说到Coroutine，我们必须提到两个更远的东西。在操作系统（os）级别，有进程（process）和线程（thread）两个（仅从我们常见的讲）实际的“东西”（不说概念是因为这两个家伙的确不仅仅是概念，而是实际存在的，os的代码管理的资源）。这两个东西都是用来模拟“并行”的，写操作系统的程序员通过用一定的策略给不同的进程和线程分配CPU计算资源，来让用户“以为”几个不同的事情在“同时”进行“。在单CPU上，是os代码强制把一个进程或者线程挂起，换成另外一个来计算，所以，实际上是串行的，只是“概念上的并行”。在现在的多核的cpu上，线程可能是“真正并行的”。
IEnumerator YieldSomeStuff()
{
yield "hello";
Console.WriteLine("foo!");
yield "world";
}
IEnumerator e = YieldSomeStuff();
while(e.MoveNext())
{
Console.WriteLine(e.Current);
}
Normal coroutine updates are run after the Update function returns. A coroutine is a function that can suspend its execution (yield) until the given YieldInstruction finishes. Different uses of Coroutines:
yield; The coroutine will continue after all Update functions have been called on the next frame.
yield WaitForSeconds(2); Continue after a specified time delay, after all Update functions have been called for the frame
yield WaitForFixedUpdate(); Continue after all FixedUpdate has been called on all scripts
yield WWW Continue after a WWW download has completed.
yield StartCoroutine(MyFunc); Chains the coroutine, and will wait for the MyFunc coroutine to complete first.
Unity的Coroutine,布布扣,bubuko.com
原文：http://blog.csdn.net/tinyhum3d/article/details/27177279