Keyboard
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Input and pointing methods
A brief description of available devices for inputting of
information and pointing.
Cursor control keys
The cursor on the VDT screen is a positionmarking symbol, such as a solid
block or underscore. It may blink or be brighter than other symbols to identify
its location easily. In test display applications, the cursor control keys
may be used to relocate the cursor to a desired position. Four keys are marked
with arrows for the four rectilinear directions of possible movement. These
keys are usually "typamatic," that is, if the key is depressed for
more than about half a second, a sequence of movements at a variable or fixed
rate, such as 10 steps per second, will occur. Single steps are generated when
the keys are kept depressed for less than half a second. A study by Emmons
(1983) indicated that cursor keys arranged in a cross, or cruciform, pattern
are more efficiently used than keys arranged in a box configuration, particularly
for less experienced users. However a later study by Emmons and Schronka showed
that an inverted-T arrangement (now widely used on keyboards) was preferred
to cross arrangements, with no loss of efficiency.
In the discussion of cursor control, The BSR/HFES 100 draft standard makes
the following statement:
"A two dimensional cursor control (e.g., cursor keys, mouse, trackball)
shall be provided for text- and graphics-processing tasks. If cursor keys are
provided they shall be arranged in a two dimensional layout and they should
be dedicated to cursor movement. If the cursor keys have collateral functions,
their operational mode status shall be clearly indicated."
The two dimensional layout may be in the form of a "cross" or inverted-T.
Light pens
The light pen is the traditional pointing method for graphic applications
on CRTs. The pen senses the phosphor excitation at the time of its vertical
and horizontal scanning position, which activates a cursor or "crosshair" visual
feedback. The light pen typically employs a pressure switch so that it is not
active until the switch is depressed against the faceplate.
Other techniques
Many other techniques are being used for inputting commands and designating
display positions. Joysticks and trackballs are technologies often employed
in military applications and specialized industrial and commercial settings.
Digitizing tablets transform the tablet area into an equivalent of the display
screen when a "digitizer" is moved over the tablet. A "touch
screen " is a thin transparent screen placed over the display screen.
This can be activated with fingertip pressure. Of more recent development is "voice
input". Significant advances have been made in this technology and a number
of products are available on the market. When using this technology, the user
is usually required to go through a process of "training" to get
the system to "recognize" the user's voice.
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