As-level ICT blog by G
Monday, November 22, 2010
Sunday, November 7, 2010
Storage Devices and Media
‘Writing’ data or ‘saving’ data are other ways of saying ‘storing’ data.
‘Reading’ data, ‘retrieving’ data or ‘opening’ a file are ways of saying that we are getting our data back from its storage location.
Backing Storage vs Main Memory
Main Memory
Main memory (sometimes known as internal memory or primary storage) is another name for RAM (and ROM).
Main memory is usually used to store data temporarily. In the case of RAM, it is volatile (this means that when power is switched off all of the data in the memory disappears).
Main memory is used to store data whilst it is being processed by the CPU. Data can be put into memory, and read back from it, very quickly.
Memory is fast to access, but only holds data temporarily...
Backing Storage
Backing storage (sometimes known as secondary storage) is the name for all other data storage devices in a computer: hard-drive, etc.
Backing storage is usually non-volatile, so it is generally used to store data for a long time.
Storage Media & Devices
The device that actually holds the data is known as the storage medium (‘media’ is the plural).
The device that saves data onto the storage medium, or reads data from it, is known as the storage device.
Sometimes the storage medium is a fixed (permanent) part of the storage device, e.g. the magnetic coated discs built into a hard drive
Sometimes the storage medium is removable from the device, e.g. a CD-ROM can be taken out of a CD drive.
Accessing Stored Data
We refer to a collection of data stored in a computer system as a ‘file’. Files are often organised into ‘folders’.
Whenever you click ‘Save’ in an application, burn files to a CD-R, copy music onto your MP3 player, or drag and drop a file onto memory stick, you are using storage devices - devices that can store and retrieve data.
Serial / Sequential Access
A serial (or sequential) access storage device is one that stores files one-by-one in a sequence.
A non-computer serial access device that will be familiar to you is a VHS videotape. Because video is stored on a long piece of tape, when TV shows are recorded onto the tape, they go on one-by-one, in order...
If you want to watch a show that you recorded earlier, you have to rewind / fast-forward through all other shows until you find it.
The shows are only accessible in the same order that you recorded them. This type of one-by-one storage and access is called serial access.
Systems that store things on tape (video, music, computer data, etc.) are always serial access
Direct / Random Access
A direct (or ‘random’) access storage device is one that stores files so that they can be instantly accessed - there is no need to search through other files to get to the one you want.
An example of a direct access device would be a DVD movie. Unlike the VHS videotape movie, you can jump to any scene on a DVD.
All parts of the DVD are directly accessible. This type of file storage is called direct access.
Data Storage Capacity
Some storage media can only store a very limited amount of data, whilst others can store vast amounts...
Data storage capacity is measured in bytes (B).
A thousand bytes is known as a kilobyte (kB)
1,000B = 1kB
A million bytes is known as a megabyte (MB)
1,000,000B = 1MB
A thousand million bytes is called a gigabyte (GB)
1,000,000,000B = 1GB
A million million bytes is called a terabyte (TB)
1,000,000,000,000B = 1TB
Even a very basic storage devices like a floppy disc can storage over a megabyte of data - that's over 1 million letters or numbers!
And modern hard drives can store a terabyte of data or more - that's more words than you could type even if you started now, and typed until your old age!
Data Access Speeds
Some storage devices can access data very quickly, whilst others are extremely slow...
* Note: Modern back-up tapes have very fast access speeds, but only to save/read data sequentially (they are serial access devices). Tapes are very slow if you want to read files out of order, since the tape has to be rewound and fast-forwarded.
Magnetic Storage Devices / Media
Why Magnetic?
Magnetic storage media and devices store data in the form of tiny magnetised dots. These dots are created, read and erased using magnetic fields created by very tiny electromagnets.
In the case of magnetic tape the dots are arranged along the length of a long plastic strip which has been coated with a magnetisable layer (audio and video tapes use a similar technology).
