0]=

ary[0][1]=

ary[0][2]=

ary[1][0]=

ary[1][1]=

ary[1][2]=

0x22ff48 = 31

0x22ff4C = 32

0x22ff50 = 33

ary[2][0]=

ary[2][1]=

ary[2][2]=

333231

232221

131211

Calculating Square of a Matrix#include <iostream>using namespace std;int main(){ const int row=3, col=3; int i,j; int A[row][col]; cout << "Square of a " <<row

<<"x"<<col<<"Matrices"<<endl; for(i=0 ; i< row ; i++){ for(j=0 ; j<col; j++){ cout << "A[" << i+1 << "][" << j+1 << "]= "; cin >> A[i][j]; } } for(i=0 ; i< row ; i++) for(j=0 ; j<col; j++) A[i][j] = A[i][j]*A[i][j]; for(i=0 ; i< row ; i++){ for(j=0 ; j<col; j++) cout << A[i][j] << "\t"; cout << endl; }

return 0;}

Passing 2D Array to Function#include <iostream>using namespace std;void get_data(float a[][3],int row, int col){ int i,j; for (i=0; i<row; i++) for (j=0; j<col; j++){ cout << "A["<<i+1<<"]["<<j+1<<"]:"; cin >> a[i][j];}}void show_data(float a[][3],int row, int col){ int i,j; for (i=0; i<row; i++){ for (j=0; j<col; j++) {cout << a[i][j] << "\t";} cout << endl; }}int main(){ float matrix[4][3]; // 4 rows and 3 columns get_data(matrix,4,3); show_data(matrix,4,3); return 0;}

Passing 3D Array to Function (1/2)

#include <iostream>

using namespace std;

void get_data(float a[][3][2],int row, int col,int page){

int i,j,k;

for (k=0; k<page; k++){

for (i=0; i<row; i++){

for (j=0; j<col; j++){

cout <<"A["<< i <<"]["<< j <<"]["<< k <<"]:";

cin >> a[i][j][k];

} // end of for (j=0

} // end of for (i=0

} // end of for (k=0

}

Passing 3D Array to Function (2/2)void show_data(float a[][3][2],int row, int col, int page){ int i,j,k; for (k=0; k<page; k++){ for (i=0; i<row; i++){ for (j=0; j<col; j++){ cout << a[i][j][k] << "\t"; } cout << endl; } cout << endl; }}

int main(){ float matrix[4][3][2]; // 4 rows, 3 columns, 2 pages get_data(matrix,4,3,2); show_data(matrix,4,3,2); system("PAUSE"); return 0;}

Sorting Data Using Bubble Sort Algo#include <iostream>using namespace std;void print( float[], int );void sort ( float[], int );int main(){ int i; float data[10]; cout << "Enter 10 Numbers for Sorting \n"; for( i=0 ; i<10 ; i++ ){ cout << "Enter No." <<i+1<< ":" ; cin >> data[i]; } sort(data,10); print(data,10);

return 0;}

Sorting Data Using Bubble Sort Algovoid sort( float a[], int n ){ // bubble sort: for (int i=1; i<n; i++) // bubble up max{a[0..n-i]}: for (int j=0; j<n-i; j++) if (a[j] > a[j+1]){ float temp = a[j]; a[j]=a[j+1]; a[j+1] = temp; }}

void print( float a[], int n ){cout << " Sorted Data is " << endl;for (int i=0; i<n; i++)

cout << a[i] <<" ";}

Using C-string#include <iostream>#include <iomanip.h>using namespace std;int main(){ char str[] = { 'M','.',' ','A','l','i',0,' ', 'I','I','U',0}; // char ch [] = "M. Ali"; int size = sizeof(str); cout << "\n The Character Array Size is :" <<size << " Bytes" << endl; for ( int i=0 ; i<size ; i++ ) cout << "str[" << i << "]=" <<str[i] <<" =[" << int(str[i]) << "]" << endl; cout << endl << str << endl; system("PAUSE"); return 0;}

Reading Embedded Blanks// blanksin.cpp reads string with embedded blanks#include <iostream>using namespace std;int main(){

const int MAX = 80; // max characters in stringchar str[MAX]; // string variable strcout << "\nEnter a string: ";// cin.get() means a member function get() of the stream// class of which cin is an objectcin.get(str, MAX); // put string in str// first argument to get() is the array address where the// string being input will be placed.// The second argument specifies the maximum size of the// arraycout << "You entered: " << str << endl;return 0;

}

Copying a String the Hard Way// strcopy1.cpp// copies a string using a for loop#include <iostream>#include <cstring> //for strlen()using namespace std;int main(){ //initialized string

char str1[] = "Oh, Captain, my Captain! ""our fearful trip is done";

const int MAX = 80; int j; // MAX is size of str2 bufferchar str2[MAX]; //empty stringfor( j=0; j<strlen(str1); j++) //copy strlen characters

str2[j] = str1[j]; // from str1 to str2str2[j] = '\0'; //insert NULL at endcout << str2 << endl; //display str2system("PAUSE"); return 0;

}

Copying a String the Easy Way// strcopy2.cpp

// copies a string using strcpy() function

#include <iostream>

#include <cstring> //for strcpy()

using namespace std;

int main(){

char str1[] = "Tiger, tiger, burning bright\n"

