Output devices and techniques - Sample Essay
For this assignment we have to produce a report on the types of hardware and software requirements, and their purposes, for an IT system. In the context of this essay I have decided that bullet point form along with brief descriptions and graphics is the best way to present this assignment. 6 STAGE MODEL Shown above is the six-stage model, showing the processes undertaken by a computer system. Below is what each of my pictures represents: Mouse: Input Device The Tower: Central Processing Unit Monitor: Output Device Floppy Disk: Backing Store.
Head: Main Memory Telephone: Communications Devices e. g. Internet Input Devices and Techniques ‘Input devices are the means whereby computers can accept data or instructions’ (Heathcott P M, 2000, p 159) Keyboard: The keyboard is the most commonly used of all input devices. It can be used for a various number of tasks, form entering programs, to typing documents using a word processor, or entering a persons personal details etc. Mouse: The mouse and its variants such as the trackball is well known with all PC users.
Scanner: A scanner can be used to scan graphical images and photographs, and software can then be used to edit or touch up the images. Scanners can also be used to read typed or hand-writtten documents and this can then be interpreted by using OCR software, which can then export it to a word processor or data file. Scanners can also be used to input large volumes of data on pre-printed forms such as credit card payments, where the customers account number and amount paid are printed at the bottom of the payment slip. Web Cam: This transfers images onto the screen.
In can be used via the internet for video conferencing or you can even pre-record messages and send them via E-mail. Bar Code Reader: Bar codes appear on almost everything we buy, whether it is a new CD or a tin of bins. The pattern of thick thin lines represents the 13 – digit number underneath the bar code. There are four main pieces of information on a bar code. The first few two or three digits represent in which country the product was registered. The next five digits represent the manufacturer’s code. The second group of five numbers represents the product and package size.
The last digit is a check digit, which is calculated from the other digits in the code and ensures that the barcode is keyed in or read correctly. A very similar process to that used in the ASCII code where the spare digit is used as the parity. A Product Bar Code Light Pen: A light pen is a device which incorporates a light sensor so that when it is held close to a screen over a character or part of a graphic, the object is detected and can be moved to create or modify graphics. Microphone: An input devise for sound recording.
OMR (Optical Mark Recognition): An Optical Mark Reader can detect marks made in present positions on a form. The most common example of this is the lottery. It is also widely used for marking, multiple choice exams and market research questionnaires. OCR (Optical Character Recognition): Light is emitted, bounced back and then received. This is how the OCR reads its characters. The light emitted is in different resolutions depending on the character. OCR is used widely in services such as gas and electricity etc. MICR (Magnetic Ink Character Recognition): All banks use MICR for processing cheques.
Along the bottom of a cheque the banks sort code, customer account number and cheque number are encoded in special characters in magnetic ink. The amount of the cheque is encoded in magnetic ink when it is handed in at the bank. The cheques can then be processed by MICR devices that read, sort and store the data on disk. MICR has several advantages for processing cheques: 1. It is hard to forge the characters 2. The characters can be read even if the cheque is crumpled, dirty or smudged 3. The characters are readable by humans, unlike bar codes The disadvantage of MICR though is the expense.
This is why you don’t find many other examples of it being used. Swipe Cards: Swipe cards are operated by using a magnetic strip. They are used in credit cards, debit cards, railway tickets, phone cards and many others. The magnetic strip can be encoded with upto 220 characters of data and other 83% of adults in Britain own at least one card. Unfortunately because there are only 220 characters of data this makes the cards very easy to copy, which is why the strips will eventually, disappear and be replaced by a chip, which is almost impossible to fake. Something slightly similar to the smart card.
Smart Cards: Smart cards are of a similar appearance to that of the swipe cards, but instead of using the magnetic strip they contain a small 1-millimeter square microprocessor which is stored in the centre of the card. This is then protected by a small gold electrical contact the card can still read information through this. Unlike the swipe card the smart cards can hold millions of characters of data. In the future banks hope to replace all the swipe cards with a ‘Super card’ which will also be able to be used to pay for smaller goods such as milk and newspapers without the need to carry cash.
This card will almost be unbreakable. In Belgium they already have a similar system working to this it is called the ‘Proton Card’, which incorporates the use of both magnetic strip and a microprocessor chip for bank withdrawals and payments of small goods. The Smart Card Touch Sensitive Screens: A touch sensitive screen allows the user to touch an area of the screen rather than having to type the data on a keyboard. They are widely used in tourist centres, where tourists can look up various local facilities and entertainment’s, in fast food stores such as McDonald’s for entering customer orders, in manufacturing, and also bars.
