狠狠撸

Disadvantages of structure
?Standard C does not treat structure as an built-
in data type
?Suppose we have declared C1,C2,C3 as object
of above class at that time we can not perform
operation like
?C3=C1+C2
?Structure do not permit data hiding. All
structure members are public members.

Structures in C++
? C++ support all the features as defined in C, but
C++ has some expanded capabilities such as data
hiding, Inheritance.
? In C++ a structure can have both function and
variable as member(declaration)
? It also declare some members as private so that
they cannot accessed directly by external
function.
? C++ incorporates all these extension in another
user defined type known as Class.

What is Class in C++
? A class is a way to bind data and its associated
function together.
? It allows the data and function to be hidden, if
necessary.
? When defining class we are creating new abstract
data type that can be treated as other built-in
data type

Class specification has two parts:
1.Class declaration
2.Class function definition
The class declaration describes the type and
scope of its members, The class function
definition describe how the class function are
implemented

static member and static member fumctions.ppt

? The keyword class specifies, that what follows
is an abstract data of type class_name
? Body of a class is enclosed within braces and
terminated by semicolon.
? Class body contains declaration of variables
and functions
? These variabes are collectively called as class
members
? The keyword PUBLIC and PRIVATE are known
as visibility labels
? If we don’t specify this label by default they
are PRIVATE.

Creating Object
Syntax
Class_name object_name;
Example: item x;
OR
item x,y,z //multiple object
We can also create object after class declaration as
we do for structures(i.e declaring after semicolon)

Defining member function
Member function can be defined in two places”
1.Outside the class definition
2.Inside the class definition
The function should perform the same task
irrespective of the place of definition.

Outside definition:
?An important difference between a member
function and normal function is that a member
function incorporates a membership ‘identity label’
in the header i.e class_name::
?This ‘label’ tells the compiler which class the
function belongs to.
Syntax

The member function have special characteristics
that are often used in the program development.
Characteristics are:
?Several different classes can use the same
function name. the membership label will resolve
their scope.
?Member function can access private data of the
class
?The member function can call another member
function directly, without using the dot operator

Inside class definition:
?Another method of defining member function is
to replace the function declaration by the actual
function definition.
?When function is defined inside class is called as
inline function
?Normally small functions are defined inside a
class.

Making outside function inline:
when we define member function outside the class
definition and still make it inline by just using the
qualifier inline in the header line of function
definition

Memory allocation for object
? The memory space for object is allocated when
they are declared and not when the class is
specified.
? This is only partly true the member funaction are
created and placed in the memory space olny once
when they are defined as a part of class
specification
? Since all the objects belonging to that class use the
same member function,no separate space is
allocated for member functions when the objects

Array of Object
? Array of a Variables that are of type class are
called array of object.
Syntax:
classname objectname[size];
Example:
employee e1[3];

Mememory allocation for array of
a object
Name
Age
Name
Age
Name
Age
EMP[0]
EMP[1]
EMP[2]

Object as function argument
Object can be used as function arguement and
this is done by two ways.
1. A copy of teh entire object is passed to the
function
2.Only the address of the object is transferred to
the function

1. A copy of teh entire object is passed to the
function
? The first method is called pass-by-value
? A copy of a object is passed to the function
any changes made to the object inside the
function do not affect the object used to call
the function

2.Only the address of the object is transferred
to the function
? The second method is called pass-by-
reference.
? When an address of the object is passed, the
called function directly work on actual object
used in the call.
? Any changes made to the object inside the
function will reflect in the actual object.

Static data members
Following are the characteristics of static
member
? It is initialized to zero when the first object of
its class is created. No other initialization is
permitted
? Only one copy of that member is crated for
the entire class and is shared by all the object
of that class, no matter how many objects are
created

? It is visible only within class, but its lifetime is
the entire program.
? Static variables are used to maintain values
common to the entire class.
Eg. This can be used as a counter that records
the occcurences of all the objects
Syntax:
static datatype variblename;
Eg:
static int a;

Static Member function
? Like a static member variable we can also
have static member function. A member
function declared with static keyword is
called as static member function. static
member function has following
characteristics:
1.Static function can have access to only other
static members/functions declared in same class
2.Static member function can be called using
class name(instead of object) as
Class_name:: function_name;

Friend Function
? We have seen that private members can't be
accessed from outside class. Non member
function cannot have access to the private
data of a class.
? There would be situation where we would
like two classes to share particular function.
Eg consider two classes manager and scientist.
We like to use a function income_tax() to
operate on object of both d classes.

? C++ allows the common function to be made
friendly with the both the classes to have
access to the private data of these classes
? To make an outside function “friendly” to a
class, we have to simply declare this function
as a friend function of that class.
Syntax:
Friend returntype function_name(arguements);
Eg:
Friend void add();

? The function that is declared with the
keyword friend is known as friend function
? This function can be defined else where in
the program.
? The function definition does not use either
keyword friend or the scope operator::
? A function can be declared as a friend in any
number of classes.
? A friend function although not a member
function, has full access right to the private
members of the class

A friend function has certain special
characteristics:
1. It is not in the scope of class to which it has
been declared as friend
2. Since it is not in the scope of class, it cannot
be us called using object of that class
3. It can be invoked like a normal function
without the help of any object.
4. Unlike member function it can’t access
member names directly and has to use an
object name and dot membership operator
with each member name

? It can be declared either in the public or
private part of a class without affecting its
meaning

狠狠撸

static member and static member fumctions.ppt

Recommended

More Related Content

Similar to static member and static member fumctions.ppt (20)

Recently uploaded (20)

static member and static member fumctions.ppt