"In the forests of the night";

const int MAX = 80; //size of str2 buffer

char str2[MAX]; //empty string

strcpy(str2, str1); //copy str1 to str2

cout << str2 << endl; //display str2

system("PAUSE"); return 0;

}

Array of Strings// straray.cpp// array of strings#include <iostream>using namespace std;int main(){

const int DAYS = 7; //number of strings in arrayconst int MAX = 10; //maximum size of each string//An array of stringschar star[DAYS][MAX] = { "Sunday", "Monday", "Tuesday",

"Wednesday", "Thursday", "Friday" , "Saturday" };for( int j=0 ; j<DAYS ; j++) //display every string

cout << star[j] << endl;system("PAUSE");return 0;

}

Array of Strings

Lab Task

Write a and test a program to calculate Determinant and Reverse of a 3x3 matrix

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References







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Thanks



1. Composition2. Aggregation3. Friend Functions



Pointer to Objects

• Pointer to objects are similar as pointer to built-in types• They can also be used to dynamically allocate objects

Example

class Student{

…

public:

Studen();


void setRollNo(int aNo);

};

Example (Aggregation)

int main(){

Student obj;

Student *ptr;

ptr = &obj;

ptr->setRollNo(10);

return 0;

}

Allocation with new Operator

• new operator can be used to create objects at runtime

Exampleint main(){

Student *ptr;

ptr = new Student;

ptr->setRollNo(10);

return 0;

}

Exampleint main(){

Student *ptr;

ptr = new Student(“Ali”);

ptr->setRollNo(10);

return 0;

}

Breakup of new Operation

• new operator is decomposed as follows• Allocating space in memory• Calling the appropriate constructor

Case Study

Design a class date through which user must be able to perform following operations

• Get and set current day, month and year• Increment by x number of days, months and year• Set default date

Attributes

• Attributes that can be seen in this problem statement are• Day• Month• Year• Default date

Attributes

• The default date is a feature shared by all objects• This attribute must be declared a static member

Attributes in Date.h

class Date

{

int day;

int month;

int year;

static Date defaultDate;

…

};

Interfaces• getDay• getMonth• getYear• setDay• setMonth• setYear

• addDay• addMonth• addYear• setDefaultDate

Interfaces

• As the default date is a static member the interface setDefaultDate should also be declared static

Interfaces in Date.h

class Date{…public:void setDay(int aDay);int getDay() const;void addDay(int x);…

…};

Interfaces in Date.h

class Date{…public:static void setDefaultDate(

int aDay,int aMonth, int aYear);…};

Constructors and Destructors in Date.h

Date(int aDay = 0,

int aMonth= 0, int aYear= 0);

~Date(); //Destructor

};

Implementation of Date Class

• The static member variables must be initialized

Date Date::defaultDate (07,3,2013);

Constructors

Date::Date(int aDay, int aMonth, int aYear) {

if(aDay==0) {this->day = defaultDate.day;

}else{

setDay(aDay);}//similarly for other members

}

Destructor

• We are not required to do any house keeping chores in destructor

Date::~Date

{

}

Getter and Setter

void Date::setMonth(int a){

if(a > 0 && a <= 12){

month = a;

}

int getMonth() const{

return month;

}

addYear

void Date::addYear(int x){year += x;if(day == 29 && month == 2

&& !leapyear(year)){day = 1;month = 3;

}}

Helper Function

class Date{

…

private:

bool leapYear(int x) const;

…

};

Helper Function

bool Date::leapYear(int x) const{if((x%4 == 0 && x%100 != 0)

|| (x%400==0)){return true;

}return false;

}

setDefaultDate

void Date::setDefaultDate(

int d, int m, int y){

if(d >= 0 && d <= 31){

day = d;

}

…

}

AggregationComposition vs. Aggregation

►Aggregation is a weak relationship

Room(char *, int)~Room()FoldChair(int) : bool…

Chair()DoSomething() : voidFoldChair() : boolUnFoldChair() : bool~Chair()…

area : floatchairs[50]:Chair *

Room

…Chair

Aggregation►In aggregation, a pointer or reference to an object is created inside a class

►The sub-object has a life that is NOT dependant on the life of its master class

►e.g:Chairs can be moved inside or outside at anytimeWhen Room is destroyed, the chairs may or may not be destroyed

Aggregationclass Room{private:

float area;Chair * chairs[50];

Public:Room();void AddChair(Chair *, int chairNo);Chair * GetChair(int chairNo);bool FoldChair(int chairNo);…

};

AggregationRoom::Room(){

for(int i = 0; i < 50; i++)

chairs[i] = NULL;}void Room::AddChair(Chair *

chair1, int chairNo){if(chairNo >= 0 && chairNo <

50)chairs[chairNo] = chair1;

}

AggregationChair * Room::GetChair(int chairNo){

if(chairNo >= 0 && chairNo < 50)return chairs[chairNo];

elsereturn NULL;

}

bool Room::FoldChair(int chairNo){ if(chairNo >= 0 && chairNo < 50)

return chairs[chairNo]->FoldChair(); else

return false;}

Aggregationint main(){ Chair ch1; { Room r1;

r1.AddChair(&ch1, 1); r1.FoldChair(1);

} ch1.UnFoldChair(1); return 0;}

Friend Functions

►Consider the following class:class X{

private:

int a, b;

public:

void MemberFunction();

…

}

Friend Functions

►Global function:void DoSomething(X obj){

obj.a = 3; //Errorobj.b = 4; //Error

}

Friend Functions

►In order to access the member variables of the class, function definition must be made a friend function:

class X{

private:

int a, b;

public:

…

friend void DoSomething(X obj);

}

►Now the function DoSomething can access data members of class X

Friend Functions

►Prototypes of friend functions appear in the class definition►But friend functions are NOT member functions

Friend Functions

►Friend functions can be placed anywhere in the class without any effect

►Access specifiers don’t affect friend functions or classes

class X{

...

private:

friend void DoSomething(X);

public:

friend void DoAnything(X);

...

