Serial
Serial communication operates in one direction, this is in contrast
with parallel, which operates in both directions. Serial communication
is one bit at a time. Serial ports are either 25 pin male, "D" Connector,
or a 9 pin male, "D" Connector.
Today's computers generally operate their serial ports in a bidirectional
form, so the standard definition doesn't always apply.
Serial communication is usually use for data devices such as modems
or peripherals such as mice.
