VISUAL
TECHNOLOGY
INCORPORATED,
RAILROAD
AVENUE,
DUNDEE
PARK,
ANDOVER,
MA
01810
the scroll
is
stored in
the
buffer
and
an
XOF
F (DC3) code
is
transmitted. Data received
from
this
point
on
is
also stored in the
buffer.
When the operator types the scroll key, the scrolling character
is
extracted
from
the
buffer,
causing the screen
to
scroll. Data continues
to
be
extracted
from
the
buffer
and displayed
until
the
next
scrolling character
is
encountered
or
until
the
buffer
empties.
If
the
buffer
empties,
an
XON (DC1) code
is
transmitted.
If
another scrolling character
is
encountered,
the
emptying
of
the
buffer
halts
with
that
scrolling character
as
the
first
character remain-
ing in the
buffer.
When
the
operator again types the scroll key,
extraction
begins and
continues
line
by
line
until
the
buffer
empties.
Using the
shift
key
with
the
scroll key modifies
the
operation
from
a line
by
line
basis
to
a
page
(24 line)
basis.
When shifted scroll
is
used, all data
from
the
buffer
is
scrolled
onto
the screen,
an
XON (DC
1)
is
sent
at
the
time
the
buffer
empties, and new data
is
scrolled
onto
the screen
as
received,
until
a
total
of
24
lines have been displayed. When the
24th
line
is
displayed,
the
terminal transmits
an
XOFF
(DC3) and places subsequent data
into
the
buffer.
Scroll
or
shifted scroll
functions
are then repeated.
RESET
HOLD
SCREEN: This command resets
the
hold
screen mode immediately
if
the
operator
has
previously scroll.ed all
buffer
data
onto
the screen (the
computer
has
received
an
XON).
If
buffered data
has
not
be~n
scrolled
onto
the screen when the command
is
received, the command
will
be
stored in
the
buffer
and acted upon
only
when the operator
has
scrolled
that
line
onto
the
screen.
4.7
EDIT
COMMANDS
INSERT
LINE:
The
insert line command
causes
the
data on the entire line in which the
cursor
is
located and all lines below this line
to
move
down
one line. The
bottom
line
is
lost
and the
line where
the
cursor
is
located
is
blank. The cursor
is
positioned
at
the
beginning
of
the
blank
line.
DELETE
LINE:
The delete line command deletes the line in which the cursor
is
located,
moves
all lines
below
this
line up one line, and places the cursor on
the
left
margin.
INSERT
CHARACTER:
Insert character
function
is
a mode enabled
by
the set insert
character command and
is
disabled
by
the reset insert character command. Once in
the
mode,
an
input
character
will
move the data starting
at
the cursor location
right
one posi-
tion,
place
the
new character at the cursor location, and move the cursor one position
to
the right. Data moving
to
the right margin
will
be
lost. Where
half
intensity
data
is
present
to
the
right
of
the insert
point
data moving
to
the
right
will
be
lost at the beginning
of
the
half
intensity
area.
When the cursor reaches the
half
intensity data,
it
will
overwrite the
half
intensity
area
because in the character mode
unit
half
intensity data
is
not
protected.
The
bell
will
ring on
each
character entered
from
the
keyboard.
DELETE
CHARACTER:
The delete character command deletes the character at the cursor
location and moves high
intensity
data located
to
the
right
of
the cursor one position
to
the
left.
Only
data
onthe
line which contains
the
cursor
is
affected.
4.8
KEYBOARD
COMMANDS
LOCK
KEYBOARD:
The keyboard
lock
command
is
effective
only
when the terminal
is
on line. The
lock
command
inhibits
all operation
of
the
keyboard except reset (RST) which
will
cause
the keyboard
to
unlock.
16
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