Asynchronous operation: The child is spawned and the parent continues execution. This is the most common operation mode because the parent will typically need to manage the data generated by its child as soon as it is available. At any point, the parent process can decide to synchronize with its child, effectively waiting for its termination. Synchronous operation: In this scenario, the parent blocks until its newly spawned children finishes execution. This can be useful in those cases where the parent does not directly receive data generated from its child (e.g. because it is redirected to a file on disk). Disconnected operation: The parent forgets about the existence of its child , which can continue to exist even when the parent dies.