Introduction to pointer in C | pointer operations in C | Operators associated with a pointer variable in C | Null pointer in C

It is the way to refer a memory location. A pointer variable  can contain the address of another variable.

Suppose we declare integer variable a as :

int a=10;

Variable a has following properties :

1. Name of variable:

A variable must have a name. In above example, a is a variable of int consuming 2 bytes of memory because  int has memory of 2 bytes.

2. Value of variable:

It is the value assigned to the variable.

3. Memory location of variable:

Variable is stored at some memory location. Memory location is represented as a number be in decimal or hexadecimal form.

Operators associated with a pointer variable

There are two operators associated with pointers. They are as follows:

i. * (Indirection)

This operator is used to specify that variable being declared is a pointer variable. It is also used to used to refer to the value of variable whose address is stored in pointer variable.

Example:

int *x;

ii. &(Address )

It is  used to refer to the memory location of a variable.

Example:

int x=10,*y;
y=&x;

NULL Pointer in C Language

NULL specifies “points to nothing”. It represents that a pointer variable does not have any address stored into it.

Accessing address of a variable in C Language

We can determine the address of a variable with the help of address operator (&).

Example:                         

int a=10,*b;
b=&a;                                   

Accessing value of a pointer variable in C Language

We can access value of a pointer variable using indirection operator.

Example:        

int x=20,*y,z;
y=&x;        /* y contains the address of variable x*/
z=*y;        /* *y contains the value of variable x whose address is contained in pointer variable y*/

#include<stdio.h>
int main()
{
int a=20,*b;
b=&a;  
printf("\n%d",a);   /*15*/
printf("\n%u",&a); /*65524*/
printf("\n%u",b);   /*65524*/
printf("\n%d",*b); /*15*/
return (0);
}