In the case of magnetic discs (e.g. floppy disc or hard-drive), the dots are arranged in circles on the surface of a plastic, metal or glass disc that has a magnetisable coating.
Hard Drives
Hard-drives have a very large storage capacity (up to 1TB). They can be used to store vast amounts of data. Hard-drives are random access devices and can be used to store all types of films, including huge files such as movies. Data access speeds are very fast.
Data is stored inside a hard-drive on rotating metal or glass discs (called ‘platters’).
Fixed Hard Drive
A hard-drive built into the case of a computer is known as ‘fixed’. Almost every computer has a fixed hard-drive.
Fixed hard-drives act as the main backing storage device for almost all computers since they provide almost instant access to files (random access and high access speeds).
Portable Hard Drive
A portable hard-drive is one that is placed into a small case along with some electronics that allow the hard-drive to be accessed using a USB or similar connection.
Portable hard-drives allow very large amounts of data to be transported from computer to computer.
Many portable music players (such as the iPod classic) contain tiny hard-drives. These miniature devices are just not much bigger than a stamp, but can still store over 100MB of data!
Magnetic Tape
Magnetic tape is a large capacity, serial access medium. Because it is a serial access medium, accessing individual files on a tape is slow.
Tapes are used where large amounts of data need to be stored, but where quick access to individual files is not required. A typical use is for data back-up (lots of data, but rarely only accessed in an emergency)
Tapes are also used and in some batch-processing applications (e.g. to hold the list of data that will be processed).
Removeable Media Magnetic Discs
Floppy Disc
A removable, portable, cheap, low-capacity (1.44MB) storage medium. Floppy discs are random access devices used for transfer small amounts of data between computers, or to back-up small files, etc. Access times are slow.
Almost every PC used to have a floppy disc drive. These are obsolete now, having been replaced by higher capacity technology such as CD-ROMs, DVDs and USB memory sticks.
Zip Disc
A removable and portable storage medium, similar in appearance to a floppy disk, but with a much higher capacity (100MB, 250MB or 750MB).
Zip discs are random access devices which were used for data back-up or moving large files between computers.
Another obsolete storage device, zip discs were a popular replacement for floppy discs for a few years, but they never caught on fully before being superseded by cheaper media like CD-ROMs and CD-Rs
Jaz Disc
A removable and portable storage medium based on hard-drive technology, with a large capacity (1GB or 2GB).
Jaz discs are random access devices which were used for data back-up or moving large files between computers.
Discs were expensive to buy and not very reliable.
Like the Zip disc, this system never really caught on and was superseded by far cheaper and more reliable and cheaper technology.
Optical Storage Devices / Media
Why 'Optical'?
Optical storage devices save data as patterns of dots that can be read using light. A laser beam is the usual light source.
The data on the storage medium is read by bouncing the laser beam off the surface of the medium. If the beam hits a dot it is reflected back differently to how it would be if there were no dot. This difference can be detected, so the data can be read.
Dots can be created using the laser beam (for media that is writable such as CD-Rs). The beam is used in a high-power mode to actually mark the surface of the medium, making a dot. This process is known as ‘burning’ data onto a disc.
This is a magnified view of the dots on the surface of a CD.
The different patterns of dots correspond to the data stored on the disc.
Read-Only Optical Discs
Read-only optical discs have data written onto them when they are manufactured. This data cannot be changed.
CD-ROM
Compact Disc - Read-Only Memory (CD-ROM) discs can hold around 800MB of data. The data cannot be altered (non-volatile), so cannot be accidently deleted. CD-ROMs are random-access devices.
CD-ROMs are used to distribute all sorts of data: software (e.g. office applications or games), music, electronic books (e.g. an encyclopaedia with sound and video.)
DVD-ROM
Digital Versatile Disc - Read-Only Memory (DVD-ROM) discs can hold around 4.7GB of data (a dual-layer DVD can hold twice that). DVD-ROMs are random-access devices.