};

Friend Functions

►While the definition of the friend function is:

void DoSomething(X obj){

obj.a = 3; // No Error

obj.b = 4; // No Error

…

}

►friend keyword is not given in definition

Friend Functions

►If keyword friend is used in the function definition, it’s a syntax error

//Error…

friend void DoSomething(X obj){

…

}

Friend Classes•Similarly, one class can also be made friend of another class:

class X{

friend class Y;

…

};

•Member functions of class Y can access private data members of class X

Friend Classes•Example:

class X{friend class Y;private:

int x_var1, x_var2; ...};

Friend Classesclass Y{private:

int y_var1, y_var2;X objX;

public:void setX(){

objX.x_var1 = 1;}

};

Friend Classes

int main(){Y objY;objY.setX();return 0;

}

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References







421

Thanks



1. Operator Overloading

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Operator overloading►Consider the following class:

class Complex{

private:

double real, img;

public:

Complex Add(const Complex &);

Complex Subtract(const Complex &);

Complex Multiply(const Complex &);…

}

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Operator overloading►Function implementation:

Complex Complex::Add(

const Complex & c1){

Complex t;

t.real = real + c1.real;

t.img = img + c1.img;

return t;

}

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Operator overloading

►The following statement:Complex c3 = c1.Add(c2);

Adds the contents of c2 to c1 and assigns it to c3 (copy constructor)

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Operator overloading►To perform operations in a single

mathematical statement e.g:c1+c2+c3+c4

►We have to explicitly write:►c1.Add(c2.Add(c3.Add(c4)))

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Operator overloading►Alternative way is:► t1 = c3.Add(c4);► t2 = c2.Add(t1);► t3 = c1.Add(t2);

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Operator overloading►If the mathematical expression is big:

• Converting it to C++ code will involve complicated mixture of function calls

• Less readable• Chances of human mistakes are very high• Code produced is very hard to maintain

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Operator overloading►C++ provides a very elegant solution:

►“Operator overloading”►C++ allows you to overload common operators like +,

- or * etc…►Mathematical statements don’t have to be explicitly

converted into function calls

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Operator overloading►Assume that operator + has been

overloaded►Actual C++ code becomes:c1+c2+c3+c4

►The resultant code is very easy to read, write and maintain

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Operator overloading ►C++ automatically overloads operators for

pre-defined types►Example of predefined types:

int

float

double

char

long

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Operator overloading ►Example:

float x;

int y;

x = 102.02 + 0.09;

Y = 50 + 47;

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Operator overloading ►The compiler probably calls the correct

overloaded low level function for addition i.e:// for integer addition:

Add(int a, int b)

// for float addition:

Add(float a, float b)

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►Operator functions are not usually called directly

►They are automatically invoked to evaluate the operations they implement

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Operator overloading►List of operators that can be

overloaded in C++: April

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Operator overloading►List of operators that can’t be

overloaded:

►Reason: They take name, rather than value in their argument except for ?:

►?: is the only ternary operator in C++ and can’t be overloaded

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Operator overloading►The precedence of an operator is NOT

affected due to overloading►Example:

c1*c2+c3

c3+c2*c1

both yield the same answer

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►Associativity is NOT changed due to overloading

►Following arithmetic expression always is evaluated

from left to right:c1 + c2 + c3 + c4

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►Unary operators and assignment operator are right associative, e.g:a=b=c is same as a=(b=c)

►All other operators are left associative:

c1+c2+c3 is same as

(c1+c2)+c3

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Operator overloading►Always write code representing

the operator►Example:

Adding subtraction code inside the + operator will create chaos

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►Creating a new operator is a syntax error (whether unary, binary

or ternary)► You cannot create $

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Operator overloading►Arity of an operator is NOT affected by

overloading►Example:

Division operator will take exactly two operands in any case:

b = c / d

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Binary operators►Binary operators act on two quantities

►Binary operators:

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Binary operators►General syntax:

Member function:

TYPE1 CLASS::operator B_OP(

TYPE2 rhs){

...

}

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Binary operators►General syntax:

Non-member function:

TYPE1 operator B_OP(TYPE2 lhs, TYPE3

rhs){

...

