A key board is simply a way that the user may interface a fixed number of commands (equal to the number of keys that the manufacturer places on the board). The standard keyboard for home PCs is a QWERTY key board, but they are not restricted to this format as in industry they can be used to send different common commands to a computer for example a farm may have a key board controlling the environmental setting in the sheds with a button to dim the lights or turn them up or a button to turn on the water supplies.
The keys on a QWERTY keyboard will work in two different way.

Captive key: When this key is pushed a plunger is pressed down allowing a current to flow across a pad.

Hard contact: When the key is pressed to conectors are pressed together forming a physical conection creating a current.

The key board has in side it a small microprocessor this will scan the keyboard once every millisecond to check for changes in the current when the key is pressed the processor finds that the current has increased and reacts accordingly and the same when the current is depressed and the current decreases.
Over the years many new types of keyboard have been thought up these are mostly more ergonomically designed than there older counter parts this is done in order to reduce R.S.I a problem that effects a lot of typists
One of the most interesting keyboard is a device called a data hand this will take a combination of hand movement and clicks and convert them in to working commands.
Another type of keyboard is the virtual keyboard this removes the physical keyboard and replaces it will a digital interpretation that the user can interact with this is most popular with machines too small to use a standard keyboard such as palmtop computers.


A mouse is a way of removing the clumsy use of a keyboard a mouse’s primary function is to convert movement of the mouse ball to movement of the on screen pointer making computer use quicker and simpler.
Mice have opened up mass of programs moving us away from user unfriendly operating systems such as MS DOS to systems such as windows where users can perform functions by simply clicking or double clicking on icons representing the file.
A mouse works in a number of steps.

1. As the mouse ball is pushed it rotates
2. When it turns the mouse ball pushes two rollers one controlling the vertical movement and the other the horizontal.
3. The rollers rotate two wheels known as encoders these have rows of metal contacts these make connection with a contact bar inside the mouse when turned resulting in electrical signal
4. The electrical signal is sent to the PC informing it to move the cursor slightly and the more signals the further the mouse will move.
5. When a button is clicked it sends a signal to the computer to indicate that this has been done.

Most mice work to this principle though they may come in numerous shapes and sizes including trackballs with which you move the ball with your hand.

Examples of mice:

Hard disks

If you imagine a floppy disk this is an independent platter, a hard disk however has lots of these with only a very small gap separating them. Once the platters are in place then the drive heads move and the disk spins allowing the computer to read the disk.


1. A sealed protective metal case that ensures that none of the major components get damaged by dust or other foreign bodies this is because there is not much room in between the platters and the heads
2. Underneath the drive is the logic board where all of the information sent from the controller and operating system is translated into fluctuations of the current, these force the head actuator to move over the platters. The board is also responsible for making sure the spindle is spinning at a constant speed.
3. The spindle that drives unto eight magnetically coated platters at many thousand rotations a minute, the number of platters on the spindle dictate how large the drive will be.
4. This head actuator plate moves the read write heads across the platter in order to read and write the disk this is done