DVD-ROMs are used in the same way as CD-ROMs (see above) but, since they can hold more data, they are also used to store high-quality video.
High Capacity Optical Discs
Blu-Ray
Blu-Ray disks are a recent replacement for DVDs. A Blu-Ray disc can hold 25 - 50GB of data (a dual-layer Blu-Ray disc can hold twice that). Blu-Ray discs are random-access devices.
Blu-Ray discs are used in the same way as DVD-ROMs (see above) but, since they can hold more data, they are also used to store very high-quality, high-definition (HD) video.
The 'Blu' part of Blu-Ray refers to the fact that the laser used to read the disc uses blue light instead of red light. Blue light has a shorter wave-length than red light (used with CDs and DVDs).
Using a blue laser allows more data to be placed closer together on a Blu-Ray disc, than on a DVD or CD, so Blu-Ray has a much higher storage capacity than these older discs.
HD DVD
High-density DVD (HD-DVD) discs can hold around 15GB of data (a dual-layer HD-DVD can hold twice that). HD-DVDs are random-access devices.
HD-DVD discs are used in the same way as DVD-ROMs (see above) but, since they can hold more data, they are also used to store very high-quality, high-definition (HD) video.
The HD-DVD format was launched at the same time as Blu-Ray. For about a year they competed to be the 'next DVD'. For various reasons, Blu-Ray won the fight, and the HD-DVD format has been abandoned.
Recordable Optical Discs
Recordable optical discs can have data written onto them (‘burnt’) by a computer user using a special disc drive (a disc ‘burner’).
CD-R and DVD-R
CD-Recordable (CD-R) and DVD-recordable (DVD-R) discs can have data burnt onto them, but not erased. You can keep adding data until the disc is full, but you cannot remove any data or re-use a full disc.
CD-RW and DVD-RW
CD-ReWritable (CD-RW) and DVD-ReWritable (DVD-RW) discs, unlike CD-Rs and DVD-Rs, can have data burnt onto them and also erased so that the discs can be re-used.
When CD-Rs and DVD-Rs are burnt, the laser makes permanent marks on the silver-coloured metal layer. This is why these discs cannot be erased.
When CD-RWs and DVD-RWs are burnt the laser makes marks on the metal layer, but in a way that can be undone. So these discs can be erased.
DVD-RAM
DVD-Random Access Memory (DVD-RAM) discs are a type of re-writable DVD. They often come in a floppy-disc style case (to protect the disc).
DVD-RAM discs have a similar capacity to a normal DVD, holding 4.7GB of data. DVD-RAM discs are random-access devices.
DVD-RAM discs are used in many camcorders (video recording cameras).
The discs are much higher quality than normal DVD-RWs and can reliably store data for up to 30 years. This means that they are often used for video and data back-up and archiving.
Solid-State Storage Devices
'Solid-State'?
The term ‘solid-state’ essentially means ‘no moving parts’.
Solid-state storage devices are based on electronic circuits with no moving parts (no reels of tape, no spinning discs, no laser beams, etc.)
Solid-state storage devices store data using a special type of memory called flash memory...
Flash Memory
Flash memory is a type of Electronically-Erasable Programmable Read-Only Memory (EEPROM). Flash memory is non-volatile (like ROM) but the data stored in it can also be erased or changed (like RAM).
Flash memory can be found in many data storage devices...
You might wonder why, since flash memory is non-volatile, normal computers don’t use it instead of RAM. If they did we would have computers that you could turn off, turn back on again and no data would be lost – it would be great!
The reason is speed – saving data to flash memory is very slow compared to saving it to RAM. If a computer were to use flash memory as a replacement for RAM it would run very slowly.
However some portable computers are starting to use flash memory (in the form of solid-state ‘discs’ as a replacement for hard-drives. No moving parts mean less to go wrong and longer battery life.
