Overloading Binary Operator

Binary operations are performed which require two operands to perform operations.

To add two numbers generally we use statement like
   C = sum(A,B);      //Functional Notation

This functional Notation can be replaced by natural looking expression
   C = A + B;
             By overloading '+' operator using an operator +( ) function.

The Overloaded function can be invoked by expression such as for binary operators-
   Syntax :
   X op Y;



#include<conio.h>
#include<iostream.h>
class complex 
{
float x;
float y;
public:
complex(double real, double imag)
{
x = real;
y = imag;
}
complex( )
{


}
complex operator+(complex c);
void display( );
};
complex complex ::operator+(complex c)
{
complex temp;
temp.x = x+c.x;
temp.y = y+c.y;
return (temp);
}
void complex::display( )
{
cout<<x<<" +j"<<y;
}
void main( )
{
complex c1(2.5,3.5);
complex c2(1.6,2.7);
complex c3;
clrscr( );
c3 = c1 + c2;
cout<<"\n\n\tc1 is--->"<<"\t";
c1.display( );
cout<<"\n\n\tc2 is--->"<<"\t";
c2.display( );
cout<<"\n\n\tc3 is--->"<<"\t";
c3.display( );
getch( );
}

Output:-
c1 is--->               2.5    +j3.5
c2 is--->               1.6    +j2.7
c3 is--->               4.1    +j6.2

Binary Operator Overloading using friend function

In many cases whether you overload an operator by using a friend or member function makes no functional difference. In those cases it is usually best to overload by using member function. However there is one situation in which overloading by using a friend increase flexibility of an overloaded operator.

We have seen how unary operator is overloaded, similar way we can overload binay operator. Binary operator requires two operands.

The syntax for overloading binary operator using friend function as follows:

friend Return_type operator op(Arguments)
{                      //Body of the operator function

}

WAP to overload binary '+' operator to add two complex numbers using friend function

#include<conio.h>
#include<iostream.h>
class complex
{
double real, ima;
public:
void getdata( )
{
cout<<"\n\tEnter real part of complex no.";
cin>>real;
cout<<"\n\tEnter imaginary part of complex no";
cin>>img;
}
void display( )
{
cout<<"\t"<<real<<"+i"<<img;
}
friend complex operator +(complex,complex);
};

complex operator +(complex c1, complex c2)
{
complex temp;
temp.real = c1.real + c2.real;
temp.img = c1.img + c2.img;
return temp;
}
void main( )
{
complex A,B,C;
clrscr( );
cout<<"\n\tEnter data for first object";
A.getdata( );
cout<<"\n\tEnter Data for second object";
B.getdata( );
C = A + B;
cout<<"\n\tData for first object--->";
A.display( );
cout<<"\n\tData for second object--->";
B.display( );
cout<<"\n\tAddition of two complex no is--->";
C.display( );
getch( );
}

Output:-
Enter data for first object
Enter real part of complex no12

Enter imaginary part of complex no5.6

Enter Data for second object
 Enter real part of complex no5

Enter imaginary part of complex no3.5

Data for first object--->    12+i5.6 
Data for second object--->   5+i3.5
Addition of two complex no is--->      17+i9.1

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Overloading Unary Operator

First we consider the unary operator. Let consider unary operator unary minus ( - ) , when it is used, it takes just one operand.

We know that unary minus (-) operator changes the sign of an operand when applied to basic data item.

We have overloaded this operator so that it should be operated to an object in the same way as applied to an int or float variables.

The unary minus when applied to an object should change the sign of each of data item.

Overloaded function can be invoked by expression such as for unary operator

                   Op  x;

                      OR

                   x  op;

#include<conio.h>
#include<iostream.h>
class space
{
int x, y, z;
public:
void getdata(int a, int b, int c)
{
  x = a;
  y = b;
  z = c;
}
void display( );
void operator-( );
};

void space::display( )
{
cout<<"\n\tx is--->"<<x;
cout<<"\n\ty is--->"<<y;
cout<<"\n\tz is--->"<<z;
}
void space::operator-( )
{
x = -x;
y = -y;
z = -z;
}
void main( )
{
space s;
clrscr( );
s.getdata( 10, -20, 30);
cout<<"\n\tBefore Overloading:";
s.display( );
-s;
cout<<"\n\tAfter Overloading:";
s.display( );
getch( );
}

Output:-
Before Overloading:
x is--->10
y is--->-20
z is--->30
After Overloading:
x is--->-10
y is--->20
z is--->-30

Unary Operator overloading using Friend function

We can also use unary operator with the friend function. By using this concept we can use operator function with different classes. The following program illustrates this features.

