Keyboards
QWERTY keyboards are the most common type of keyboard. The name comes from the first row of letters on the keyboard. Each key is connected to a switch which closes when the key is pressed, which sends a signal to the CPU. The CPU then changes this code into an ASCII code, which is the code that is used to represent characters on the computer keyboard. However, keying in can be slow unless the user has been trained or knows how to type. A QWERTY keyboard was used in the design of the Howard Health Centre website.
Concept keyboards are another type of keyboard. They are mostly found in shops and restaurants. Each switch has a symbol, representing a piece of data and is used if you want to key in similar information over and over again. They are quicker, if you know how to use them, and are less tiring to use. However, you do have to get used to them and they are more limited, so they are not as popular as the standard QWERTY keyboard. This is an example of a concept keyboard you would find in a fast food restaurant, such as McDonalds or Burger King. It makes the assistant at the checkout till’s job a lot easier. So instead of typing in what the customer wants in full, they just have to touch the picture, or word. Then it comes up with the correct price and this information is sent to the kitchen. The kitchen staff then produces the food and send it out. The customer also gets their food quicker because they do not have to wait for the checkout assistant to type out what they want and work out how much it will cost.
Scanner
I could have used a scanner, another input device, to input photos of the health centre for my website, but I chose not to. Scanners are used to scan pictures or text into a computer’s memory. A scanner works similar to a fax machine, light and dark parts of the picture are given different codes. Scanners are useful and pictures can be easily edited after being scanned, however, these bitmap files can be very large and take up a lot of memory. A digital camera works in the same way as a scanner. You take the photo, upload it, then you can edit it.
Microphone
A different input device is a microphone. Microphones convert sound into text or commands for the computer. The can be used to record sound so it can be stored digitally. These are useful because instead of typing, you can just dictate what you want written and can play it back also. However, this takes up a lot of memory.
OUTPUT DEVICES
An output device is a piece of hardware used to show the result of data carried out by the CPU. The result can be shown in many ways. Below are so different output devices.
Visual Display Units (VDUs) or Monitors
A VDU or monitor is the most commonly used output device. They are used when results want to be viewed, but no printout is needed. There are two ways in which monitors are different from one another, size and resolution. Size is measured in inches across the diagonal of the monitor. Most monitors are about 17 inches, but laptops are usually smaller. Resolution is measured by the number of pixels that make up the image on the screen. There are different sizes, the main ones are high (1024x768), medium (800x600) and low (640x480).
There are two main types of monitor, Cathode Ray Tubes and LCDs.
Cathode Ray Tubes are the same screens that are used in televisions. When touched, they do not affect the appearance of the screen (unlike LCDS where the colour changes and the picture is affected on the part that is touched), however, if used for long periods of time, they can be damaging on the eyes.
LCDs, or Liquid Crystal Display screens, are most common in laptops because they are light, and they are the screens that are used in flat screen computers because they are small.
Printers
Printers are used to produce a hard copy of the information on paper. There are three main types of printer, Dot-Matrix printers, Laser printers and Ink-Jet printers.
Dot-matrix printers are also called impact printers and are the cheapest type of printer to buy and operate. They have been almost completely replaced by ink-jet and laser printers. Dot-matrix printers consist of the print head and the ribbon. The print head is a group of pins arranged in a straight line in blocks. Each letter is created by using a set pattern of some of the pins. The ribbon is a long strip of material with ink on one side. The pins push the ribbon onto the paper producing a series of dots.
Above, on the other page, is a pattern for the letter B using 9 pins. The letter will not be that big so from normal reading distance you will not notice that all of the letters are made up of dots. Dot-matrix printers are cheap, but the print quality is poor, they are very slow and can be very noisy.
Laser printers work in a similar way to photocopiers. The data is sent to the printer in complete pages. Laser printers work differently to dot-matrix printers. Laser printers have a very high resolution which means they can print high quality images, and also they are very fast. They can print over 10 pages per minute which makes them much better than dot-matrix printers, which can print only about 100 letters a minute. Laser printers are also extremely quiet, though they are very expensive and because of all the complex equipment inside, they are also expensive to repair.
Ink-jet printers cost less than laser printers and produce better quality print-outs than dot-matrix printers. The print head has lots of nozzles, smaller than a dot-matrix printer so the print resolution is better. Small jets of ink are sprayed through the nozzles. The have good resolution, so they can print good quality documents and they are quite small, so they are ideal for homes or offices with limited space. They are quite, slow however, especially in colour, and although they are cheap to buy, they are expensive to run, as cartridges cost more than laser printer cartridges.
Input and Output devices are essential to a computer system like the Howard Health Centre one. You cannot have one without the other because the computer system just wouldn’t exist.
STORAGE DEVICES
A storage device is any type of computer hardware used to hold or store data or digital information and they come in many different tools.
RAM Memory
RAM is a fast temporary type of memory in which programs and are stored whilst the computer is switched on. For example, when you load a word processing it is loaded into RAM. The contents of the computer's screen are also held in RAM. If the computer loses power, data stored in RAM is lost.
ROM Memory
ROM is memory that cannot be changed by a or user. ROM retains its memory even after the computer is turned off. For example, ROM stores the instructions for the computer to start up when it is turned on again. The operating system is loaded from the hard disk and stored in RAM whilst the machine is being used.
Floppy Disks
The 3.5 inch floppy disk is the most common type of magnetic disk. You can read data from and write data on to the floppy and you can move the data also. They are quite small and thin so they don’t take up much space and they are quite cheap to buy. However, they are usually too small for typical file sizes so to keep a lot of files backed up you will need a lot of floppy disks and this will take up a lot of space.
CD ROM
CD-ROM stands for Compact Disc – read only memory. CDs are optical discs, this means that a laser beam is used to read the data off the disc. CD-R is blank optical disks that you can write data onto with a CD writer.
DVDs use the same principals as CDs but they can hold a lot more data and can hold multimedia material.
Memory Sticks
A memory stick is a small device that can hold a lot of memory. It is similar to a floppy disk as in you can add and remove files from it, but instead of inserting it into the floppy drive, you insert it into a USB port. Memory Sticks are a good idea as they can hold large quantaties of data and are very portable as they are only about the size of a pen.
I used a 1Gb Memory Stick to store my work for this project on. I decided to use this instead of a floppy as it can hold a lot more information and it is smaller and easier to carry around. I also kept my work backed up on my computer at home, just in case I lost my memory stick.
