First  Program
Malik Jahan Khan
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A Simple Example
• Each person in Pakistan is identified by a
unique ID
• For sake of simplicity, assume that each ID is a
simple integer
• We don’t need any other attribute of the
person
• The simplest behavior which a person can
exhibit is that it may be assigned (set) a new
ID or it may display its ID when requested
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using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
void main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
}
First OO Program
3
#include<iostream>
using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
void main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
First OO Program
Class Definition
4
First OO Program
#include<iostream>
using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
void main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
}
Attributes of Class
(Data Members)
5
First OO Program
#include<iostream>
using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
void main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
}
Class Behavior
(Member Functions)
6
First OO Program
#include<iostream>
using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
//Class Definition must end with a semicolon
void main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
}
7
First OO Program
#include<iostream>
using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
//Class Definition must end with a semicolon
int main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
}
Objects Definition
8
First OO Program
#include<iostream>
using namespace std;
class Person
{
private:
int id;
public:
void setID(int d)
{
id=d;
}
void showID()
{
cout<<"\n My ID is "<<id;
}
};
//Class Definition must end with a semicolon
void main()
{
Person p1,p2,p3;
p1.setID(10);
p2.setID(20);
p3.setID(30);
p1.showID();
p2.showID();
p3.showID();
}
Using Member
Functions
9
Instantiation of Objects
Person
data: ID
methods: setID(id), showID()
Class
person 1
data: 10
person 2
data: 20
person 3
data: 30
10
Private and Public
• Data is concealed (hidden or masked) within a
class so that it cannot be accessed mistakenly by
functions out side the class
• The primary mechanism for hiding data is to put
it in class and make it private
• Private data or functions can only be accessed
from within the class
• Public data or functions are accessible from
outside the class
• Usually, functions are public and data is private
11
Graphics Example
#include "msoftcon.h"
class circle
{
private:
int xCo, yCo, radius;
color fillcolor;
fstyle fillstyle;
public:
void set(int x,int y,int r, color fc, fstyle fs)
{
xCo=x;
yCo=y;
radius=r;
fillcolor=fc;
fillstyle=fs;
}
void draw()
{
set_color(fillcolor);
set_fill_style(fillstyle);
draw_circle(xCo,yCo,radius);
}
};
int main()
{
init_graphics();
circle c1,c2,c3;
c1.set(15,7,5,cBLUE,X_FILL);
c2.set(41,12,7,cRED,O_FILL);
c3.set(65,18,4,cGREEN,MEDIUM_FILL);
c1.draw();
c2.draw();
c3.draw();
return 0;
}
12
Self-Reading
• Previous example of Graphics (also given in
textbook)
• Example of Widget Parts (page 223)
• C++ objects as data types (page 226)
– Example of Distance
• There may be a surprise quiz next time from
the stuff which we covered so far ;)
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