MOUS, JOY STICK, SCANNERS

TYPES OF KEYBOARD

There are two basic styles of keyboard commonly found eith micro computers. PC/XT style keyboards and AT style. The PC/XT style keyboard was first one developed by IBM. Later AT style was developed with a slightly different keyboard having 101 keys. Different manufacturers have developed diferent keyboards with slight alternation with keys ranging from 84 to 108 using different style.

MOUSE

A mouse is an input device. Unlike the keyboard where the information is typed, mouse is a pointing device and is used to select various option. A mouse consists of a small hand held unit with one, two or three buttons and a small ball at the bottom on which it can roll. As the mouse is moved across the desk on a mouse pad, it guides a small locator symbol (often an arrow, a cross hairs or a cursor) which moves across the screen. A mouse can also be used to draw pictures on the screen and edit text.

JOY STICK

Joystick is an input device, a small box with moving stick and buttons. It is generally found with micro computer and is used primarily for games, educational sofware and computer aided design (CAD) system. You manipulate the handle of the joystick to position the cursor and click on a button to send impulses to the computer. The joystick does not interfere with your view of the screen nor does it require the movement of an object like a mouse. A joystick is fun to use because of the speed with which it moves the cursor on the screen.

 SCANNERS

Image scanners convert any image into electronic from by shining light onto the image and sensing the intensity of the reflection at every point. Colour scanners use filters to separat the components of colour into the primary additive colours red, green and blue at each point. Red, green and blue and known as primary additive colours because they can by combined to create any other colour. The image scanner is useful because it translates printed imagtes into an electronic format that can be sotred in computer's memory. The soted image can be transferred into a paint programme or directly into a word processor. A flatbed scanner easily scan documents books or periodicals. Flatbed scanners have higher quality reproduction and can scan a page in a single pass. Scanners difers in resolution: the more dot a scanned image contained, the sharper it is. An inexpansive scanner produces images at about 300 dots per inch or 600 dpi. The more expensive scanners produce images at a higher resolution.

PC/XT, (CAD)