non-recursive quicksort

[nanu2010]

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.

[cma]

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

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); } 
    } 
}