non-recursive quicksort

can you give me a non recursive version of quicksort that uses a stack. the version should store at the stack indicies[i,j] of subarrays that have not been sorted yet.
what is the number of [i,j] pairs, non-sorted subarrays that can belong to stack simultaneously.

Any particular language? Here's one implementation in Java paraphrased from Robert Sedgewicks data structure's book:

Code:

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static void quicksort(ITEM[] a, int l, int r)
{  Stack S = new Stack(50);
    S.push(l); S.push(r);
   
    while (!S.empty())
    {
        r = S.pop(); l = S.pop();
       
        if (r <= l) continue;
       
        int i = partition(a, l, r);
       
        if (i-l > r-i) { S.push(l); S.push(i-1); }
       
        S.push(i+1); S.push(r);
       
        if (r-i >= i-l) { S.push(l); S.push(i-1); }
    }
}

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