Note : 
 In the friend function , we are passing argument as the reference . If we pass argument as by value it will not reflect the correct result because we need all the changes outside which are made inside the operator function.

//WAP to overload unary '-' operator to negate different variables using friend function

#include<conio.h>
#include<iostream.h>
class space
{
int x, y, z;
public:
void getdata(int a, int b, int c)
{
z = a;
y = b;
z = c;
}
void display( )
{
cout<<"\n\tData--->";
cout<<"\t"<<x<<"\t"<<y<<"\t"<<z;
}
friend void operator -(space &op);
};
void operator -(space &op)
{
op.x = -op.x;
op.y = -op.y;
op.z = -op.z;
}
void main( )
{
space s;
clrscr( );
s.getdata( 10, -20, 30);
cout<<"\n\tBefore Operator overloading---";
s.display( );
-s;
cout<<"\n\tAfter Operator overloading---";
s.display( );
getch( );
}

Output:-
Before Operator overloading--- 
Data is--->  10   -20   30
After Operator overloading---
Data is--->   -10    20    -30

Read More

Operator Overloading

Cpp allows user to overload most operators so that they should perform special operations relative to classes that user create.

Cpp tries to make user defined data types behaves in much the same way as in built in types.

Cpp permits us to add two variables of user defined types with the syntax that is applied to basic types.

Cpp provides the operator special meaning to operator on user defined data type known as operator overloading.

Operator can overloaded by creating operator functions.

An operator function defines the operation that the overloaded operator will perform relative to class.

An operator function is created using keyword 'operator'.


Syntax is->

return type classname :: operator op(argument list)
{
  //operations

}

Where return type is the type of the value returned by the specified operations and 'op' is the operator being overloaded.

When unary operator is overloaded then the argument list is empty.

When binary operator is overloaded the argument list has only one parameter.

Here 'operator' is a keyword in a member function which tells that it's a operator overloading function.

A member function called as operator overloaded function should be created under public section of the class.

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'new' and 'delete' Operators

In 'C' , we have used malloc( ), calloc( ), and realloc( ) function to allocate memory dynamically that is at the run time. 'C++' also provides these function but other than this it supports new unary operators 'new' and 'delete' to allocate and to free memory at run time in a better and easier way than the above functions.

Advantages of using 'new' an 'delete' over above functions are
 1. It automatically computers the size of the data object. So no need to computer the use sizeof( ) operator.
 2. It automatically returns the correct pointer type , so that it is not need to use type casting.
 3. Like any other operator , new and delete can be overloaded.

The 'new' operator can be used to create object of any data type. It has the following general form
pointer_variable = new data_type;

Here pointer_variable is a pointer of type data_type. The pointer_variable holds the address of the memory space allocated. 

The data_type may be any valid data_type.
Ex:
int *p;
p = new int;

The 'new' operator can be used to create memory space for any data type including user define data type , such as array , structure and class.

The general form of one dimensional array is as follows.
pointer_variable = new data_type[size];

Here size gives information about the number of elements in the Array


Ex int foo
foo = new int[5];

In this case, the system dynamically allocates a space for five elements of type of int and returns a pointer to the first element of the sequence.
⬜⬜⬜⬜⬜⬜⬜⬜
↑
foo

Here foo is a pointer variable and thus the first element pointed by foo can be accessed either the expression foo[0] or *foo an second element as foo[1] or *(foo+1).

Note:
There is a substantial difference between declaring a normal array and allocating dynamic memory for a block of memory using new. The most important difference is that the size of a regular array needs to be constant expression  and thus the size has to be determined at the moment of designing the program before it is run where as dynamic memory allocation performed by 'new' allows to assign memory during runtime using any variable value as size

'delete' Operator
Syntax: 
             delete pointer;
             Delete[ ] pointer;


The first statement releases the memory of a single element allocated using new and second one releases the memory allocated for array of element using 'new'.

