Output Devices

A monitor (or screen) is the most commonly used output device.

They come in many different shapes, sizes and forms. In an exam question, you will need to be able to choose the best type of monitor and then explain your reasons.

The picture on a monitor is made up of thousands of tiny coloured dots called pixels.

The quality and detail of the picture depends on the number of pixels that the monitor can display.

The higher the number of pixels, the better quality the output.

Larger monitors make working at the computer much easier on the eyes, but the larger the monitor, the more money it costs!

A typical monitor size is a 19 inch diagonal.

Modern operating systems can easily handle a dual monitor setup, (as long as the graphics card also has dual sockets).

For example, in the photo of my working setup above, there are two monitors in use on a single computer. The one on the right is set to hold most of the icons and the one on the left may be used to open applications without losing sight of the the icons. This is a very effective way of increasing your working area.

 television is quite a popular way of displaying IT or computer related output.

For example, video consoles connect to a television screen for maximum impact. Smart TVs connect to the internet directly and so can view content directly such as videos or catch-up services.

Every year the screen size available seems to become larger and now TV screens up to 60" or more are available.

A standard TV screen is '720p' which means it is 720 pixels down and 1280 pixels across. This is OK for displaying video but not so good for viewing text.

A 1080p screen is 1080 pixels down and 1920 pixels across which is far better for displaying text information. This is excellent for High Definition (HD) and Blu-ray content.

Uses of television screens:

• TV screens in the home
• As computer monitors for watching downloaded video / films
• Screens in public areas for information, advertising or displays
• Screens in video conferencing suites for meetings

Advantages of plasma screensDisadvantages of television screens Very large screen size Standard 720p resolution not good for displaying text compared to 1080p Thin profile, sometimes only an inch depth. Has to be viewed from a distance compared to a standard computer monitor Large viewing angle (160 degrees) compared to LCD screens (40 degrees) Large TVs need a lot of room around it for comfortable viewing Brighter display than rear projection TVs More expensive than a standard computer monitor Unaffected by magnetism (unlike old CRTs)   Can be mounted on a wall or free standing - more flexibility than other screens  

Printers are another common output device. They are used to create a 'hard' copy of your work i.e. something that you can hold, hand to someone else or file away.

Most printers produce their output on paper.

However, paper isn't the only thing that you can print things onto, for example some printers are able to print directly on to CD or DVD disks with a suitable holder.

A major factor with printers is the cost of the ink. Ink-jets are good for low volume use as they produce excellent text and photo outputs, but cost-per-page can be very expensive, in which case a laser printer is the more cost-effectve choice.

Laser printers are used in many workplaces because they are quiet, they print a large number of sheets very quickly and they produce high quality documents.

They print in the same way as photocopiers. Powdered ink, called 'Toner', is fused onto paper by heat and pressure.

You can purchase a laser printer which prints black and white copies only or you can pick a colour laser printer.

Black and white versions are relatively cheap to purchase and you only need to buy black toner (which is also expensive).

Colour laser printers offer good quality for work such as flyers or other commercial material.

Advantages of laser printersDisadvantages of laser printers High quality printouts - better than ink-jet or dot-matrix Most expensive printer type to buy, especially colour lasers Fast printouts - faster than ink-jet or dot-matrix Toner is more expensive than ink-jet cartridges Prints very quietly - quieter than ink-jet or dot-matrix Expensive to repair - lots of complex equipment inside Cost per page is low - cheaper than ink-jet or dot-matrix Fairly bulky - larger than ink-jet printers   Can't use continuous or multi-part stationary to create carbon copies like you can with a dot-matrix printer

Ink-jet printers have been popular for a long time because they are relatively cheap to buy and most of them can combine both black and white and colour printing at the same time.

These printers use cartridges that contain the ink.

They operate by heating the ink as it flows through a set of tiny nozzles.

The heating process causes a small droplet of ink to form. This is then released as a single dot which forms part of a letter or image. This is why the printouts often come out of an ink-jet printer still slightly wet.

Colour ink-jet printers are ideal for use at home where only a few documents need to be printed and the quality of the printout doesn't need to be perfect.

They can produce superb photographic prints if suitable high quality photo paper and inks are used.

