Topic 29 of 91 5. C++ Pointers and References Interactive Tutorial

Pointers With Arrays in C++: Traversing Elements Through Addresses

15 mins read Last updated: 26 Sep 2026 21,800 views

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Direct Answer & Core Concept

In C++, array names decay into pointers to their first elements (&arr[0]). Pointer arithmetic allows navigating elements where adding an integer n to a pointer (ptr + n) advances the memory address by n * sizeof(T) bytes. Array indexing arr[i] is syntactically equivalent to *(arr + i).

Detailed Explanation & Mechanics

1. Pointer Arithmetic & Scaling:

main.cpp

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ARRAY MEMORY LAYOUT (int = 4 bytes):
Index:        arr[0]      arr[1]      arr[2]      arr[3]
Address:      0x1000      0x1004      0x1008      0x100C
Pointer:       ptr       ptr + 1     ptr + 2     ptr + 3

2. Equivalences:

arr[i] == *(arr + i) == *(i + arr) == i[arr]

Runnable Code Example: Pointers With Arrays in C++

C++20 / C++23

main.cpp

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#include <iostream>

int main() {
    int buffer[5] = {10, 20, 30, 40, 50};
    int* ptr = buffer; // Decays to &buffer[0]

    std::cout << "Traversing via Pointer Arithmetic:
";
    for (int i = 0; i < 5; ++i) {
        std::cout << "Element [" << i << "]: " << *(ptr + i) 
                  << " at address: " << (ptr + i) << "
";
    }

    // Pointer difference (number of elements between pointers)
    int* endPtr = buffer + 5;
    std::cout << "Total elements (end - start): " << (endPtr - ptr) << "
";
    return 0;
}

Common C++ Technical Interview Questions & Answers

Interview Prep

Q: What happens when you subtract two pointers in C++?

A: Pointer subtraction (`ptr2 - ptr1`) returns a signed integer of type `std::ptrdiff_t` representing the number of array elements between the two memory addresses, not the raw byte difference.

Q: Why is pointer decay a potential source of bugs?

A: When an array is passed to a function, it decays to a pointer, losing its compile-time size information (i.e. `sizeof(arr)` returns pointer size 8 bytes rather than total array bytes).

Key Takeaways, Modern Best Practices & Idioms

C++ Best Practices & Production Rules

1. Use std::array or std::vector instead of C-style raw arrays to preserve size information.
2. Use std::span (C++20) for non-owning views over contiguous memory buffers.
3. Never increment pointers beyond the past-the-end element (arr + N).

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