Input devices

• Input device

  A hardware device that allows a user to enter data into a computer system
• Types of input devices

  • Manual
  • Automatic
• Manual input device

  Devices that need a user to physically enter the data into a computer system
• Manual input devices

  • keyboard, mouse, scanner
• Automatic input device

  Devices that will automatically read data and input it into a computer system
• Automatic input devices

  • sensor, touch screen
• Keyboard

  • Most common and efficient way used for data entry
  • Used as input devices in many electronic items like computers and tablets
  • Connected to the computer using the USB port or wireless connection
  • In tablets and mobile phones, keyboards appear as virtual or a type of touch screen technology
  • Each character pressed is converted into a digital signal which the computer interprets
• Types of keys in keyboard

  • Letter
  • Number
  • Symbol
  • Special
  • Function
  • Arrow
• Keyboards are a relatively slow method of data entry and are also prone to errors, however keyboards are still the easiest way to enter text into a computer
• Frequent use of keyboards can lead to injuries, such as repetitive strain injury (RSI) in the hands and wrists
• Ergonomic keyboards

  • Designed to give more support to the wrists and hands when doing a lot of typing
• How a keyboard is recognised by a computer

  1. There is a membrane or circuit board at the base of the keys

  2. Key is pressed and this completes a circuit

  3. The CPU in the computer can then determine which key has been pressed

  4. The CPU refers to an index file to identify which character the key press represents

  5. Each character on a keyboard has a corresponding ASCII value
• On Screen Keyboard

  • Keys that are displayed on a screen and when pressure is applied to a "key" they will enter the data of that key
  • Created by software rather than being a hardware device
  • Similar to a normal keyboard
  • Also known as virtual keyboard
• Advantages of a keyboard

  • Very simple to use
  • If a person is trained to type fast then inputting data using a keyboard can be very efficient
• Disadvantages of a keyboard

  • It is easy to make a mistake when using a keyboard to input data
  • If a person is not trained to type fast then inputting data using a keyboard can be slow
• Concept keyboard

  • A surface that is flat and has a grid of buttons on it
  • Each button in a concept keyboard can be programmed do a specific task
  • There is a limited amount of data that needs to be entered into a system
• Advantages of a concept keyboard

  • Reduces the training required as they are easy to use
  • Ideal when options/choices are few
  • May speed up data entry
• Disadvantages of a concept keyboard

  • Not suitable for large amount of options/choices
  • Not suitable for all tasks
• How key presses on the keyboard are processed by the computer

  1. When a key is pressed it completes a circuit

  2. The location of the keypress is calculated

  3. Each character has an ASCII / Unicode value

  4. The ASCII / Unicode value has a binary value

  5. The binary can then be processed by the CPU to action the key press
• Mouse

  An input device that is used to control a pointer or a cursor on a screen
• Mouse buttons

  • Left
  • Right
  • Scroll
• Mechanical mouse

  Older style of mouse with a ball in the underside
• Optical mouse

  • Uses an optical laser
  • An example of a pointing device
  • Uses tiny cameras to take 1500 images per second
  • Can work on virtually any surface
  • Uses a red LED in the base and the red light is bounced off the surface and the reflection is picked up by a complementary metal oxide semiconductor (CMOS)
  • The CMOS generates electric pulses to represent the reflected red light and these pulses are sent to a digital signal processor (DSP)
  • The processor can now work out the coordinates of the mouse based on the changing image patterns as it is moved about on the surface
  • The computer can then move the on-screen cursor to the coordinates sent by the mouse
• Benefits of an optical mouse

  • No moving parts, therefore it is more reliable
  • Dirt can't get trapped in any of the mechanical components
  • No need to have any special surfaces
• Benefits of a wired mouse

  • No signal loss since there is a constant signal pathway (wire)
  • Cheaper to operate (no need to buy new batteries or charge batteries)
  • Fewer environmental issues (no need to dispose of old batteries)
• Advantages of a mouse

  • A mouse is very simple to use
  • A mouse lets the user efficiently navigate around a screen
• Disadvantages of a mouse

  • The user needs a flat surface next to the computer to move the mouse around in. If this space is limited it can restrict the use of a mouse
  • If the roller ball gets clogged with dirt, or if dirt covers the optical laser, this can stop a mouse working properly
• Alternative pointing devices

  • Track ball
  • Foot mouse
• Advantages of a track ball

  • Needs little desk space
  • Fine control over the pointer
• Disadvantages of a track ball

  • May take some getting used to
  • Can be integrated into a keyboard
• Scanner

  • Used to scan a physical documents (image, text)
  • Shining light into the surface of the document
  • Light source moves across the document and the reflected light is captured onto a light-sensitive device using mirrors and lenses
  • Captured image is converted into a digital format
• 2D scanner or flatbed scanner

  Scans the whole image automatically
• Handheld scanner

  • Scan for smaller images
  • Scan with light and sensor
  • Manually pushed along the image to scan it
• Applications of 2D scanners

  • Used at airports to read passports
  • Use of OCR technology to produce digital images which represent the passport pages
  • OCR software is able to review these images, select the text part, and then automatically put the text into the correct fields of an existing database
  • It is possible for the text to be stored in an ASCII format
  • The two-dimensional photograph in the passport is scanned and stored as a JPEG image
  • The passenger's face is also photographed using a digital camera
  • The two digital images are compared using face recognition/detection software
• Optical Character Recognition (OCR)

  • A process where text on a scanned document is recognized and converted to digital text (PDF)
  • If the original document was a photograph or image, then the scanned image forms an image file such as JPEG
  • Software can be edited but is not very reliable and can be prone to errors
• Optical Mark Recognition (OMR)

  • A process where scanned marks on a page are automatically converted to inputs (Research Paper, Quantitative Survey)
  • Widely used to automatically mark multiple-choice question papers
  • To avoid the user having to handwrite text (recording the numbers on a lottery ticket)
• Advantages of a scanner

  • Flatbed scanner produce high quality documents
  • Can be edited with software such as graphics creators, photograph editors and word processors
  • Could be attached to an email or included in another digital document
• Disadvantages of a scanner

  • Use a lot of memory space, especially scan for photographs
  • Not likely to be as high quality as the original
  • If the quality of the original document is not very good then the quality of the scanned image is likely to be even worse
• 3D scanner

  • Use a laser or a light source (or sometimes X-rays)
  • Input the geometry of an object and create a model of it (physical model or replica)
  • The scanned images can be used in computer aided design (CAD) or sent to a 3D printer to produce a working model of the scanned image
• Advantages of 3D scanner

  • The technology can scan through clothing and other materials
  • 3D scanning provides accurate 3D computer models