USB Memory Sticks
Memory sticks (or ‘thumb-drives’) have made many other forms of portable storage almost obsolete (why burn a CD or DVD when you can more easily copy your files onto a memory stick?).
Memory sticks are non-volatile, random-access storage devices.
Each of these small devices has some flash memory connected to a USB interface. Plug it into your computer and it appears as a drive. You can then add files, erase files, etc. You can use it to move any type of file between computers.
Flash memory used to be very expensive, but in recent years it has become much cheaper and you can now buy a 16GB memory stick for just a few dollars.
Memory Cards
Many of our digital devices (cameras, mobile phones, MP3 players, etc.) require compact, non-volatile data storage. Flash memory cards provide this and come in a variety of shapes and sizes.
One of the most common formats used by digital cameras is the SD Card. The cards store the digital images taken by the camera.
Mobile phones contain a Subscriber Identity Module (SIM) card that contains the phone’s number, the phonebook numbers, text messages, etc.
Many phones also have extra memory cards to store music, video, photos, etc. (e.g Tiny Micro-SD cards).
Smart Cards
Many credit cards (e.g. ‘chip-and-pin’ cards), door entry cards, satellite TV cards, etc. have replaced the very limited storage of the magnetic strip (the dark strip on the back of older cards) with flash memory. This is more reliable and has a much larger storage capacity.
Cards with flash memory are called smart cards.
Output AIO
Audio/ Visual
CRT Monitor
A monitor displays text and image data passed to it by the computer.
A cathode-ray tube (CRT) monitor is the type that has been around for years and is large and boxy.
CRT monitors are heavy and they take up a lot of desk space. They have largely been replaced by flat-screen monitors. However some are still used in the design industry since the colour accuracy and brightness of CRT monitors is excellent, and designers need to see true-to-life colours.
Also, CRT monitors are generally cheaper than flat-screen monitors.
Flat-Screen Monitor (TFT or LCD)
Over the past few years, as they have come down in price, flat-screen displays have replaced CRT monitors.
Flat-screen monitors are light in weight and they take up very little desk space.
Modern flat-screen monitors have a picture quality that is as good as CRT monitors.
TFT and LCD are two of the technologies used in flat-screen monitors: TFT is Thin-Film-Transistor, and LCD is Liquid-Crystal Display.
Another technology that may replace these is OLED, or Organic Light-Emitting Diodes.
Digital / Multimedia Projector
Digital projectors are used in situations when a very large viewing area is required, for example during presentations, for advertising, or in your home for watching movies.
A projector connects to a computer, a DVD player or a satellite receiver just like a ordinary monitor.
The image is produced inside the device and then projected out through a large lens, using a powerful light source.
Loudspeaker
If you want to hear music or sounds from your computer, you will have to attach loudspeakers. They convert electrical signals into sound waves.
Loudspeakers are essential for applications such as music editing, video conferencing, watching movies, etc.
Printing and Plotting
If you want a physical copy of some data on paper (a ‘hardcopy’) you will need a device that can make marks on paper - a printer or a plotter...
Dot Matrix Printer
A dot-matrix printer is named after the pattern (a grid or ‘matrix’) of dots used when creating the paper printout.
These dots are formed by tiny pins in the printer’s print head that hit an inked ribbon against the paper leaving marks. As the print head moves along it leaves a pattern of dots behind it which can form letters, images, etc.
Dot matrix printers often use continuous stationary: long, continuous strips of paper (rather than separate sheets of A4 like ink-jet and laser printers use).
After printing, the printout is torn off from the long strip.
Dot-matrix print quality is poor, the printers are noisy, and there are much better printing systems available today. However, the dot-matrix printers are still used in certain situations:
Since the pins actually hit the paper, several ‘carbon-copies’ can be printed in one go. An example of this is airline tickets which have several duplicate pages, all printed in one go
The print mechanism is very cheap, and the inked ribbons last for a long time. So, where cheap, low-quality printouts are required, dot-matrix printers are used. An example is shop receipts.
