(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)