A data channel that transfers digital data in a serial fashion: one bit after the other over one wire or fiber. The serial port on a PC is a serial interface that is typically used to attach modems and data acquisition terminals. On earlier PCs, mice also used the serial port. USB and FireWire (IEEE 1394) are high-speed serial interfaces that have superseded the serial port. Serial interfaces may have multiple lines, but only one line is used for data. Contrast with parallel interface. See serial port, RS-232, USB and FireWire.