InkJet Printer
Cheap, high-quality, full-colour printing became available during the 1980s due to the development of ink-jet printers.
These printers have a similar print-head mechanism to a dot-matrix printer. The print-head passes left and right across the paper. However, instead of using pins to hit inky marks onto the paper, the ink-jet squirts tiny droplets of ink onto the surface of the paper. Several coloured inks can be used to produce full-colour printouts.
The droplets of ink come from tiny holes (the jets) which are less than the width of a human hair in size. Each droplet creates a tiny dot on the paper. Since the dots are so small, the quality of the printout is excellent (1200 dots-per-inch are possible). This is perfect for photographs.
Ink-jet printers are very quiet in use. Since they have so few moving parts they are also cheap to manufacture and thus cheap to purchase. However, the ink is very expensive to buy (this is how the printer companies make their profits!) so the printers are expensive to use.
This is a close-up of the tiny ink dots on a page. The dots combine to form light and dark areas.
Laser Printer
Laser printers are very complex devices, and thus expensive to buy. However they are very cheap to use. This is because they produce marks on paper using a fine dust called toner which is relatively cheap to buy. A single toner cartridge will often last for 5,000-10,000 pages of printing.
The laser printer uses a complex system, involving a laser, to make the toner stick to the required parts of the paper. (This system is very different to a dot-matrix or ink-jet, and you don’t need to know the details.)
The laser and toner system allows very fast printing compared to other printers (just a few seconds per page).
Laser printers are very common in offices since they print very quickly, are cheap to use and are reasonably quiet.
Plotter
Plotters create hard-copy in a very different way to printers. Instead of building up text and images from tiny dots, plotters draw on the paper using a pen.
The pens are held in an arm which can lift the pen up or down, and which can move across the paper. The arm and pen create a drawing just like a human could, but much more accurately and more quickly.
Different coloured pens can be used to produce coloured line drawings.
Plotters are often used by designers and architects since they work with huge pieces of paper, far bigger than anything a normal printer could work with...
CONTROL ACTUATORS
A normal PC has no way of affecting what is happening around it. It can’t turn on the lights, or make the room hotter. How do we change what is happening around us? We use our muscles to move things, press things, lift things, etc. (and we can also make sound using our voice).
A normal PC has no muscles, but we can give it some. In fact we can give it the ability to do lots of things by connecting a range of actuators to it…
An actuator is a device, controlled by a computer, that can affect the real-world.
Examples of actuators, and what they can do are... Actuator What it Can Do
Light bulb or LED Creates light
Heater Increases temperature
Cooling Unit Decreases temperature
Motor Spins things around
Pump Pushes water / air through pipes
Buzzer / Bell / Siren Creates noise
Actuators are used extensively in computer control systems.
Note: some of these devices require an analogue signal to operate them. This means that they need to be connected to the computer using a digital-to-analogue convertor (DAC)
Motor
Motors can provide movement.
For example, the motor in a washing machine can be controlled by a computer - it is switched on when the clothes are loaded for washing and switched off at the end of the wash.
Computer-controlled motors are also found in microwave ovens (to turn the food around) and air-conditioning units (to drive the fan)
Pumps
A pump is basically a motor attached to a device that can push water or air along pipes. When the motor is switched on, water or air flows along the pipes to places it is needed.
Pumps are used in many places: as part of watering systems in greenhouses, in factories, etc.
Buzzer
Buzzers can provide noise.
For example, the buzzer in a microwave oven can be switched on by the controlling computer when the food is cooked.
Louder noises can be made using a siren or an electric bell, for example in a burglar alarm system.
Lights
Lightbulbs and LEDs can by used to provide light, or to indicate something.
For example, computer-controlled lights are used in traffic lights, at music concerts. Lights are used in car dashboards to show if the any of the systems in the car have problems.
Heaters / Coolers
Heaters can provide heat, and coolers can cool things down.
