How does a computer's parallel port work?

When a PC wants to send data to a printer, it sends it either through a parallel port, a serial port or a network connection.

When using a parallel port, the computer sends the data 1 byte at a time (8 bits in parallel, as opposed to 8 bits serially as in a serial port). With each byte sent out, it sends a handshaking signal so the printer can latch the byte.


If you want to accept data from a parallel port, all you really need is an 8-bit latch and a little glue logic.

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Frequently Answered Questions

What is the parallel port used for?
A parallel port is a type of interface found on computers (personal and otherwise) for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once, as opposed to serial ports which send bits one at a time.
What devices use parallel ports?
Some devices that use parallel ports are printers, scanners, CD burners, and external hard drives.