Unix Protothreads

Protothreads is a programming model invented by Adam Dunkels that combines the advantages of event-driven (sometimes also called state machine) programming and threaded programming. The main advantage of the event-driven model is efficiency, both speed and memory usage. The main advantage of the threaded model is algorithm clarity. Protothreads gives you both. A protothread is an extremely lightweight thread. As with event-driven programming, there is a single stack; but like threaded programming, a function can (at least conceptually) block.