A computer can switch a heater on or off when needed to keep a room or a greenhouse at the correct temperature during winter.
A computer can switch a cooling unit on or off to keep a room at the correct temperature during hot weather, or to keep food fresh.
Everything else for input
Many plastic cards, such as credit cards, have a strip of material that can be magnetised on the back. Data can be stored here in the form of magnetised dots.
Usually the data stored on this strip in the same data shown on the front of the card (e.g. the credit card number, expiry date and customer name).
The stripe allows this data to be input to a computer system faster and more accurately than by typing it in.
A magnetic strip/stripe reader is used to read the data from the stripe. This is usually done by ‘swiping’ the card through a slot on the reader.
Smart Card / 'Chip' Reader
Modern credit cards and ID cards don’t use a magnetic strip. Instead they have a tiny ‘chip’ of computer memory embedded inside them. (These cards are often referred to as smart cards.)
Data can be stored in this memory and read back using a ‘chip’ reader.
A card is inserted into the reader where metal contacts connect to the metal pads on the front face of the card. The reader can then access the memory chip and the data stored on it.
Smart cards can store much more data than magnetic strip cards, e.g. an ID smart card would store not only the owner’s name and card number, but might also have a digital image of the person.
Satellite TV decoders use smart cards to store which channels a user has paid for. The data is encrypted so that it is not easy to alter (you can’t add new channels without paying!)
Many types of card use this system: id cards, phone cards, credit cards, door security cards, etc.
Reading Text/ Codes
All data could be input to a computer using a keyboard, but this would often be a slow process, and mistakes would be made.
Sometimes speed and accuracy is required...
MICR Reader
Magnetic Ink Character Recognition (MICR) is a technology that allows details from bank cheques to be read into a computer quickly and accurately.
The cheque number and bank account number are printed at the bottom of each bank cheque in special magnetic ink using a special font. These numbers can be detected by an MICR reader.
OMR Scanner
Optical Mark Recognition (OMR) is a technology that allows the data from a multiple-choice type form to be read quickly and accurately into a computer.
Special OMR forms are used which have spaces that can be coloured in (usually using a pencil). These marks can then be detected by an OMR scanner.
Common uses of OMR are multiple-choice exam answer sheets and lottery number forms.
OCR Scanner
Optical Character Recognition (OCR) is a software technology that can convert images of text into an actual text file that can then be edited, e.g. using word-processing software). The result is just as if the text had been typed in by hand.
OCR is typically used after a page of a book has been scanned. The scanned image of the page is then analysed by the OCR software which looks for recognisable letter shapes and generates a matching text file.
Advanced OCR software can recognise normal handwriting as well as printed text - this is usually called handwriting recognition.
Barcode Reader / Scanner
A barcode is simply a numeric code represented as a series of lines.
These lines can be read by a barcode reader/scanner.
The most common use of barcode readers is at Point-of-Sale (POS) in a shop. The code for each item to be purchased needs to be entered into the computer. Reading the barcode is far quicker and more accurate than typing in each code using a keypad.
Barcode can be found on many other items that have numeric codes which have to be read quickly and accurately - for example ID cards.
SENSORS
A normal PC has no way of knowing what is happening in the real world around it. It doesn’t know if it is light or dark, hot or cold, quiet or noisy. How do we know what is happening around us? We use our eyes, our ears, our mouth, our nose and our skin - our senses.
A normal PC has no senses, but we can give it some: We can connect sensors to it...
A sensor is a device that converts a real-world property (e.g. temperature) into data that a computer can process.
Examples of sensors and the properties they detect are... Sensor What it Detects
Temperature Temperature
Light Light / dark
Pressure Pressure (e.g. someone standing on it)
Moisture Dampness / dryness
Water-level How full / empty a container is
Movement Movement nearby
Proximity How close / far something is
Switch or button If something is touching / pressing it
A sensor measures a specific property data and sends a signal to the computer. Usually this is an analogue signal so it needs to be converted into digital data for the computer to process. This is done using by an Analogue-to-Digital Converter (ADC).
