In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel.

(serial ports)

<hardware, communications> (Or "com port") A connector on a computer to which you can attach a serial line connected to peripherals which communicate using a serial (bit-stream) protocol. The most common type of serial port is a 25-pin D-type connector carrying EIA-232 signals. Smaller connectors (e.g. 9-pin D-type) carrying a subset of EIA-232 are often used on personal computers. The serial port is usually connected to an integrated circuit called a UART which handles the conversion between serial and parallel data. In the days before bit-mapped displays, and today on multi-user systems, the serial port was used to connect one or more terminals (teletypewriters or VDUs), printers, modems and other serial peripherals. Two computers connected together via their serial ports, possibly via modems, can communicate using a protocol such as UUCP or CU or SLIP. (1995-01-12)