(I/O) Communication between a computer and its users, its storage devices, other computers (via a network) or the outSIde world. The devices the computer uses to do this are called "peripherals". What actually counts as I/O depends on what level of detail you are conSIdering, e.g. communication between processors would not be conSIdered I/O when conSIdering a multiprocessor as a SIngle system. Important aspects of I/O are throughput, latency, and whether the communications is synchronous or asynchronous (uSIng some kind of buffer). (2003-12-04)