#include<conio.h>
#include<iostream.h?
void main( )
{
int i,n;
int *p;
clrscr( );
cout<<"\nHow many elements you want to store ?";
cin>>n;
p = new int[n];
cout<<"\nEnter elements in Array";
for(i=0;i<n;i++)
{
cin>>p[i];
}
cout<<"\nYou have elements";
for(i=0;i<n;i++)
{
cout<<"\t"<<((p+i);
}
cout<<"\nHow many elements you want to store ?";
cin>>n
p = new int[n];
cout<<"\nEnter elements in Array";
for(i=0;i<n;i++)
{
cin>>p[i];
}
cout<<"\nYou have elements";
for(i=0;i<n;i++)
{
cout<<"\t"<<*(p+i);
}
delete[ ]p;              .//Deallocating memory
getch( );
}


Output:-
 How many elements you want to store ?4
Enter elements in Array 1 2 3 4 
You have element 1    2   3   4   

 How many elements you want to store ?6
Enter elements in Array 6  5   4   3  2  1
You have  6    5     4    3    2   1

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'this' Pointer

We know that pointer is a variable which holds address of some other variable an we can access the data of another variable using pointer technique.

'this' is special type of pointer which holds the address of objects which invokes the member function of the class.

Whenever any object calls its member function, 'this' pointer is automatically set and contains the address of that object. In other words , whenever a member function gets called , an address of the object get passed to the function and this address gets collected in the 'this' pointer.

Hence 'this' pointer acts as an implicit argument to all the member function of the class and it is automatically passed to the member function when member function of class is called.

In operator overloading , we have been implicitly using the pointer 'this' to the member function.

When a unary operator is overloaded using a member function , we pass no argument to the function. When a binary operator is overloaded using a member function , we pass only one argument to the function and other argument is implicitly passed using pointer 'this'

#include<conio.h>
#include<iostream.h>
class abc
{
int a;
public:
void accept(int a1)
{
this->a=a1;
}
void display( )
{
cout<<"\n\tAddress of calling object is--->"<<this;
cout<<"\n\tValue of a is--->"<<this->a;
}
};
void main( )
{
abc A1;
clrscr( );
cout<<\n\tAddress of object is--->"<<&A1;
A1.accept(10);
A1.display( );
getch( );
}

Output:-
Address of object is--->0⤫8f9afff4
Address of calling object is--->0⤫8f9afff4  
Value of a is--->10

One important application of 'this' pointer is to return the object it points to.

The Statement 
return *this

inside a member function will return the object that invokes the function. This statement assumes importance when we want to compare two or more objects inside a member function and return the invoking object as a result.

#include<conio.h>
#include<iostream.h>
#include<string.h>
class person
{
char name[20];
int age;
public:
person(char nm[20],float ag)
{
strcpy(name,nm);
age=ag;
}
person *great(person *x)
{
if(x->age>=age)
return x;
else
return this:
}
void display( )
{
person p1("Irawen",101);
person p2("Pirawen",102);
clrscr( );
person *p=p1.great(&p2);
p->display( );
getch( );
}


Output:-
Name is--->Irawen              Age is--->101

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Function Returning Pointer Object

We know that function can return any data type. In the same way we can return pointer variable that is user defined pointer variable or system defined pointer variable from the function.

The general syntax:
returntype * functionname(Argument_list)
{

}

Here returntype is the data type of the value which is returned by the function and functionname follows the usual rule of naming the identifiers.

Write a program to implement the concept of returning pointer object from function.

