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.

Here are some interesting links:

How Parallel Ports Work
How USB Ports Work
How Serial Ports Work
Interfacing the IBM PC Parallel Printer Port
ePanorama PC hardware page

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.