Sensors are used extensively in monitoring / measuring / data logging systems, and also in computer control systems.
Audio / Visual Devices
A device that ‘scans’ images, book pages, etc.
Scanning is basically taking a close-up photograph (just very slowly and with great detail). The scanned image data is passed to the computer.
The most common type of scanner is the flat-bed scanner which has a glass plate on which the item to be scanned is placed. The item is illuminated and an image of it is captured by a moving scan ‘head’.
Scanned images can be further processed once inside the computer, e.g. OCR of printed text.
Digital Camera
A device that captures digital photographs.
Most digital cameras do not directly input data into a computer - they store photographs on memory cards. The photographs can later be transferred to a computer.
A modern digital camera can capture 10 Megapixels or more per photograph - that’s 10,000,000 coloured dots (pixels) in every photo!
Video Camera
A device that captures moving images, or video.
Like a digital camera, most video cameras do not directly input data into a computer – the captured movies are stored on video-tape or memory cards and later transferred to a computer.
However, there are some situations where video cameras do feed video data directly into a computer: television production and video-conferencing. In these situations the video data is required in real-time.
Web Cam
This is a very basic video camera used to feed live video into a computer.
The video data from a web cam is low quality compared to a full video camera. However it is good enough for web chats (e.g. using a messenger application such as MSN Messenger or Skype).
Usually a web cam is clipped to the top of a monitor, but many laptops now have web cams built into the edge of the screen.
Microphone
An input device that converts sound into a signal that can be fed into a computer.
The signal from a microphone is usually analogue so, before it can be processed by a computer, it must be converted into digital data. An Analogue-to-Digital Convertor (ADC) is used for this (usually built into the computer’s sound card)
Many headphones now come with microphones to allow them to be used with chat and phone applications
Tuesday, November 2, 2010
Pointing devices
These devices are used to move an on-screen pointer or cursor (usually an arrow). They are commonly used with graphical user interfaces (GUIs) 
Often used to control the pointer in a GUI.
Usually used to control the pointer in a GUI.
It can be used to control a GUI pointer.
Tracker balls are often used by people with limited movement (disabled) or by the very young since they are easier to use than a mouse. Touch ScreenA touch screen is an alternative to a separate pointing device. With a touch screen the user selects items on the screen by touching the surface. This makes touch screen systems very intuitive and simple to use.
Often used for information terminals in public places e.g. libraries or museums where mice or keyboards may be stolen or damaged.
Keyboards
A keyboard is simply a set of buttons. Each button has a symbol
assigned. Used to enter numeric data into computers such as those in ATMs.
Most computer keyboards have a numeric keypad on the right side, and most mobile phones (there are also computers) have a one for entering phone numbers, etc. PIN PadThis is a device with a numeric keypad used to enter a person’s Personal Identity Number (PIN) e.g. when paying with a credit card.
PIN pads are also found on electronic door locks – you enter a PIN to unlock the door.
Input and Output Devices
a. identify the following input devices:
o keyboards,
o numeric keypads,
o pointing devices (including mouse, touch pad and tracker ball),
o remote controls,
o joysticks,
o touch screens,
o graphics tablet,
o magnetic stripe readers,
o chip readers,
o PIN pads,
o digital cameras,
o video cameras,
o web cams,
o scanners,
o microphones,
o sensors,
o MICR,
o OMR,
o OCR,
o barcode readers,
o light pens;
b. identify suitable uses of the input devices stating the advantages and disadvantages of each;
c. identify the following output devices:
o monitors (CRT, TFT),
o printers (laser, ink jet and dot matrix),
o plotters,
o speakers,
o control devices (motors, buzzers, lights, heaters);
d. identify suitable uses of the output devices stating the advantages and disadvantages of each.