Classes
- Class is a user defined data type just like structures, but with a difference
- It also has three sections namely private, public and protected
- Using these, access
to member variables of a class can be strictly controlled.
The following is the general format of defining a class template
class tag_name
{
public : // Must
type member_variable_name;
:
type member_function_name();
:
private : // Optional
type member_variable_name;
:
type member_function_name(); :
};
1.The
keyword class is used to define a class template.
2.The private and public sections of a class are given by the keywords ‘private’ and
‘public’ respectively.
3.Determine the accessibility of the members. All the variables declared in the class, whether in the private or the public section, are the members of the class.
4.The class scope is private
by default.
Conventions
for naming classes
–Should be meaningful
–Should ideally be a noun
–First letter of every word should be in upper case
Rules
for naming classes
–Must not contain any embedded space or symbol
–Must begin with a letter, which may be followed by
a sequence of letters or digits
–Cannot be a keyword
Member functions
-Are means of passing messages and responding to them
-Are
declared inside the class body
Example:
class Car
{
void honk()
{
cout<<"BEEP BEEP!";
}
};
Object
-Once
a class is declared, an object of that type can be defined.
-An object is
said to be a specific instance of a class just like Maruti car
is an instance of a vehicle or pigeon is the instance
of a bird.
-Once
a class has been defined several objects of that
type
can be declared
-Objects can be passed to a function and returned back just like normal variables.
-When an object is passed by content , the compiler creates another object as a formal
variable in the called function and copies all the data members from the actual variable to it.
-Objects can also be passed by address
class check
public :
check add(check);
void get()
{
cin >> a;
}
void put()
{
cout << a;
}
private :
int a;
};
void main()
{
check c1,c2,c3;
c1.get();
c2.get();
c3 = c1.add(c2);
c3.put();
}
check check :: add ( check c2)
{
check temp;
temp.a =
a + c2.a;
return ( temp);
}
The above example creates three objects of class
check.
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