In computing, a context switch is the process of storing and restoring the state (more specifically, the execution context) of a process or thread so that execution can be resumed from the same point at a later time. This enables multiple processes to share a single CPU and is an essential feature of a multitasking operating system.
https://en.wikipedia.org/wiki/Context_switch
原文：http://www.cnblogs.com/feng9exe/p/7891502.html