Week 4: Peripherals

Printers are actually one of the oldest I/O devices for computers, along with card readers (albeit the originals were punch cards, not SecureDigital or memory sticks).  Tape drives, discussed previously, are also one of the older I/O devices.

Anyway, printers are used to put text and pictures on paper.  Virtual printers also exist, for making electronic books or similar documents, or for previewing items before printing them.

Physical printers can work in several ways.  Early computer printers (such as daisy-wheel printers) worked similarly to typewriters and block printing presses, by striking the page with a character on the end of a rod or lever.  Another early design of computer printer that could actually print images, not just text, was the dot-matrix printer.  These worked by printing dots on a page, similar to pointillist artwork, by pushing down a rod with ink on the end.  Modern ink jet printers also print using dots, but spray a jet of ink onto the page to make the dots instead of hitting the page with a rod. Laser printers operate similarly to some industrial-scale ink printers by using a rotating drum, but use a laser and static electricity to cause toner (a dry powder that will stick to paper) to form the pattern that will be printed on each page.  Color laser printers need to use three colors of toner and pass the paper over a drum three times to finish printing full-color images.

There are quite a few other types of peripherals.  Everything from keyboards and mice, printers, external storage devices like drives and card readers, network adapters both wired and wireless (also Bluetooth), to webcams (much like the famous coffee pot webcam) and even mini lava lamps exist as peripherals.  For example, I have several LED lamps and other lights that charge using USB.  Digital cameras function as peripherals when connected to a PC.  An example of a newer USB network adapter is the QNAP QNA-UC5G1T USB 3.0 to Single Port RJ45 5 GbE / 2.5 GbE / 1 GbE / 100MB Adapter, Bus Powered, USB type-c, 20CM USB-C to USB-A Cable.

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