pointer in c with example

Hello, hope you are well. So now we will talk about pointers in C programming language. Today we talk about various sub topics of pointers are:- What is a pointer, Printing address present in pointer,  Accessing a memory block with help of pointer, pointer to a pointer in c and Pointer to an Array. Read full article to better understanding, Lets start...

pointer in c

Introduction of pointer in c:-

To store data, we can create a variable or we can create an array. A variable is of scalar type while an array is of aggregate type. Whenever an array or a variable is created, space is allocated in the memory(RAM).

For eg:-

        int   a[5];      //array
	int   x;	 //variable(scalar)

Each and every memory block which is created during the execution of a program is assigned a unique address automatically. The address in the hexadecimal format.

0 - 9

A - 10

B - 11

C - 12

D - 13

E - 14

F - 15

We can excess a memory block using its address. This is done using the concept of pointer.

Also Read: Control Statements In C - language

Pointer allow as to work on memory block with help of the its address. Pointer is used to perform dynamic memory allocation. In dynamic allocation, the size is specified at run time. The memory is allocated at run time and as application executes(run), The size of memory can grow or 

shrink(decrease).

What is a pointer in c?

A pointer is a special variable which stores address of some another variables. To create a pointer variable, We use the following syntax:-

 

datatype * pointer var name;

The datatype specified at the time of creating the pointer is the data type of the variable whose address can be saved in the pointer.

For ex:-

long * ptr;
/*(here ptr is a pointer which can store address of any variable of long type only)*/

To assign address of a variable to a pointer variable, we use &(address of operator).

Also Read:  What is String in C Language and String handling function

Syntax:-

pointer name=&variable name;

For ex:

int  d;
int  *p;
p=&d;

C Printing address present in pointer

a pointer is a special variable which stores address of some another variable. Once a pointer has been assigned address of some variable, we can print/display the address int he pointer by using type specifier %p in printf().

Syntax:-

printf("%p",pointer var name);

sample code:-

//program using Printing address present in pointer

#include<conio.h>
#include<stdio.h>

void main()
{
lang *ptr;
/*here ptr is a pointer which can stored address of any variable of type long.*/
long d;
clrscr();
ptr=&d;
/*the address of a variable 'd' have been stored in the pointer named ptr*/
printf("the address of d is %p",ptr);
/*here pointer named ptr is being printed. Whenevr a pointer is printed, the address in that pointer gets printed*/
getch();
} 

C Accessing a memory block with help of pointer 

A pointer stores address of a memory block. Using a pointer, we can access a memory block. To do so, we use *(dereference operator).

Also Read: Format Specifier In C Programming

Whenever dereference operator is used with the pointer name, then the pointer can be used to access the memory block. Whose address is present in the pointer.

syntax:-

*pointer name;

whenever * is used with the pointer name, it denotes value at the complete meaning of  * followed by pointer name his value at that address.

For Eg:

float *x;
float a;
a=90.8;
x=&a;

 Referring to the address present in the pointer is pointer name. Value present in the variable where address is with pointer is *pointer name.

Sample code:-

//program Accessing a memory block with help of pointer 

#include<conio.h>
#include<stdio.h>

void main()
{
long *a;
long d=600000;
clrscr();
a=&d;
printf("the address of d is %p",a);
printf("\n the value at d is%ld",*a);
getch();
}

pointer to a pointer in c

In c programming language, A special variable called pointer variable stores the address of a variable. Each and every variable is assigned a unique address by the operating system. Pointer store this address and allows manipulation of the variable through the address stored in it.

A pointer variable is also assigned on address. To store the address of a pointer variable, we create a special type of reference variable called pointer to a pointer.

Creating pointer to a pointer

datatype **pointer name;

Here pointer which will store address of some another pointer which is storing address of a variable of type int. To store address of a pointer in another pointer, we use &(address of operator).

Syntax:-

pointer to a pointer name = &pointer name;

sample code:-

//program Creating pointer to a pointer 

#include<conio.h>
#include<stdio.h>

void main()
{
int x;	//variable
int *a;	//pointer
int **b;	//pointer to a pointer
a=&x;	/*address of x assigned to a pointer a*/
b=&a;	/*address of pointer a assigned to pointer to pointer b*/
printf("the address of x is%p",a);
printf("\nthe address of a is%p",b);
getch();
}
  

C Pointer to an Array

A pointer is a reference variable which stores the memory address of a variable or an array or a structure. Each and every variable which is created in an application is assigned unique address by the system. This address can be used to access the memory block. We can create a special pointer which points to an array. Such a pointer is called pointer to an array.

Also Read: Format Specifier In C Programming

C Pointer to an Array

To create pointer to an array, we use same syntax as used when creating a pointer to a scalar variable.

Syntax:-

   datatype  *pointer name;

For Ex:

float   *b;     /*here b is a pointer to an array of the float */

Once pointer to an array has been created, we can use the following techniques to store address of an array in that pointer.

1) pointer name=array name;

address of array will be stored in the pointer.

For Ex:

int  *p;
int  a[5];
p=a;	//address of a assigned to p

2)pointer=&array name[0];

For Ex:

int  *ptr;
int  c[10];
ptr=&c[0];

Once address of an array has been assigned to a pointer, then we can use the pointer to access each and every element of the array. The pointer name can be used just like the array name.

Also Read: Structure Of C Language Program 

Sample code:-

//program of pointer to an array 

#include<conio.h>
#include<stdio.h>

void main()
{
int i;
int *p;
int a[10];
clrscr();
printf("enter 10 values\n");
for(i=0;i<=9;i=i+1)
{
scanf("%d",&a[i]);
}
p=a;
/*address of a assigned to pointer p */
for(i=0;i<=9;i=i+1)
{
printf("%d",p[i]);
}
getch();
}