Output devices Monitors: screens or Visual Display Units (VDUs) display the effects of what the user is doing can vary in size and resolution. Printers: produce a paper copy of the user’s work: a ‘hard copy’ come in three main types: laser, inkjet and dot matrix. Some businesses also use plotters. Sometimes we just need to see the information, on screen or on paper, so we use a monitor or a printer.

 When a computer has finished processing information, the information needs to be output so that it can be used.  Output devices are used to get information out of a system.  They should be able to do this as accurately and quickly as possible, and with the minimum of human intervention.

 The most common types of output devices are:  Visual devices (including Visual Display Units [VDUs], screens, and monitors)  Hard copy devices (including ink jet printer, laser printers, dot-matrix printers, and plotters)  Sound devices  Computer controlled devices (including robots)

 The most common visual device is the visual display unit (VDU).  These are also known as computer screens and monitors.  The types of visual display unit found in common usage are based on cathode ray tube or liquid crystal display (LCD) technology.

Visual Display Unit (Monitor) (Screen) Liquid Crystal Display (LCD)

 These are very useful in circumstances where a user wants to show a large group of people the same information simultaneously.

A typical projector. Used for projecting presentations etc so that several people can see at one time.

 The most common types of printer are the laser and the ink jet printers.  A less common type of printer is the dot-matrix printer.

Ink jet printer Laser printer

 Plotters are a very specialised type of output device, and are usually found where high quality technical drawings or graphs have to be produced.

Typical plotters

Used with CAD/CAM systems to create prototypes of car parts etc news/

Output devices – visual and printed

When a computer has finished processing information, the information needs to be output so that it can be used. Speakers: are used to output sound, whether music or voice vary a lot in quality. Headphones: work in the same way as speakers can be cordless. Sometimes we need to hear the information, so we use loudspeakers or headphones.

 The speakers and headphones used with computers are usually compatible with other devices such as stereo systems.

Sometimes we want it to control something, so we send a signal to a motor or a switch that is part of another device, like a robotic arm or a computerized sewing machine. When a computer has finished processing information, the information needs to be output so that it can be used.

 A variety of different control devices can be connected to a computer.  These include robotic arms and motors (also known as actuators).  The most common use of computer controlled devices is in computer-aided manufacturing.

A typical computer controlled device used in computer- aided manufacturing – a robotic arm

 A computer can’t actually control the flow of water round a heating system on its own, but it can turn a motor on or off.  Motors are often used in heating systems/washing machines etc.

 Buzzers (or similar sound- generation devices) are often used in monitoring/control situations  Used as an alert or an alarm, or as an audible confirmation that something has happened

 These are switched on and off by actuators.  Used in:  Automatic Cookers  Automatic Washing machines  Computer Controlled Greenhouses  Central Heating Systems

 Used to convert computer signals into movement.  Often used to turn lights on and off, to turn buzzers on or off, to turn heaters on or off.

 An actuator is connected from the computer to the lightbulb, and is set to switch it on or off.  Lights are used in computer controlled greenhouses to increase the amount of light for the plants

 Lights are also used in computer control/monitoring,  Security lighting  Burglar alarms  As warning lights  As a visual alarm system

Output devices – control and sound

Device suitable for purpose

DeviceBenefits CRTCheapest monitor to buy; gives a sharp picture LCDSlim screen; Used for laptops and digital display TFTSlim screen; quick to refresh because each pixel has its own transistor SpeakersGood for loud music; can address a whole room HeadphonesCan listen without disturbing others; good for private conversation LaserQuick and best quality printer; large paper tray InkjetCheap colour printing; good for printing photos Dot matrixImpact printer; good for multi-part forms PlotterLarge drawing size; clear lines for technical drawings ControlSafe in all conditions; good for repetitive tasks

Summary There are four kinds of output devices; devices that produce a visual or printed output, those that produce an audio output and others that use control as output. The three main types of monitors at Cathode Ray Tube (CRT), Liquid Crystal Displays (LCD) and Thin Film Transistor (TFT). There are three main types of printers: dot matrix, inkjet and laser. Sound devices include speakers and headphones. Control devices include hydraulics, pneumatics and motors.