Pointers

 Pointer is a variable that holds a memory address of another variable.

Pointer declaration:

Syntax:  Dataype *variable_name;

Data_type – any valid data type supported by C++.

variable_name – name of pointer variable.

* indicates that it is a pointer variable

Pointer Initialization:

ptr=#

The ‘&’ is the address operator, and it represents the address of the variable.

In the above statement ptr is a pointer variable, num is a normal variable. The address of num variable is stored in pointer variable ptr.

#include<iostream.>

void main( )

{

          int num,*p;

          num=5;

          p=&num;

          cout<<”value of num”<<num<<”\naddress of num=”<<p;

}

Pointer operator or Indirection operator:

The declarator operator (*) is also called as dereference operator or indirection operator.

Dereference is the process of accessing and manipulating data stored in the memory location pointed to by a pointer.

Direct addressing: Accessing a variable in one step by using the variable name.

Ex: num5;

Indirect addressing: Accessing a variable in two steps by first using a pointer that gives the location of the variable and then accessing the variable using the location.

Ex: int *p;

      *p=5;

 

Difference between ‘*’ and ‘&’ operator in pointer:

‘*’ dereference operator.                                       ‘&’ address of operator

Used to declare the pointer variable,                        used to get the address of variable.

Used to access the value to which the pointer

 points to.

 

Pointer Arithmetic and Pointer Expressions:

C++ supports four arithmetic operations, that can used with pointers, such as addition (+), subtraction (-), Incrementation (++), decrementation(--).

We can add integer value to a pointer.

Ex: p=p+5; // p is a pointer variable

We can subtract integer value to a pointer.

Ex: p=p-5; // p is a pointer variable

We can perform increment and decrement operations on pointer variable.

Ex: p++;  p--;

We cannot perform multiplication and division operations on pointers.

Advantages of pointers:

·       Pointers save memory space

·       Execution time with pointer is faster

·       It supports dynamic allocation and de allocation of memory blocks

·       It allows passing variables, arrays, functions etc. as function arguments

·       Used to create and manipulate complex data structures.