}

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Binary operators►The “operator OP” must have at least one formal parameter of type class (user

defined type)►Following is an error:

int operator + (int, int);

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Binary operators►Overloading + operator:

class Complex{

private:

double real, img;

public:

…

Complex operator +(const Complex & rhs);

};

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Binary operators

Complex Complex::operator +(const Complex & rhs){

Complex t;

t.real = real + rhs.real;

t.img = img + rhs.img;

return t;

}

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Binary operators►The return type is Complex so as to facilitate complex

statements like:Complex t = c1 + c2 + c3;

►The above statement is automatically converted by the compiler into appropriate function calls:

(c1.operator +(c2)).operator +(c3);

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Binary operators

►If the return type was void, class Complex{

...► public:

► void operator+(► const Complex & rhs);

};

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Binary operators

void Complex::operator+(const Complex & rhs){

real = real + rhs.real;

img = img + rhs.img;

};

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Binary operators

►we have to do the same operation c1+c2+c3 as:c1+c2

c1+c3

// final result is stored in c1

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Binary operators

►Drawback of void return type:Assignments and cascaded expressions are not possibleCode is less readableDebugging is toughCode is very hard to maintain

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References







Thanks



1. Inheritance



Inheritance in Classes• If a class B inherits from class A, then B contains all

the characteristics (information structure and behavior) of class A

• The parent class is called base class and the child class is called derived class



UML Notation


Parent Class

Child Class

Base Class

Derived Class

Inheritance in C++

• There are three types of inheritance in C++

• Public• Private• Protected


“IS A” Relationship

• IS A relationship is modeled with the help of public inheritance

• Syntaxclass ChildClass

: public BaseClass{

...

};


Exampleclass Person{

...

};

class Student: public Person{

...

};


Accessing Members• Public members of base class become public member

of derived class• Private members of base class are not accessible from

outside of base class, even in the derived class (Information Hiding)



char *name;

int age;

...

public:

const char *GetName() const;

int GetAge() const;

...

};


Exampleclass Student: public Person{int semester;int rollNo;...

public:int GetSemester() const;int GetRollNo() const;void Print() const;...

};


Example

void Student::Print()

{

cout << name << “ is in” << “ semester ” << semester;

}


ERROR

Example

void Student::Print()

{

cout << GetName()

<< “ is in semester ” << semester;

}


Exampleint main(){

Student stdt;

stdt.semester = 0;//error

stdt.name = NULL; //error

cout << stdt.GetSemester();

cout << stdt.GetName();

return 0;

}


Allocation in Memory• The object of derived class is represented in memory

as follows


Data members of base class

Data members of derived class

base member1base member2

...

derived member1derived member2

...

Allocation in Memory• Every object of derived class has an anonymous

object of base class


Constructors• The anonymous object of base class must be

initialized using constructor of base class• When a derived class object is created the constructor

of base class is executed before the constructor of derived class


Constructors


Base class constructor initializes the anonymous object

Derived class constructor initializes the derived class object

base member1base member2

...

derived member1derived member2

...

Exampleclass Parent{public:Parent(){ cout <<

“Parent Constructor...”;}};class Child : public Parent{public:Child(){ cout <<

“Child Constructor...”;}};


Exampleint main(){

Child cobj;

return 0;

}


Output:Parent Constructor...Child Constructor...

Constructor• If default constructor of base class does not exist then

the compiler will try to generate a default constructor for base class and execute it before executing constructor of derived class


Constructor• If the user has given only an overloaded

constructor for base class, the compiler will not generate default constructor for base class


Exampleclass Parent{

public:

Parent(int i){}

};

class Child : public Parent{

public:

Child(){}

} Child_Object; //ERROR


Base Class Initializer• C++ has provided a mechanism to explicitly call a

constructor of base class from derived class

• The syntax is similar to member initializer and is referred as base-class initialization



public:

Parent(int i){…};

};


public:

Child(int i): Parent(i)

{…}

};



public:

Parent(){cout <<

“Parent Constructor...”;}

...

};


public:

Child():Parent()

{cout << “Child Constructor...”;}

...

};


Base Class Initializer• User can provide base class initializer and

member initializer simultaneously


Exampleclass Parent{public:Parent(){…}

};class Child : public Parent{int member;

public:Child():member(0), Parent() {…}

};


Base Class Initializer

• The base class initializer can be written after member initializer for derived class

• The base class constructor is executed before the initialization of data members of derived class.


Initializing Members• Derived class can only initialize members of base class

using overloaded constructors

• Derived class can not initialize the public data member of base class using member initialization list


Exampleclass Person{public:int age;char *name;...

public:Person();

};


Exampleclass Student: public Person{

private:

int semester;

...

public:

Student(int a):age(a)

{ //error

}

};


Reason

• It will be an assignment not an initialization


Destructors

• Destructors are called in reverse order of constructor called

• Derived class destructor is called before the base class destructor is called



public:

Parent(){cout <<“Parent Constructor”;}

~Parent(){cout<<“Parent Destructor”;}

};


public:

Child(){cout << “Child Constructor”;}

~Child(){cout << “Child Destructo”;}

};


ExampleOutput:

Parent Constructor

Child Constructor

Child Destructor

Parent Destructor


Protected Access Specifier


Date Classclass Date{

int day, month, year;static Date defaultDate;

public:void SetDay(int aDay);int GetDay() const;void AddDay(int x);… static void SetDefaultDate(

int aDay,int aMonth, int aYear);

Date Class

...private:

bool IsLeapYear();};

int main(){Date aDate;aDate.IsLeapYear(); //Errorreturn 0;

}

Creating SpecialDate Class

Special Date

Date Special Date

AddSpecialYear...

Creating SpecialDate Class

class SpecialDate: public Date{…

public:void AddSpecialYear(int i){

...if(day == 29 && month == 2&& !IsLeapyear(year+i)){ //ERROR!

