When applying a continuation, the stack is (logically) unwound and then rewound with the stack of the continuation. This is not the only way to implement continuations; for example, using multiple, explicit stacks, application of a continuation can simply activate its stack and wind a value to be passed. The Scheme programming language allows arbitrary thunks to be executed in specified points on "unwinding" or "rewinding" of the control stack when a continuation is invoked.