#include<conio.h>
#include<iostream'h>
class abs
{
int a;
public:
void accept(int a1)
{
a=a1;
}
abc *display(abc *B2)
{
abc *ab;
ab=B2;
cout<<"\n\tAddress of object accepted as argument--->"<<ab;
cout<<"\n\tValue of a is--->"<<ab->a;
return ab;
}
};
void main( )
{
abc ab1;
abc *B1;
clrscr( );
ab1.accept(10);
B1=ab1.display(&ab1);
cout<<"\n\tAddress of returning object--->"<<B1;
getch( );
}


Output:-
Address of object accepted as argument--->0⤫8f7bfff4
Value of a is--->10
Address of returning object--->0⤫8f7bfff4

Read More

Array of Pointers to Objects

We can create an array of objects using pointers. For this we can use following syntax.

classname *pointer_var[size];

WAP to demonstrate array of pointers to objects

#include<conio.h>
#include<iostream.h>
class emp
{
char name[20];
float age;
public:
void getdata( );
void putdata( );
};
void emp::getdata( )
{
cout<<"\n\nEnter name and age of employee";
cin>>name>>age;
}
void emp::putdata( )
{
cout<<"\n\n\t"<<Name is--->"<<name<<"\tAge is--->"<<age;
}
void main( )
{
emp lct[3];
emp *lect[3];
int i;
for(i=0;i<3;i++)
{
lect[i]=&lct[i];
}
for(i=0;i<3;i++)
{
cout<<"\n\tEnter Details of Lecturer"<<(i+1);
lect[i]->getdata( );
}
cout<<"\n\tInformation about of employee";
for(i=0;i<3;i++)
{
lect[i]->putdata( );
}
getch( );
}


Output:-
Enter Details of Lecturer 1
Enter name and age of employee Irawen 101
Enter Details of Lecturer 2
Enter name and age of employee Pirawen 102
Enter Details of Lecturer3
Enter name and age of employee Ntirawen 103
Information about of employee
Name is---> Irawen        Age is--->101
Name is--->Pirawen       Age--->102 
Name is--->Ntirawen     Age--->103

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Pointer To Object

As we create a simple object of class similarly we can create object of the pointer type of class.

For Example if we have a class with the name item, then we can create an object for item class as
item x;

Whenever item is a class and x is an object of item class, similarly we can define object of the type pointer as item *ptr;

There are two ways to access the members of class using pointers
 1. The members of class can be accessed by using the arrow operator in the similar way as it is used in the structure variable.
 pointer_var->class_member;
  2. Another way is (*pointer_var).class_member;
      
  In this notation parenthesis is necessary since dot has a higher precedence over the indirection operator(*).


#include<conio.h>
#include<iostream.h>
class max
{
int m,n;
int largest(void)
{
if(m>n)
{
return m;
}
else
{
return n;
}
}
public:
void getdata( )
{
cout<<"\n\tEnter any two nos--->";
cin>>m>>n;
}
void putdata( )
{
cout<<"\n\tLargest no is--->"<<largest( );
}
};
void main( )
{
clrscr( );
max *obj;
obj->getdata( );
(*obj).putdata( );
getch( );
}

Output:-
Enter any two nos---> 34 89
Largest no is---> 89

Read More

Pointers to Strings

A string is an array of characters terminated by a special character called as a null character.

Pointer to the string is a pointer which is initialized to the base address of the first location in string.

Syntax for declaring a pointer to string.

Datatype *pointer_variable;
Ex : char *ptr;

To initialize the pointer to the address of the string , assign the pointer to the name of string or to the address of the first element of the string.

char str[10]="Irawen";

char *ptr;

ptr=str;    OR       ptr=&str[0];

WAP to find the length of string using pointer

#include<conio.h>
#include<iostream.h>
void main( )
{
char str[10], *ptr;
int cnt=0;
clrscr( );
cout<<"\n\n\tEnter Any String";
cin>>str;
ptr=&str[0];
while(*ptr!='\0')
{
cnt++;
ptr++;
}
cout<<"\n\n\tLength of the Given String is--->"<<cnt;
getch( );
}

Output:-
Enter Any String Irawen
Length of the Given String is--->6

WAP to copy one string into another string and print both the strings on output screen using pointers to strings.

