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Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today. # I was just wondering if anyone could break this down and explain to me how this works...?

let numbers = [2,8,1,16,4,3,9] var sum = 0 var counter = 0

while counter < numbers.count { sum += numbers[counter] counter += 1}

print(sum)

Hey Michael, I've posted your code with my comments below. Hope this helps.

```//declares an array of Int's named numbers
let numbers = [2,8,1,16,4,3,9]
//declares an Int variable named sum, initialised with a zero value
//used to keep track of the sum total
var sum = 0
//declares an Int variable named counter, initialised with a zero value
//this is used as an index value, as well as an indicative value
//to compare to the number of items in the numbers array
var counter = 0

//While Loop
//This should read as "While the counter is less than the amount of items in the numbers array, execute the below."
//While this conditional is true, the body of the loop will execute.
while counter < numbers.count {
//The += operator takes the current value of sum, and adds
//the number at the index specified by the counter property.
//can also be written as sum = sum + numbers[counter]
sum += numbers[counter]
//We then add 1 onto the current counter property so that
//the index next time will be one more than this execution.
//If this was the last index in the array, the boolean
//of the while loop condition will become false and stop executing
//because the counter is now higher than the amount of items in the numbers array.
counter += 1
}
```