Today, the parallel port interface is virtually non-existent in new computers because of the rise of Universal Serial Bus (USB) devices, along with network printing using Ethernet and Wi-Fi connected printers.

It was primarily designed to operate printers that used IBM's eight-bit extended ASCII character set to print text, but could also be used to adapt other peripherals.

When power was applied to the solenoids, the pin was pushed forward to strike the paper and leave a dot.

A parallel port makes this simpler; the entire ASCII value is presented on the pins in complete form.

Wang happened to have a surplus stock of 20,000 Amphenol 36-pin micro ribbon connectors that were originally used for one of their early calculators.

To improve performance, printers began incorporating buffers so the host could send them data more rapidly, in bursts.

This was accomplished by allowing the data lines to be written to by devices on either end of the cable, which required the ports on the host to be bidirectional.

[6] This used four existing status pins, ERROR, SELECT, PE and BUSY to represent a nibble, using two transfers to send an 8-bit value.

The introduction of new devices like scanners and multi-function printers demanded much more performance than either the Bi-Tronics or IBM style backchannels could handle.

The Enhanced Parallel Port (EPP), originally defined by Zenith Electronics, is similar to IBM's byte mode in concept, but changes details of the handshaking to allow up to 2 MB/s.

[8] The Extended Capability Port (ECP) is essentially an entirely new port in the same physical housing that also adds direct memory access based on ISA and run-length encoding to compress the data, which is especially useful when transferring simple images like faxes or black-and-white scanned images.

In 2000, the EPP and ECP modes were moved into the standard, as well as several connector and cable styles, and a method for daisy chaining up to eight devices from a single port.

[9] Some host systems or print servers may use a strobe signal with a relatively low voltage output or a fast toggle.

Before the advent of USB, the parallel interface was adapted to access a number of peripheral devices other than printers.

Some of the earliest portable MP3 players required a parallel port connection for transferring songs to the device.

In some cases, the BIOS supports a fourth printer port as well, but the base address for it differs significantly between vendors.

Since the reserved entry for a fourth logical printer port in the BIOS Data Area (BDA) is shared with other uses on PS/2 machines and with S3 compatible graphics cards, it typically requires special drivers in most environments.

Some operating systems (like Multiuser DOS) allow to change this fixed assignment by different means.

Some DOS versions use resident driver extensions provided by MODE, or users can change the mapping internally via a CONFIG.SYS PRN=n directive (as under DR-DOS 7.02 and higher).

This set of invalid file and directory names also affects Windows 95 and 98, which had an MS-DOS device in path name vulnerability in which it causes the computer to crash if the user types "C:\CON\CON", "C:\PRN\PRN" or "C:\AUX\AUX" in the Windows Explorer address bar or via the Run command.

USB-to-EPP chips can also allow other non-printer devices to continue to work on modern computers without a parallel port.

[16] For electronics hobbyists the parallel port is still often the easiest way to connect to an external circuit board.

However, Microsoft operating systems later than Windows 95/98 prevent user programs from directly writing to or reading from the LPT without additional software (kernel extensions).

)[18] The base address 0x3BC is typically supported by printer ports on MDA and Hercules display adapters, whereas printer ports provided by the mainboard chipset or add-on cards rarely allow to be configured to this base address.

The port addresses assigned to slot can be determined by reading the BIOS Data Area (BDA) at 0000h:0408h.

), the microprocessor is operated in a different security ring, and access to the parallel port is prohibited, unless using the required driver.

[20][better source needed] Pinouts for parallel port connectors are: Inverted lines are true on logic low.