Keyboards

Normal Keyboards

In its many differant froms, this is the input device that many suers will be most familair with. Keyboards are still the most common method for entering text and numerical data. In addition, certain key combinations on a keyboard can be used to access commands in the computer, for e.g to access the cut and paste menu commands. Standard Keyboards inclue alphanumeric keys, a numeric keypad, function keys and control keys. Smaller keyboards, such as those found on a laptop, may omit certain keys such as the numeric keypad. A keyboard is traditionally connected to a computer via a cable, though wireless connections are increasingly common.

CL Sholes designed the QWERTY key layout in 1878 with the remit of preventing stuck keys on mechanical typewriters, by ensuring that the most commonly-used letters were spaced far apart. Technology has moved on and we no longer have the issue of stuck keys. However this keyboard layout remains simply because people are used to it. There have been some attempts to revise the keyboard layout , such as August Dvorak's 1936 design that allows for less finger movement when typing but these have not met widespread acceptance
Because the Qwerty Keyboard is designed around the frequency of certain letters in English, a differant layout is often adapted in non-English speaking countries. France uses the AZERTY keyboard, while Germans will be used to using the QWERTZU layout.

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How does a keyboard work?

When a key is pressed, an electronic signal is sent to the prcoessor which interprets the signal. Software then takes the appropiate action, for example making a letter appear in a word-processed document. This is the procedure when a user types Shift-B;
· The Keyboard has a small microprocessor within it that continuously monitors for key presses.
· When a key press or a combination of key presses ( in this case the shift key plus a letter ) is detected, the ASC11 code specific to that combination of keys is sent to the processor.
· If a "b" on tis own had been pressed the code 1100010 would have been sent to the processor. However, the shift key means that instead the code for "B" (1000010) is transmitted.
· This binary code is stored in a buffer ( a temporary storage location used when data is being moved from one location to another ) where it is transmitted serially ( one bit at a time) to the CPU
· The character "B" is then displayed on the screen and the buffer is emptied.

Concept Keyboards

Instead of the usual keys, an overlay sheet containing different pictures is placed on top of a touch sensitive pad. The user indicates input by pressing one of the pictures. Related software then interprets the input. It can be used:

· To help people with physical disabilities.
· In young children’s Computer based Learning systems.
· Fast food restaurants or bars where there is need for quick, efficient input of menu choices. It has the advantage of having a water and dirt resistant surface.

With a concept keyboard it is possible to change the overlay to provide a different set of pictures. A concept keyboard can only be used when all the inputs are anticipated and the range of options is small.
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Alternative Keyboards

These are designed around the form of the human body, for example having a split or curved keyboards to minimise wrist and arm strain.

Repetitive Strain Injury (RSI) is often associated with poor keyboard design or poor seating. A traditional QWERTY keyboard forces a user to rotate their forearms so that the palms are down and lift their middle fingers so that all four can touch the keys, which is not a natural body movement. Alternative keyboards have been designed to alleviate the likelihood of such injury, and may include some or all of these features:

· Split Keyboard, which straighten the wrists by increasing the distance between the left and right sides of the keyboard and by rotating the keys to align them to the forearms.
· Tented Keyboard, which is tilted up at the centre to reduce forearm rotation.
· Alternative key positions arranged into curved rows in concave wells, instead of horizontal rows, to allow the fingers to straighten more.
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Advantages & Disadvantages Of Keyboards



The advantages of keyboard are:

1. Keyboards have special key that perform specific functions.

2. Instead of using the mouse to move the cursor you can use the arrow key situated on the keyboard to move the cursor on the monitor.

3. Keyboards are less expensive because it comes with every computer.

The disadvantages of keyboard are:

1. The person using the keyboard have to learn how to type.

2. The frequent movement from keyboard to move and back could cause carpal tunnel syndrome or RSI

Exam Questions


A keyboard is used in typing a word document.
(a) Explain how data is captured using a keyboard.


Mark Scheme


  1. The Keyboard has a small microprocessor within it that continuously monitors for key presses.
  2. When a key press or a combination of key presses ( in this case the shift key plus a letter ) is detected, the ASC11 code specific to that combination of keys is sent to the processor.
  3. If a charecter on its own had been pressed the code 1100010 would have been sent to the processor. However, the shift key means that instead the code for the charecter for e.g 1000010 ( Letter B) is transmitted.
  4. This binary code is stored in a buffer ( a temporary storage location used when data is being moved from one location to another ) where it is transmitted serially ( one bit at a time) to the CPU
  5. The character "B" is then displayed on the screen and the buffer is emptied.




References

  1. http://www.compkeyboard.com ( Most Images)
  2. Real World ICT for AS and A2 2nd Edition ( Clarke Rice, Karen Ward, Keith Redfern)
  3. http://www.crn.com
  4. http://store.aramedia.com
  5. http://www.instablogsimages.com/images/2007/12/29/optitact-text_3858.jpg