The most widely used input device is a keyboard. This is a set of keys used to operate a PC. Numeric keyboards only have keys to input numbers and few special characters. A QWERTY keyboard may have a numeric keyboard built into the right hand side.
- Keyboards are almost always available as an input device. They are widely used at work.
- Many people know how to use a QWERTY keyboard, so help is usually available.
- To use a keyboard efficiently, you need to know the layout and be able to touch-type.
The mouse is the most widely used pointing device. Some have the ball underneath that moves when you move the mouse, resulting in a similar movement of the pointer on the screen. A optical mouse detects movement using light instead of a ball.
A tracker ball is like an upside-down mouse. The ball is on the top of the device and you move it with your thumb.
A joystick is a lever that gives you similar control to a mouse but its behaviour is slightly different. Joystick can be used separately or can be built into a gamepad, where there are often two simple joysticks, one for each thumb.
Graphics tablet or a graphics pad is a flat rectangular pad between 6 and 20 inches wide. It works with a stylus which you move along the surface of the pad to produce drawings in the computer. There are several types of stylus. One, the puck, is small rounded device with cross-hairs for tracing lines accurately and with a number of buttons. The stylus can also be pen-shaped. A graphics tablet is used mainly for computer-aided design and drawing.
A scanner reads printed data into the computer. A number of different devices are referred to as scanners:
- A hand-held scanner reads the image while being dragged over it.
- In the case of a flatbed scanner, the image is laid flat on the scanner’s surface, and is captured in a similar manner to that of a photocopier.
- A sheet-fed scanner feeds the image in through rollers. The scanner reads the image as the paper goes through. The image must be printed on flexible sheet of paper.
- Scanners quickly convert printed images on paper to electronic form.
- The accuracy of the data input is unlikely to be verified.
Digital cameras store pictures on a memory card in a format suitable for saying and displaying on a computer. Pictures can be transferred from the camera to the computer where they can be edited and enhanced in graphics software or viewed on screen. The pictures can be transferred to a computer directly by connecting the camera to the computer, or the memory card can be removed and read using a memory card reader, which may be built into the computer or connected to it. Television sets can also have memory card readers built in or connected so that several people can view the pictures together on a large screen. The picture made by digital camera is formed by a quantity of very small dots of different colours, merging to form a picture. The picture quality is related to the density of the dots making the picture, the accurate placement of the dots and correctness of the colours being displayed. Thus an eight mega-pixel camera uses eight million dots to form a picture and so would produce better output than a two mega pixel camera. A digital video camera or camcorder has similar functions to a digital camera but records moving images with sound. Camcorders can save recordings on memory card but may also use DVD, miniDV tape or a built-in hard disk.
A webcam is a type of digital video camera where the image captured is viewed using a computer. The computer connects to the webcam over the Web and the image is displayed on the computer screen. This has a variety of different uses:
- You could see if the weather is suitable for skiing by viewing the webcam in the mountains above Grindelwald in Switzerland.
- You could install a webcam at home for security and view this when you are out at work.
- You could attach a webcam to your computer and contact a friend who has a webcam so that you could both see each other while you are talking.
- You could set up a webcam in a classroom and listen to a teacher from another school. This might be useful if you were learning to speak English and could not find a teacher locally.
- Photos and videos can be recorded in a digital form that can be saved on computer. This makes backup easier, more reliable and more extensive.
- Digital photos and video can be displayed on a wide variety of devices,
- Digital phots and videos can be sent by email.
- Digital video can be broadcast over the Internet so that TV programmes can be available on demand. Disadvantages of webcams:
- Users tend to have more photos and longer videos and this creates a need for more backing storage.
- High-quality photos and videos can be in very large files. When these are sent by email or broadcast over the Internet, this uses bandwidth and slows down the network.
Microphone is a device used to record sound, to give voice commands and for voice communication over the Internet.
A touch screen is a two way user interface. It is both an input and output device. You can interact with the computer by touching pictures or words on the screen. Touch screens are widely used with tablet PCs, PDAs and smart phones.
OMR technology is used to interpret pencil marks on a piece of paper. An OMR reader can recognize the position of a mark or set of marks on paper, because the mark is darker than an unmarked area. The computer then records the mark’s position and can analyse it to determine the meaning of the data. Marks made on this kind of form must be very clear or they may not be properly recognized.
- There is no requirement to type in the information written on the paper form. Because of this, input is faster and less expensive.
- The person who fills in the form is responsible for the accuracy of the information on it.
