C++ Pointers

data_type *pointer_name; 

Here, * is used to denote that “pointer_name” is pointer variable and it is not the normal variable.

Advantage Of Pointer:-

There are major advantages of pointers using in C++ program:

• Allows management of structures which are allocated memory dynamically.
• Allows passing of arrays and strings to functions more efficiently.
• Possible to pass the address of the structure instead of the whole structure of the functions.
• Possible to return more than one value from the function.

Example:-

#include < iostream> 
using namespace std;

int main() 
{   
    int a=10;   
    int *p;      
    p=&a; /* store address of a variable in pointer variable*/
    cout << "Address of a variable is " << &a << endl;
    cout << "Address of p variable is " << p << endl;
    /* access the value using the pointer */
    cout << "Value of *p variable is  " << *p << endl;
    return 0;
}

Usage of pointers - Dynamic memory allocation

Pointers are used in three different ways:

• It is used to create dynamic data structures.
• It is used to pass and control variable parameters passed to functions.
• It is used to access information stored in arrays.

Address of the operator:

Address operator is denoted by ‘&’ symbol. When we use this symbol as a prefix to a variable name, it gives the address of the variable.

&x - It gives an address of the x variable.

Declaring a pointer:

Syntax:

data_type *pointer_name;

Data_type

• This is the type of variable that the pointer points to
• A data type whose address is stored in pointer name

Asterisk( * )

• It is called as an indirection operator
• It is also called as the value at address operator
• It indicates variable declared as a pointer type

Pointer_name

• It must be any valid C++ identifier
• It must follow all rules of variable name declaration

Null Pointer:

A pointer that is assigned nothing is called the null pointer. The null pointer points out the base address of the segment. A pointer that initialized with the null value is known as the null pointer. In case, if you don’t have an address to assign a pointer then you can use null.

Example:-

#include    
using namespace std;

int main() 
{   
    int *p=NULL;      
    cout << "The value of p is " << p << endl;
    return 0;
}

Defining null value

#define NULL 0