from
The Free On-line Dictionary of Computing (8 July 2008)
software handshaking
XON/XOFF
<communications> The transmission of extra data on a channel
in order to control the device sending data in the other
direction on that channel. For an {EIA-232} connection, this
means sending {Control-S} and {Control-Q} characters to stop
and start transmission.
Since software handshaking requires the transmission and
processing of extra data it can be less efficient than
{hardware handshaking}.
(1996-10-16)