Message-Passing and Notification

Amiga processes communicate by message-passing. A process registers with the operating system to receive certain classes of messages, and the messages are routed to the process when they occur.

A typical Amiga application program reflects this message-passing structure, shown in the following pseudocode: 

    while (1)
    {
            mask    = Wait(port);       /* Wait for a message.  Non-busy-wait. */
            message = GetMessage(mask); /* What message arrived? */
            class   = message->class;   /* Save important message info. */
            Reply_To_Message(message);
            switch (class)
            {
                    case MOUSE_MOVE:                        ...
                    case WINDOW_RESIZE:                     ...
                    case FILE_WAS_MODIFIED:                 ...
                    case CONTROL_C_WAS_PRESSED:             ...
                    case USER_CHANGED_SYSTEM_COLORS:        ...
                    case MY_OWN_SPECIALLY_DEFINED_MESSAGE:  ...
                    ...
            }
    }

Many routine messages such as window resizings may be handled by the operating system rather than the application. See Section [*] for more information.