BOOT CAMP 003

PRINTERS AND PERIPHERALS

On its own a personal computer is not much use, unless you are content playing games or gazing at whatever appears on the screen. In order to get a PC to do anything worthwhile it needs to be connected to external devices or peripherals, that make it possible for the machine to interact and communicate with the outside world.

Most peripherals are linked to a Windows PC by parallel or serial ‘ports’. A port is simply another name for a connector; parallel and serial refer to the way the port conveys data or information. Parallel connectors and cables generally have eight conductors, so eight bits of information can be sent simultaneously. A serial link uses a single conductor and data is sent sequentially. Parallel connections are fast and some peripherals can be ‘daisy chained’ together, to enable two device to share a single port. However, cable length is limited to around three or four metres. Serial links are slower, but because there’s fewer wires they are cheaper and more reliable, moreover they can operate over greater distances. A PC can have up to three parallel ports (designated LPT 1 to LPT 3) and four serial ports (COM 1 though to COM 4), though most machines leave the factory with one parallel and two serial ports.

A printer is often the first and most useful peripheral a new PC owner acquires. Printers fall into three basic categories: impact, laser and ink jet. Impact printers include dot-matrix and Daisywheel types, both are on the way out and really only suitable for plain text and simple graphics. Laser printers are appropriate for high demand business applications, where speed and quality are important. Ink jet printers are ideal for the home PC user and small office environment. They produce crisp-looking documents, sharp graphics, and most new models print in colour, in near photographic quality. Colour inkjet printers cost from as little as £100, there are many different models to choose from, so it’s worth visiting your local PC store, to see and compare as many of them as possible.

Other devices that commonly use a parallel port connection are external disc and tape drives, and scanners. The majority of tape and disc drives are used for mass data storage or backup, a subject we will be covering in greater detail in a few weeks time. Scanners are like printers, but in reverse! They provide a means of getting text, graphics and images into a computer. Virtually all scanners come with bundled optical character recognition (OCR) software, that converts the image of a document into text, that can be read by word processor software. Flatbed colour scanners, which look like desktop photocopiers, can be brought for less than £100. Incidentally, not all scanners use the PC’s parallel port, some dearer models often use a dedicated interface card, which helps improve scanning speed and frees the printer port.

On many PCs the COM 1 serial port is used by the mouse, trackball or pointing device. COM 2 is normally the default port for an external modem; we will be taking a closer look at them shortly. In the past few years a variety of other devices have appeared, that also require a serial connection. They include digital cameras, video and frame ‘grabbers’, radio tuners and camcorder edit controllers. If required most PCs can be fitted with extra parallel and serial ports, though it’s normally easier to use an external switch-box -- costing between £10 to £15 --  so that a number of devices can share one port.

JARGON FILTER

DAISYWHEEL

Impact printer; characters are mounted on a spinning wheel and  stamped on to an inked ribbon, to leave an impression on a sheet of paper

DOT MATRIX

Impact printer; characters are built up by a row of tiny moving print heads, that stamp dots on to the paper, via an inked ribbon

INK JET

Images are built up by tiny drops of ink, squirted from a moving print head or cartridge, on to paper. Most colour ink jet printers use a mixture of cyan, magenta and yellow inks, sometimes with black, to produce a full range of colours

VIDEO GRABBER

Device used to convert a video image, from a camera or VCR, into a form that can be viewed and processed by a PC

 

TOP TIP

Help is always at hand! If you encounter a problem or get into difficulty, just press F1 and the associated Help file will be displayed. Swapping between open applications in Windows 95 is easy; hold down the left ‘Alt’ key and press the ‘tab’ key. Pressing tab again steps through all of the programs the machine is currently running. If for any reason a program freezes, or the mouse stops moving try pressing ‘Alt’ and you may find that you can still select menus and options, using the four arrow cursor keys. If an application refuses to respond then press and hold down ‘Ctrl’, ‘Alt’ and ‘Delete’ in that order -- once only -- and the PC will display the Close Program window. This gives the opportunity to shut down the offending application, without having to exit Windows.