YieldableProgram

'Yieldable' means a flow of instructions can be interrupted to let other flow of instructions run. The flow of instructions can contain 'yield' points at any places, and when the execution comes to that place, the execution returns to its caller, so that the caller can execute another flow of instructions. It is analogous to the operating system when it switches a thread context to another. The execution information is stored when a flow yielded, and is resumed later starting at the place of the yield.

Typical use case of this is when you execute multiple things on single execution thread. It is often seen as 'Reactor pattern' or 'Event Driven Execution pattern'