If I understand this algorithm correctly it will sort an array (A) with p being a pointer to the first element, and r being a pointer to the last element in descending order.
1.Quicksort(A,p,r)
2. if p < r then
3. q = Partition(A,p,r)
4. Quicksort(A,p,q)
5. Quicksort(A,q+1,r)...