(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)