Key features of a VDU terminal:
1. The VDU is really 2 devices: A keyboard and a screen display. The keyboard is for data input while the screen display is for output of data.
2. Data is fed in via a keyboard which is like a typewriter keyboard, and is both passed into the computer and displayed on the screen. The VDU can also receive and display messages from the computer.
3. VDUs are mainly used connecting them directly to the computer. This mode is known as
on-line data entry.
4. VDUs lack the processing capabilities of PCs and thus they are referred to as
5. VDUs were used in the past in conjunction with some other special purpose data entry system in order to prepare data on a fast and reliable input medium. The most popular example was the key-to-floppy-disk or key-to-diskette system. These were basically microcomputer-based systems that took in data from the VDU and stored it on floppy disk.
6. When the VDU is used to provide a graphics display capacity e.g. for management information systems applications, some or all of the following control devices may be incorporated in addition to the high-definition colour monitor:
o Mouse or trackball devices
These use the rolling motion of a ball (a mouse being rolled on a flat surface, a trackball being moved manually) to act as a cursor control or to move data about the screen quickly.
o Voice Data Entry (VDE)
These employ a modified VDU and microphone to accept vocal input. The simplest
speech recognition systems may be programmed to recognize a limited number of key words.
o Light pen and touch screen inputs
These use the VDU screen as part of the input medium. A light pen connected to the terminal is placed against the screen, and a light sensitive device recognizes the position X and Y coordinates. A touch screen uses an inlaid screen to accept input through the act of physically touching the screen.