pointers in c++

Saturday 8 April 2023

POINTERS

BY

GIRISH SHARMA RAJAT BUSHEHERI

{61264} {61279}


OVERVIEW

What pointers actually are…… How can we declare pointers…… Pointer to Pointer…… How many levels of pointers can you have? Pointers as function arguments…… Dynamic memory allocation using pointers……


What pointers actually are……

A pointer is a variable used to store the address of any memory cell, and can be used to access and manipulate data stored at the address to which it is pointing


Difference between pointer and variable:

◦Pointer holds the address

◦Variable holds the value.

Getting variable`s memory address …….

Different computers number this memory using different complex schemes.

We must happy ,as a programmer, We don’t need to know the particular address of any given variable because the compiler handles the details.

If we want this information , though, you can use the address-of operator(&),which returns the address of an object in memory.


More info …….

A pointer that is not initialized is called a wild pointer because you have no idea what it is pointing to.

A pointer whose value is zero is called a null pointer.

void pointer is a special type of pointer that can be pointed at objects of any data type! A void pointer is declared using data type void


How can we declare pointers :

Just like other variables ,pointers have to be declared before their usage.

Syntax :

data_type *pt;

ex : int *p;

Here p is a pointer which will store the address of the variable of type int .


int *p;

This tells the compiler three things about variable p :

The asterisk (*) tells that the variable p is a pointer variable.

p needs a memory location.

p points to a variable of type int.


How to initialize pointers :

The process of assigning address of a variable to a pointer variable is known as initialization

{ int a;

int *p; //declaration

p= &a; } //initialization


example :

int main()

{

int x= 10;

int *p ;

p= &x;

cout<<“value stored at x:”<<p;

}


Pointer to Pointer……


How many levels of pointers can you have?

int i = 0;

int *ip01 = & i; there is no limit , but just use that

int **ip02 = & ip01; that much levels which u can

int ***ip03 = & ip02; understand easily and programs

int ****ip04 = & ip03; programs does not become confusing.

int *****ip05 = & ip04;

int ******ip06 = & ip05;

int *******ip07 = & ip06;

int ********ip08 = & ip07;

int *********ip09 = & ip08;


Pointers as function arguments: #include <stdio.h>

swap (int *, int *);

main()

{

int a, b;

printf("\nEnter value of a & b: ");

scanf("%d %d", &a, &b);

printf("\nBefore Swapping:\n");

printf("\na = %d\n\nb = %d\n", a, b);

swap(&a, &b);

printf("\nAfter Swapping:\n");

printf("\na = %d\n\nb = %d", a, b);getch();}swap (int *x, int *y){int temp;temp = *x;*x = *y;*y = temp;}


dynamic allocation of memory

Pointers need to be used for dynamic allocation of memory

Use the operator new to dynamically allocate space

Use the operator delete to later free this space


The new operator

If memory is available, the new operator allocates memory space for the requested object/array, and returns a pointer to (address of) the memory allocated.

If sufficient memory is not available, the new operator returns NULL.

The dynamically allocated object/array exists until the delete operator destroys it.


The delete operator

The delete operator deallocates the object or array currently pointed to by the pointer which was previously allocated at run-time by the new operator.the freed memory space is returned to Heapthe pointer is then considered unassigned

If the value of the pointer is NULL there is no effect.


Thanks ……

:)