(a) Most computers in use today have open architecture which enables users to open them easily and install new devices. The need to buy new computers is reduced since the existing capability may be enhanced using expansion slots on the computer motherboard to plug in expansion cards.
Describe any three types of expansion cards.
(b) List four scanning devices and explain how a scanning device works.
(c) Digital video disk (DVD) is a relatively new type of data storage device that may be used for diverse data storage tasks.
Describe three characteristics of a DVD.
– Network Interface card (N.I.C)
– VGA card
– Sound card
– Image scanner – converts images on a page to electronic signals
– Character and mark Recognition devices – scanning devices used to read marks on documents.
– Fax machine – converts light and dark areas of an image into format that can be sent over telephone lines.
– Barcodes readers – photoelectric scanner that reads vertical stripped marks printed on items.
How a scanning device(Scanner) works
A light bar moves across the object being scanned (the target) and the light is reflected to the charge coupled device (CCO) a system of mirrors. Each cell produces an electrical signal proportional to the strength of the reflected light that hit it. The signal which represents one pixel in the original images is converted into binary number and sent to the computer. Darker portions of the target reflect less light and are given lower numbers
– As a disc, DVD looks very much like the CD. Both are shiny discs that are 4.75‖ (112.0cm) in diameter. Both are optical formats containing digital information.
– Smaller pit size
– Tighter track spacing
– Multiple layer capability
– The DVD may be used for video, audio, or data storage.