#include<conio.h>
#include<iostream;h>
void main( )
{
char str1[20], str2[20];
char *ptr1, *ptr2;
clrscr( );
cout<<"\n\n\tEnter First String";
cin>>str1;
ptr1=&str1[0];
ptr2=&str2[0];
while(*ptr1!='\0')
{
*ptr2=*ptr1;
ptr1++;
ptr2++;
}
*ptr2='\0';
cout<<"\n\n\tEnter String is--->"<<str1;
cout<<"\n\n\tCopied String is--->"<<str2;
getch( );
}

Output:-
Enter First String Irawen
First String is--->Irawen
Coiped String is--->Irawen

WAP to concat two strings by using pointers to strings.

#include<conio.h>
#include<iostream.h>
void main( )
{
char str1[20], str2[10], *ptr1, *ptr2;
clrscr( );
cout<<"\n\n\tEnter the First String";
cin>>str1;
cout<<"\n\n\tEnter the Second String";
cin>>str2;
ptr1=&str1[0];
ptr2=&str2[0];
while(*ptr1!='\0')
{
ptr1++;
}'
while(*ptr2!='\0')
{
*ptr1=*ptr2;
ptr1++;
ptr2++;
}
*ptr1='\0'
cout<<"\n\n\tConcatenated String is--->"<<str1;
getch( );
}

Output:-
Enter the First String Ira
Enter the Second String wen
Concatenated String is--->Irawen

WAP to reverse the given string using pointers

#include<conio.h>
#include<iostream.h>
void main( )
{
char str1[10], *ptr1;
int len=0;
clrscr( );
cout<<"\n\n\tEnter the String";
cin>>str1;
ptr1=&str1[0];
while(*ptr1!='\0')
{
len=len+1;
ptr1++;
}
len--;
ptr1--;
cout<<"\n\n\tReverse String is--->";
while(len>0)
{
cout<<*ptr1;
ptr1--;
len--;
}
getch( );
}

Output:-
Enter the String irawen
Reverse String is--->newari

Read More

Pointer in Arrays

Consider the declaration
int b[5];
int *ptr;
The pointer to array is given as below
ptr=&b[0];
which is same as
ptr=b;
If the pointer is incremented to the next data elements , then address of the incremented value of the pointer will be same as the value of the next element.

ptr=&b[0]            *ptr=b[0]
ptr+1=&b[1]        *(ptr+1)=b[1]
ptr+2=&b[2]        *(ptr+2)=b[2]
ptr+3=&b[3]        *(ptr+3)=b[3]

The expression-
  value[i] is same as (value+i)
that is
b[i] ==*(b+i)
b[0] ==*(b+0)
b[1] ==*(b+1)
b[2] ==*(b+2)
b[3] ==*(b+3)

WAP to initialize and display five elements from array by using pointer to array.

#include<conio.h>
#include<iostream.h>
void main( )
{
int a[5]={10,20,30,40,50};
int *ptr, i;
clrscr( );
ptr=&a[0];
cout<<"\n\n\tElements in array are--->";
for(i=0;i<5;i++)
{
cout<<" "<<*ptr;
ptr++;
}
getch( );
}


Output :-
Element in array are---> 10 20 30 40 50

WAP to search  an element from array using pointers to array

#include<conio.h>
#include<iostream.h>
void main( )
{
int a[5];
int *ptr, i, f=0, item;
clrscr( );
ptr=&a[0];
cout<<"\n\n\tEnter Five elements";
for(i=0;i<5;i++)
{
cin>>*ptr;
ptr++;
}
cout<<"\n\n\tEnter Element to search";
cin>>item;
ptr=&a[0];
for(i=0;i<5;i++)
{
if(*ptr==item)
{
cout<<"\n\n\tElement is searched in array at"<<" "<<i+1<<"th location";
f=1;
break;
}
ptr++;
}
if(f==0)
cout<<"\n\n\tElement is not searched in array";
getch( );
}

Output:-
Enter Five element 12 23 34 45 56

Enter Element to search 56

Element is searched in array at 5 th location

WAP to insert an element at location of array by using pointer to array.

