4. CPU - Central Processing Unit VDU - Visual Display Unit CD-ROM – Compact Disk-Read Only Memory DVD - Digital Versatile Disk RAM – Random Access Memory ROM – Read - Only Memory BIT – Binary Digit MG - Megabyte GB - Gigabyte LCD – Liquid Crystal Display DPI – Dots Per Inch OCR – Optical Character Recognition SVGA – Super Video Graphics Array PPM – Pages Per Minute CD-R – Compact Disk - Recordable CD-RW – Compact Disk- Rewritable WORM – Write - Once Read - Many GUI – Graphical User Interface WIMP – Windows,Icons,Menus,Pointers CPU - Central Processing Unit VDU - Visual Display Unit CD-ROM – Compact Disk-Read Only Memory DVD - Digital Versatile Disk RAM – Random Access Memory ROM – Read - Only Memory BIT – Binary Digit MG - Megabyte GB - Gigabyte LCD – Liquid Crystal Display DPI – Dots Per Inch OCR – Optical Character Recognition SVGA – Super Video Graphics Array PPM – Pages Per Minute CD-R – Compact Disk - Recordable CD-RW – Compact Disk- Rewritable WORM – Write - Once Read - Many GUI – Graphical User Interface WIMP – Windows,Icons,Menus,Pointers

5. Keyboard Has a standard QWERTY layout. Used to enter large amounts of text into the computer Used on tills, remote controls and most ATMs. These keyboards may have fewer keys with emphasis on numeric keys. Concept keyboards are special keyboards which have keys pictures or words. For example, they are used in supermarket fruit and vegetable departments for customers to weigh their own purchases. They are also used on vending machines The speed of input depends on the human operator Can be slow compared with other input devices. Prone to human error since all data is entered ‘by hand’. Concept keyboards provide ‘shortcuts’ for users who do not have to be specially trained to use them. Mouse Also referred to as a ‘pointing device’. Designed to fit under the hand. When it is moved a pointer on the screen moves in the same direction. A ball moves and built-in sensors pick up the movements and send corresponding Easy to use Inexpensive compared with other input devices. Experienced users may find using a mouse slow compared with using ‘hot keys’. For example they might

6. Mouse cont.Signals back to the computer.