InputInput tools, originally introduced as a language model for interactive systems and based on high-level, input-driven objects, have been developed into a model for communicating parallel processes, called the input tool process model (ITP).In this model every process contains an input rule, comparable to the right-hand side of a production rule.This rule specifies in an expression the patterns and sources of input it exPects and where the input is to be handled.The reception of the input triggers action inside the too! process.As part of the action, messages may be sent to other processes, with destination specified to a varying degree of identification.A potential candidate for a message is any tool process with the correct type of message slot.Because sending tool processes do not have to specify completely the identity of receiving tool processes, and vice versa, ITP provides a fully dynamic communication model.Most communication aspects of other recently developed models are contained in this model.Synchronization of processes is accomplished implicitly by the input specification; explicit synchro-nizatiQn constructs such as monitors and guarded regions can therefore be easily simulated.The ITP constructs provide a general concept for interprocess communication.Its application areas range from interaction via process control to operating systems.From a programming point of view, the language constructs offered are not in any way dependent on whether processes run on single or multiple processors.