A signal route to which several items of a computer system may be connected in parallel so that signals can be passed between them. A bus is also called a trunk in the US, and a highway in the UK. The signals on a bus may be only of a particular kind, as in an address bus or data bus, or they may be intermixed. To maximize throughput, the number of lines in the bus should equal the sum of the number of bits in a data word, the maximum address, and the number of control lines. As this is expensive to implement, a multiplexed bus may be used.

There is a widely used instrumentation bus standard, referred to as IEEE 488 or as GPIB, general-purpose interface bus. For microprocessors there are a number of standardized bus systems, one of the first to be widely used being the VME bus. The rapid development of the home computer has led to the introduction of several generations of bus systems of ever increasing speeds. Examples are ISA bus, PCI bus, accelerated graphics port, USB, FireWire, and PCI Express.