...}

}};

Modify Access Specifier

• We can modify access specifier “IsLeapYear” from private to public

Modified Date Classclass Date{public:

...bool IsLeapYear();

};

Modified AddSpecialYear

void SpecialDate :: AddSpecialYear(int i){

...if(day == 29 && month == 2

&& !IsLeapyear(year+i)){ ...

}}

Protected members

• Protected members can not be accessed outside the class• Protected members of base class become protected member of

derived class in Public inheritance

Modified Date Class

class Date{…

protected: bool IsLeapYear();

};

int main(){Date aDate;aDate.IsLeapYear(); //Errorreturn 0;

}

Modified AddSpecialYear

void SpecialDate :: AddSpecialYear(int i){

...if(day == 29 && month == 2

&& !IsLeapyear(year+i)){ ...

}}

Disadvantages• Breaks encapsulation

• The protected member is part of base class’s implementation as well as derived class’s implementation

References



• National University of Computer & Emerging Sciences ,FAST [www.nu.edu.pk]




Thanks



1. Inheritance



Hierarchy of Inheritance• We represent the classes involved in inheritance

relation in tree like hierarchy


Example


GrandParent

Parent1 Parent2

Child1 Child2

Direct Base Class

• A direct base class is explicitly listed in a derived class's header with a colon (:)

class Child1:public Parent1...


Indirect Base Class• An indirect base class is not explicitly listed

in a derived class's header with a colon (:)• It is inherited from two or more levels up

the hierarchy of inheritance

class GrandParent{};class Parent1:

public GrandParent {};class Child1:public Parent1{};


Base Initialization

• The child can only perform the initialization of direct base class through base class initialization list

• The child can not perform the initialization of an indirect base class through base class initialization list


Example

class GrandParent{int gpData;

public: GrandParent() : gpData(0){...}GrandParent(int i) : gpData(i){...} void Print() const;

};


Example

class Parent1: public GrandParent{int pData;

public:Parent1() : GrandParent(), pData(0) {…}

};


Example

class Child1 : public Parent1 {public:

Child1() : Parent1() {...}Child1(int i) : GrandParent (i) //Error{...}void Print() const;

};


Overriding

• Child class can override the function of GrandParent class


Example


GrandParentPrint()

Parent1

Child1Print()

Example

void GrandParent::Print() { cout << “GrandParent::Print”

<< endl;}

void Child1::Print() { cout << “Child1::Print” << endl;

}April 10, 2023 COMSATS Intitute of Information Technology 515

Example

int main(){Child1 obj;obj.Print();obj.Parent1::Print();obj.GrandParent::Print();return 0;

}


Output

• Output is as follows

Child1::PrintGrandParent::PrintGrandParent::Print


Types of Inheritance• There are three types of inheritance

• Public• Protected• Private

• Use keyword public, private or protected to specify the type of inheritance


Public Inheritance

Member access in Base Class Derived Class

Public Public

Protected Protected

Private Hidden

class Child: public Parent {…};

Protected Inheritance


Public Protected

Protected Protected

Private Hidden

class Child: protected Parent {…};

Private Inheritance


Public Private

Protected Private

Private Hidden

class Child: private Parent {…};

Private Inheritance

• If the user does not specifies the type of inheritance then the default type is private inheritance

class Child: private Parent {…}is equivalent to

class Child: Parent {…}


Private Inheritance

• We use private inheritance when we want to reuse code of some class• Private Inheritance is used to model “Implemented in terms of”

relationship


Example

class Collection {...public:

void AddElement(int);bool SearchElement(int);bool SearchElementAgain(int);bool DeleteElement(int);


Example

• If element is not found in the Collection the function SearchElement will return false

• SearchElementAgain finds the second instance of element in the collection


Class Set

class Set: private Collection {private:

...public:

void AddMember(int);bool IsMember(int);bool DeleteMember(int);


Class Set

void Set::AddMember(int i){if (! IsMember(i) )

AddElement(i);}bool Set::IsMember(int i){

return SearchElement(i);}


References







Thanks



1. Private Inheritance2. Specialization



Private Inheritance

• If the user does not specifies the type of inheritance then the default type is private inheritance

class Child: private Parent {…}is equivalent to

class Child: Parent {…}


Private Inheritance

• We use private inheritance when we want to reuse code of some class• Private Inheritance is used to model “Implemented in terms of”

relationship


Example

class Collection {...public:

void AddElement(int);bool SearchElement(int);bool SearchElementAgain(int);bool DeleteElement(int);

};April 10, 2023 COMSATS Intitute of Information Technology

Example

• If element is not found in the Collection the function SearchElement will return false

• SearchElementAgain finds the second instance of element in the collection


Class Set

class Set: private Collection {private:

...public:

void AddMember(int);bool IsMember(int);bool DeleteMember(int);

};April 10, 2023 COMSATS Intitute of Information Technology

Class Set

void Set::AddMember(int i){if (! IsMember(i) )

AddElement(i);}bool Set::IsMember(int i){

return SearchElement(i);}



• the derived class is behaviourally incompatible with the base class

• Behaviourally incompatible means that base class can’t always be replaced by the derived class



• Specialization (Restriction) can be implemented using private and protected inheritance



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Personage : [0..125]

Adultage : [18..125]

setAge( a )

setAge( a )

age = a

If age < 18 then errorelse age = a

Private Inheritance


Public Private

Protected Private

Private Hidden

class Child: private Parent {…};


…protected:

int age;public:

bool SetAge(int _age){if (_age >=0 && _age <= 125) {

age = _age;return true;

}return false;

}};


Exampleclass Adult : private Person {

public:bool SetAge(int _age){

if (_age >=18 && _age <= 125) {age = _age;return true;

}return false;

}};April 10, 2023 COMSATS Intitute of Information Technology

“Abstract” Base Class• In the examples so far, inheritance has been used to add functionality to an

existing class. Now let’s look at an example where inheritance is used for a different purpose: as part of the original design of a program.

