This enables computers without standard dedicated networking hardware, such as Ethernet, but with older parallel port devices, to communicate.
Early personal computers did not have Ethernet hardware in their design, and bus adapters were initially expensive.
A solution was to use, at the time, a standard parallel port, typically used for connection to a printer or similar output device.
The status lines ERROR, SLCT, PAPOUT, ACK, and BUSY on one device are connected to data pins d0 through d4, respectively, on the other.
Other point-to-point connections, such as USB host-to-host bridges or cables, are also used to transfer files between two computers where a network is not necessary or available.