🔗 Understanding Pointers and Arrays in C

🔗 Pointers and Arrays in C

In C programming, arrays and pointers are closely related. Understanding how they interact is essential for mastering C. This tutorial explains how pointers work with arrays, with step-by-step examples.

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📘 Relationship Between Arrays and Pointers

When you declare an array, the array name itself acts as a pointer to the first element.

int arr[5] = {10, 20, 30, 40, 50};

Here, arr is equivalent to &arr[0].

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📌 Accessing Array Elements Using Pointers

#include <stdio.h>

int main() {
    int arr[5] = {10, 20, 30, 40, 50};
    int *p = arr;  // same as p = &arr[0]

    for(int i = 0; i < 5; i++) {
        printf("Element %d: %d\n", i, *(p + i));
    }

    return 0;
}

🧪 Output:

Element 0: 10
Element 1: 20
Element 2: 30
Element 3: 40
Element 4: 50

Explanation: p + i points to the i-th element, and *(p + i) accesses the value.

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🔁 Pointer Notation vs Array Notation

Array Notation	Pointer Notation
arr[i]	*(arr + i)
*(p + i)	p[i]

All these expressions are equivalent when working with 1D arrays.

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🔁 Modifying Arrays Using Pointers

#include <stdio.h>

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int *p = arr;

    for(int i = 0; i < 5; i++) {
        *(p + i) = *(p + i) * 2;  // double each element
    }

    for(int i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    }

    return 0;
}

🧪 Output:

2 4 6 8 10

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⚠️ Important Notes

• arr points to the first element, but it is a constant pointer – you cannot modify it with arr++.
• p = arr is allowed, and p++ is valid.

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🧩 Practice Exercises

1. Write a program to calculate the sum of all elements in an array using a pointer.
2. Reverse an array using pointer notation.
3. Find the maximum and minimum values in an array using pointers.
4. Write a program to copy one array to another using pointers.

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🧠 Summary

• arr is equivalent to &arr[0].
• arr[i] == *(arr + i) and p[i] == *(p + i).
• Pointers offer a flexible and powerful way to work with arrays.

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