assigning priority to task

[Stribor40 <ikamzic@gmail.com>]

I am playing with example from here..
http://www.infres.enst.fr/~pautet/Ada95/e_c26_p2.ada

and each run i get different output which is ok but what I am trying to do is somehow control running of each of those 3 tasks by assigning priority to each task by using pragma PRIORITY(some int) where higher the int higher the priority.
So my question is this ....If i assign first task priority(8) and second priority(4) and third priority(2) does that mean that first task will always run first second second and third third? How does OS time slicing fit into this when priority is assigned to each task?

Thanks