Schedulable lightweight virtual processes and concurrent loops P&L: -11.5 (≃ -12 HUR)
Imagine a nested for loop, it is composed of multiple loops. We can simulate concurrency by executing parts of loops and rapidly switch between them.
This is what a kernel scheduler does and I think it's a very interesting part of an operating system. Unfortunately most programs are not written to be multithreaded so computers use very little of resources available to them.