Key Board

1
Key Board

• The keyboard is the most common device used to
  input data into a computer system.
• The keyboard operates through a grid of circuits
  so that when a key is pressed, the key comes into
  contact with the circuit, causing an electric
  current to be generated through the circuits.
  This is detected and a signal is sent to the main
  system unit, advising that the key has been
  pressed.
• The standard 102-key keyboard incorporates 12
  function keys, cursor control keys and a numeric
  keypad. The function keys are provided so that a
  computer can quickly access commands, for
  example, to save a document. The cursor control
  keys, which include up, down, left and right
  arrows, govern the movement of the cursor on the
  screen. The numeric keypad is particularly
  useful if large amounts of numeric data need to
  be entered

2
Mouse

• On personal computers and workstations the mouse
  is frequently used to provide command input into
  computer systems
• A mouse has a tracking ball underneath, and when
  you move the mouse across a surface the ball
  turns. There are two rollers inside the mouse
  which are turned by the tracking ball, and the
  movement of these rollers sends a signal for the
  screen pointer to move up or down, left or right.
  
• For best results, always use a mouse pad and keep
  the surface clean.
• There are many different mouse designs. Some are
  made to conform to the shape of your hand others
  require no leads - they send a radio signal to
  move the pointer on the screen. Others have no
  tracking ball, but use an optical grid, pressure
  pad, or have movement-sensitive feelers.
• The mouse can have two or three buttons, The way
  in which a mouse operates depends on the software
  being used. A common approach with modern
  software is to click the left mouse button to
  select an option and the night mouse button to
  display a pop-up menu. You can select
  context-sensitive options from this pop-up menu
• The mouse can be used on either the left or
  right-hand side of the keyboard. If you are
  left-handed, Microsoft Windows includes a mouse
  driver, which can be changed to swap the
  functions of the left and right mouse buttons.

3
Optical Scanner

• A scanner is used to scan an image (graphic or
  picture) into a computer system. You can capture
  graphics or pictures and incorporate them into
  word-processing documents, spreadsheets, desktop
  publishing packages or databases. Two popular
  types of scanners are the small hand-held devices
  and page scanners
• As the name implies, hand-held scanners are held
  in the hand and moved across the area to be
  scanned. The hand-held devices are good for
  scanning small areas.
• Scanners can be used to scan in pictures and or
  text and and then stored as graphics. OCR
  software can be used to load scanned text into a
  word processor allowing you then to edit the
  text.

4
Digital Camera

• Scanning pictures by using a scanner does not
  provide the quality of pictures actually taken
  with a digital camera. The digital camera works
  by storing the pictures as electronic images that
  can be copied directly into a personal computer.
  The picture can then be manipulated using
  appropriate software on the computer and then
  printed or sent to other computers.