Define Asynchronous Messages and Synchronous Messages-01884

Asynchronous Messages:

Asynchronous messages are "signals," denoted by a half arrow. They do not block the caller. Asynchronous messages typically perform the following actions:

1. Create a new thread
2. Create a new object
3. Communicate with a thread that is already running

Synchronous Messages:

Synchronous messages are "call events" and are denoted by the full arrow. They represent nested flow of control which is typically implemented as an operation call. In case of a synchronous message, the caller waits for the called routine to complete its operation before moving forward.