Why is the output like that?

Question

Why does

int[ ] arr = {2, 4, 7};
for(int k=0; k<arr.Length; k++) {
Console.WriteLine(arr[k]);
}

output 2,4,7 when k is never given the actual value f.e 2

Answer 1

An array is a data structure which content can be accessed by index.
The first element of an array is always indexed as 0, and so on.

As you have declared an array (int[] arr = {2, 4, 7};) of 3 elements, to get the first one you use 0 as an index (arr[0]) and you get the first element (2).

Your for loop gives k the values 0, 1 and 2, so your code prints the whole array, index by index

Console.WriteLine(arr[0]); // 2
Console.WriteLine(arr[1]); // 4
Console.WriteLine(arr[2]); // 7