Yeah, that's how you end up doing this: store coroutine state in a struct, with an integer that lets you decide where to jump to when you resume the coroutine.

Yeah, that's how you end up doing this: store coroutine state in a struct, with an integer that lets you decide where to jump to when you resume the coroutine. With compiler support that can be pretty efficient (gcc has computed goto, for instance). Things get quite awkward in C but similar techniques are manageable in C++. I've never used Protothreads before, but Contiki (the tiny operating system written by the same person) uses them for its process implementation. Similar technique is also used by Putty as well: http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html