An array is a row of boxes

An array is several boxes of the same type side by side in memory. squares[0] is the first box and squares[4] is the last; there is no squares[5].

Watch the loop write one box per pass, using i as the index.

#include <stdio.h>

int main(void) {
    int squares[5] = {0};
    for (int i = 0; i < 5; i++) {
        squares[i] = i * i;
    }
    printf("%d %d\n", squares[2], squares[4]);
    return 0;
}

Output:

4 16

From the lesson: Arrays