(b) Uses. Data can be entered on the keyboard and displayed on the
screen for verification as it is keyed in. Video Display Terminals can also be used for
applications in which inquiry and response are needed, but no permanent record is
required. Monitors can be used for capturing data to be transmitted from remote offices
to a central computer. Faster and quieter than printers, they have a display capability of
10,000 characters per second. A printer can be connected to a terminal, to provide
hard copy of the screen contents, if needed.
(c) Options. Video Display Terminals have a variety of options.
Resolution or clarity will depend on the size of the dots that form the characters.
Smaller dots make sharper images. Standard terminals are monochrome, but color
provides added flexibility. Many programs can use or require a color monitor. Most
VDTs can read only standard shapes, i.e., letters or numbers. The graphics capability
is an additional option.
Figure 2-29. Video display terminal (VDT).
(2) Graphic display devices are monitors that display drawings (graphs,
charts, complex curves) as well as characters. With some terminals data can be altered
using a light pen. A light-sensitive cell at the tip of the pen communicates with the
screen's electronics to tell the computer where the pen is pointing. The light pen gives
computer users another way to interact with the machine without resorting to the
keyboard. Using the light pen, complex drawings, such as those used in airplane or
automobile design, can be made. Items can be selected on the screen, and even music
can be composed through the use of a special program. In figure 2-31, the program
causes each note to sound as the user positions the note on the screen. Pressing a
box labeled PLAY causes the whole piece to play.