Pointers in C++ allow programs to store and manipulate memory addresses. Pointers contain the address of another variable. They are used to pass variables by reference into functions and access array elements. A pointer is initialized by assigning the address of a variable to it using the & operator. The * operator is used for indirection to access the value at the address stored in the pointer. Pointers can also point to other pointers. Arrays of pointers store multiple memory addresses. The name of an array acts as a constant pointer containing the base address of the array.

1. POINTERS IN C++

2. Topics
• Pointers
• Memory addresses
• Indirection (*) Operators
• How to initialize pointers
• NULL pointer
• Pointers to pointer
• Array Of Pointer

3. Pointers
A pointer is a reference to another variable (memory location) in a
program
• Used to change variables inside a function (reference parameters)
• Used to remember a particular member of a group (such as an array)
• Used in dynamic (on-the-fly) memory allocation (especially of
arrays)
• Used in building complex data structures (linked lists, stacks, queues,
trees, etc.)

4. 100… … 1024 …
Memory address:
1024 1032
…
1020
integer pointer

5. Indirection (*) Operators
• A pointer variable contains a memory address To refer to
the contents of the variable that the pointer points to, we
use indirection operator
• Syntax: *PointerVariable
Example:
int V = 101;
int *P = &V;
/* Then *P would refer to the contents of the variable V (in this case, the
integer 101) */
printf(“%d”,*P); /* Prints 101 */

6. 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

7. Example :
int main()
{
int x= 10;
int *p ;
p= &x;
cout<<“value stored at x:”<<p;
}

8. NULL pointer
• NULL is a special value that indicates an empty pointer
• If you try to access a NULL pointer, you will get an error
int *p;
p = 0;
cout << p << endl; //prints 0
cout << &p << endl;//prints address of p
cout << *p << endl;//Error!

9. Pointer to Pointer……
A pointer can also be made to point to a pointer variable (but the pointer must be of a
type that allows it to point to a pointer)

10. Example
1. #include <iostream>
2. using namespace std;
3. int main ()
4. { int var = 20; // actual variable declaration.
5. int *ip; // pointer variable
6. ip = &var; // store address of var in pointer variable
7. cout << "Value of var variable: ";
8. cout << var << endl;
9. // print the address stored in ip pointer variable
10. cout << "Address stored in ip variable: ";
11. cout << ip << endl;
12. // access the value at the address available in pointer
13. cout << "Value of *ip variable: ";
14. cout << *ip << endl;
15. return 0;
16. }

11. Output
• Value of var variable: 20
• Address stored in ip variable: 0xbfc601ac
• Value of*ip variable: 20

12. Array Of Pointer
• A common use of array of pointers is an array of pointers to strings.
• Like any other array, we can also have an array of pointers
• C++ treats the name of an array as constant pointer which contains base
address i.e. address of first location of array.
For Example:
int x[10];
• Here x is a constant pointer which contains the base address of the array x.

13. • We can also store the base address of the array in a pointer variable. It can be used to
access elements of array, because array is a continuous block of same memory
locations.
For Example:
int x[5];
int * ptr=x; // ptr will contain the base address of x
• we can also write
• int * ptr= &x[0]; //ptr will contain the base address of x
0
1
2
3
4
ptr
x

14. Array Name is a pointer constant
#include <iostream>
using namespace std;
void main (){
int a[5];
cout << "Address of a[0]: " << &a[0] << endl
<< "Name as pointer: " << a << endl;
}
Result:
Address of a[0]: 0x0065FDE4
Name as pointer: 0x0065FDE4

15. Thank You………….