Advantages of ink-jet printersDisadvantages of ink-jet printers Cheap to buy - cheaper than a laser printer Noisier than a laser printer (but not as noisy as a dot-matrix) More compact than a laser printer Colour printing can be extremely slow Cartridges cost less to replace than toners Cost of printouts per page are more expensive than a laser printer Produce good quality printouts better than a dot-matrix but not as good as a laser Cartridges need to be replaced more often than a laser printer Speed - faster than a dot-matrix but not as fast as a laser Ink will smudge while it is still wet   Colours can become saturated and often don't look the same as on the screen   If not used for a while, the cartridges can dry out

Plotters are a specialist type of printer which is able to draw high quality images on very large pieces of paper, for example 3 foot wide by 10 foot long.

They are used by engineers, architects and map-makers to draw plans of buildings, diagrams of machines or large scale maps. They can also be used for many other similar tasks.

A plotter differs from a printer in that it draws images using a pen that can be lowered, raised and moved across the paper to form continuous lines. The electronically controlled pen is moved around the paper by computer controlled motors.

There are plotters now which are 'pen-less'. these are used for creating high density drawings such as the one shown in the image above.

There are three different types of plotter:

Flatbed plotters - These hold the paper still while the pens move

Drum plotters - These roll the paper over a cylinder

Pinch-roller plotters - These are a mixture of the two types above

A touch screen is the only device which works as both an input and an output device. You view the options available to you on the screen (output) and you then use your finger to touch the option that you have chosen (input).

Touch screens work particularly well with a menu driven interface. For example, a cashpoint (ATM) at a bank would first of all ask which service you want. You touch the option 'withdraw cash' on the screen. You are then presented with another choice, 'how much cash do you want to withdraw?'. Once you have chosen how much, you then get other options such as 'do you want a receipt?'.

Another major use of touch screens are on smart phones and modern tablet computers. Each 'app' is accessed by an icon on the touch screen.

Touch screens are easy to use and are often found in public places such as cashpoints at banks, ticket collection terminals at theatres or airports, information centres at museums.

Touch screens are not commonly used to input large amounts of data because they are not very accurate and they would be tiring on the hands to use for long periods of time.

A digital projector is a device which connects to a computer and is used to project the video output from the computer onto a wall or screen.

In classrooms they are often used with electronic whiteboards.

The projector can be portable and placed on a stand or it can be permanently fixed to the ceiling.

Uses of digital projectors:

• Classroom teaching
• Staff training sessions
• A presentation to an audience
• Home cinemas

Although most digital projectors are fairly large in size, new technology is currently being developed to incorporate digital projection into small hand-held devices.

Most computers are fitted with a small internal speaker which can produce beeping sounds to alert you if you make an error.

Computers can also be fitted with a sound card (or chip) which will enable sound to be output through external speakers. These usually produce a much higher quality sound than the internal speaker.

Advantages

• Everyone in the room can hear the output from the computer.
• They can help create an atmosphere or ambiance to accompany a presentation
• They help blind people to use the computer because text can be converted into sound

Disadvantages

• The output from speakers can disturb others who are trying to work
• High quality external speakers can be expensive

Headphones and earphones consist of a pair of small loudspeakers which are worn over or in the ears.

They are connected either by cable or wirelessly to a device such as a computer, radio or MP3 player.

A transducer converts the electronic signals from the device into sounds which can then be heard by the user via the phones.

Advantages

• The sound can only be heard by the user (mostly)
• Portability - lightweight and easy to carry around
• Can listen to music on the move
• Although prices vary, many headphones and earphones are inexpensive

Disadvantages

• If music is played too loudly or for long periods of time there is a risk of permanent hearing loss
• Often not aware of surrounding noises such as cars in traffic or people talking
• If the music is too loud or the headphones not fitted correctly then others can hear an annoying sound from them.
• Can be uncomfortable to wear for long periods of time.
• If the device is large e.g. a computer, it is not easy to move about the room while wearing the headphones

Lights such as LEDs (Light Emitting Diodes) can be connected to a computer or within equipment 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.

The picture on the right is showing that the black toner is low on a colour laser printer. Note that it is very common to use an icon next to the light rather than text. This is for two reasons

1. It is very compact, only a tiny space is needed for an icon compared to text
2. It is independent of language, so this printer can be sold just as well in English or Spanish countries without modification.

This light is controlled by the microprocessor inside the laser printer.

Advantages

• Very cost effective way of indicating the status of equipment (on / off / ready / offline etc)
• They can provide a warning for users with hearing loss who might not be able to hear the error beeps produced by the internal speaker.
• They come in a large range of different colours

Disadvantages

• The light may break or wear out and need replacing
• There may be a loose connection which means the light doesn't switch on even if the circuit or control program is correct
• They can only indicate simple status (on/off) - anything more complicated would need a dedicated display for example a DVD player may have an LED display to show power on/off and a separate display to show disk loading status.