Pointers in C

Why Pointers?

• Access memory directly
• Modify values using reference
• Efficient for arrays & strings
• Needed for dynamic memory allocation
• Essential in data structures (Linked List, Trees…)

Pointer Declaration

int *p;
float *q;
char *str;

Address (&) and Dereference (*) Operators

• & → gives address
• * → gives value at that address

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

printf("%p", p);   // address
printf("%d", *p);  // value

Types of Pointers

• Null Pointer
• Void Pointer
• Wild Pointer
• Dangling Pointer
• Function Pointer

Pointer Memory Size

• 4 bytes in 32-bit
• 8 bytes in 64-bit

Size is same for all pointer types.

Pointer Rules

• Always initialize pointers
• Never access freed memory
• Return pointer only to dynamic memory
• Pointer must match data type

Pointer Examples (15 Examples)

1. Basic Pointer

#include <stdio.h>

int main(){
    int x = 10;
    int *p = &x;

    printf("%d", *p);
    return 0;
}

2. Print Address

#include <stdio.h>

int main(){
    int x = 42;
    printf("%p", &x);
    return 0;
}

3. Modify Value Using Pointer

#include <stdio.h>

int main(){
    int a = 5;
    int *p = &a;
    *p = 50;

    printf("%d", a);
    return 0;
}

4. Pointer to Float

#include <stdio.h>

int main(){
    float n = 3.14;
    float *p = &n;

    printf("%.2f", *p);
    return 0;
}

5. Pointer to Char

#include <stdio.h>

int main(){
    char c = 'A';
    char *p = &c;

    printf("%c", *p);
    return 0;
}

6. Null Pointer

#include <stdio.h>

int main(){
    int *p = NULL;
    printf("%p", p);
    return 0;
}

7. Void Pointer

#include <stdio.h>

int main(){
    int a = 20;
    void *p = &a;

    printf("%d", *(int*)p);
    return 0;
}

8. Pointer to Pointer

#include <stdio.h>

int main(){
    int x = 5;
    int *p = &x;
    int **pp = p;

    printf("%d", **pp);
    return 0;
}

9. Incrementing Pointer

#include <stdio.h>

int main(){
    int a = 10;
    int *p = &a;

    p++;
    printf("%p", p);
    return 0;
}

10. Pointer with Array

#include <stdio.h>

int main(){
    int arr[3] = {1,2,3};
    int *p = arr;

    printf("%d", *(p+1));
    return 0;
}

11. Pointer in Function

#include <stdio.h>

void update(int *p){
    *p = 100;
}

int main(){
    int a = 10;
    update(&a);

    printf("%d", a);
    return 0;
}

12. Swapping with Pointers

#include <stdio.h>

void swap(int *x, int *y){
    int t = *x;
    *x = *y;
    *y = t;
}

int main(){
    int a = 10, b = 20;
    swap(&a,&b);

    printf("%d %d", a, b);
    return 0;
}

13. Pointer to String

#include <stdio.h>

int main(){
    char *name = "Sourav";
    printf("%s", name);
    return 0;
}

14. Pointer Arithmetic on Array

#include <stdio.h>

int main(){
    int arr[] = {10, 20, 30};
    int *p = arr;

    printf("%d", *(p+2));
    return 0;
}

15. Dynamic Memory Address Check

#include <stdio.h>
#include <stdlib.h>

int main(){
    int *p = (int*)malloc(sizeof(int));
    *p = 500;

    printf("%d", *p);
    free(p);

    return 0;
}