Digitisers: A digitiser can draw quality illustrations. It has a flat rectangular slab onto which a stylus (anything that terminates in a point) is placed. Output Devices and Techniques ‘The ultimate aim of the computer is to produce useful information, the information that is produced by the computer is in binary digits, we therefore need devices to translate these into a form we can use’ (Corbitt T, 1990, p 11) VDU: (Visual Display Unit) The VDU is similar in appearance to the television receiver, an alternative name is the monitor. VDUs have better resolution than TVs and therefore are better for graphical work.
It has its own fixed amount of RAM (Random Access Memory) associated with it to store the image being displayed on the screen. So the more RAM it has the better the resolution displayed on the screen. The number of pixels used to represent a full-screen image determines the resolution. Example: If 1 bit represents each pixel then two colours can be displayed, so to display 256 colours you would need 8 bits (1byte) It is usually possible to adjust both the resolution and the number colours – if you select a high resolution you won’t be able to have as many colours because of the memory available on the VDU.
Printers The results of processing are usually required in printed form. Printers come in all shapes and sizes, there are two main categories of printers: Impact Printers which transfer the image on to the paper by applying pressure against a ribbon onto the paper, this transfers ink form the ribbon to the paper forming the image Non-impact Printers which produce the image on the paper without any contact. Impact Printers Dot-matrix: The characters on this are formed by dots. The print head contains a number of needles, the more there are of these the better the quality of print.
A head with nine needles would take seven horizontal movements to print a character, this printer would be said to have a seven-by-nine-character matrix. In the latest type near letter quality is produced by double printing. The line of type is printed, the head moves back to the beginning of the line, moves down fractionally and then prints the line a second time. This doubles the time taken to print a document. To overcome this more expensive models use twice the number of needles and near letter quality can be achieved with one pass of the head.
The dot-matrix can also print out graphics and pictures of a basic quality. Dot-matrix printers, which can print in colour, are available, these use a ribbon which contains red, green and blue. Coloured output is obtained by repeated printing, repositioning of the paper, print head and ribbon. The dot-matrix can print between 30 and 200 characters per second (cps). Daisy-wheel printers: The print head consists of flexible arms extending from a centre hub, the characters are at the tips of the arms. When printing the hub revolves bringing the required character next to the ribbon.
Some daisy-wheel printers are bi-directional and the print head can turn in either direction so that quickest possible print time is achieved. The print can be changed so that different font styles can be used. Daisy wheel printers are unable to print graphics unlike the dot-matrix. It is capable of speed ranges 12 to 55 cps. Non-impact printers Thermal printers: These use specially treated paper, which is affected by heat generated by the print head as it passes across the paper. The main advantages are that they are silent and fast, printing 30-120 cps.
Disadvantages are that the paper is expensive and that the printed image degrades in time. Ink-jet printer: With this type of printer the characters are formed on the paper by spraying it with a stream of ink dots. They are fast, printing 150-270 cps and almost soundless, the quality of print is very good. A Canon Bubble Jet Printer BJC7000 Plotters: Plotters are used to produce drawings, diagrams and other types of graphical output. There are two varieties in use, the flatbed plotter which is used where accuracy is important and the drum plotter which is used for business applications.
The flatbed type is fixed while the pen moves over the top of the device while the axis moves up and down, whilst the drum variety uses continuous stationery. In both types the pens, under the program control, are moved to the down position, the movement of the pens is then controlled to draw the image. There are from one to six pens, which can be used to output different colours. There is also the less commonly known graph plotter. This is most commonly seen in use for lie detector tests. COM: (Computer Output on Microfilm) The problem of storing information on paper can be considerable in a large business.
One way to solve this is to have output from the computer photographed as microscopic images directly onto microfilm. Two methods of storage are used, one put the information onto a roll of 16mm film while the other uses microfiche. Microfiche can store upto 100 pages of A4 on a single piece, to see it you must have a microfiche reader. The most recent examples of this being used is in libraries and in garages for checking car parts. Data can be stored onto microfilm directly from the computer or off line using magnetic tape as an intermediary store.
Voice output: The output of the computer can be given in spoken form by using voice synthesisers to transform words stored in the computer into human speech, this is great for disabled people who cannot speak as it allows them to communicate. The user can hear through a loudspeaker. Secondary device techniques A permanent, non-volatile form of storage is required by all computer systems to save software and data files. Magnetic tape, magnetic disks, CD-ROM (Compact Disk Read Only Memory), and microfilm are all examples of what is known as secondary storage.