C++ Arrays: Contiguous Memory Layout, 2D Matrices & Safety Rules

An Array is a fixed-size, sequential collection of elements of identical data type stored in contiguous (unbroken) memory locations. Because memory is contiguous, any element can be accessed in constant time $O(1)$ via its index offset.

1D Array Declaration & Traversal

#include <iostream>

int main() {
    // 5 integers stored contiguously on the Stack
    int marks[5] = {85, 92, 78, 65, 95};

    int sum = 0;
    for (int i = 0; i < 5; ++i) {
        sum += marks[i];
    }

    double average = static_cast<double>(sum) / 5;
    std::cout << "Class Average: " << average << "\n";
    return 0;
}

2D Matrix Processing (Row-Major Order)

#include <iostream>

int main() {
    // 3 rows x 3 columns Matrix
    int matrix[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    std::cout << "Matrix Diagonal Elements: ";
    for (int i = 0; i < 3; ++i) {
        std::cout << matrix[i][i] << " ";
    }
    // Output: 1 5 9
    std::cout << "\n";
    return 0;
}