Multitasking theory question

["Kai Schuelke" <kai.schuelke@gmx.net>]

Hello,

during my programming course we learned about tasks, too. One qustion that
couldn't be answered was:

Is an Ada-Task a process of the operating system or is it a kind of process
inside the whole program?

I tend to agree with the second opinion, based on what I have seen during
some personal "experiments". But it seems to depend on how the compiler
handles the tasks.
The example consisted of two tasks. In one case, using DOS and an old Ada83
compiler the second task never could do anything, because all resources
(CPU-Time) where blocked by Task #1. The same code run in a WinNT DOS-Box
and compiled with the actual Aonix compiler switched between the task with
intervals of about 1 second.

Under DOS tasks ran cooperative, under Win preemtive. Why this difference?
Is it because of the OS, the compiler or the change from Ada83 to Ada95?

Thanks a lot

Kai Schuelke