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Pointers

10/02/11 & 14/02/11

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Simple Program

#include

int main()

{

int var1 = 11;

int var2 = 37;

int var3 = 55;

cout

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Pointers

Its a variable which holds the memory

address of another variable

The address of a variable is the address of the

first byte of the memory block allocated to the

variable.

We can dig out the memory address of a

variable by using address-of-operator( & ) also

called reference operator.

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#include

int main()

{int var1 = 11;

int var2 = 37;

int var3 = 55;

cout

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Declaration of Pointers

By mentioning the type of the variable, followed byindirection operator, also called dereference operator(*), and the name of the pointer variable.

The illustration of pointer declaration for int variablesare given below :

int m, n ; // m and n are integer variables

int *ptr = &n ;//ptr is pointer to any integer number

int* ptr = &m ; //ptr now points to m.int* ptr = 0 ; // now ptr is initialized to 0.

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Pointers to different data type

float PI = 3.14159 ; float PIpf = Π

float *pf ; points to

char chchar ch = A ; points to

pc = &ch;

char *pc ;

double D = 4328.6543 double D

pd = &D;

double *pd ; points to

pf 3.14159

pc A

pd 4328.6543

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Indirection or Dereference Operator

The value of variable may be obtained from itspointer by using indirection operator also calleddereference operator(*).

It is called indirection because it obtains the valueindirectly.

An application of dereference operator is :

int n = 60, *ptrn ;

ptrn = &n ;

*ptrn = 60 ; //use of dereference operator.

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example

#include

using namespace std;

int main(){ int n = 60;

double B = 8.56 ;

int* ptrn = &n;double *pB = &B;

cout

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Contd..

cout

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Expected output

The expected output is :

n = 60, B = 8.56

The address of n is = 0012FF7C , ptrn = 0012FF7C*ptrn = 60, *pB = 8.56

The address of B = 0012FF74 pB = 0012FF74

Address of ptrn = 0012FF70

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Pointers in Class

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Declaration

List L1 ;

List *ptr;

ptr = &(List) L1;The last line may be written as

ptr = &List(L1) ;

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Example

#includeclass List

{

private :

int x,y ;public :

void Setdata(int a, int b)

{

cout a;

coutb;

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Contd..

x = a;y = b;

}

void Display1()

{

cout

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Contd..

void Display3()

{

cout

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Contd..

void main()

{

List L1;

List *ptr;

ptr = &(List) L1;int i , j ;

(*ptr).Setdata(i, j);

ptr -> Display1();

ptr -> Display2();(*ptr) .Display3();

}

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Contd..

void Setprice(int a, int b, int c)

{

x = a, y = b, z = c;

}

void Display2(){

cout

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Contd..

void main()

{

List L1;

List *ptr;

ptr = &(List) L1;

ptr -> Setprice(6,8,10);

ptr -> Display1();

cout

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Contd..

ptr -> Setprice(32,27,38) ;

ptr -> Display1();

cout

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Pointer to objects of a class

Let L1 be an object of class List, the pointer to

L1 be declared and assigned as:

List *ptr = &L1;

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#include

class List

{

private :int x, y, z ;

public :

List (int a, int b, int c) {

x = a, y = b, z = c;

}

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Contd..

void Display()

{

cout

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Contd..

void main()

{

int n = 0;List L1(12, 15, 27);

cout