this is slide...by C++...

1. Mr. Fourcan Karim Mazumder
Faculty
Dept. of Computer Science and
Engineering

2. Class and Object:
Object
In the real world, Objects are the entities of which
the world is comprised. Everything that happens
in the world is related to the interactions between
the objects in the world. Just as atoms, which are
objects, combine to form larger objects, the
interacting entities in the world can be thought of
as interactions between and among both singular
("atomic") as well as compound ("composed")
objects.

3. The real world consists of many, many objects
interacting in many ways. While each object may
not be overly complex, their interactions create
the overall complexity of the natural world. It is
this complexity that we wish to capture in our
software systems. In an object-oriented software
system, objects are entities used to represent or
model a particular piece of the system. Objects
are the primary units used to create abstract
models.

4. An object that does not interact with anything else
effectively does not exist. Access to internally stored
data is necessarily through some sort of defined
behavior of the object. It is impossible for an outside
entity to truly "know" whether or not a particular
piece of data is being stored inside of another object.
The real meaning of the object is in how the object
behaves in relationship to its data, should it contain
any. The existence of data in an object is an
implementation technique used to generate the
required behavior of that object.

5. Objects are variables of type class. Once a class
has been defined, we can create any number of
objects belonging to that class. Objects contain
data and code to manipulate that data. Object is
using to allocate memory space for class member
variables and member functions.

6. Classes :
Many objects differ from each other only in the value
of the data that they hold. For example, both a red
light and a blue light are lights; they differ only in the
value of the color attribute, one has a red color and
the other a blue color. Our object-oriented system
needs a way to capture the abstraction of a light,
independent of the value of its color. That is, we
want to express that a set of objects are abstractly
equivalent, differing only in the values of their
attributes.

7. Object-oriented systems use classes to express the
above concept of abstract equivalence. A class is a
summary description of a set of objects. A class thus
contains the descriptions of all the behaviors of the
objects that it represents. In computer science
parlance, we call the individual behaviors of a class its
methods. In addition, a class contains descriptions of
the internal data held by the objects. Turning the
description around, we can say that a class is a pattern
for the creation of a particular type of object.

8. That is, one can use a class to create objects of the
type described by the class. A class is an
arrangement of a set of objects, it is not the actual
object. In technical terms, a class defines a new
type in the system. Types are identifies used to
differentiate different kinds of data. For instance,
integers, characters, strings and arrays are all types
of data.

9. A class is a way to bind the data and its associated
functions together. It allows the data (and
function) to be hidden, if necessary from external
use. A class is a collection of objects of similar
type. Classes are user defined data types and
behave like the built in data types of a
programming language.

10. example:
class muna
{
memberfunction()
{
datatype:
}
};
main()
{
muna ob1;
ob1.memberfunction();
}

11. Example: if a is a class name and ob is a object of class a, then
the format of using class and object in C++ program is look like as
follows:
class a
{
public:
int x;
void getdata()
{
}
void display()
{
}
};

12. void main()
{
a ob; //object declaration
ob.getdata();// accessing class member function
ob.display(); //accessing class member function
}