PC Hardware - Do yourself - Part-1: Serial & Parallel Ports

The next important topic we should discuss about Serial and Parallel devices like Modems, Printers, Plotters and Scanners etc. All these are connected to your PC externally. So it is good to know about the cables used to connect them. There are so many Converter-Adaptors available now-a-days to connect systems through them.

A brief introduction about Serial and Parallel Data:

Data is transmitted and moved in one of two formats: parallel or serial. Parallel data is sent one character at a time with all of it’s bits moving at the same time over parallel wires. Serial data is transmitted one bit at a time over a single wire. And the mode of communication between two devices may be in 3 formats:

Simplex: can communicate in only one direction. Ex. A speaker wire.
Half-duplex: can carry data in two directions, but only in one direction at a time. Ex. A two-way-wireless set or A Citizen’s band Radio. Here one party must wait until the other party is finished before speaking.
Full-duplex: can carry data into two directions with both directions flowing simultaneously. Ex. Telephone line.

Figure showing Serial(COM)/Parallel(LPT) Ports

Serial Ports:
Serial ports were added to the PC through an expansion board that added one to four serial ports. Most newer PCs have one Serial/COM port mounted directly on the motherboard. Serial ports are easy to recognize on the back panel of the PC and one can easily recognize on the back panel as DB-9 and DB25 male D type connectors.

Parallel Ports:
Parallel ports on a PC are female DB-25 connectors that connect to male DB-25 connectors. Parallel ports are originally designed for use by printers. However, other devices have been adopted to them, including other types of output devices, input devices and storage devices, all taking advantage of the bidirectional capabilities of most of the newer parallel ports and devices. These include some external CD-ROMs, external tape drives, and ZIP drives.