• Our example models a database of employees of a widget company. We’ve simplified the situation so that only three kinds of employees are represented. Managers manage, scientists perform research to develop better widgets, and laborers operate the dangerous widget-stamping presses.

• The database stores a name and an employee identification number for all employees, no matter what their category. However, for managers, it also stores their titles and golf club dues. For scientists, it stores the number of scholarly articles they have published. Laborers need no additional data beyond their names and numbers.

• Our example program starts with a base class employee. This class handles the employee’s last name and employee number. From this class three other classes are derived: manager, scientist, and laborer. The manager and scientist classes contain additional information about these categories of employee, and member functions to handle this information, as shown in Figure



Exercise 1

• Imagine a publishing company that markets both book and audiocassette versions of its works. Create a class publication that stores the title (a string) and price (type float) of a publication. From this class derive two classes: book, which adds a page count (type int), and tape, which adds a playing time in minutes (type float). Each of these three classes should have a getdata() function to get its data from the user at the keyboard, and a putdata() function to display its data. Write a main() program to test the book and tape classes by creating instances of them, asking the user to fill in data with getdata(), and then displaying the data with putdata().


Exercise 2

• Start with the publication, book, and tape classes of Exercise 1. Add a base class sales that holds an array of three floats so that it can record the dollar sales of a particular publication for the last three months. Include a getdata() function to get three sales amounts from the user, and a putdata() function to display the sales figures. Alter the book and tape classes so they are derived from both publication and sales. An object of class book or tape should input and output sales data along with its other data. Write a main() function to create a book object and a tape object and exercise their input/output capabilities.


Exercise 3

• Assume that the publisher in Exercises 1 and 3 decides to add a third way to distribute books: on computer disk, for those who like to do their reading on their laptop. Add a disk class that, like book and tape, is derived from publication. The disk class should incorporate the same member functions as the other classes. The data item unique to this class is the disk type: either CD or DVD. You can use an enum type to store this item. The user could select the appropriate type by typing c or d.


References







Thanks



1. Overriding & Overloading2. Multiple Inheritance3. Virtual Inheritance4. Virtual Functions/Members



Overriding Member Functions of Base Class

• Derived class can override the member functions of its base class

• To override a function the derived class simply provides a function with the same signature as that of its base class


Overriding


Parent...

Func1

Child...

Func1

Overriding

class Parent {public:

void Func1();void Func1(int);

};

class Child: public Parent {public:

void Func1();};April 10, 2023 COMSATS Institute of Information Technology 555

Overloading vs. Overriding

• Overloading is done within the scope of one class• Overriding is done in scope of parent and child• Overriding within the scope of single class is error due to duplicate

declaration


Overriding

class Parent {public:

void Func1();void Func1(); //Error

};



• Derive class can override member function of base class such that the working of function is totally changed


Example

class Person{public:

void Walk();};class ParalyzedPerson: public Person{public:

void Walk();};April 10, 2023 COMSATS Institute of Information Technology 559


• Derive class can override member function of base class such that the working of function is similar to former implementation


Exampleclass Person{char *name;public:Person(char *=NULL);const char *GetName() const;void Print(){

cout << “Name: ” << name << endl;

}};April 10, 2023 COMSATS Institute of Information Technology 561

Example

class Student : public Person{char * major;

public:Student(char * aName, char* aMajor);

void Print(){cout<<“Name: ”<< GetName()<<endl

<< “Major:” << major<< endl;}

...};


Example

int main(){

Student a(“Ahmad”, “Computer Science”);

a.Print();

return 0;

}


Output

Output:

Name: AhmedMajor: Computer Science



• Derive class can override member function of base class such that the working of function is based on former implementation


Exampleclass Student : public Person{char * major;

public:Student(char * aName, char* m);

void Print(){Print();//Print of Personcout<<“Major:” << major <<endl;

}...};


Example

int main(){


a.Print();

return 0;

}


Output

• There will be no output as the compiler will call the print of the child class from print of child class recursively

• There is no ending condition


Exampleclass Student : public Person{char * major;

public:Student(char * aName, char* m);

void Print(){Person::Print();cout<<“Major:” << major <<endl;

}...};


Example

int main(){


a.Print();

return 0;

}


Output

Output:

Name: AhmedMajor: Computer Science


{Before New Topic……}• I need Your anonymous Feed Back

• About the Instructor•&• About the CourseApril 10, 2023 COMSATS Institute of Information Technology 572


• A class can inherit from more then one class




Transmitter...

Transmit()

Receiver...

