1. In an operating system, a means of running more than one program at a time. In cooperative multitasking, one application program cannot force another to do something. An application yields to another voluntarily, but only after checking the electronic equivalent of a message box to see if any other applications have made a request. If the applicatio nis involved in a lengthy operation, howeber, it may not check the message box until the opeation is completed. See pre-emptive multitasking. From QUECID