The RS-232 serial port was widely used in the 20th century for character I/O devices (teletype, printer, dumb terminal).
A pair of simplex channels (output and input) make it full duplex.
Additional wires are sometimes used for hardware flow control, or a software Xon/Xoff protcol can be used.
Baud rate and number of bits per words must be pre-agreed.
|11: (C) 2008-13, DJ Greaves, University of Cambridge, Computer Laboratory.|