#include<conio.h>
#include<iostream.h>
void main( )
{
int a[10], i, *ptr1,n,loc,ele;
clrscr( );
cout<<"\n\n\tEnter Size of the Array";
cin>>n;
ptr1=&a[0];
cout<<"\n\n\tEnter Element in the Array";
for(i=0;i<n;i++)
{
cin>>*ptr1;
ptr1++;
}
cout<<"\n\n\tEnter Location to insert in to array";
cin>>loc;
cout<<"\n\n\tEnter Element to insert into Array";
cin>>ele;
ptr1--;
for(i=n-1;i>=0;i--)
{
if(i==loc-1)
{
*(ptr1+1)=*ptr1;
*ptr1=ele;
}
*(ptr1+1)=*ptr1;
ptr1--;
}
ptr1=&a[0];
cout<<"\n\n\tElement in the Array after Insertion--->";
for(i=0;i<n+1;i++)
{
cout<<" "<<*ptr1;
ptr1++;
}
getch( );
}

Output:-
Enter Size of the Array 5
Enter Element in the Array 12 23 34 45 56
Enter Location to insert in to array 3
Enter Element to insert into Array 90
Element in the Array after Insertion is---> 12 12 23 90 45 56

WAP to delete an element from an array from the specified location using pointers to array.

#include<conio.h>
#include<iostream.h>
void main( )
{
int a[10],i,*ptr1,n,loc;
clrscr( );
cout<<"\n\n\tEnter Size of the Array";
cin>>n;
ptr1=&a[0];
cout<<"\n\n\t Enter the Elements in the Array";
for(i=0;i<n;i++)
{
cin>>*ptr1;
ptr1++;
}
cout<<"\n\n\t Enter the Location of element to be deleted";
cin>>loc;
ptr1=&a[loc];
for(i=loc-1;i<n;i++)
{
*ptr1=*(ptr1+1);
ptr1++;
}
ptr1=&a[0];
cout<<"\n\n\tElements in Array after deletion is--->";
for(i=0;i<n-1;i++)
{
cout<<" "<<*ptr1;
ptr1++;
}
getch( );
}

Output:-
Enter Size of the Array 5
Enter the Elements in the Array 12 23 34 45 56
Enter the location of element to be deleted 3
Elements in Array after deletion is---> 12 23 34 56

Read More

Pointers to Functions

1. Cpp allows functions to be referenced by a pointer.
2. A pointer to a function must be declared to be a pointer to the datatype returned by the functions like void , int , float and so on....
3. In addition , the argument type of the function must also be specified when a pointer is declared.
4. The argument declaration is a list of a formal argument separated by commas and enclosed in parenthesis.
5. The general Syntax of a pointer to a function is
    Returntype (*variable) (list of parameters);
   Ex : void (*ptr) (float a, float b, float c);
   In the above declaration , a pointer to a function returns void and takes formal arguments of two float and one int.
 Ex : float (*ptr) (char a, double b, int c, float d)
 In the above declaration , a pointer to a function returns a floating point value and takes the formal argument of char , double , int and float type.
6. After the declaration of pointer to a function , the address of the function must be assigned to a pointer.


WAP to find sum of three numbers and average using pointer to function.

#Include<conio.h>
#include<iostream.h>
void calavg(int a, int b, int c);
void (*ptr)(int a, int b, int c);
void main( )
{
int a1, b1, c1;
clrscr( );
cout<<"\n\tEnter Any three Values";
cin>>a1>>b1>>c1;
ptr=&calavg;
(*ptr)(a1,b1,c1);
getch( );
}
void calavg(int a, int b, int c)
{
int sum;
float avg;
sum=a+b+c;
avg=sum/3.0;
cout<<"\n\n\tSum of three nos is--->"<<sum;
cou<<"\n\n\tAverage is--->"<<avg;
}

Output:-
Enter Any three Values 2.23  45
Sum of three nos is--->80
Average is--->26.66666

WAP to demonstrate how a pointer to a function is declared to perform simple arithmetic operation addition, subtraction, multiplication and division of two nos.

