Editing Coroutine (section)

===Threads===
Coroutines are very similar to [[Thread (computing)|threads]]. However, coroutines are [[cooperative multitasking|cooperatively multitasked]], whereas threads are typically [[Preemption (computing)|preemptively multitasked]]. Coroutines provide [[concurrency (computer science)|concurrency]], because they allow tasks to be performed out of order or in a changeable order, without changing the overall outcome, but they do not provide [[parallel computing|parallelism]], because they do not execute multiple tasks simultaneously. The advantages of coroutines over threads are that they may be used in a [[hard realtime|hard-realtime]] context ([[context switch|switching]] between coroutines need not involve any [[system calls]] or any [[blocking (computing)|blocking]] calls whatsoever), there is no need for synchronization primitives such as [[mutex]]es, semaphores, etc. in order to guard [[critical sections]], and there is no need for support from the operating system.

It is possible to implement coroutines using preemptively-scheduled threads, in a way that will be transparent to the calling code, but some of the advantages (particularly the suitability for hard-realtime operation and relative cheapness of switching between them) will be lost.