Pointers in C: Definition, Types, Examples, and Applications

In C programming, a pointer is a variable that stores the memory address of another variable. Instead of holding actual data, pointers hold the location of data in memory. This makes pointers a powerful feature of C that enables direct memory access and efficient programming.

int x = 10;  
int *p = &x;   // pointer 'p' stores the address of variable x

Why Use Pointers?

To access and manipulate memory directly.
To work with arrays and strings efficiently.
To pass large structures or arrays to functions without copying data.
For dynamic memory allocation (malloc, calloc, free).
For implementing data structures like linked lists, trees, etc.

Pointer Declaration and Initialization

data_type *pointer_name;

int a = 5;
int *p = &a;   // p stores the address of a

Here:

& → Address-of operator (gives address of a variable).
* → Dereference operator (gives value stored at an address).

Example Program

#include <stdio.h>

int main() {
    int x = 10;
    int *p;   // pointer declaration
    p = &x;   // storing address of x in pointer p

    printf("Value of x: %d\\n", x);
    printf("Address of x: %p\\n", &x);
    printf("Value stored in pointer p: %p\\n", p);
    printf("Value pointed by p: %d\\n", *p);

    return 0;
}

Types of Pointers in C

1. Null Pointer

int *p = NULL;

A pointer that doesn’t point to any valid memory address.

2. Void Pointer

void *ptr;

A generic pointer that can point to any data type.

3. Wild Pointer

An uninitialized pointer that points to a random memory location (dangerous).

4. Dangling Pointer

A pointer that points to a memory location which has been freed or deleted.

5. Function Pointer

void (*funPtr)(int, int);

Used to store the address of a function.

6. Pointer to Pointer

int x = 10;
int *p = &x;
int **pp = &p;

A pointer that stores the address of another pointer.

Pointer Arithmetic

Pointers support arithmetic operations like ++, --, +, -.

Operation	Description
p++	Moves pointer to next memory location
p–	Moves pointer to previous memory location
p + n	Moves pointer forward by n locations
p – n	Moves pointer backward by n locations

Applications of Pointers

Dynamic memory management (malloc(), calloc(), free()).
Efficient array and string handling.
Passing variables by reference to functions.
Creating advanced data structures like linked lists, trees, graphs.
Implementing system-level programming (OS, device drivers).

What is a Pointer in C? Complete Explanation with Examples