#include<conio.h>
#include<iostream.h>
void calop(int a, int b);
void (*ptr)(int a, int b)
void main( )
{
int a1,b1;
clrscr( );
cout<<"\n\n\tEnter Any two nos";
cin>>a1>>b1;
ptr=&calop;
(*ptr)(a1,b1);
getch( );
}
void calop(int a1,int b1)
{
cout<<"\n\n\tAddition is---><<(a1+b1);
cout<<"\n\n\Subtraction is--->"<<(a1-b1);
cout<<\n\n\tMultiplication is--->"<<(a1*b1);
cout<<"\n\n\tDivision is---><<(a1/b1);
}

Output:-
Enter Any two nos 12  6
Addition is--->18
Subtraction is--->6
Multiplication is--->72
Division is--->2

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Pointers and Functions

1. Pointers are very much used in function and declaration.
2. Sometimes with the use of pointer , a complex function can be easily represented and accessed.
3. The use of pointers in a function definition may be classified into two groups.
     Call by Value
     Call by Reference

Call By Value:-

 1.In a call by value , whenever a portion of program invokes a function with a formal arguments , then control is transferred from main function to calling function and value of actual argument is copied to argument of function.
 2. While calling a function , when copy of formal argument is sent to arguments of the called function then it is known as call by value.
 3. In a call by value, when a control is transferred back from called function to the calling function of the program then altered values are not transferred back.

WAP for implementation of 'call by value' concept.

#include<conio.h>
#Include<iostream.h>
void main( )
{
int x,y;
clrscr( );
x = 12;
y = 13;
cout<<"\n\n\tValue of x--->"<<x<<"\t"<<"Value of y--->"<<y;
funct(x,y);
cout<<"\n\n\tValue of x--->"<<x<<"\t"<<"Value of y--->"<<y;
getch( ); 
}
void funct(int a, int b)
{
a = a*a;
b = b*b;
}

Output:-
Value of x--->12     Value of y--->13
Value of x--->12     Value of y--->13


Call By Reference:-

 1. When a function is called by a portion of a program , the address of actual arguments are copied on to formal arguments though they may be referred by different variable name.
 2. While calling a function, when the address or reference of actual arguments are sent to the called function then it is known as call by reference.
 3. The content of that address can be accessed freely either within a function or within a calling routine.
 4. In a call by reference when the address of actual arguments are sent then these address are stored within the pointer arguments of called function.
 5. Thus the use of pointers as function arguments permits the corresponding data item to be altered globally from within the function.
 6. Any change that is made to the data item will be recognized in both functions and calling portion of the program.

WAP to implement the concept of call by reference.

#include<conio.h>
#include<iostream.h>
void main( )
{
int x,y;
clrscr( );
x = 12;
y = 13;
cout<<"\n\n\tValue of x--->"<<x<<"\t"<<"Value of y--->"<<y;
funct(&x,&y);
cout<<"\n\n\tValue of x--->"<<x<<"\t"<<"Value of y--->"<<y;
getch( ); 
}
void funct(int *p1, int *p2)
{
*p1 = *p1 **p1;
*p2 = *p2**p2;
}

Output:-
Value of x is--->12           Value of y is--->13
Value of x is--->144          Value of y is--->169

WAP to exchange the values of two variable using call by value.

#include<conio.h>
#Include<iostream.h>
void exchange(int a, int b)
{
int temp;
temp=a;
a=b;
b=temp;
cout<<"\n\n\tAfter Exchange Value of A is--->"<<a<<"\tValue of B is--->"<<b;
}
void main( )
{
int a=12,b=14;
clrscr( );
cout<<"\n\n\tBefore Exchange Value of A is--->"<<a<<"\tValue of B is--->"<<b;
exchange(a,b);
getch( );
}

Output:-

 Before Exchange Value of A is--->12       Value of B is--->14
 After Exchange Value of A is--->14          Value of B is--->12

WAP to exchange the value of two variables using call by reference

#include<conio.h>
#include<iostream.h>
void exchange(int *a, int *b)
{
int *temp;
*temp=*a;
*a=*b;
*b=*temp;
}
void main( );
{
int a=12,b=14;
clrscr( );
cout<<"\n\n\tBefore Exchange Value of A is--->"<<a<<"\tValue of B is--->"<<b;
exchange(&a,&b); 
cout<<"\n\n\tAfter Exchange Value of A is--->"<<a<<"\tValue of B is--->"<<b;
getch( );
} 

Output:-
 Before Exchange Value of A is--->12       Value of B is--->14
 After Exchange Value of A is--->14          Value of B is--->12

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Pointers

A pointer is a variable which holds the memory address of another variable.

