&quot;A SPNT OS has no real need of a scheduler.&quot;<p>I would rather disagree: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Computer_multitasking" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Computer_multitasking</a>. OS in the most of the cases needs to be interactive, what would be impossible without multitasking. Multitasking would not be possible without a scheduler. So, we would not swap the active task and we would be stuck with the current task forever (or until it finishes), without even the ability to interrupt it.