- OMR forms must be printed very accurately because the position of the mark on the paper affects the accuracy of the input. Because of this, printing costs more.
- Verification checks on the input are unlikely to be carried out, so mistakes inputting the data are less likely to be detected.
OCR is the identification of printed or written text characters by a computer. Printed text is scanned and input to the computer, which attempts to recognize the characters in it. These are then stored as text that can be word-processed. OCR can also be used to read handwriting. OCR software is often included when you purchase a scanner, so that any office with a scanner has OCR capabilities. A similar process of character recognition is used to interpret handwriting on the screen of a PDA or tablet computer. PDAs and tablet computers have touch-screen of a PDA or tablet computer. PDAs and tablet computers have touch-sensitive screens that accept handwriting as input and have character recognition software that can convert it to text characters that can be word processed. Advantages:
- Text printed on paper can be converted to electronic form and edited. This is especially useful for creating electronic versions of books printed before computers were available.
- Character recognition is not always accurate and the electronic text has to be checked carefully.
A bar code scanner or bar code reader reads a pattern of bars representing the code number of the item on which it is printed. The bar code scanner usually passes a small laser beam over the pattern and reads in the pattern of reflected light. Bar code scanners may be hand-held, but some are built into the surface of a supermarket checkout counter.
A biometric scanner is a pattern recognition which makes a personal identification based on a person’s unique physical characteristics. Biometric scanners can use face recognition, fingerprint matching, iris and retinal scans, voice recognition and hand geometry. Biometric scanners can be built into mobile phones, desktop and laptop computers, and smart cards. They can be used to control entry to buildings and can even replace keys in cars.
- There is no need to remember to carry personal identification.
- The person has to be present. This makes identification theft and fraud much less likely.
- Identification using biometric scanners is not yet sufficiently accurate. Permitted users will not be recognized at times, and blocked users will sometimes be permitted.
A magnetic stripe card reader reads information from a magnetic strip on the surface of a plastic card when it is swiped through the reader. Magnetic stripe cards are also used as bank or credit cards. In addition to being able to read the magnetic stripe, some devices can also write information to it. The stripe can store a permanent value, such as an account number, or a value that could change, such as the amount of cash you are allowed to withdraw from a cash point.
- They are often used as a form of identification that is small and light and can be carried all the times.
- The data recorded on the magnetic stripe is in electronic form and can be input directly into a computer.
- The data recorded on the magnetic stripe can be affected by electromagnetic radiation, such as that from televisions and computers.
- The data recorded on the magnetic stripe can be copied or deleted. This is an opportunity for determined criminals to commit identity theft and fraud.
A smart card or Chip and PIN is similar to a magnetic stripe card but has a microprocessor chip embedded in it. The chip can do some processing, as well as storing information. Special devices can communicate with the chip to read and write information on the card. Security features can be programmed into the chip. Bank and credit cards used to be magnetic stripe cards but are now more usually smart cards. These cards can be used to withdraw cash at a cash point. Cash points are specialized computer terminals with a small screen numeric keyboard and smart card reader. The customer puts their card in the reader and is prompted to enter their four-digit PIN. If the pin entered on the keyboard matches the PIN read from the cards the customer can proceed: if not, the card is either confiscated or returned to the customer.
- Often used as form of identification that is small and light and can be carried at all times.
- The data recorded on the chip is in electronic form and can be input directly into a computer.
- The data recorded on the chip is more secure than data recorded on a magnetic stripe.
- The data recorded on the chip can be updated during transactions.
- The data recorded on the chip can be affected by electromagnetic radiation.
- The data recorded on the chip can be copied or edited by very determined criminals used for fraud.
Sensors are used to input data about the environment into a computer. There are many types of sensors. They are available in many different shapes and sizes and they have a wide variety of uses. For example, sensors can be used to record light intensity, temperature and pressure. Sensors usually produce a low-voltage which must be converted to a digital signal for the computer using an analogue-to-digital converter (ADC).
- Sensors can be placed in dangerous locations where people would be hurt.
- Sensors can continuously and reliably record data whereas to organize this using people could be much more unreliable and expensive.
- Sensors can record data that people do not sense or do not sense accurately, such as humidity.
- The data recorded by sensors can automatically record in a form that can be processed by a computer.
- Data can be collected by a central computer from sensors in remote locations. People do not need to travel and this saves time and allows data to be collected more frequently.
- Sensors cannot interpret the data.
- Sensors detect a very restricted range of the different types of data.