A video terminal or visual display unit consists of a television screen and a key board similar to typewriter key board with additional function keys. A VDU uses a cathod ray tube [CRT] to display information. When the key is pressed the corresponding character is displayed on the screen. Simultaneously the cursor moves to the position where the next character will be displayed. A cursor is a small arrow or small square which can be moved horizontally or vertically to indicate the position of the character.
There are two types of VDU, those which display only ordinary alphanumeric characters and those which can display graphical symbols as well [computer graphic unit\terminal]. The screen size vary from" to 20" is standard size]. and can display 20 to 30 lines and the number of character/lines from 32 to 80.
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