Visual Output
Screens and monitors
Most PC’s are connected to a monitor. The image quality depends on its size and its resolution. Screens set to a high resolution display have smaller images and lower resolution displays have bigger images. Graphics artists and architects need big, good quality displays and therefore need high-resolution monitors. The resolution is measured in pixels.
Most monitors are either CRT or TFT types.
CRT monitors are based on cathode ray tubes that fire electrons at a screen. The cathode ray tube is long, which means these types of monitors are deep and take up a lot of room. They are usually cheaper than TFT’s. Most new computers have TFT (thin film transistor) screens. These are flatter and take up less space and are very popular. They use liquid crystals to form an image.
Large displays
If a computer image needs to be shown to large numbers of people there are several options:
Digital projectors. These can be used to project a large version of the monitor output onto a screen, so that it can be viewed by a large audience in a classroom or for business presentations. They can be portable but are often ceiling mounted.
Interactive whiteboards. Digital projectors can alsoproject on to special screens called interactive whiteboards. They are touch-sensitive, can be written on using a stylus shaped pen or a finger. Handwriting recognition can be used to convert handwritten text to computer text, which can then be saved or printed. Interactive whiteboards are both input and output devices.
Plasma screens. These large screens can be used as TV’s as well as computer monitors. They are often seen in business reception areas e.g. hotels and in shopping centres. They work by illuminating tiny fluorescent lights to make the image.
Small displays
Mobile phone screens. More and more people use their mobile phones to access the internet for various reasons. 3G phones can also display live video and therefore need a good quality image. However the tiny screens are a challenge for web designers to develop usable images and content. TV content can also be downloaded and viewed or listened to on a mobile phone.
PDAs. They generally have a larger screen than mobile phones and can be used to run word processor and spreadsheets software. They usually have touch screens and virtual keyboards operated by a stylus.
PRINTERS
Many computer processes need information output in a paper-based format.
Laser printers – fast and good quality documents are produced. Mostly used by businesses.
Inkjet printers – They are cheaper to buy (though can be expensive to run)and are very popular, especially for home users. They tend to be a bit slower. They can be used to produce photographs using special paper.
Multi-function printers – These include a built-in scanner and can scan, photocopy, print and sometimes fax too. They usually use inkjet technology.
Dot-matrix printers – They use dot-matrix technology to print on multipart stationary e.eg continuous paper. They can be found in industry where high volume prints are needed and quality is not so important. They are much less common nowadays.
Plotters. These are used to produce large sized technical drawings e.g by engineers and architects. They are expensive and only used for specialist purposes.
Professional printers. A professional printing company can be used to print large professional quality documents and saves office staff time and wear and tear on office printers
Photo printing. Special printers can be used to print images from digital cameras.
SPEAKERS
They produce audio/sound output. They can be external and plugged into computers. The quality and level of volume are variable.Most laptops and monitors these days have built-in speakers. Satellite navigation systems also have built-in speakers. Built-in speakers tend to be low volume and quality. Headphones can be plugged into a computer or MPS player to hear sound that nobody else in the room can hear. Prolonged use of headphones could cause hearing damage, unless the volume is kept low.
SPECIAL PURPOSE OUTPUT DEVICES
Output devices for people with disabilities. Large monitors which can display large font sizes and magnified images would be useful for partially-sighted people. Text can be read out as it is typed.
Out of all these output devices the inkjet printer is my favourite because it can print out photographs in colour, which enables you to get the most out of your favourite memories.
