Skip to main content

​
Pointers and Arrays in C

In C, the name of an array is a pointer to its first element. This tight relationship means you can traverse and manipulate arrays entirely through pointer arithmetic. 
int arr[5] = {10, 20, 30, 40, 50};
int *ptr = arr;   // same as: int *ptr = &arr[0];

​
Accessing Array Elements via Pointer

#include <stdio.h>

int main() {
    int num[5] = {10, 20, 30, 40, 50};
    int *ptr = num;

    for (int i = 0; i < 5; i++) {
        printf("num[%d] = %d\t Address = %p\n", i, *(ptr + i), (ptr + i));
    }
    return 0;
}
*(ptr + i) and num[i] are completely equivalent — the compiler translates num[i] to *(num + i) internally.

​
Array of Pointers

An array where each element is a pointer: 
data_type *array_name[size];

int *ptr[3];    // array of 3 integer pointers

​
Example 1: Array of Integer Pointers

#include <stdio.h>

int main() {
    int a = 10, b = 20, c = 30;
    int *ptr[3];

    ptr[0] = &a;
    ptr[1] = &b;
    ptr[2] = &c;

    for (int i = 0; i < 3; i++) {
        printf("Value of ptr[%d]: %d\n", i, *ptr[i]);
    }
    return 0;
}
Output: 
Value of ptr[0]: 10
Value of ptr[1]: 20
Value of ptr[2]: 30

​
Example 2: Array of String Pointers

Useful for storing a list of strings without a 2D character array: 
#include <stdio.h>

int main() {
    char *names[] = {"Rahul", "Parvej", "Aman"};

    for (int i = 0; i < 3; i++) {
        printf("Name[%d]: %s\n", i, names[i]);
    }
    return 0;
}
Output: 
Name[0]: Rahul
Name[1]: Parvej
Name[2]: Aman

​
arr[i] vs *(arr + i)

These two are identical in C: 
int arr[] = {5, 10, 15};

arr[2]       // 15
*(arr + 2)   // 15  — pointer arithmetic equivalent

​
Key Points

  • arr (array name) decays to &arr[0] when used in an expression
  • sizeof(arr) gives the total array size; sizeof(ptr) gives only the pointer size
  • You can increment a pointer (ptr++) but not an array name (arr++ is illegal)