Receive()

Phone

Example

class Phone: public Transmitter, public Receiver

{...};



• Derived class can inherit from public base class as well as private and protected base classes

class Mermaid: private Woman, private Fish



• The derived class inherits data members and functions form all the base classes

• Object of derived class can perform all the tasks that an object of base class can perform


Example

int main(){Phone obj;obj.Transmit();obj.Receive();return 0;

}



• When using public multiple inheritance, the object of derived class can replace the objects of all the base classes


Example

int main(){Phone obj;Transmitter * tPtr = &obj;Receiver * rPtr = &obj;return 0;

}



• The pointer of one base class cannot be used to call the function of another base class

• The functions are called based on static type


Example

int main(){Phone obj;Transmitter * tPtr = &obj;tPtr->Transmit(); tPtr->Receive(); //Errorreturn 0;

}


Example

int main(){Phone obj;Receiver * rPtr = &obj;rPtr->Receive(); rPtr->Transmit(); //Errorreturn 0;

}



• If more than one base class have a function with same signature then the child will have two copies of that function

• Calling such function will result in ambiguity




Amphibious Vehicle


Car Boat

Example

class LandVehicle{public:

int GetMaxLoad();};class WaterVehicle{public:

int GetMaxLoad();};April 10, 2023 COMSATS Institute of Information Technology 586

Example

class AmphibiousVehicle: public LandVehicle, public WaterVehicle{

};int main(){

AmphibiousVehicle obj;obj.GetMaxLoad(); // Errorreturn 0;

}April 10, 2023 COMSATS Institute of Information Technology 587


• Programmer must explicitly specify the class name when calling ambiguous function


Example

int main(){AmphibiousVehicle obj; obj.LandVehicle::GetMaxLoad();obj.WaterVehicle::GetMaxLoad();return 0;

}



• The ambiguous call problem can arise when dealing with multiple level of multiple inheritance




Amphibious Vehicle


Vehicle

Car Boat

Example

class Vehicle{public:

int GetMaxLoad();};class LandVehicle : public Vehicle{};class WaterVehicle : public Vehicle{};April 10, 2023 COMSATS Institute of Information Technology 592

Example


};int main(){

AmphibiousVehicle obj;obj.GetMaxLoad(); // Errorreturn 0;

}April 10, 2023 COMSATS Institute of Information Technology 593

Example

int main(){

AmphibiousVehicle obj; obj.Vehicle::GetMaxLoad(); //Errorreturn 0;

}• Vehicle is accessible through two pathsApril 10, 2023 COMSATS Institute of Information Technology 594



Amphibious Vehicle


Vehicle

Car Boat

Vehicle

Exampleint main(){

AmphibiousVehicle obj; obj.LandVehicle::GetMaxLoad();obj.WaterVehicle::GetMaxLoad();return 0;

}



• Data member must be used with care when dealing with more then one level on inheritance


Example

class Vehicle{protected:

int weight;};class LandVehicle : public Vehicle{};class WaterVehicle : public Vehicle{};April 10, 2023 COMSATS Institute of Information Technology 598

Example


public: AmphibiousVehicle(){ LandVehicle::weight = 10;WaterVehicle::weight = 10;}

};• There are multiple copies of data member weightApril 10, 2023 COMSATS Institute of Information Technology 599

Memory View

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Data Members of Vehicle

Data Members of LandVehicle

Data Members of AmphibiousVehicle


Data Members of WaterVehicle

Virtual Inheritance

• In virtual inheritance there is exactly one copy of the anonymous base class object


Example

class Vehicle{protected:

int weight;};class LandVehicle :

public virtual Vehicle{};class WaterVehicle :

public virtual Vehicle{};April 10, 2023 COMSATS Institute of Information Technology 602

Example


public: AmphibiousVehicle(){ weight = 10;}

};April 10, 2023 COMSATS Institute of Information Technology 603

Memory View



Data Members of LandVehicle

Data Members of AmphibiousVehicle

Data Members of WaterVehicle

Virtual Inheritance

• Virtual inheritance must be used when necessary• There are situation when programmer would want to use two distinct

data members inherited from base class rather then one


Example


Student

BS Student MS Student PhD Student

MS/PhD Student

GPA

References







Thanks



1. Generic Programming2. Templates



Quiz

• Explain “Diamond of Death” with help of Class Diagram, also write code for your class diagram.


Feed Back

• High level course , contents , lectures assignments etc etc• Level of class/students …. • Too much course contents---- ???? What???• ITP Semester 1, Check Concepts• Basic concepts…. Should I start the ITP again???• 1 concept 1 topic 1 program per class --- Nice Joke ;-) • Questions during lectures-OK Noted • Programs, programs, & programs , …..and then coding• Where is the Theory?????• Revision Classes --- ok Sure, when ??? Tell me• Shortcuts ---- (There is no shortcut in life BTW )• Attention to backbenchers --- How can I do that??


Feed Back ……

• Tough time , assignments, project why us???? • Don’t get angry why? --• Body language ….. Well concentrate more on the course ;-)• Entertain students ….well exactly how? can u explain ;-)• Practical life, students doing masti during lectures…• Fast speed…Why, seems to b in hurry always ???• Faviourism , u r not neutral… • Not all students are programmers most of them are normal human beings, ;;;;• Not put your self in a situation so that u have to…….• -----------• Dress code for presentation…April 10, 2023 COMSATS Institute of Information Technology 612

Motivation

• Following function prints an array of integer elements:

void printArray(int* array, int size)

{

for ( int i = 0; i < size; i++ )

cout << array[ i ] << “, ”;

}

...Motivation

• What if we want to print an array of characters?

void printArray(char* array,

int size)

{


cout << array[ i ] << “, ”;

}

...Motivation

• What if we want to print an array of doubles?