Advantage of pointer :
 1. It supports dynamic allocation and de allocation of memory segments.
 2. It allows creation of data structure such as linked list, stacks, queues, trees and graphs.
 3. With the help of pointer , variable can be swapped without physically moving them.
 4. It allows to pass variable , arrays , function , strings an structure as a function argument.
 5. Pointer allows to return structure variable from functions.

A pointer variable of two parts:
 1. The Pointer operator
 2. The Address operator

Pointer Operator :
 1. A pointer variable can be represented by a combination of *(Asterisk) with a variable.
 2. If a variable of integer data type is declared with *(Asterisk) then if means the variable is of type 'pointer to integer'.
 3. int *ptr
     When ptr is a pointer variable which holds the address of an integer data type variable.
 4. All pointer variable must be declared before it is used in a program like any other variable.
 5. When a pointer variable is declared , the variable name must be preceded by an asterisk(*).
 6 The general format of declaration is
     Datatype *pointervariable;
     Ex : char *cptr;
            float *fptr;
            double *dptr;

The Address Operator :
 1. An address operator can be represented by the combination by the combination of '&'(ampersand) with the variable.
 2. The '&' is a unary operator the returns the memory address of its operand.
 3. ptr = &x;
      The meaning of this statement is 'ptr' is a pointer variable which receives the address of a variable 'x'.


WAP to display the content of a pointer

#include<conio.h>
#include<iostream.h>
void main( )
{
 int x;
int *ptr;
clrscr( );
cout<<"\n\tEnter Value of x";
cin>>x;
ptr=&x;
cout<<"\n\ntx--->"<<x"\t"<<"ptr is--->"<<ptr;
cout<<"\n\n\tx--->"<<x"\t"<<"*ptr is--->"<<*ptr;
getch( );
}

Output :-
  Enter Value of x15
 x--->15  ptr is--->0⤬8fc1fff4
 x--->  *ptr is--->15

WAP to assign the pointer variable to another pointer and display the content of both the pointer variable.

#include<conio.h>
#include<iostream.h>
void main( )
{
int x=12;
int *ptr1, *ptr2;
clrscr( );
ptr1=&x;
ptr2=ptr1;
cout<<"\n\n\tValue of x is--->"<<x;
cout<<"\n\n\tContent at ptr1 is--->"<<*ptr1;
cout<<"\n\n\tContent at ptr2 is--->"<<*ptr2;
getch( );
}

Output :-
 Value of x is--->12
 Content at ptr1 is--->12
 Content at ptr2 is--->12

WAP to display the content of the pointer variable using arithmetic operation.

#include<conio.h>
#include<iostream.h>
void main( )
{
int x,y;
int *ptr;
x=12;
ptr=&&x;
cout<<"\n\n\tValue of x is--->"<<x<<"\t"<<"Value at pointer is--->"<<*ptr;
y=*ptr+1;
cout<<"\n\n\tValue of y is--->"<<y<<"\t"<<"Value at pointer is--->"<<*ptr;
getch( );
}

Output :-
 Value of x is--->12                  Value at pointer is--->12
 Value of y is--->13                  Value at pointer is--->12

WAp to display the memory address of a variable using pointer before incrementation and decrementation and after incrementation and decrementation.

#include<conio.h>
#include<iostream.h>
void main( )
{
int x=12;
int *ptr1, *ptr2;
clrscr( );
ptr1=&x;
ptr2=&x;
cout<<"\n\n\tMemory Address before incrementation--->"<<ptr1<<endl;
cout<<"\n\n\tMemory Address before decrementation--->"<<ptr1<<endl;
ptr1++;
ptr2--;
cout<<"\n\n\tMemory Address after  incrementation--->"<<ptr1<<endl;
cout<<"\n\n\tMemory Address after decrementation--->"<<ptr1<<endl;
getch( );
}

Output :-
   Memory Address before incrementation--->0⤫8fd2fff4
   Memory Address before decrementation--->0⤫8fd2fff4
   Memory Address after incrementation--->0⤫8fd2fff6
   Memory Address before incrementation--->0⤫8fd2fff2

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