Why the -1 in this for loop

[burton1995]

Why in the bottom for loop is it "index = numbers_used - 1;..."
index was initialized to 0 and then numbers_used was set to index. If index started at one I would get it. Is it because if I input: " a b c ." I have filled a[0,1,2,3] ??

  #include <iostream>
using namespace std;

const int MAX = 10;

int main()
{
    char a[MAX], next;
    int index = 0;

    cout << "Please enter in up to 10 letters ending with a period: " << endl;
    cin >> next;

    while((next != '.') && (index < 10))
    {
        a[index] = next;
        index++;
        cin >> next;
        //cout << " " << next << endl;
    }

    for(index = numbers_used -1; index >= 0; index--)
        cout<<a[index];
    cout << endl;

[ResidentBiscuit]

I don't see where numbers_used is even defined. But my guess is at that point numbers_used is equal to the size of the array, which is not a valid index (points one past the last element). So this code uses numbers_used - 1 to point to the last element in the array, and then iterate backwards through that array.

[wildblue]

index gets incremented in the while loop to one element past the last one written into the array, so if numbers_used gets set to index after the while loop, you'd need to go back one element to get to the first element you want to output.

[burton1995]

biscuit it was a cut and paste misfire. I changed the code and added a cout after it to see what numbers_used was using input ' a b c . ' It came out to three not the expected four??? Now if I subtract the one I get 2. 0 - 2 is three cycles so everything is okay but why not the four?

[burton1995]

nevermind it only increments after checking for the period