void printArray(double* array,

int size)

{


cout << array[ i ] << “, ”;

}

...Motivation

• Now if we want to change the way function prints the array. e.g. from

1, 2, 3, 4, 5

to

1 - 2 - 3 - 4 - 5

...Motivation

• Now consider the Array class that wraps an array of integers

class Array {

int* pArray;

int size;

public:

…

};

...Motivation

• What if we want to use an Array class that wraps arrays of double?

class Array {

double* pArray;

int size;

public:

…

};

...Motivation

• What if we want to use an Array class that wraps arrays of boolean variables?

class Array {

bool* pArray;

int size;

public:

…

};

...Motivation

• Now if we want to add a function sum to Array class, we have to change all the three classes

Generic Programming

• Generic programming refers to programs containing generic abstractions

• A generic program abstraction (function, class) can be parameterized with a type

• Such abstractions can work with many different types of data

Advantages

• Reusability

• Writability

• Maintainability

Templates

• In C++ generic programming is done using templates

• Two kinds• Function Templates• Class Templates

• Compiler generates different type-specific copies from a single template

Function Templates

• A function template can be parameterized to operate on different types of data

Declaration

template< class T >

void funName( T x );

// OR

template< typename T >

void funName( T x );

// OR

template< class T, class U, … >

void funName( T x, U y, … );

Example – Function Templates

• Following function template prints an array having almost any type of elements:


void printArray( T* array, int size )

{


cout << array[ i ] << “, ”;

}

…Example – Function Templates

int main() {int iArray[5] = { 1, 2, 3, 4, 5 };void printArray( iArray, 5 );// Instantiated for int[]

char cArray[3] = { ‘a’, ‘b’, ‘c’ };void printArray( cArray, 3 );// Instantiated for char[]return 0;

}

Explicit Type Parameterization

• A function template may not have any parameter

template <typename T>

T getInput() {

T x;

cin >> x;

return x;

}

…Explicit Type Parameterization

int main() {

int x;

x = getInput(); // Error!

double y;

y = getInput(); // Error!

}

…Explicit Type Parameterization

int main() {

int x;

x = getInput< int >();

double y;

y = getInput< double >();

}

User-defined Specializations

• A template may not handle all the types successfully

• Explicit specializations need to be provided for specific type(s)

Example – User Specializations


bool isEqual( T x, T y ) {

return ( x == y );

}

… Example – User Specializations

int main {

isEqual( 5, 6 ); // OK

isEqual( 7.5, 7.5 ); // OK

isEqual( “abc”, “xyz” );

// Logical Error!

return 0;

}


template< >

bool isEqual< const char* >(

const char* x, const char* y ) {

return ( strcmp( x, y ) == 0 );

}


int main {isEqual( 5, 6 );// Target: general templateisEqual( 7.5, 7.5 );// Target: general template

isEqual( “abc”, “xyz” );// Target: user specializationreturn 0;

}

References







Thanks


LEC 20 TEMPLATE.CPP• // function template• #include <iostream> • using namespace std; • template <class T> • T GetMax (T a, T b)• {• T result; • result = (a>b)? a : b; • return (result); • } • int main ()• { • int i=5, j=6, k;• float l=10.5, m=5.6, n; • k=GetMax< int >(i,j); • n=GetMax< float >(l,m); • • cout << k << endl; • cout << n << endl; • return 0; • }

EXE LEC 18

` // exp09_04.cpp (pub3)// three classes derived from publication class#include <iostream>#include <string>using namespace std;

enum disktype {CD, DVD}; ////////////////////////////////////////////////////////////////class publication { private: string title; float price; public: void getdata() { cout << "\n Enter title (one word only): "; cin >> title; cout << " Enter price: "; cin >> price; } void putdata() { cout << "\n Title: " << title; cout << "\n Price: " << price; } };////////////////////////////////////////////////////////////////class book : private publication { private: int pages; public: void getdata() { publication::getdata(); cout << " Enter number of pages: "; cin >> pages; } void putdata() { publication::putdata(); cout << "\n Pages: " << pages; } };////////////////////////////////////////////////////////////////class tape : private publication { private: float time; public: void getdata() { publication::getdata(); cout << " Enter playing time: "; cin >> time; } void putdata() { publication::putdata(); cout << "\n Playing time: " << time; } };////////////////////////////////////////////////////////////////class disk : private publication { private: disktype type; public: void getdata(); void putdata() { publication::putdata(); cout << "\n Disk type: "; cout << (type==CD ? "CD" : "DVD"); } };//--------------------------------------------------------------void disk::getdata() { char ch; publication::getdata(); // get title and price do { // loop until correct size cout << " Enter disk type (c for CD, d for DVD): "; cin >> ch; switch(ch) { // set disk type case 'c': type = CD; break; case 'd': type = DVD; break; default: cout << "Incorrect type\n"; } } while(ch!='c' && ch!='d'); }////////////////////////////////////////////////////////////////int main() { book book1; // define publications tape tape1; disk disk1;

cout << "\nBook"; // get data for them book1.getdata(); cout << "\nTape"; tape1.getdata(); cout << "\nDisk"; disk1.getdata();

cout << "\nBook"; // display their data book1.putdata(); cout << "\nTape"; tape1.putdata(); cout << "\nDisk"; disk1.putdata(); cout << endl; return 0; }

Umer Tanvir

Education

All in 1