Output devices

There is no point in having a computer that can do wonderful things unless it can tell you the results of what it has been doing. This is where we need an output device. They are all of those things that let your computer 'talk' back to you and present information.

Examples of devices for these formats are: Monitors (Visual Display Units - VDUs) These are the most common output device and include: Desktop monitors which are also known as Cathode Ray Tube (CRT)

Liquid Crystal Displays (LCD) which are also known as Thin Film Transistors (TFT) Visual Display Units display images and text which are made up of small blocks of coloured light called pixels. The resolution of the screen improves as the number of pixels is increased. pixels

Recent standard has been 640 x 480 pixels on the screen (this is called VGA) and the present standard is 800 x 600 (called SVGA) x 768 This has enabled the use of an increasingly sophisticated visual interface, utilizing graphical user interfaces (GUIs) such as Microsoft Windows and MAC OS as well as more highly developed user friendly software.

Printers Laser printers produce a very high quality output, are very quiet and very fast. Laser colour printers are quite expensive to buy. A photoconductive drum is initially charged and then a high intensity laser beam is used to discharge selected areas on the drum. These discharged areas correspond to the white areas of the printed document. Toner is attracted to parts of the drum with a high charge. The drum rotates and transfers the toner to the paper which has an even greater electrical charge. Finally a heater fixes the toner onto the paper.

Ink-jet printers offer black and white or colour printing with reduced levels of quality and speed. Colour ink jet printers are cheaper to buy than colour laser printers. Characters are formed as a result of electrically charged or heated ink being sprayed in fine jets onto the paper. Individual nozzles in the printing head produce high resolution (up to 400 dots per inch or 400 dpi)

Inkjet printers use colour cartridges which combine magenta, yellow and cyan inks to create colour tones. A black cartridge is also used for crisp monochrome output. This method of printing can generate up to 200 cps and allows for good quality, cheap colour printing. Colour cartridge showing inkjet nozzles

Dot-matrix printers are not so common today. They are comparatively noisy and low quality but are cheap to run and are used when carbon copies or duplicates need to be made, such as for wage slips. Also, they are useful in dirty environments such as a garage because they are much sturdier than the other two types of printer. Impact Printers use a print head containing a number of metal pins which strike an inked ribbon placed between the print head and the paper.

The speed is usually characters per second (cps). They are useful for low quality carbon copy printing.

Plotters A plotter can be used to produce high quality, accurate, A3 size or bigger drawings. They are usually used for Computer Aided Design (CAD) and Computer Aided Manufacture (CAM) applications such as printing out plans for houses or car parts. Flatbed plotter: This is a plotter where the paper is fixed on a flat surface and pens are moved to draw the image. This plotter can use several different colour pens to draw with.

Flatbed plotter

Robots Robots are able to perform a variety of tasks as a result of executing instructions contained within a program. We are still a long way from the science fiction robots and androids portrayed by the film industry. Robots in a business sense mean automated machines designed to perform mundane operations which require accuracy, such as assembling cars. They are seldom manufactured to resemble the human form. Robot arm

LED Lights such as LEDs (Light Emitting Diodes) can be connected to a computer and respond to electrical signals which tell them to switch on and off. Control devices such as lights, buzzers and motors are used when the computer is controlling a situation such as traffic lights.

Touchscreen A touchscreen is an output and input device which can detect the presence and location of a touch within the display area. The term generally refers to touch or contact to the display of the device by a finger. Touchscreens can also sense other passive objects, such as a stylus

Other devices: Speakers LCD projectors Output can also be in the form of instructions to a device such as a robot arm.